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Title: Proton polarizability of hydrogen-bonded network and its role in proton transfer in bacteriorhodopsin

Abstract

Room-temperature time-resolved step-scan Fourier Transform Infrared (FTIR) spectroscopy has been used to study the photocycle of native bacteriorhodopsin (bR) suspension in both H{sub 2}O and D{sub 2}O. The kinetics of the retinal isomerization, and that of the protonation/deprotonation of the proton acceptor, Asp85, are compared in the {micro}s to ms time domain. It is found that hydrogen/deuterium (H/D) isotope exchange does not significantly affect the kinetics of the retinal isomerization and relaxation processes. However, the protonation/deprotonation processes of Asp85 COO{sup {minus}} become slower in D{sub 2}O. The authors also studied the kinetics of the continuum absorbance change in the 1850-1800 cm{sup {minus}1} frequency region, which has previously been proposed to correspond to the absorption of the delocalized proton that is involved in the proton transport to the surface during the photocycle. An H/D isotope shift of the frequency range of this continuum absorbance has been confirmed by the observation that the band in the 1850-1800 cm{sup {minus}1} disappears in the photocycle of bR in D{sub 2}O. These results could support the previous proposal that the intramolecular proton release pathway consists of an H-bonded network. Their results also suggest that the two independent processes, the transfer of a proton from themore » Schiff base to Asp85 and the release of a different proton to the extracellular surface, are closely coupled events.« less

Authors:
;
Publication Date:
Research Org.:
Georgia Inst. of Tech., Atlanta, GA (US)
Sponsoring Org.:
USDOE
OSTI Identifier:
20075903
DOE Contract Number:  
FG02-97ER14799
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory
Additional Journal Information:
Journal Volume: 104; Journal Issue: 18; Other Information: PBD: 11 May 2000; Journal ID: ISSN 1089-5639
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; BACTERIA; PROTEINS; KINETICS; FOURIER TRANSFORM SPECTROMETERS; RETINA; ISOMERIZATION; POLARIZATION; PROTONS; CHEMICAL BONDS

Citation Formats

Wang, J., and El-Sayed, M.A. Proton polarizability of hydrogen-bonded network and its role in proton transfer in bacteriorhodopsin. United States: N. p., 2000. Web. doi:10.1021/jp994460u.
Wang, J., & El-Sayed, M.A. Proton polarizability of hydrogen-bonded network and its role in proton transfer in bacteriorhodopsin. United States. doi:10.1021/jp994460u.
Wang, J., and El-Sayed, M.A. Thu . "Proton polarizability of hydrogen-bonded network and its role in proton transfer in bacteriorhodopsin". United States. doi:10.1021/jp994460u.
@article{osti_20075903,
title = {Proton polarizability of hydrogen-bonded network and its role in proton transfer in bacteriorhodopsin},
author = {Wang, J. and El-Sayed, M.A.},
abstractNote = {Room-temperature time-resolved step-scan Fourier Transform Infrared (FTIR) spectroscopy has been used to study the photocycle of native bacteriorhodopsin (bR) suspension in both H{sub 2}O and D{sub 2}O. The kinetics of the retinal isomerization, and that of the protonation/deprotonation of the proton acceptor, Asp85, are compared in the {micro}s to ms time domain. It is found that hydrogen/deuterium (H/D) isotope exchange does not significantly affect the kinetics of the retinal isomerization and relaxation processes. However, the protonation/deprotonation processes of Asp85 COO{sup {minus}} become slower in D{sub 2}O. The authors also studied the kinetics of the continuum absorbance change in the 1850-1800 cm{sup {minus}1} frequency region, which has previously been proposed to correspond to the absorption of the delocalized proton that is involved in the proton transport to the surface during the photocycle. An H/D isotope shift of the frequency range of this continuum absorbance has been confirmed by the observation that the band in the 1850-1800 cm{sup {minus}1} disappears in the photocycle of bR in D{sub 2}O. These results could support the previous proposal that the intramolecular proton release pathway consists of an H-bonded network. Their results also suggest that the two independent processes, the transfer of a proton from the Schiff base to Asp85 and the release of a different proton to the extracellular surface, are closely coupled events.},
doi = {10.1021/jp994460u},
journal = {Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory},
issn = {1089-5639},
number = 18,
volume = 104,
place = {United States},
year = {2000},
month = {5}
}