@article {2015|1755, title = {How osmolytes influence hydrophobic polymer conformations: A unified view from experiment and theory.}, journal = {Proc. Natl. Acad. Sci. Usa}, volume = {112}, year = {2015}, pages = {9270{\textendash}5}, abstract = {

It is currently the consensus belief that protective osmolytes such as trimethylamine N-oxide (TMAO) favor protein folding by being excluded from the vicinity of a protein, whereas denaturing osmolytes such as urea lead to protein unfolding by strongly binding to the surface. Despite there being consensus on how TMAO and urea affect proteins as a whole, very little is known as to their effects on the individual mechanisms responsible for protein structure formation, especially hydrophobic association. In the present study, we use single-molecule atomic force microscopy and molecular dynamics simulations to investigate the effects of TMAO and urea on the unfolding of the hydrophobic homopolymer polystyrene. Incorporated with interfacial energy measurements, our results show that TMAO and urea act on polystyrene as a protectant and a denaturant, respectively, while complying with Tanford-Wyman preferential binding theory. We provide a molecular explanation suggesting that TMAO molecules have a greater thermodynamic binding affinity with the collapsed conformation of polystyrene than with the extended conformation, while the reverse is true for urea molecules. Results presented here from both experiment and simulation are in line with earlier predictions on a model Lennard-Jones polymer while also demonstrating the distinction in the mechanism of osmolyte action between protein and hydrophobic polymer. This marks, to our knowledge, the first experimental observation of TMAO-induced hydrophobic collapse in a ternary aqueous system.

}, keywords = {Atomic Force, Computer Simulation, Hydrophobic and Hydrophilic Interactions, Mechanical, Methylamines, Methylamines: chemistry, Microscopy, Molecular Dynamics Simulation, Normal Distribution, Polymers, Polymers: chemistry, Polystyrenes, Polystyrenes: chemistry, Protein Binding, Protein Conformation, Protein Folding, Proteins, Proteins: chemistry, Software, Solvents, Solvents: chemistry, Stress, Thermodynamics, Urea, Urea: chemistry, Water, Water: chemistry}, isbn = {1215421109}, issn = {1091-6490}, doi = {10.1073/pnas.1511780112}, url = {http://www.pnas.org/content/112/30/9270}, author = {Mondal, Jagannath and Halverson, Duncan and Li, Isaac T S and Guillaume Stirnemann and Walker, Gilbert C and Berne, Bruce J} } @article {2009|1830, title = {Replica exchange molecular dynamics simulations of coarse-grained proteins in implicit solvent.}, journal = {J. Phys. Chem. B}, volume = {113}, number = {1}, year = {2009}, month = {jan}, pages = {267{\textendash}274}, keywords = {Amino Acid Sequence, Computer Simulation, Magnetic Resonance Spectroscopy, Molecular Sequence Data, Peptides, Protein Folding, Protein Structure, Proteins, Secondary, Solvents, Temperature, Thermodynamics}, doi = {10.1021/jp805309e}, author = {Y Chebaro and Xiao Dong and Rozita Laghaei and Philippe Derreumaux and Normand Mousseau} } @article {2009|2019, title = {Thermodynamics and dynamics of amyloid peptide oligomerization are sequence dependent}, journal = {Proteins: Struct., Funct., Bioinf.}, volume = {75}, number = {4}, year = {2009}, month = {jun}, pages = {954{\textendash}963}, keywords = {Amino Acid Sequence, Amyloid beta-Protein, beta 2-Microglobulin, Cluster Analysis, Computer Simulation, Models, Molecular, Peptide Fragments, Protein Multimerization, Protein Structure, Secondary, Structure-Activity Relationship, Thermodynamics}, doi = {10.1002/prot.22305}, author = {Lu, Yan and Philippe Derreumaux and Guo, Zhi and Mousseau, Normand and Wei, Guanghong} }