Fatty Acid Aggregates Simulated using Constant pH Molecular Dynamics with a Coarse-Grained Model

863-Pos Board B632 Hydrogen Bond Strength Modulates the Mechanical Strength of FerricThiolate Bonds in Rubredoxin Peng Zheng, Shin-ichi J. Takayama, A Grant Mauk, Hongbin Li. University of British Columbia, Vancouver, BC, Canada. It has long been recognized that hydrogen bonds formed by protein backbone amides with cysteinyl Sulfur atoms play important roles in modulating the functional and structural properties of the iron-sulfur centers in proteins. Here we use single molecule atomic force microscopy, cyclic voltammetry and protein engineering techniques to investigate directly how the strength of N/H-Sg hydrogen bonds in the secondary coordination sphere affects the mechanical stability of Fe(III)-thiolate bonds of rubredoxin. Our results show that the mechanical stability of Fe(III)-thiolate bonds in rubredoxin correlates with the strength of N/H-S hydrogen bonds as reflected by the midpoint reduction potential, providing direct evidence that N/H-S hydrogen bonds play important roles in modulating the mechanical and kinetic properties of the Fe(III)-thiolate bonds of iron-sulfur proteins and corroborating the important roles of the protein environment in tuning the properties of metal-thiolate bonds.