Key assumptions about hydrophobic behavior in protein folding have been tested by Isaac Li and Gilbert Walker, University of Toronto, Canada. They have applied single molecule force spectroscopy to a hydrophobic polymer. The data reveal three phenomena that could be used to improve molecular simulations of macromolecules. First, hydration free energy per monomer depends on temperature but does not follow interfacial thermodynamics. Second, temperature dependence differs depending on the hydrophobic size effect at the sub-nanometer scale. Third, hydration free energy of a monomer is different from free monomers corrected for having neighboring molecules.
These are the first experiments to hint at the mechanism of hydration of hydrophobic polymers and bring chemistry closer to a theoretical understanding of polymer folding with relevance to proteins.
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