David Leigh, Raymond Astumian, Alberto Credi: The Advent of Artificial Molecular Machines
8:18AM Feb 20, 2021
Speakers:
Keywords:
system
non equilibrium
energy
equilibrium
talk
state
molecule
kinetic
light
thermodynamic
molecular
dissipative
machines
problem
pump
point
reactions
molecular machines
concentration
fast
So Hello, everyone. Welcome back to the molecular machines group. I'm really delighted to have everyone here. And we've got almost 50 people now, which is fantastic. So today, we've got three talks. So we've got Dave Lee, Dennis, Damian, and Alberto creating, each talk will be around about 20 to 25 minutes. After each one, there'll be maybe five to 10 minutes of discussion. And what we're really looking for here is to have discussions that focus on challenges in this research area that the talks are meant to help for sort of guide the conversation in the group. If people have specific questions about details in the talks, they want to ask the speakers, we'd encourage that to be dealt with in the chat rather than the relatively short time that we have in the public forum today. At the end of everything, we'll have a quick introduction to what's going on in the next session, and an enabling application session that we have next week. And we'll also have a networking session and gather. And I'll post up a slide for that where you can collect all the information. So with my bit out of the way, without further ado, we'll hand the floor over to you, Dave, if you want to share your screen. I one thing I will say if you have questions, post them in the chat, and Allison will curate them. And then we'll ask people to speak out and ask their questions once the talk is done. So I should have mentioned that before. As long as you're safe.
Thanks. Thanks very much. I hope everyone can hear and see me. Okay, I've got the world's worst internet connection here. So if I do fall out, please bear with me for 30 seconds. If I don't come back, and then demon del Berto get much more time. Anyway. Thanks very much indeed. for having me. It's actually my second time speaking to the foresight Institute. Were 714 years ago, as a founder of side effects. And over on, on my left is pedal chain, who was the the president of foresight at the time. And I don't know what happened to this guy in the in the middle. Actually, I, I do know what happened to him, because I was emailing him having an email exchange last night. But yeah, so it's great to have a chance to come back and speak again, to this sort of group. So the last five minutes of our talks today are supposed to be talking about really what the potential applications of electrical machines might be over the next 515 30 years, and don't really know what that going to be. But it's a bit like one of the questions that I like to challenge my group with, which is, what will technology be liking in 30 years time? And in fact, this is of course, a question that, although this guy is not one of my group, even buffoons like him, asking questions like, like this. And these kinds of questions are useful, because they put us on the right sort of path for inventing the future. We'll get there quicker, perhaps, maybe before someone else does. And also, maybe it'll be the future that we want to have. But the further ahead you look, the more unlikely and hazy these sorts of things seem to seem to be in any kind of accuracy in these sort of predictions is, well, it's intrinsically likely because of all the things that we don't know that we don't know. But I think these sort of visions are important anyway, because of the useful directions that they point to that we might want to explore. And there's plenty of examples in history of that from Christopher Columbus, Christopher Columbus onwards. So it's, it's really the sort of directions that we want to get in this sort of area, which I think is important, and this is really the reason to invent and explore artificial molecular machinery, at least for me. I'm sure it will lead to molecular nanotechnologies, whatever those might eventually be. And along the way, it's also going to provide insights into other matters. There's into physics into biology.
So
although these sorts of visions are important of these sort of paths forward, I do think that science fiction has these sort of scales of, of likelihood associated with it. So there from this on this sort of scale, we've got things like artificial life, which are very likely possible in, in my view, to things such as time travel that are very unlikely to ever happen to occur at the start the 21st century, although there are ways to begin to tackle something like how do we make artificial life or discover the origins of life, there's literally no point trying to design systems that might allow us to do time travel. So even if we think that's a great concept, try to move towards that, by experimentation, simply isn't worthwhile. And you can see lots of examples of that, as well. For example, HG Wells in 1923, was writing about something that was, could be considered email about wireless transmissions where people got messages, and didn't talk. But even though he was thinking about these things back in the 1920s, that vision didn't and couldn't lead to any scientific experiments to try and achieve those goals. Because it was simply too distant, there was no way that scientists could even attempt to do those sort of things, they didn't have the tools to allow them to start. And that brings me to another point that I think it's very important in this in this voyage of scientific discovery, and that is, what, what scientists need to do is to identify problems that are difficult enough that they haven't been solved, but they're interesting enough to be worth spending all that time and energy and effort trying to investigate. But there's another crucial point, people have to be able to recognize, or the scientist needs to recognize that the time has come for solving that particular problem. And if it's simply too early, if we don't have the tools to tackle it, then we simply can't do productivity search those sorts of areas. And this brings me sorted to the start of this story, then have a five minute course. And there's plenty of room at the bottom, which he imagined all of these wonderful, amazing things. And one of the sentences in this lecture is that byman thinks that this is such an exciting area that in the year 2000. When they look back, scientists will wonder why people didn't start looking in this direction until the 1960s. And in fact, that didn't happen at all. Even though Fineman thought about nanotechnology or the after the very smallest dose sort of ages, the possibilities are very small. Scientists just weren't able to even begin to move in that direction until much later. And this is in fact, this is the anniversary of Eric Drexler so famous penis paper from 1981, where this sort of areas started to become discussed. And it's a fantastic paper even now, 40 years later. It's contains lots of wonderful ideas and connections that Eric made. There's lots of visionary ideas linking biology and machinery. And many of the things that Eric talks about in this paper are things that we can all get behind as scientists. Today, all sorts of things including manipulators abled, molecular manipulators able to wield a variety of tools, the comparison of macroscopic and microscopic components and the functions that they they might have. Protein synthetic organic chemistry talks about doing reactions at specific sites, and all these sorts of things are things that molecular science is today can can see as visionary, and the exciting possibilities of them. But by the mid 1990s, of course, a different way of looking at this subject to become
I'd come into interview and there was controversy in this area. And it became because the really this outlining of a, of this sort of mechanical engineering path to, to molecular machines and the idea of obstructions such as planetary gears, and other sorts of systems. So there's nothing wrong with those, per se, those sorts of very advanced ideas, things with strange silicon shells with predominantly sulfur termination. The The problem is for Molecular scientists, that we can't see how to make anything even remotely even beginning to approach anything like those sorts of structures. And so when technical information starts to appear, or things that are called technical information on on these sorts of things, molecular dynamics simulations, then the scientists lost, like scientists not competence in those sort of concepts. And really, this is because even if this mechanical engineering path is feasible, the time for solving that problem has just not come. Because, as molecular scientists, we don't know how to begin to create those sort of structures. but crucially, it's unnecessary, because we can see that there are more reasonable approaches to work on to achieve these kinds of content intended goals. And so calculations on these sort of mythical rather than real potential structures, to us implied a sort of false equivalency in the different sort of strategies towards molecular kind of nanotechnology. And this, of course, ended up with a discussion between draxler and, and smallie on in cabanon, at the start of the 2000s when smally and Whitesides also pointed out these problems of fat fingers and sticky finger kind of problems, that that sort of put the into to that sort of way of looking at this type of technology, I think, and that was kind of unfair, because even though the real, the solutions that Drexler and others put forward, didn't break physical laws, and who knows what will be possible in the long, long term. The real problem is that these sort of analogs of macroscopic engineerings are simply not appropriate for things that we
do.
