Direct Evidence for Modified Solvent Structure within the Hydration Shell of a Hydrophobic Amino Acid

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 93; no. 20; pp. 10769 - 10774
• Main Authors: Pertsemlidis, Alexander, Saxena, Anand M., Soper, Alan K., Head-Gordon, Teresa, Glaeser, Robert M.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01-10-1996; National Acad Sciences
• Subjects: Amides; Amides - chemistry; Amino acids; Amino Acids - chemistry; Aqueous solutions; Glutamine - analogs & derivatives; Glutamine - chemistry; Leucine - analogs & derivatives; Leucine - chemistry; Lysine - analogs & derivatives; Lysine - chemistry; Molecular dynamics; Molecular structure; Molecules; Neutron scattering; Neutrons; Sandals; Scattering, Radiation; Solubility; Solutes; Solvents; Water
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.20.10769

Neutron scattering experiments are used to determine scattering profiles for aqueous solutions of hydrophobic and hydrophilic amino acid analogs. Solutions of hydrophobic solutes show a shift in the main diffraction peak to smaller angle as compared with pure water, whereas solutions of hydrophilic solutes do not. The same difference for solutions of hydrophobic and hydrophilic side chains is also predicted by molecular dynamics simulations. The neutron scattering curves of aqueous solutions of hydrophobic amino acids at room temperature are qualitatively similar to differences between the liquid molecular structure functions measured for ambient and supercooled water. The nonpolar solute-induced expansion of water structure reported here is also complementary to recent neutron experiments where compression of aqueous solvent structure has been observed at high salt concentration.