title: Ultrafast Fluctuations of High Amplitude Electric Fields in Lipid Membranes.
abstract: Understanding the electrostatics of lipid membranes at a molecular level has the potential to offer great insight into the mechanism of voltage-gated processes but has been challenging to study experimentally. In this study, we characterize the equilibrium electric field fluctuations at the interfacial region of lipid bilayers by using a combination of ultrafast time-resolved infrared spectroscopy, molecular dynamics (MD) simulations, and spectral modeling. By monitoring the dynamics of the ester carbonyl stretching vibration in hydrated phosphocholine lipid bilayers, we are able to measure a correlation function for the femtosecond and picosecond fluctuations in the local electric field of the membrane, estimating the standard deviation in these fluctuations as ∼10MV/cm. The addition of gramicidin D at a 1:20 mol ratio with DMPC results in the formation of protein-lipid hydrogen bonds, which alter the dynamics of the ester groups. Using MD simulations, we conclude that ultrafast local field fluctuations exist whether or not water interacts with the ester groups; however, water does accelerate the time-scale of these fluctuations.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Ave., Cambridge, Massachusetts 02139, United States.|Department of Chemistry, James Frank Institute, and The Institute for Biophysical Dynamics, The University of Chicago , 929 E 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Paul
authors.identifier: 0000-0002-6616-0328
authors.initials: P
authors.lastname: Stevenson
authors.affiliation: Department of Chemistry, James Frank Institute, and The Institute for Biophysical Dynamics, The University of Chicago , 929 E 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Andrei
authors.identifier: 0000-0002-2434-8744
authors.initials: A
authors.lastname: Tokmakoff
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D013055:Spectrophotometry, Infrared; D055672:Static Electricity; D013997:Time Factors
chemical_list: D008051:Lipid Bilayers; D004134:Dimyristoylphosphatidylcholine