That artificial molecular machinery sort of changed in their viewpoint. And so for example, biology already has lots of nice things that Erica recognized as machines. For example, things that really are like later assemblers, the fatty acid synthase carry out chemical synthesis. And as an example of what it's in our group, it started to make molecule the same as those biological machines. And here's an example of that. It consists of a platform with two sites on the platform, which are catalytics
ethers, organic catalysts nearly differ in their handedness, a robotic arm containers will switch the reason this rotary switch we can control whether the substrates held with the art catalyst or the catalysts and we can carry out sequential chemical reactions. So we can tell this molecule to first do a reaction with a nucleophile and iminium activation over the site, then switch the robotic arm tell the substrate over the other side well, where we had an electrophile activation mechanisms in the mean activation. And because these reactions are carried out in the under the auspices of a Tyrell promoter of the reaction, we should different stereo control to those reactions and we should be able to add the nucleophile and the electrophile to get the
Cairo's structure, and if we carry these reactions out, when the, when you electrify the deputy s catalyst, we should get different stereo chemical control. And if we do both reactions over one side or both, we accidentally hit the side we share the full sort of stereoisomer. And so in this way, we should be able to use this molecular machine to generate all possible stereoisomers from a single substrate. And in fact that that that really works in this prototype, this is the chemical structure here with one of these Luckily, rotary switches introduced by Ethernet Brahimi rahimian, the two organic catalytic sites. And this is the substrate this past alpha alpha beta unsaturated aldehyde. And the position of this switch just controls the side of that these reactions can be carried out on and we can add this nucleophile and this electrophile to eat psi. And depending on how we control the position of the arm, we can send selectivity over which product that we get out at the end. And this is really just like programming, as you would a any kind of decision tree in leading to the outcome that you want from this kind of synthesis. You can choose which product is selectively produced. And so this is you can get a pair of syneron to a pair of auntie and anthemis. So that includes a set of antennas that you die students that you can't get by conventional iminium ion in the mean photolysis. So each one of those two isomers can be prepared stereoselectivity for the single substrate, a common set of reagents, all in one pot by the programmed operation of a single artificial molecular machine. And when that was published, Ross Kelly and Mark snapper wrote this very nice news and views explaining that this idea of scale machines that Eric came up with and before that Fineman had taken assemble molecules as long as he thought of the stuff of science fiction, and that such machines might Herald new models for organic synthesis. So whether that turns out to be true doesn't isn't the important thing. What's the important thing really is to see that these, this sort of system does start to fulfill this real original idea of Drexler is that you can combine organic synthetic chemistry with this sort of machine like manipulation to select individual bonds on the basis of position alone. And from a chemical point of view, this is interesting, because it's a new form or new format of photolysis. It's not like using transition metals to lower the transition state of a reaction to fundamentally different process, but it's still catalysis, you're still starting from building blocks, and using them to select a new product. And so all these sort of concepts are, I think, interesting, going forward. And this is the sort of way that we thought about in our group of addressing molecular machines, or going about the concept of molecular machines over the last 2025 years. It's inspired by biology, and how that nanotechnology works. And we've tried to use those techniques to and principles to construct our own kind of artificial nano technology. So we learn lessons from biological machines, because that is a working nanotechnology. And that doesn't mean that we have to always follow exactly what biology does. So for example, biology works at ambient temperatures, and always uses chemical energy. But we'll, we'll see fantastic examples from Alberto later that use light energy. And of course, there are the finger boaters that use light energy. We're not restricted to ambient temperatures, we're not restricted to, to work in water. All these are, are things that biology is restricted to that we don't actually have to follow. But still the basic guidelines of how biology approaches the concept of trying to make molecular machines is one that we try to follow. And so that requires, we think the the idea of trying to reimagine, not reproduce concepts from the big world engineering concepts and other sorts of concepts, just like fuel architecture, what does that what does that mean at the molecular level, what function does that really
perform? All these kinds of things are things that we try and think about what that process is in in big world, how can we do do something that achieves the same sort of goal at the molecular level. So biology provides working examples. But it's limited in in many ways, by evolution, just going down the whatever it happens to work and moderate, it finds first and modifying that the very limited number of building blocks and conditions it has to work with. And what we've found and others have found is that you can achieve some of those things in synthetic systems by using in a much simpler, smaller way, nothing as sophisticated as biological machines yet, but beginning to do some of those sorts of things. Because when, with much smaller, simpler systems, because we're not limited to just 20 amino acids, and working in water, we're finding that the way to look at machines is to think of them as having been built of modules that can each perform certain tasks, but then act together to accomplish more than the sum of those parts, but that they don't work in the same way as macroscopic engineering machines, because they simply those those, those sort of techniques are not appropriate for the area that we're working. And physics, as Dean will tell us about provides not only understanding of how you get this length scale, but also great mechanistic designs that can inform how molecular machines can be designed. And we can then in by having to really make molecular machines that use all the restrictions imposed by real life chemistry, I think we can then provide insights back into fundamental biology and physics and provide explanations of how those sort of systems work. So I think that there's a lot of exchange between those disciplines that are useful, right, I think I've used up all of my time. So I'm going to skip through my little slides that I wanted to show and just get on to just talking very briefly about a couple of the things and just talk about these applications and challenges for 515 and 30 years. And I really don't have too much to say about that. And I thought I would just choose four challenges. And what I think there'll be breakthroughs in the next five years in things that we're not working on, but things that I see fantastic things that are being done by other groups around the world, and especially young groups that are just starting out. So compartmentalization, I think it's going to be increasingly important. Working in vesicles. That's what biology does. There must be reasons for organizing machines in that way, organizing machines, in solids, and on surfaces. Again, I'm sure that there are going to be lots of important developments that are going to come from that and fantastic work is being done in those sorts of areas. And just in general systems chemistry, having molecules work on their own, just doing simple things isn't going to going to change the world, I don't think but having lots of them working in complex ways. We'll we'll do that. And then a longer time scale, what I hope to see things that may be will approach artificial lifelike systems, a reinvention of photolysis, to include some of the concepts that I touched on briefly. And eventually, of course, what the field really means to progress as a killer app. Okay, that's enough for me. Sorry, I've gone on longer than I wanted. I hope that the that you could hear me. Okay. I just like to thank my group and all our collaborators for all their hard work and creativity. Thanks a lot.
Excellent, fantastic. That was a really, really great introduction, Dave. That was fabulous. So thank you very much. And then the other usual if everyone can share their their appreciation for today's talks, always, always welcome. So we've had one question from I use, man. So nice. When do you want to unmute yourself and pose your question today?
Oh, yes. So So back to the fat finger. So So Dave, I understand that the systems might work in a solvent because the solving can push off the product that you're trying to make or manufacture or whatever. Would these things ever work in the absence of a solvent In the solid state you think?
Well, of course, it's hard to say it depends what version of nanotechnology you're talking about. This is one of the big, the big issues raised by by Whitesides and smallie. And of course, what we're used to is having salvation and, and the incredible importance that that plays in all kinds of biology and all the molecular machines that we know about. But if you don't break, you know, and I don't really want to defend the other way of looking at nanotechnology, because I don't think it's something that we can realistically work towards. But if you do not break physic fundamental physical laws, I think it's very dangerous to say that those things are absolutely impossible. I think it's better to say that they're there. They're like time travel, they're not the way to usefully spend your time, especially when the soft approach to nanotechnology using solvents. And using things that are in solids in bulk sand on surfaces look so much more reasonable and exciting and, and still incredibly challenging. No, no,
I agree with you. All I'm trying to say is that at this scale, and I'm not trying to defend this Molly or Whitesides, but at the scale, the van der Waals forces become dominant. And unless you have, you can somehow negate that by having a solvent bind instead and pushing off here. Whatever product you have, it might remain stuck. So maybe there's a reason why nature always works in in water. Well,
I'm absolutely sure that's true. Yeah, I'm sure you're absolutely right, that for sure. And so for all foreseeable systems that we can think of, I think that you're absolutely right.
Thanks, beautiful talk.
there any others people can put a put their hands up where you can post them in the chat? Otherwise, I'll take an opportunity. Or you can unmute yourself if you want to does anyone.
