COLL 156 |
| Dietmar Porschke, Biomolecular Dynamics, Biomolecular Dynamics, Max Planck Institut für biophysikalische Chemie, Am Fassberg 11, Göttingen, 37077, Germany |
| A quantitative approach to molecular electro-optics with automatic calculation of electric dichroism data from known macromolecular structures is reviewed. Examples for application of this procedure and its use for structure analysis in solution to various examples are demonstrated. – The electric dichroism of bacteriorhodopsin shows a special pH-dependence with a lambda-point at pH 4.9 – close to the pH where a reversal of the dipole moment has been reported. However, the dichroism does not approach zero, which would be expected for a simple dipole reversal. Stationary dichroism data demonstrate a minimum of the dipole moment m at pH 4.9, but m-values are far from zero. This is attributed to a fluctuating dipole moment. Measurements using a field+pH-jump-instrument confirm reversal of the dipole moment at pH 4.9. Comparison of experimental with calculated dipoles demonstrate a large dipole component directed opposite to the protein dipole. Implications of these results for biological function are discussed. |
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Colloidal and Molecular Electro-Optics
Division of Colloid and Surface Chemistry |