Contractile machines

Contractile Machines That Perform Mechanical Work by Pulling... 

Elemental Contractile Event as One Aspect of Protein-based Machines... 

Such shape changes cause contractile protein-based machines to perform mechanical work. 

By this means, contractile protein-based machines can lift or pull weights they can pump iron. 

The contractile protein machines of Life, however, accomplish more than the mechanical work of pumping iron or of rotation. 

Knowledge of how contractile protein machines can sustain Life provides the capacity to design protein-based materials. 

What can be demonstrated with model proteins functioning as contractile molecular machines is that two of the most effective means of lowering the temperature of an inverse temperatine transition to drive contraction are positively charged calcium ions (Ca ) binding at paired negatively charged carboxylates (COO ) to decrease net charge... 

Synthetic Elastic-contractile Model Protein Machines to Energize Phosphates... 

The families of proteins that consume ATP while functioning as protein-based machines are called ATPases. Muscle contraction, just noted above, is a member of the family of linear (contractile) protein motors that also includes ATPases that walk along protein tubules and transport elements from one part of the cell to another. Another class of protein motors that uses ATP rotary and nonrotary ion pumps transports ions from one side to the other of the... 

Due to the struggle to survive under circumstances of limited food supply, organisms evolve to use the most efficient mechanism available to their composition. The most efficient mechanism available to the proteins that sustain Life would seem to be the apolar-polar repulsive free energy of hydration as observed for the inverse temperature transitions for hydrophobic association. The efficiency of designed elastic-contractile protein-based machines and a number of additional properties make designed protein-based materials of substantial promise for the marketplace of the future. 

As shown in the hexagonal array in Figure 5.22, five different energy inputs can perform mechanical work by the consilient mechanism. The set of elastic-contractile model proteins capable of direct utilization of hydrophobic association for contraction are called protein-based molecular machines of the first kind. These are enumerated below with brief consideration of the reversibility of these machines. 

V in Table 5.5 with 0,2,3,4, and 5 F residues per 30-mer exhibits a systematic nonlinear increase in steepness, that is, in positive cooperativity, and an associated nonlinear increased pKa shift, as plotted in Figure 5.34. The energy required to convert from the COOH state to the COO" state systematically in a supralinear way becomes less and less, as more Phe residues replace Val residues. The energy required to convert from the hydrophobically dissociated state of COO" to the hydrophobically associated (contracted) state of COOH becomes less, as the model protein becomes more hydro-phobic. The elastic-contractile protein-based machine becomes more efficient as it becomes more hydrophobic. The cooperativity of Model Protein iv with a Hill coefficient of 2.6 is similar... 

Accordingly, the perspectives in Chapter 5, developed on elastic-contractile protein-based polymers, introduce new concepts into the functional description of biology s protein-based machines. As with the introductory comments in Chapter 7, the footnote relevant to reactions toward new concepts in science is repeated here in footnote form. ... 

Even so, crystal structures provide the best snapshots of forces in action. Crystal structures provide an unparalleled opportunity to assess relevance to the major protein-based machines of biology of the free energy transduction so dominantly displayed by elastic-contractile model proteins (as developed in Chapter 5). If the apolar-polar repulsive free energy of hydration, AG.p, the operative component of the Gibbs free energy of hydrophobic association, AGha> is active in ATP synthase, then it should become apparent in these snapshots. 

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