So as most of you saw, you mentioned things like art like these, these really grand goals of like artificial life in Britain bringing analysis I mean, to my mind when you when you say like compartmentalization of vesicles that's one of certainly my research areas that I'm interested in. I know a lot of people are, which would be classed as a big stepping stone to a to a system such as that. But do you have any idea? Like, do you have a personal opinion on like stepping stones and big challenges that this area has in terms of like goals from your work that you would would see in the future that you need to address to start meeting these higher end goals? And then to answer that, are there things that this group could help support you with to reach those? And is there things that this group you think will work together to address as well? So it's a very sort of long winded question. But
yeah, well, I
say I tried to try to say that our philosophy is to know the general direction that we want to move in and then to take Well, what are still big steps but not to, you know, to try at this stage to say make artificial light. So a reasonable, long, or medium term goal could be to have molecular machines that operate cooperatively within vesicles within compartmentalized systems. So that would be a really cool, amazing thing. To demonstrate that would require. Well, all sorts of advances that we have, no one else knows how to do yet. So I just having molecular machines work cooperatively in solution at the moment is something that's not being that's not easy to demonstrate, and then to have that happen in cells in compartmentalised systems like vesicles, being able to pass fuel and waste and substrates and products in and out of the vesicle even though those things are going to be incredibly challenging to do. And yeah, that's going to you know, those are sort of medium term goals, I guess.
Yeah, completely agree. So that mean Thanks, Dave, for elaborating a bit more especially gives us an idea of maybe what the next big problem that we should be addressing is, and music to my ears at least. We should thank Dave, Dave again, we'll move on to the to the next Talk which will be DNS do mean, to keep things to time, we'll have a chance for a very general discussion at the end before we move in together. So yeah, Dean, if you'd like to share your screen, great, I couldn't see you. So fabulous.
So, I want to discuss, and from a very practical from the standpoint of fundamental, and sort of details, talk about the kinetics versus the thermodynamic stability and non equilibrium chemistry. Now, one of the things to remember is that at the turn of the century, when, when we had the Industrial Revolution, thermodynamics played an extraordinarily important role theory was back and forth, driving, development of practical applications. Now, in equilibrium, we always think in terms of thermodynamics is governing the distribution of all of states of transitions and things like that. Away from equilibrium, what we're going to see one of the main points of the talk is that kinetics dominates the non equilibrium behavior of systems. Now, if we think about thermodynamics, we think typically in terms of strong versus weak, all right, you can have a strong bond, a bond that is very tight, or you can have a weak bond, a bond that is loose, and it's described by equilibrium constants, which in turn depend on free energies of states. And these free free energies of states can be thought of as energy minima in an energy landscape. And if we think about how you break bonds, that are governed by thermodynamics, you'll typically tend to break the weakest first, and intermediate strength bonds second, and the strongest bond third. And when you reform those bonds, the first bond to reform is strongest. And then the second is intermediate, and the third is the weakest. So if you think about the order of breaking and making, it goes, weak, intermediate stronger than strong, intermediate, weak, the orders are the reverse or microscopic reverse of one another. Now, in kinetics, kinetics talks about fast versus slow, lay bio versus non Lee bio. And it's governed if we talk about rate constants, and the rate constants are governed by the free energies of transition states. Now in freshman chemistry, we oftentimes draw one dimensional energy surfaces where you have a minimum connected by a maximum to another minimum. Now, of course, that's a very Miss topologically misleading representation. Because the states the minima are actual energy minima on the higher dimensional landscape. The transition states, on the other hand, are saddle points. Now, top illogically what a saddle point is, is it's a point where along one coordinate, if you move backwards or forwards you decrease the energy. But in a coordinate that's orthogonal to that, if you move forward or backwards, you increase the energy. Now, these energy increasing and decreasing coordinates do not need to be the principal coordinates of the system. But if you can picture that in your mind, we see that the saddle points intrinsically have directionality. Because it's preference preferable to go along the direction in which you're decreasing the energy and not in the direction where you're increasing the energy. Now, if we think in terms of breaking bonds in terms of their kinetics, we'll break the fastest most labile bond first, and an intermediate Li rapid or intermediate Li laybuy Oban, second, and the least label or slowest bond will be last. And then when we reform we will of course reform the fastest bond, the most label bond because it's coming on and off fast. And then the intermediate bond and then the slowest or least label bond. And if we think about the order of breaking and maybe We see fastest intermediate slowest,
repeating fastest, intermediate and slowest. That is not the microscopic reverse of the two processes of breaking and making. Now, this is the only equation in the slide. So at equilibrium, the ratio of any two states DNA is determined by an equilibrium constant k a, b, away from equilibrium when we're putting energy into the system. And typically, we might think about catalyzing a reaction, where a and b are bound forms of an enzyme or something like that. We can show it's easy straightforward to show that the steady state ratio is given by the product of the thermodynamic effect, they act librium constant. And a function that depends on the kinetic asymmetry. We'll talk about that in a bit more detail, but it is a quote unquote dissipative effect, and it is purely kinetics. What we'll see if for example, is that those curly A's, the kinetic asymmetry factors depend on the Delta mew of the reaction being catalyzed. And on the ratio of off rates, in other words, it does not depend on the free energies of the states at all. And another way of writing it and more physically way, if you will, is as in terms of the exponential of the free energy difference between a and b, the path independent part so so in going from A to B, typically, you can go by many, many different routes. And there will be a path independent part that is the exponential of the free energy difference between the two. And it will be multiplied by something that is the average, the exponential average of the work exchanged with the path dependent work exchanged average over all of the different trajectories. The key point here is the teasing apart of thermodynamic effects, which dot which tell you everything there is to know about the equilibrium behavior and kinetic effects, which are the effects that dominate, oftentimes the behavior away from equilibrium.
Okay, now, so actually, let me go back. Now, this is the part the average of the path dependent part is subject to design. This exponential average is the key thing that we're going to try it engineer in making molecules that do interesting things. Here's a molecule that does something interesting. It's what is called a poly rotaxane synthesizer that was synthesized in Fraser Stoddard lab last year. And the idea is now we have this dumbbell like rod which is sort of coiled because it has a polyethylene glycol chain, and it's going to be extensible. But the key is this peridinium group and ISO propyl phenol group, which are how the kinetics are controlled sandwiching a bippy Group A by peridinium Group, which is how the stability of the ring is controlled. Now, this structure of an electrostatic barrier, a recognition site and the steric barrier is what has come to be known as a pumping cassette. Because by switching the oxidation state of the cycle, this paraquat, the blue box ring from a oxidized where it does not have any particular attraction to the by peridinium. And further, it can't get on because it would have to pass over the positively charged peridinium group. But then when we make it reduced when we make this system reducing, that will change to make the radical of the cycle this paraquat, the die cat ionic radical, which now can engage in radical pair interactions with the now singly charged by peridinium. And because it's only positive plus two, it can pass over the peridinium group. So when we go into reducing conditions, it threats, then we make the solution, oxidizing, which oxidizes the cycle of this paraquat and the bippy. And now those two charges in the plus for charge, has no attraction, no stability at all. And so the positively charged tetra cat ion will move off of the bippy and eventually over the ISO propyl phenol steric barrier, not over the electrostatic barrier, because it's positively charged, and then eventually move on to a collecting chain, that polyethylene glycol chain. Now, the key point here is that we have plagued with the kinetics by CIT. So we have in the reduced form, the peridinium barrier is smaller than the barrier of the ISO propyl phenol. In the oxidized form, the peridinium barrier is much larger than the ISO propyl phenol as seen in this ratchet like structure. And so by playing with the kinetics, we've made it such that in going through a cycle of oxidation, reduction and oxidation, we pump a ring onto the collecting chain. By repeating this, it is possible to get well up to 10 rings onto this poly ethylene glycol chain. That's that's the largest number that we've gotten so far. And it has a charge of 46 plus, this is a highly non equilibrium structure. If you do any kind of estimation of its free energy, it's extraordinarily high free energy. And yet, because there's no kinetic route for it to get off, its meta stable, it will remain for weeks and months in that high energy form.
