@article {2673, title = {Structures of Water Molecules at the Interfaces of Aqueous Salt Solutions and Silica: Cation Effects}, journal = {Journal of Physical Chemistry C}, volume = {113}, number = {19}, year = {2009}, note = {ISI Document Delivery No.: 443FLTimes Cited: 6Cited Reference Count: 53Yang, Zheng Li, Qifeng Chou, Keng C.}, month = {May}, pages = {8201-8205}, type = {Article}, abstract = {Structures of water molecules at water/silica interfaces, in the presence of alkali chloride. were investigated using infrared-visible sum frequency vibrational spectroscopy. Significant perturbations of the interfacial water structure were observed on silica surfaces with the NaCl concentration as low as 1 x 10(-4) M. The cations, which interact with the Silica Surface via electrostatic interaction, play key roles in Perturbing the hydrogen-bond network of water molecules at the water/silica interface. This cation effect becomes saturated at concentrations around 10(-2) to 10(-1) M, where the sum frequency generation peaks at 3200 and 3400 cm(-1) decrease by 75\%. Different alkali cation species (Li+, Na+, and K+) produce different magnitudes of perturbation, with K+ > Li+ > Na+. This order can be explained by considering the effective ionic radii of the hydrated cations and the electrostatic interactions between the hydrated cations and silica Surfaces. The interfacial water structure associated with the 3200 cm(-1) band is more vulnerable to the cation perturbation, Suggesting that the more ordered water structure on silica is likely associated with the vincinal silanol groups, which create a higher local surface electrical field on silica.}, keywords = {ADSORPTION, charge, DYNAMICS SIMULATIONS, ELECTROLYTE INTERFACE, hydration, INTERFACE, LIQUID WATER, SOLID/LIQUID, SUM-FREQUENCY SPECTROSCOPY, SURFACE, vibrational spectroscopy}, isbn = {1932-7447}, url = {://000265895500034}, author = {Yang, Z. and Li, Q. F. and Chou, K. C.} } @article {2247, title = {Stabilization provided by neighboring strands is critical for the mechanical stability of proteins}, journal = {Biophysical Journal}, volume = {95}, number = {8}, year = {2008}, note = {ISI Document Delivery No.: 352NMTimes Cited: 5Cited Reference Count: 37Sharma, Deepak Feng, Gang Khor, Dingyue Genchev, Georgi Z. Lu, Hui Li, Hongbin}, month = {Oct}, pages = {3935-3942}, type = {Article}, abstract = {Single-molecule force spectroscopy studies and steered molecular dynamics simulations have revealed that protein topology and pulling geometry play important roles in determining the mechanical stability of proteins. Most studies have focused on local interactions that are associated with the force-bearing beta-strands. Interactions mediated by neighboring strands are often overlooked. Here we use Top7 and barstar as model systems to illustrate the critical importance of the stabilization effect provided by neighboring beta-strands on the mechanical stability. Using single-molecule atomic force microscopy, we showed that Top7 and barstar, which have similar topology in their force-bearing region, exhibit vastly different mechanical-stability characteristics. Top7 is mechanically stable and unfolds at similar to 150 pN, whereas barstar is mechanically labile and unfolds largely below 50 pN. Steered molecular dynamics simulations revealed that stretching force peels one force-bearing strand away from barstar to trigger unfolding, whereas Top7 unfolds via a substructure-sliding mechanism. This previously overlooked stabilization effect from neighboring beta-strands is likely to be a general mechanism in protein mechanics and can serve as a guideline for the de novo design of proteins with significant mechanical stability and novel protein topology.}, keywords = {BARSTAR, DYNAMICS SIMULATIONS, IMMUNOGLOBULIN DOMAINS, MICROSCOPE, MOLECULE FORCE SPECTROSCOPY, resistance, SINGLE PROTEIN, TITIN, TOPOLOGY, UBIQUITIN}, isbn = {0006-3495}, url = {://000259503900036}, author = {Sharma, D. and Feng, G. and Khor, D. and Genchev, G. Z. and Lu, H. and Li, H. B.} }