High-Pressure Near-Infrared Raman-Spectroscopy Of Bacteriorhodopsin Light To Dark-Adaptation

    Authors

    A. Schulte;L. Bradley

    Comments

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    Abbreviated Journal Title

    Biophys. J.

    Keywords

    DRIVEN PROTON PUMP; PURPLE MEMBRANE; RESONANCE RAMAN; ADAPTED; BACTERIORHODOPSIN; HALOBACTERIUM-HALOBIUM; VIBRATIONAL ANALYSIS; PHOTOCHEMICAL CYCLE; SCHIFF-BASE; PROTEINS; CHROMOPHORE; Biophysics

    Abstract

    Near-infrared (NIR) Raman spectroscopy is employed as an in situ probe of the chromophore conformation to study the light to dark-adaptation process in bacteriorhodopsin (bR) at variable pressure and temperature in the absence of undesired photoreactions. in dark-adapted bR deconvolution of the ethylenic mode into bands assigned to the all-trans (1526 cm(-1)) and 13-cis (1534 cm(-1)) isomers yields a 13-cis to all-trans ratio equal to 1 at ambient pressure (Schulte et al., 1995, Appl. Spectrosc. 49:80-83). Detailed spectroscopic evidence is presented that at high pressure the equilibrium is shifted toward the 13-cis isomers acid that the light to dark adaptation kinetics is accelerated. The change in isomeric composition with temperature and pressure as well as the kinetics support a two-state model with activation volumes of -16 ml/mol for the transition of 13-cis to all-trans and -22 ml/mol for the reverse process. These compare with a conformational volume difference of 6.6 ml/mol, which may be attributed to the ionization of one or two residues or the formation of three hydrogen bonds.

    Journal Title

    Biophysical Journal

    Volume

    69

    Issue/Number

    4

    Publication Date

    1-1-1995

    Document Type

    Article

    Language

    English

    First Page

    1554

    Last Page

    1562

    WOS Identifier

    WOS:A1995TJ02100035

    ISSN

    0006-3495

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