The properties of the lipid bilayer-water interface will be studied by observing the kinetics of photo-generated charge transfer across the interface, of ensuing reverse reaction at that interface and of transmembrane movement of products. Electrical measurements directly probe the charge transfer with subnanosecond time resolution and angstrom (Debye length) distance from the surface. The unique ability of photoreactions to transfer this charge in sub-nanosecond times allows the study of an unprecedented time range, some ten orders of magnitude. The study will be aimed at obtaining information on the electrical and other potentials at the interface, on the molecular motion or viscosity of the interface and on the relaxation of ion atmospheres at these charged interfaces. This information is obtained by detailed analysis of the kinetics of reactions with differently charged or polar lipids and a variety of charged or polar reactants. The transit time of charged species across bilayers will be directly measured in attempts to resolve discrepancies in the literature. These measurements will be applied to the study of charge transfer in modified membrane ion channels, in bacteriorhodopsin and in photosynthetic reaction centers.
The aim will be to understand the molecular determinants of the charge transfer by direct measure of the charge movements. New methodologies to measure the thermodynamic properties via kinetically resolved heat formation of photochemical cycles such as occur in phototransduction in rhodopsin, bacteriorhodopsin and photosynthetic reaction centers will be developed. They will be the extension of photoacoustic methodology to the nanosecond time range and the use of a novel method based on changes in ionic conductivity.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Molecular and Cellular Biophysics Study Section (BBCA)
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Rockefeller University
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New York
United States
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Hou, Harvey J M; Sakmar, Thomas P (2010) Methodology of pulsed photoacoustics and its application to probe photosystems and receptors. Sensors (Basel) 10:5642-67
Liu, Yan; Edens, Gregory J; Grzymski, Joseph et al. (2008) Volume and enthalpy changes of proton transfers in the bacteriorhodopsin photocycle studied by millisecond time-resolved photopressure measurements. Biochemistry 47:7752-61
Hou, Harvey J M; Mauzerall, David (2006) The A-Fx to F(A/B) step in synechocystis 6803 photosystem I is entropy driven. J Am Chem Soc 128:1580-6
Mauzerall, David; Liu, Yan; Edens, Gregory J et al. (2003) Measurement of enthalpy and volume changes in photoinitiated reactions on the ms timescale with a novel pressure cell. Photochem Photobiol Sci 2:788-90
Boichenko, V A; Hou, J M; Mauzerall, D (2001) Thermodynamics of electron transfer in oxygenic photosynthetic reaction centers: volume change, enthalpy, and entropy of electron-transfer reactions in the intact cells of the cyanobacterium Synechocystis PCC 6803. Biochemistry 40:7126-32
Hou, J M; Boichenko, V A; Wang, Y C et al. (2001) Thermodynamics of electron transfer in oxygenic photosynthetic reaction centers: a pulsed photoacoustic study of electron transfer in photosystem I reveals a similarity to bacterial reaction centers in both volume change and entropy. Biochemistry 40:7109-16
Hou, J M; Boichenko, V A; Diner, B A et al. (2001) Thermodynamics of electron transfer in oxygenic photosynthetic reaction centers: volume change, enthalpy, and entropy of electron-transfer reactions in manganese-depleted photosystem II core complexes. Biochemistry 40:7117-25
Sun, K; Mauzerall, D (1996) Evidence for ion chain mechanism of the nonlinear charge transport of hydrophobic ions across lipid bilayers. Biophys J 71:295-308
Sun, K; Mauzerall, D (1996) Charge transfer across a single lipid-water interface causes ion pumping across the bilayer. Biophys J 71:309-16
Sun, K; Mauzerall, D (1996) A simple light-driven transmembrane proton pump. Proc Natl Acad Sci U S A 93:10758-62

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