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| Session Chair, Richard Pastor, CBER, FDA |
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| Richard W. Pastor was born in Oceanside, New York in 1951. He received a B.A. degree from Hamilton College in philosophy, a M.S. in chemistry from Syracuse University with Prof. Jerry Goodisman, a Ph.D. in biophysics from Harvard University with Prof. Martin Karplus, and was a postdoctoral fellow at the National Institutes of Health with Dr. Attila Szabo. He joined the Center for Biologics Evaluation and Research, FDA in 1984, and is presently the Chief of the Laboratory of Biophysics. Dr. Pastor's primary research area is the computer simulation of membranes. His simulations have ranged from stochastic dynamics of a single lipid chain to all-atom molecular dynamics of DPPC bilayers (see Accounts of Chemical Research, 35, 438-446, 2002). His methodological contributions to the field include mean field stochastic dynamics; distribution biased Monte Carlo; constant anisotropic pressure algorithms and long ranged cutoff corrections designed for interfaces; and specialized boundary conditions and potential energy parameters for lipid bilayers. Dr. Pastor continues development of force fields, and motional models derived from NMR relaxation and simulations of pure bilayers. His current application studies include simulations of membranes containing proteins (e.g., aquaporin) and peptides (fusion peptide from Influenza Hemagglutinin); peptide/micelle complexes; and the interaction of trehalose with bilayers and monolayers.
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Response of Lipid Bilayers and Monolayers to Trehalose: Molecular Dynamics in Constant Area and Surface Tension Ensembles
Richard W. Pastor, Laboratory of Biophysics, Center for Biologics Evaluation and Research, FDA, 1401 Rockville Pike, Rockville, MD20852-1448, USA
Surface tensions evaluated from molecular dynamics simulations of fully hydrated DPPC bilayers and monolayers at surface areas/lipid of 54, 64 and 80 square Angstroms are uniformly lowered 4-6 dyn/cm upon addition of trehalose in a 1:2 trehalose:lipid ratio. Constant surface tension simulations of bilayers yield the complementary result: an increase in surface area consistent with the surface pressure-surface area (pi-A) isotherms. Additional validation of the potential energy functions is provided by agreement of calculated and experimental monolayer pi-A isotherms, and bilayer bulk and area compressibilities, and densities. These results indicate that the 20-30 dyn/cm difference in surface tension of the bilayer leaflet and monolayer arises from differences in the chain regions, not the headgroup/water interfaces. Consequently, measurements on the interactions of surface active components such as trehalose with monolayers can yield quantitative insight to their effects on bilayers.
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