Now, what I want to dry now we're going to move from the situation where we were looking at external modulation. To ask the question, can we do similar things by using photolysis. Now, note here that you could even you could talk about the the transition from between the by cat ionic by peridinium. And the tetra cat ionic cycle this paraquat to the collecting chain is sort of a power stroke. This is a high energy form, what you've done is you've used oxidation energy to raise the energy of the resin make it such that it has to move off of that high energy state. And you control the kinetics by having the electrostatic barrier on one side with the bulk and the ISO propyl. phenol can blocking its motion onto the collecting chain. And so it preferentially goes over the ISO propyl fennel, and so you've used the kinetics to steer the direction. But you have put in the energy by raising the energy of the state of the interaction between the cyclist paraquat and the bippy. Now, what I want to draw your attention to is what I have termed kinetic asymmetry. And I want to describe this in terms of a simple Michaela menten enzyme. Now, this is a typical energy profile for a catalyst. And what we have is it when it's catalyzing a reaction, typically substrate has a higher chemical potential than product and there's a bound state. And now look at the bounce. So first off, notice that there are two pathways to go from the Free State e to the bounce state, E and I've written it with a l, meaning that it is neither substrate nor product, when it is bound to the enzyme, and that you can't intelligently or intelligently talk about bound substrate or bound product, you can talk about the bound state of the enzyme. And that was a point made by Terrell Hill in the 1980s. And I think that has been missed a lot in the literature. But if you think about it, no one talks in terms of fundamental mykayla parameters about the ratio between k plus two or K cat and k minus one the off rate for substrate. And yet, this turns out to be an extraordinarily important parameter for described for determining under non equilibrium conditions under conditions where delta mew is much greater than one. Whether you have more bound enzyme, then you would expect that equilibrium or less. And so you see that if I have k cat much larger than K off for the substrate, then I end up with a situation where I strongly favor the free form of the enzyme and disfavor the bound form of the enzyme. So everything on the top row is done in equilibrium with delta u equal to zero. And in all cases, you have 5050 between enzyme and bound, bound and free form of the enzyme. That's because I chose it to be that way with the constants that I took. However,
if we go away from equilibrium, we're here delta nu is equal to five kt, five times a thermal energy. If I have CAKE CAKE cat be much greater than the K off, I favored the free form of the enzyme. If I have k cat much less than the off rate for the substrate, I strongly favored the bound form. In other words away from equilibrium, I can select either the free or the bound form one of the two forms of the enzyme, not by and and note, I can change k plus two and k minus one, without changing the free energies of L and D. This is a purely kinetic factor. And away from equilibrium, this kinetic factor determines whether I have one state or another favorite. And if I do the arithmetic, I can be on the on this is the on rate from free to the bound form. And this is the off rate from the bound form to the free form. And when I go through and use microscopic reversibility, this is it the this is a form into which I can manipulate the arithmetic. Okay, so now we have two different energy sources, one we talked about was changing the energy of with redox. But the other was based on photolysis. Now, let's think about and David will, of course, recognize this motor because it was inspired by his beautiful paper in nature, I believe, with Wilson, which used it's the first and so far, the only published example of a catalysis driven synthetic motor. Now, the idea here, and I'm, so I'm going to ask you to look at this and see if you can come up with an understanding in your mind of which way it goes. Now, the idea was based on trying Well, at least my idea was to try and illustrate how you could generate a power stroke. A something like the paringa motor, we're in light energy goes in, lifts, the enzyme lifts the molecule to a high energy state from which it relaxes directionally. And so here, we might imagine, for example, that in the state pf, we can use chemical energy to put that ball on this is a diass fluoro methoxy carbonyl chloride to put this back On. And despite the fact that it would be repulsive, but then the repulsion will move the small blue ring to a distal to a different to a far position. And then when it comes off, it relaxes with equal probability in both directions. And so because of this push that's, that is described by KB, you would get net clockwise rotation. Now, the truth is that the rotor that was designed by David goes around in the counterclockwise direction. And the whole point is that in this, in this form, the binding of the fuel that we used to use substrate and products, and now in the most recent literature, everybody uses fuel and waste.
Same thing. But here, the fuel molecule that's in high chemical potential is slow, the binding of the fuel is very slow because of steric hindrance. Whereas here the binding of fuel is faster. And the did cleavage, or the removal of the orange ball is with equal likelihood from either the distal or the proximal, with the net effect being to drive this process kinetically in the counterclockwise direction, in a direction opposite to that, that you would expect, from naive ideas about a power stroke, and about the way that even the energy ratchet moves. And this is known as an inflammation ratchet. And it's called an inflammation ratchet. Because because the whole mechanism of motion is based solely on the difference between the reactivity, the liability when the ring is near to the active site versus when the the dark blue ring is far from the active site. Okay, now, we can take a similar picture and ask about and note notice. So this can continue to go around. This is a rotor that it can continues motion autonomously, so long as fuel is has a higher chemical potential than waste, it will continue to go around. Now the flip side of this is what if we do something to prevent it from continuing its cycle? Can we use the same idea to as an information ratchet to select the position of the ring? And the answer is yes. Now to make it if every time I move it every so it, if we have the same setup, the binding up and release of waste is much faster, it says the binding and release of fuel, when the ring is in this proximal green recognition site is slow. And the binding and release of fuel when it's far is fast. So that fast, we'll make this transition from df to dB, highly likely, but p F to PB will be relatively less likely. And so we will form more dB. Now, you could argue that this is purely a thermodynamic effect, because just looking at the steric interactions between the orange ball and the ring, you would say that okay, well PB is thermodynamically less stable than dB. But when you tease it apart, we find that yes, there is that effect, but there is an additional effect due to the kinetic terms based on the pure information ratchet. Now, everyone in the field loves to talk about dissipative this and dissipative that and so in this situation, we could talk about this as dissipative adaptation. But in the inevitable words of Richard Nixon, that would be wrong.
Why? Well, the whole the essence here is that the if we make a Rate very slow. And these rates very fast. The fact that you have a lot of fuel will put you into this state. But there's no kinetic escape. This state is not at all dissipative. It just sits there. This is a kinetically stabilized state. But it is not a state that is in any way, particularly dissipative. We can in fact, make it such that these two pairs of rates are very fast, all of these rate constants are for for the proximal, make them all fast, then when it's in the proximal form, it will dissipate lots and lots of energy very, the dissipation rate will be huge. And over here, because it's slow, the off rate is relatively slow, you want dissipate much energy. And yet it will go to this state which dissipates less energy, rather than this state that dissipates a lot of energy. This sort of points to the answer to a question that has been posed in the literature. Does the dissipation rate of a system act as a layup, enough function, a function that attracts systems? The answer to that question, can unequivocably be given? And it is Nope. So we were asked to talk about, you know, to sort of go very, if I were asked, Where do I think molecular machines are going, it is going to be in the direction of specifically tailored molecules, catalysts, if you will, or that can accept energy from external sources, to drive reactions, that would be energetically impossible otherwise, I mean, I see the poly rotaxane as a prince prime example, putting 10 rings on the polyethylene glycol chain, and making a 40 plus 40 structure would be impossible need anywhere near at equilibrium, it's a highly non equilibrium structure it with there would be fewer than one and a million molecules of that structure at equilibrium. And yet, by designing it with the pumping cassette that we talked about, we can make it such that almost all of those polyethylene glycol collecting chains have 10, or eight or nine rings on them. So we can maintain a highly non equilibrium distribution. Now, ultimately, I think that the molecular machines are going to go into the direction of figuring out for various reactions that you want to carry out. We are for example, let's say that this is much higher energy than the two disproportion ated A plus B. Can we design a molecule that will go take this and go around in the counterclockwise direction? And the answer to that is, yes. And the kinetic thermodynamic trajectory thermodynamic, if you will, theory that I outlined here briefly, is the one that can tell us how to do that. And so with that, I'll close and be happy to take any questions.
Thanks, Dean, call me out there. That was
I didn't even have an acknowledgement slide. I forgot all about that.
very sudden stop. So yeah, if everyone can. thank Dean again, for a nice talk. We've had a couple of questions come in. So we'll do I think we probably have time for maybe for both of them. They've been answered in part by by Dave in the chat. But Ben, if you want to unmute yourself, and you can, you can ask yours first.
Oh, I mean, it's the same as a post in the chat. I'm just interested in like, is there a way to think about sort of like the the boundaries of designing these things? Like, how, how big can they be? How much energy can they be like, what what can we actually do with them? And like, even just like, how to think about that.
