Signature of hydrophobic hydration in a single polymer

Hydrophobicity underpins self-assembly in many natural and synthetic molecular and nanoscale systems. A signature of hydrophobicity is its temperature dependence. The first experimental evaluation of the temperature and size dependence of hydration free energy in a single hydrophobic polymer is repo...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2011-10, Vol.108 (40), p.16527-16532
Main Authors: Li, Isaac T. S, Walker, Gilbert C
Format: Article
Language:English
Subjects:
energy
Entropy
Free energy
Hydrophobic and Hydrophilic Interactions
hydrophobic bonding
hydrophobicity
Models, Chemical
Molecules
Monomers
Physical Sciences
Polymers
Polymers - chemistry
Protein folding
Proteins
Solutes
Solvents
Spectrum Analysis
Temperature
Temperature dependence
Thermodynamics
Water - chemistry
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Summary:Hydrophobicity underpins self-assembly in many natural and synthetic molecular and nanoscale systems. A signature of hydrophobicity is its temperature dependence. The first experimental evaluation of the temperature and size dependence of hydration free energy in a single hydrophobic polymer is reported, which tests key assumptions in models of hydrophobic interactions in protein folding. Herein, the hydration free energy required to extend three hydrophobic polymers with differently sized aromatic side chains was directly measured by single molecule force spectroscopy. The results are threefold. First, the hydration free energy per monomer is found to be strongly dependent on temperature and does not follow interfacial thermodynamics. Second, the temperature dependence profiles are distinct among the three hydrophobic polymers as a result of a hydrophobic size effect at the subnanometer scale. Third, the hydration free energy of a monomer on a macromolecule is different from a free monomer; corrections for the reduced hydration free energy due to hydrophobic interaction from neighboring units are required.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1105450108