Phosphates protein machines

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

Because hydrophobic association does not occur until the temperatiu e is above T, for the phosphorylated state, the phosphate cannot be folded into a low dielectric constant site, but instead would be fully exposed to the solvent. It is fundamental to the consilient mechanism of protein-based machines to understand how this can be As discussed in section 5.7, the high-energy state of the phosphate is due to competition for hydration between the phosphate and the hydrophobic groups, as reflected in the large change in Tt. 

Table 8.1. Standard Free Energies of Hydrolysis of Phosphate Bonds directly involved in Energy Conversion by Protein-based Machines. ...

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. 

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