So the question, one, the question that's hardest for me is what can we do with them and that I do not know the answer. But we can were you were able to harness lots of a fairly large amounts of energy. For example, the change between the by peridinium and cyclonis. paraquat in the reduced state. And in the oxidized state is about 60 kcal per mole. And that's a huge amount. And so for example, if you were to have it, so when you go between the reduced and the oxidized form, you are putting in 60, that you could cause a process that would require 60 times 60 k Cal's per mole to do by thermal energy, which would never happen. But you can tailor that. And so ultimately, I think that we're these molecular systems are going is to figure out how to put whatever you want to attach with click chemistry or something, various reactants. And then the way of putting energy into that system is redox is one great way. Does that sort of answer the question? Oh, click can sort of, okay. Other people can bet much better answer what click chemistry is, to me click chemistry is a kind of chemistry where you have tailored interactions and where you can sort of substitute things allow Lego. Where it's not. It's not covalent, but it's almost as strong as covalent. Anybody want to help me on that? I'm not a synthetic chemist,
I always thought click chemistry was just chemistry that's atom economical, and doesn't use doesn't have any wasted atoms, basically. So tries all
famous traders try reliable works.
They get Thanks, Dave. That's most much better than my long winded version of everything else show.
Like Lego bits together. That's where the name comes from.
Yeah.
Great. I think the question about the power stroke that grant posted was actually answered very well by David in the chat. So in the interest of time, as well, to keep things moving, we'll move on. So if we thank Dean again. And we'll have Alberto Creedy. Up next, if you want to share your screen, Alberto.
Yeah, good evening. Good afternoon, everyone. share the screen. I see. I see many friends the least and it's great to let me switch off my video because you don't see my face. Yes, sir. So it's great to see you and I thank you for joining and I also thank James and Allison for inviting me here. My presentation will probably be less philosophical and maybe less imaginative than that of day which I enjoy a lot I Nevertheless, we try to use some specific result. So, to discuss two points, which in my opinion, are actually very general significance, the first one is light. So the use of light energy to power molecular machines and the second aspect is a non equilibrium. So regarding light energy, I think that we always should always remember that our planet is like a spacecraft which travels in the space and will never reach a port. But fortunately, there is the sun that is sending us continuously huge amount of energy and resources basically never ending on our time scale. And it is interesting to to note that pollution has driven nature to a situation where nearly all bio molecular machines, as pointed out very corrected by Dave are fueled by chemical fuels, which are in their form produced by photosynthesis. From an artificial point of view, we are not limited to these blueprints. So in fact that towards the end of the presentation, I will try to these classes are very stimulating for me challenge is to construct the molecular machines that are able to directly address the sunlight and maybe to contribute to its conversion and storage, which as we know, are, let's say very important problems, very award exploitation of fire of solar energy. And then the the non equilibrium point the Well, probably then technically speaking, the most important difference between artificial systems and natural ones is the fact that artificial devices and materials almost always exploit the equilibrium properties. And this is not surprising, because they couldn't be mistaken is by far the easiest state to to, to prepare to obtain, because the nature of things as as a tendency to reach to reach equilibrium. So, no no surprise about that. But on the other hand, living systems operate, because they are able to stay away of equilibrium all these processes that support life are, let's say, non equilibrium processes. And in fact, when a living organism actually reaches equilibrium is usually not not not a good sign. So, these are the two points that I would like to discuss a little bit today. So, this is a very brief schematic outline of the talk, we will be speaking about molecular pumps are fueled by light and I will try to show you how we can, let's say, rationally design them on the basis of the elements that we have in supramolecular chemistry photochemistry is also addressing some comment that was made early on the chapter, how we can control the direction of the movements and this is related to things that be not discussed just some time ago, the ability of the system to process energy autonomously, so in a sort of automatic way without the need to change conditions or to change parameters, external parameters to keep the system cycling, then we will say something about the non equity capital kind of non equilibrium of operation that these things can achieve, and particularly in terms of dissipating non equilibrium and this is also related to the ability of the system to store energy. And towards the end, I will try to say something about
how we, what we could do with these systems and what are the challenges that they are we are wouldn't be encountering. So, I don't think that you need to, say, explain why I wrote Taxanes and rate the systems, the provider will show you that I will focus on these kinds of things. I don't think I don't need to explain why these things are interesting for Molecular machinery. Let me just okay, this is probably the most common realisation of the molecular machine. It's a concept with rotaxane these are called molecular shadows. And to make a molecular sharpell, you need to know how to do this, how to control a process of these kinds of here, we have a macrocytic molecule and an actual type molecule. And what you can try to do is to eat the molecules are two components are properly this other, they can self assemble to yield a pseudo toxin. So it's instead of taxing without the the bulky capsule to say. So the there can be an equilibrium between the assembled system and the separated components. And nowadays, we know very well how to realize and control these self assembly and disassembly process or threading and the threading reaction in a variety of systems. What is less trivial to do and is related to the, to our approach to the realization of a pump is to do something like that. So imagine that we make the xo oriented, so we have a non symmetric friend. And we want to, let's say thread, the axle directionally to the capital of the macrocycle and under the action of an external stimulus to push it out following the same direction. Clearly to achieve these golar it is not sufficient to just to control the stability of the assembly with respect to the separated component as we will do here in the first line, because you can obtain these species by two non equivalent pathways because you can thread the xo let's say from the blue side or from the yellow side, but you would like to have a directional preference and know that in order to achieve these, it is a necessity also to control keynetics. So in this particular case, we need to make threading through the blue extremity faster than the flooding with the yellow extremity. So keep both can at the same time of atomics are unnecessary. If we have a model of this kind if we have a system of This kind of enhancer, then one can also let's say try to use it to construct a more complicated devices like rotary motors or let's say long range linear motors and we will discuss these ideas more towards the end. So our approach to this problem was based on simple compounds, not only because we are a small lab, but we like to keep things simple. But also you know, simplicity is important also because if one day we will have to, let's say scale up these systems for real world application, it's probably good to add components which are not too complicated and don't need to don't require years of postdoc time to be synthesized. So, components are very simple Actually, these are macrocycles commercially available. And we see these well known thanks to the work of Fraser Stoddard and others that in inappropriate solvents, these ammonium ion wants to go inside the cavity of the current need to give issued or toxic kill the pointer, if we want to controller priding in the timing by light possibility is to introduce for practical photoreactive units in the axle and this is exactly what we did we choose we made a very trivial choice actually for their footwork in UNITA we selected as a benzene benzene is the most popular molecular photoswitchable. So, benzene is a interesting choice because it can exist in two configurations, which not only can be very cleanly irreversibly converted by light, but they also exhibit quite different properties physical and chemical properties. So, we hope that by playing these two states, we could modulate in some way the assembly of the actual with that
and this is to make a long story short, but to the main findings in this direction are summarized here. So we made these acts. So we the recognition side for the ring here, there's a secondary ammonium and two other benzene extremities. And what we found is that indeed the Beaufort that the trans trans axle here and the cccs x also within this molecule is both as advances have been converted into the band form. So to say, they both give rise to threaded structures, but with significant differences both in terms of thermodynamic stability and thriving the thriving kinetics, because the trans trans complex is more stable than the CCS complex and it is in a relatively faster equilibrium with the separated components. So, they are flyff of these pieces with regard to the threat in easing the order of seconds, the average life of this one is about several hours. So, there is a very big difference between these two timescales in fact that these are species behaves pretty much like a funeral toxin while the bottom one is more similar to water passing. So with these let's say four to sweep the possibility of auto switching both the stability and they kinetics the rate constants of for the system, we may the let's say a successive step which is to make an oriented axle. So they oriented axle should have therefore attractive unit on one hand, these blue spheres that are commission site which will attract during and these gray sphere on the side is what we call a pseudo stop. So it is not really a stopper. Okay, so it should, but it should hinder the passage of the ringer enough that the trading would be considerably faster over the azobenzene and with respect to the passage over the Tudor stock. So, if these is the case, what will happen is that these two threading pathways are kinetically not equivalent and the faster one way and in our design, the faster one should be the one over the tracks as events, then we reach equilibrium the complex is formed at this point the photon arrives sent to the solution and it will be absorbed by the benzene which will become bantha will become system. And then this point on the base of the fingers is out we expect a significant increase of the P 13 barrier here, but also this debilitation of their complex so we are actually just in the middle say the same time increasing the barrier and increasing the medium and so we are actually bringing this system out of equity To reach a new equilibrium, we will have the will to have some some of the pseudo rotaxane in a population in solution will have to the threat and this this reading is expected to occur this time by say passages of during over IP service doctor if the pseudo stopper has been chosen carefully. So, you see that these gray barriers here should be intermediate between the green one for the trance and this indirect one for the CS. So, this is the key design element for these type of systems.
