Theoretical methods in chemistry and biophysics

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Frank Brown of the University of California - Santa Barbara is supported by an award from the Chemical Theory, Models and Computational Methods program of the Chemistry Division for research that is helping us understand the structure and function of the molecules that make up the membranes that enclose all the cells in our bodies. These membranes, a combination of fat-like molecules, cholesterol and proteins, are complex entities across which food and other substances enter our cells while wastes and cellular products exit them. The investigators are studying the ways these events occur at a fundamental physical and chemical level. They are, thus, promoting the progress of science and having an impact on a wide array of scientific topics involving the healthy functioning of living things. The research is having a further broad impact through the training of the next generation of scientists, both in the investigator's research laboratory and through the distribution of software that results from this work. In addition, the investigators are helping to coordinate outreach programs at the UCSB institution that seek to involve elementary school students in science and encourage them to consider careers in the STEM disciplines.The investigators are developing theoretical models, numerical methods and simulation algorithms for the study of lipid bilayers, lipid and surfactant monolayers and DNA-modifying enzymes. In particular, field-theoretic models for membrane structure are being refined at two different levels of description suited to long-wavelength undulations and short-wavelength lipid tilt/thickness deformations. The investigators are generalizing the interfacial regularized Stokeslet methodology previously developed by this group to incorporate compressibility and viscoelastic effects. In a third project, the investigators are extending their analysis methods to the development of improved kinetic schemes to analyze enzymatic turnover in DNA-modificication. A number of applications of this work are expected, including: (1) extracting quantitatively accurate values of membrane bending moduli from molecular simulations; (2) interpreting NMR measurements on lipid bilayers; (3) interpreting interfacial microbutton rheology measurements; (4) relating membrane elastic properties determined via measurements taken at vastly different length scales; (5) quantifying the influence of periodic boundary conditions on simulated dynamics in lipid bilayers; (6) elucidating the kinetics and processivity of DNA modifying enzymes; and (7) understanding thickness fluctuations in lipid bilayers and their influence on neutron scattering experiments.The Biophysics Program in the Division of Molecular and Cellular Biolosciences (MCB) in Biosciences Directorate (BIO) and the Condensed Matter and Materials Theory Program in the Division of Materials Research (DMR) contribute to this award.