Equilibrium Composition Of Retinal Isomers In Dark-Adapted Bacteriorhodopsin And Effect Of High-Pressure Probed By Near-Infrared Raman-Spectroscopy

    Authors

    A. Schulte; L. Bradley;C. Williams

    Comments

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    Abbreviated Journal Title

    Appl. Spectrosc.

    Keywords

    CHROMOPHORE ISOMERIZATION; PURPLE MEMBRANE; LIGHT ADAPTATION; PROTEIN; VOLUME CHANGE; RAYLEIGH LINE REJECTION; ADAPTATION; PROTEINS; FILTER; EXCITATION; CYCLE; Instruments & Instrumentation; Spectroscopy

    Abstract

    The combination of near-infrared Raman spectroscopy and variations in external parameters offers new opportunities for site-specific studies of proteins. Using excitation at 840 nm, we have measured the near-infrared Raman spectrum of dark-adapted bacteriorhodopsin at ambient and high pressure. The C=C ethylenic stretching region shows two resolved bands at 1526 and 1534 cm(-1), corresponding to the all-trans and 13-cis isomers. From deconvolution of these bands we find an isomeric ratio between 13-cis and all-trans retinal equal to 1 at ambient pressure. The Raman spectrum gives direct spectroscopic evidence that the 13-cis component is favored at high pressure, implying that it has a smaller volume. The pressure dependence of the isomeric ratio yields a molar volume of -6.6 mL/mol, which suggests ionization of one or two residues or the formation of three hydrogen bonds.

    Journal Title

    Applied Spectroscopy

    Volume

    49

    Issue/Number

    1

    Publication Date

    1-1-1995

    Document Type

    Article

    Language

    English

    First Page

    80

    Last Page

    83

    WOS Identifier

    WOS:A1995QF28300015

    ISSN

    0003-7028

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