And
after these the threading step, the system can be reset by light or even by heat and the cycle could be repeat. So, here the key point is to select the let's say good component to play the role of that shadow stop. And we need that after some modeling and some control experiments, the psycho Banfield group can do the job properly here considering the kinetic features of the other benzene configurations. I don't want to spend time on their characterization we have to perform a lot of let's see thermodynamic and kinetic experiments to validate these operation mechanism which actually works. And in the end, though, we can summarize the thing in this short video, we can also monitor in fact that the concentration of in this particular case of the of the free macrocycle which was chosen to be fluorescent, so, we use fluorescence spectroscopy to demonstrate that this system can actually go out of equilibrium, when we when it when this it is continuously radiated. But there are three elements of interest, which make the system quite unique despite the simplicity. First one, the fact that the movements are that trading in the direction are and these were understood that it is due to their unknown symmetric energy profile, which is modulated by line by line what is called ratcheting, which both Dave and Dean are actually a leading experts. Another very important point here is that because of the so benzene for productivity, this the same fault and so the same wavelength the same color can both cause the trans to see sir, and this is to trans transformation. This is because both isomers of azobenzene are photoreactive. And they have strongly overlapped absorption spectrum. And this thing is usually, let's say a limitation of azobenzene as a molecular switch, because if you want to do a clean switching from all transparencies and vice versa, this is not good, but actually here, it's it's a good thing, because these possibility enables us to operate the system autonomously, we don't need to post the light or to change the color of the light to make cycles just send the photons of all the same candle the same type or same color and these photons will open the gate that if they find it close and close it if if they find it open. So, this is a very very important to have a system that can repeat continuously cycles under steady state irrigation, steady state recreation in this type of system affords a reference to a non equilibrium state do we choose which has a dissipative nature, let me spend a few words about that because this is very important. So in very general terms, as we say that chemical systems like to be adequate adequately, they have a tendency to reach the global thermodynamic minima in the free energy surface which is equity. But if you supply energy to a system like that, but it can happen that it can reach another minimum a local minima, which is not that the absolute department and that these minimum work which corresponds to a non equilibrium situation, because this is not to the global thermodynamic minimum and this data can persist in time, because there might be an activation barrier here. So, there is a driving force for the system to go back to equilibrium. But if the system is if there is a barrier, the system can stay here for some time, this time actually can be quite longer if the barrier is much higher than kt. So actually, some some systems can stay in this kinetically trapped state forever basically, or if the barrier is sufficiently low, then we observe let's see a relaxation on an experimental timescale. If the barrier is non existent, is vanishing basically we have another situation which I'm representing up here. So we have a cease then we stand sir. Let's say under surface here without let's say, necessarily spending a minimum and in order to maintain the system here which of course the system will quickly or electrically librium unless we continuously provide energy. So, we can create these kind of dissipated non equilibrium states by continuously and they exist the only if we supply continuously energy to the system as until as long as we we stop sending an exclusive then the system this has been we immediately relax either to a local minimum or to the global
okay this would be an example of a kinetically trapped state regarding as abandoned is a nice system that we investigate at some time ago with Fraser Stoddard. But for the sake of time, let me let's say, focus on the dissipative dissipative case, which is based on our molecular pump, now, we have a slightly improved version of the axle now, we in which the connection between the aza benzene and ammonium is now in the in the meta position knocking powder like the original one because this one works a little bit better. Their range is the same as before, what we do in this experiment now, an important difference with respect to the previous example. Now, we use NMR to measure concentrations, and we use an optical fiber to bring light to direct into the nim nmrt this is very important because, since the dissipative state that can only exist if we keep the light on if you want to if you want to measure, let's say we want to highlight the existence that dissipative state by measuring concentrations we need that to say to be able to measure these concentrations while the energy source is on. So, in this first experiment is the one that we call the light on light of experiment, we initially for a very short time on these scalar reads the photon stationary state for those organizations. So we quickly I summarize the trance which is initially the only species to the seas and then we monitor in the dark as this system evolution and we can monitor the concentration of all the species by NMR Of course, but for us it is a simple simpler to focus on what happens to the CCE complex does that complex Yeah, that the rabbit race. So, initially, this complex is produced the app to the contract concentration typical of the trance component of the transfers are banned, because they initially we have the class complex, which is very quickly converted into the C's, but the C's complex is less stable than the transfer. So, over time, we will see it differently we will see a decrease in concentration of the C's, we can see this changing concentration better here these are experimentally measured concentrations. On the other hand, if we keep the light on after we have reached the photo stationary state, we see a remarkable thing the concentration of this complex So not only does not decrease as one would expect if the system wants to work quickly even increases a little bit we can see it better here okay. So it will be higher than the concentration of the transformer. So, it is kind of counterintuitive result because this is complex is thermodynamically less stable than the trance, but if we keep the light on it will be it will be accumulated for a reason that is not so difficult to understand at least from a qualitative the qualitative point of view, because our system can be represented by a closed network of reactions in which the two horizontal branches are chemical processes, thermal processes and the vertical ones are photo actions. In this square scheme, the slowest process of all of this cycle is the defining of the CCE complex because the passage of varying over the Today's topic is very slow. So, what happens why we send light Of course, when we have the light on and the faint balance is no longer valid. So the system is not the tail balancer. And that we have that the system actually cycles so that the
the network activity network is traveled in a specific direction, we get to to a steady state the photo stationary state in which sir let's say all the rates are the same. And this is the cycle is traveled in their clockwise direction as shown here, simply because these are equity Boom is more shifted to the right than the bottom equilibrium is that there is one of these, it's a directional cycle and sees these pieces is the slowest to be, let's say consumed, it becomes a two. So this process becomes the kinetic bottleneck for the process. And if we keep the system cycling, because we keep the lights on, these pieces will be accumulated but not because it is more stable, because it is slower to adapt to the changes. So do the kinetically accumulate, we can also we can clearly see these, let's say especially stationary state non equilibrium stationary state by looking at the rate of this process, which we can calculate from real experimental concentration with this formula. And in the light on light of experiment, what we see is that at the beginning, we have, when we switch the light offer, we have created the non equilibrium concentration of this compound and into independence between the threads, we have a negative trading rate until we reach equilibrium and the rate becomes zero. But if the light is on this rate is not zero, it let's say reaches a stationary value, which is negatively negative. So if the trending rate is negative, it means that we are going in this direction. So the complex is different, we are going here, or let's say along this cycle.
