Myosin machine

Li, G. H. and Cui, Q. (2004) Analysis of functional motions in Brownian molecular machines with an efficient block normal mode approach Myosin-II and Ca +-ATPase, Biophys. J. 86, 743-763. 

Molecular motors or machines are inspired by biological molecules such as myosin which uses the chemical energy from hydrolysis of adenosine triphosphate to drive the linear push-pull motion of muscle. The different coordination demands of Cu and Cu are the basis of electro-chemically induced molecular motion in a pseudorotaxane complex of copper. As shown in Scheme 2, Cu 4, the stable, four-coordinate form is oxidized to unstable Cu°4, which rearranges to the stable five-coordinate form by sliding along the ligand. Reduction of the stable Cir s... 

Kakugo A, Sugimoto S (2002) Gel machines constracted from chemically cross-linked actins and myosins. Adv Mater 14 1124—1126... 

In Chapter 8, more structural background and molecular details of contraction exhibited by the linear myosin II motor are considered after, in Chapter 5, the physical basis for the apolar (oil-like)-polar (vinegar-like) repulsive energy that controls hydrophobic association is experimentally and analytically developed. The crystal structures of the cross-bridge of scallop muscle provide remarkable examples of the consilient mechanism functioning in this protein-based machine ... 

The consilient mechanism depicted in the elementary structures of Figure 8.2 are relevant to protein function arising out of association of globular components of molecular machines. The principles arise in almost textbook fashion in the function of the myosin II motor where the key charged species are ATP, ADP, and P, but in an important way also include the charged side chains (see section 8.5.3). 

In terms of the molecular process whereby ATP forms and functions as biology s energy coin, there are two aspects—the protonation/ deprotonation of carboxylates due to a proton concentration gradient that drives a rotor to form ATP from ADP and Pi, as in the ATP synthase, and the molecular process whereby the breakdown of ATP to ADP with release of Pj drives the protein-based machines of biology, as in the myosin II motor of muscle contraction. 

The multivalent phosphates, already significantly limited in hydration, can be expected to reach out substantially further than carboxylates in their search for adequate hydration. This effect becomes enhanced when phosphate access to water is limited. When the phosphate occurs at the base of a cleft, the direction for access of water becomes severely limited and the thirst for hydration can be directed by the cleft to target sites of hydrophobic association. In other words, the cleft functions as a conduit to direct the thirst for hydration. By means of the cleft, the capacity for disrupting hydrophobic hydration to target sites can be boosted by effecting separation of ion pairs enroute, which boost the polar species capacity to disrupt hydrophobic hydration. Accordingly, the use of structure to direct the forces of apolar-polar repulsion becomes a useful design feature in certain ATP-driven protein-based machines, such as the myosin II motor. 

Furthermore, the assumption of a uniform dielectric constant for all water structures interacting with protein-based machines and materials conceals the occurrence of competition for hydration between hydrophobic groups and charged groups. In the past there has been the practice of using a dielectric constant of 80 (that for bulk water) up to the surface of the protein and then decreasing the dielectric constant to 5 or less when within the protein. However, what Solomonic wisdom suffices for choice of dielectric constant to be used for ion-pair formation within the tortuous surfaces with clefts of varying shapes from acute to obtuse. As seen in Chapter 8, these clefts may reside inside the protein-based machine, as found in ATP synthase, or outside the protein-based machine, as occurs for the myosin II motor. 

We have discussed the nexus of hydrophobic and elastic consilient mechanisms in Complex III at the intersection of electron flow and proton translocation (electro-chemical transduction) that was unimaginable, absent the detailed analysis of structure. The hydrophobic and elastic consilient mechanisms, however, when applied to the general structure and phenomenology of the Fi-motor of ATP synthase (chemo-chemical transduction), gave rise to a host of successful predictions, and, when applied to the structure and phenomenology of the myosin II motor (chemo-mechanical transduction), resulted in a half-dozen realized expectations. These findings do much to substantiate the relevance of the hydrophobic and elastic consilient mechanisms to the protein-based machines of biology. 

The above three discussed protein-based machines—Complex III of the electron transport chain, ATP synthase/Fj-ATPase, and the myosin II motor of muscle contraction—represent the three major classes of energy conversion that sustain Life. Therefore, the facility with which the consilient mechanisms explain their function indeed support the thesis that biology s vital force arises from the coupled hydrophobic and elastic consilient mechanisms. 

Natural muscles are controlled by neurons and network of neurons. We can imagine artificial neurons and network of artificial neurons as well. Artificial muscles with motor proteins are studied and attract attention[79]. One direction is to develop deformable machine with real motor proteins, actins and myosins, and neurons. Another direction is to develop neural network software to control distributed artificial muscles. The author has been developing open brain simulator which can emulate the activities of human nervous system for estimating internal state of human through external observation [231]. Such software is also applicable to control artificial muscle systems, which is implemented on the personal robots and humanoid robots in the future. 

Kakugo, A., Sugimoto, S., Gong, J.P., Osada, Y. Gel machines constructed from chemically cross-Hnked actins and myosins. Advanced Materials 14, 1124 1126 (2002)... 

The foregoing state of affairs appears to hold for living muscle. As myosin muscle is and must be extensible, but, as a living machine, it is contractile only. We are forced, therefore, to question the work of Hill (35) and others in which it was shown that muscle in the relaxed state resembles rubber, that the stretch-strain curves of the two are similar, that the stretching forces are of the same order of magnitude, and that both rubber and muscle exhibit the same anomalous thermoelastic behavior (at... 

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