A mechanism of proton transport across biomembranes will be studied by theoretical methods. The mechanism under investigation involves transfer of protons from one residue of a hudgrogen bonded chain within a transmembrane protein to the next. This means of proton conduction appears to play a prevalent role in a number of biological processes including photosynthesis and mitochodrial oxidative phosphorylation. Quantum chemical calculations will be performed to determine the energetics of proton transfers in proteins. As the three-dimensional structure of proteins makes for a wide diversity of different types and geometries of hydrogen bond geometry. Calculations will be performed first upon systems composed of small models of each residue to facilitate the application of very accurate techniques including large basic sets and electron correlation. The simplicity of these systems will allow a focusing of attention upon the basics of the proton transfer process without competing effects obscuring the data. The sizes of the models will gradually be enlarged to more appropriate representations of each protein residue to ensure the reliability of the results. Data will be carefully examined for corrlations between electronic redistributions and energetics of proton transfer to establish relationships useful for predictions of energetics of large systems from first lprinciples. The next step of the research involves using the calcuated energetics to obtain kinetic information about the proton transfer process. This data is vital to our understanding of the efficiency and time-scale of the biological proton transport mechanism.