So in these in these simple experiments, we are actually looking at all the possible, let's say equilibrium modern equilibrium states for these, because initially the darker we are at equilibrium, then when we switch on the light, and then we switch it off, we this system is in a kinetically trapped or metal stable activity, because it will slowly evolve to equilibrium and met a stable state, but if we keep the light on we reach sorry, really a state which is somewhere up here and it is non dissipative it is a non equilibrium dissipative state, it will exist only if the light is on. I will show you later that when the light is switched off the system we are as expected the relaxer to these are metal stable, metal staples. Well, if these is a really a dissipative regime, so it exists because we are putting energy into the system. One should also expect that it's nature, it's it's a characteristic, it depends on the intensity of the light on how much light energy we put in. And this is exactly what we observe. These is the time dependent concentration of the Seas complex after different irrigation intensities. And we see that with no light that we have a relaxation, we believe the light we have reached a not a dissipative state with a concentration of CS complex just above the equilibrium value. And if we increase the intensity, we go to dissipate the state which is farther and farther away from equilibrium. So it means that actually we are, let's say, moving this system somewhere here in these, let's say different dissipative states. We wanted to bring these, let's say these observations to a more quantitative levels and so that you see the time or the will Okay, we'll quickly go towards the last pattern. And so, we improve the experiments and we use the strictly monochromatic light. So we could model the system we could also measure the photon flow by a chronometry in there and Mr Kuba and we model the the time dependent the time evolution of the concentrations by using these kinetic schemes which comprises all the rate constants for the thermal and photochemical processes, we use the math lab to cancel the numbers and as you see, there, we use the of course, the experimentally determined rate constants all these but nearly all these parameters are known from independent experiments. These rate constants for threading and the threading are measured by top floor spectrophotometry for example, we know their ratio, because we know the stability contrast constants of the complexity. So, nearly all these parameters are known. And it is nice to see that they simulated the curves match very well with experimental once a week Sir, tell us that this model is actually describing correctly the behavior of our system. And with this model in hand, we can also calculate concentrations of species which are whose concentrations are too small to be reliably measured by NMR. And we can calculate them with the model. And another nice thing that we can do with that when we have the non equilibrium concentrations or the dissipative state is to calculate how much sir these equilibrium properties sorry Four sensory processes are shifted from equilibrium. by calculating these chemical potential changes, some people call it the affinity by, say by delta from variation of the reaction portion to that we can calculate from real concentration and the equilibrium constant. So we can calculate accurately how much energy basically is stored in the, in these reactions, which are, let's say kept away from equilibrium. These let's say, chemical potential change depends on the light intensity, the more energy we put in, and the more energy remains to store that in the nonequilibrium. net. But as you see the efficiency, this is the quantity of the for cycling, the efficiency decreases. So for higher light intensity, we store more energy but with less efficiency. And the numbering in brackets here is the average number of photons required to perform let's say a full unidirectional cycle.
So, this system is a very nice playground to investigate this fascinating and very under explored problem, because in the literature, there is some information on artificial out of equilibrium systems of dissipating behavior, which are driven by chemical fluids, but there is almost nothing about artificial systems driven by the psychopath keeps you to stop it, which is so crucial for the operation of the pump is not good for functionalisation of the pump if we want something here. So one thing that we did recently was to replace these moiety with a phenol group that we can actually say modify later. But it's important that these two those topper maintains the connected features and necessity for the ratchet profile. And in order to find the appropriate substitute the performance systematic investigation, where we examine their relatively large family of stoppers, and we found that these one particularly has, let's say, Good, let's say, kinetic parameters, and so we made the new xo with these offentlig to the stopper and will not discuss this data. But just believe me, if I say that the numbers are in the correct order for reading and describing, and in fact, in the dissipative, it's a light light on experiment that the NMR also this system the exhibit set the dissipative state which can be clearly monitored by looking at concentrations when we switch off the light that the dissipative state evolves slowly towards slowly towards let's say, equilibrium with their isometric mixture between Zed and the obtain that previously by line. Okay, so what what can we do in the future what what are the let's say that the potential of these simple and time bounds and what are the challenges that we can face? Well as I was mentioning before, a possibility to change to use these directional turning and deciding to make a rotary motor. And basically the only example of autonomous rotor remote or artificial rotary motor available until now is the fairing Gemalto, there are no other models where we to exploit light in autonomous manner. And if we are able to make a company out of our pump, something that we did there already, so we have a number of molecules that we are investigating. Here, the problem is and is the outselling GS to demonstrate that the model works, because here experimentally, what we see is basically everything is constant with the photo stationary state. So the only thing to validate the only way to validate the data to demonstrate that direction or rotation is actually to measure kinetics and say benefit from a comparison of profit and other compounds. Then once we have this kind of rotary motors in hands and other challenges to explore to the rotary motion to perform a task, something that has been beautifully done with the finger Mater, we are now examples of polymers that are winded that are for surfaces that are let's say modified. And in these conditions of the cotton and I see some additional problems because we have a mechanical linker between the two rings that has to be maintained while the finger rotates and so this could cause pose constraints to the engineering of the device or if it has to be used to perform a task Another thing that we are very interested in, as I was saying is to use these pumps to convert light energy and to store it in some way. And let's say
apparently, immediate way to do with that would be to equip the pumper with a sort of reservoir in which a variant is could be stored here there are, let's say, there is no particular thermodynamic reasons for getting to decide on this portion of the thread and the idea is to push them kinetically Towards this end, this design has been dutifully implemented by phrases and natural collaboration with Dina beautiful system, but these systems are not autonomous and because of their design, it is very unlikely In my opinion, that they can be autonomously. So we have now made the molecules of this type are where there is either a secondary recognition site or no recognition site at all in the collecting chain, and see if under light irrigation, we can alter the equilibrium distribution of the rings in this axle. And, of course, also here a problem is to demonstrate to observe actually these non equilibrium states once we've trapped the rings here, so we actually store energy into this non equilibrium zero tax a problem is how to retrieve and user the energy that we are storing this way. And these, of course, is a problem that should be a face at some point. Another point, of course, there are many ways in which we can improve our bounds in terms of efficiency in terms of, let's say, cyclability, and so on. certainly an important problem is to make system that can can utilize visible or near infrared light because as a benzene wash with the near UV or let's say blue light, but of course this would imply to change the photochromic molecule of water sweetser something that can be done but of course, requires a lot of investment in time in terms of more than the medium term I hear I'm maybe less optimistic that they will leave. But I also am also convinced that that compartmentalization for molecular machines is certainly important, say development for the future. From our point of view, of course, since we have a molecular bouncer, the obvious idea is to incorporate these pumps in the membrane, and try to use these pumps to create concentration gradients, so to bumper substrates, which in our case, are a racer, but maybe farther. In the future, the design of pumps will no longer be rinser. So to create concentration gradients, this can be done by for example, by making vesicles. But also other setups are possible like planet membranes and these in this case, an advantage is that one could make a membrane incorporated in a nanopore such that you can introduce only one molecular property before. And this is important because obviously, if we key requirement to make a, let's say, to create a concentration granted in a system like this is that all the pumps in the membrane pump in the same direction. So you need to have them incorporate and remember vectorial directionally and this is difficult to achieve. Of course, if you have just one, this one is either up or down. And then also, you can measure the effect without nottoway without worrying too much about the orientation. But certainly, the engineering of the pump with respect to the membrane is an important place to take a challenging problem here. Again, we at some point, if we are able to create a gradient, we will also have to understand how to use it, change pump or substratum, maybe it's not very interesting to pump rings, it would be more important or maybe to attach some other substrate to the rings, which could carry the inside or outside of the vesicle and so on. along the same line, of course, if you if we understand how to pump things out, or in vesicles, that step towards the living cell is obvious because these could be a way to pump or twist to extract the molecules or ions from us. And it could be a way to affect their, the behavior of the central we could cure this and maybe or even killed it. So also from let's say a nanomedicine point of view. I think that there is a lot of let's say a lot of interesting things to do, from molecular farms combining with, say, living systems, but this is probably More in Bangalore. So I'm the end of the talk. Let me express my gratitude to my collaborators.
Dan and Julian are currently using the oldest Julio was very important, important contribution to develop the earlier version of the pamper. These are the three nominal rates in Milan, two years ago. And with these, thank you very much for the attention. It's almost curfew time in Italy. But I'm saying this in Santa Toma, thank you very much. And I will be happy to take questions. Thank you.
Thanks, Alberto. Absolutely fantastic. So I think people always show their appreciation for Alberto's talks. If we can, we can do that. That'd be great. And you gave a really, really fantastic summary of some of the challenges that you believe are in your area. And did anyone have any questions in the chat that they wanted to ask? There's the opportunity to put anything now if you want to otherwise? I've got at least one.
General silence as a no. So one thing I would ask Alberto is, so this compartmentalization has come up a couple of times. Now, I've said it's something that I'm interested in, you talked about the importance of these molecules being simple, which I think is a really important point. I mean, for me, that's something that matters. My group is me. So do you think it's realistic that we can imagine to retain the simplicity that these molecular machines and similar molecules have when we install them into compartments? That's a realistic goal? Or do you think that we'll encounter challenges when trying to install them into membrane like environments that necessitates us to make them more complicated, which is something that we don't want to do?
Now, this is a very good question, we are actually starting to face this problem, because we have now versions of the bamboo engineer that to the tee designed to go to be incorporated in by layer membranes. And in order to insert these things into a by layer in a controlled way, of course, you need to equip them with solubilizing groups or groups that can provide them to finish up to the molecule. And these things will affect the the operation of the system. No, no doubt about that. So for sure, it will be more and more difficult as you you are asking more and more features and more and more properties to the system to keep it simple. But of course, if you start from an already very sophisticated design, the thing is even more and more difficult to do so. But you are very right.
And directionality, I think, as you mentioned is a huge issue biology is amazing at it, I think we're pretty rubbish. That's
one of the ways actually, you can use several options to introduce a, an actual nearby layer chain perpendicularly to the to the, to the surface in a in an oriented way. So you can even make the ballet of non symmetrical. But this is not very easy to do. This is for experts of mankind.
And then we had a question in from Todd had an avatar if you wanted to unmute yourself and ask them
I think's really interesting to hear this discussion of these machines? So I often interested in what is it that ends up being the limiting factor on how fast or how effective these machines can be? So in particular, for the example you talked about the end? It's intriguing idea of putting pumps to molecules into or out of cells? What would be the limiting rate? Would it be diffusion? Or how what the capacity of the pumps is to to process through them? Or how fast or what what would be the the main physical limiting factor on how fast those machines can operate?
Why shouldn't the solution you cannot be diffused. And our machines are much slower than if you can go slow and inefficient. So of course, you can make them faster than currently than our current prototype prototypes. Then they become faster, they are almost more adult also more difficult to investigate because you need faster techniques. So I think there is a lot of room to make them faster for sure.
Yeah, so diffusion would be the absolute limit. But but it sounds like at the EU at the moment, it's the capacity of the machines is not yet fast enough to keep up with diffusion, depending on the molecule.
Yeah. This is true for small molecules I should say because small molecules diffuse very fast Yeah, but the opposite becomes larger than in the case of nature for example, to move large objects we cheat within this cellular nature does not lie in the future it uses multiple properties, spectacles, for example. So, when diffusion can becomes very slow, then you have alternatives but for small molecules, right, they want to use a diffusion.
Thank you.
And there was a i, okay, I just want us to leave. There was another question from Daniella, if you wanted to quickly ask that one if you want to.
Hi, very nice Talk. Thank you. You mentioned that the pumps of course they operate out effectively boom upon constant irradiation and that is dependent the energy they is dependent also in the intensity of life. And so, I was wondering in the idea of incorporating your pumps in the biolase system, you are also going to have fortress tactic system right? Because if you have you thought how this will operate when you place them in a gradient of light, because a light will come from one direction. I was wondering if you thought about that, how that will work?
These are good question actually, we try to use return to work at least for the vesicles in optically dilute condition, so we will not have much problems of gradients of light, but for sure, if we have an optically dense situation, then you can have you can generate different concentrations of transparency specifications the problem, depending on the position of the molecule within. But I don't think that to me, at least, we will try to avoid it.
And I What I meant is that you will have multiple vesicles, right, if you put them in a channel and then you will shine from from the right, then they will, of course, you activate the pumps in different ways, because some vesicle will be further away from the light and some will be closer to the light.
Yes, but again, if the optical density of the solution is not very high, then the let's say the light would be able to reach basically all the layers of the solution is well known. So the problem will be present, if the concentration of the vesicles and the concentration of the chromophore inside the vesicle is so high, that you have a very high absorbance. And then of course the the face of the cuvette, which is in front of the light source will receive more light why the opposite face will not be eliminated at all. But as I said we want to avoid at least in the short term. Okay.
Great. So I think that's it's good to get some engagement as well. That was fantastic. That's what we want to have going on in the group. So before we wrap up, move together, we're gonna ask I Osman Sanders, I see what he unmuted. So I have a few words about the enabling application session that we have next week. So I'm now going to attempt to share my screen which is over here. So we should be able to see that name.
Right. So So this, this series of dots was actually a great segue to next Wednesday's enabling application session and on what we thought we would do is is to is to have people bring up ideas about enabling applications, perhaps your work has shown some already. Or maybe you think that they will lead to some enabling applications in five to 10 years. And we'd love to hear those. And it would be really helpful if you can drop a quick note to Allison, for example, saying that you want to talk in this session. You can talk for two minutes, five minutes, and talk about what you see the future of nano machines are and what some of the Enable applications might be. If you're not planning to talk, I think you should still come because you can critique the poor souls who will be talking. But also these might give you some ideas about your own work and how These could lead to future applications in various sectors, maybe, maybe you have a material that has interesting dynamic properties or a sensor, or as Alberto talked about, perhaps, perhaps a pump that might help and transport molecules in and out themselves. So we'd love to hear all of those. So if you're planning to talk, you know, it would be nice if you can send something to Allison. If not, that's that's okay, too. But I hope all of you will show up at this session, which is next Wednesday. James, do you have anything to add?
Well, I would know, I mean, fantastic summary of what we're planning to do next week, what I have shared now, can I change the screen is, is one has already provided a template for the sort of way that your idea could look, we have plenty of blank spaces in this document. So you can engage your idea on there if you want to. And there isn't necessarily a requirement to do that. But certainly reach out to us and to let us know whether you want to propose something. This template here that's up there is an idea of what you could put together but it's very much freeform, you can do whatever you like. So that's my two cents. I look forward to being critiqued, apparently.
Okay, that's all I have to say.
Thanks, Harrison. Yeah. So I'll stop sharing that I don't know how to switch between sharing things, because I'm apparently technologically incompetent. So I will now reshare my screen again. So what we should be able to see now we've obviously just covered the upcoming events, which is the enabling application session, which is next Wednesday is at the same time, so 7pm, UK time 11pm 11pm. Whoops, that's a typo. I apologize. These are wrong. I'll change those. That should be 2pm 2pm cet? No, it's 8pm cet and 2pm PST, people in your can actually make it. And then on the 18th of March, we have Nicholas apone, and James Tor are going to continue our theme of artificial light machines, this will be more systems driven by light and molecular motors. And what's gonna happen now, this will happen after the end of every session, we'll have a more informal networking style environment, we'll move over to gather this link will go into the chat. The password is here, MoMA 2021 will also go into the chat, I should actually make this, I'll leave it as this. It's fine link passwords place in the shop, you can use your phone, the QR code does work. I tried it, it says it's a beta. But it does work, you'll end up in a nice little room like this. I'm in here right now by myself at the bar, which is probably where I'll be in a real conference, the TV apparently does work. So you can go and watch a YouTube video on that if you want to. But all these areas are private spaces that people can sit and interact if you want to have private conversations. There have been some issues with how people interact on there so that there might be some teething problems, but we found it to be a really, really excellent way to network. So we'd encourage you to stick around and have a bit of a chat with people if you want. And we'll keep doing that constantly after each session. So that's about
Donnie cuse me in the go back one slide. Maybe if it's really 2pm PST, then it's going to be 11pm at
11am. PST.
Thank you. Yeah, whoops. I thought that was he was he asked he
said exactly the same time as this one did. Yeah. Okay. If that makes life simpler.
Yeah, I should have said that shouldn't sorry. Yeah. Yeah, don't worry. It starts at this time. It's not some ridiculous time. Say all links are in the chat. I think Alison, we are you gonna hang around to help people out with gather if they can't port over there? I think you're supposed to close zoom before going over otherwise it can create feedback problems. So I'm going to zip over there. Now after the room starts empty. So thank you very much, everyone for coming. I think it's been a really fantastic opening session, some really great talks. It's good to get some engagements. I think we should thank all the speakers again. I think it's been really informative and a good driver for the beginning of everything is a world we're all doing this in real life.