English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
  Dipole reversal in bacteriorhodopsin and separation of dipole components

Wang, G., & Porschke, D. (2003). Dipole reversal in bacteriorhodopsin and separation of dipole components. Journal of Physical Chemistry B, 107(19), 4632-4638. Retrieved from http://pubs.acs.org/doi/pdfplus/10.1021/jp027510v.

Item is

Files

show Files
hide Files
:
123979.pdf (Publisher version), 0B
Name:
123979.pdf
Description:
-
OA-Status:
Visibility:
Public
MIME-Type / Checksum:
application/pdf / [MD5]
Technical Metadata:
Copyright Date:
-
Copyright Info:
-
License:
-

Locators

show

Creators

show
hide
 Creators:
Wang, G.1, Author           
Porschke, D.1, Author           
Affiliations:
1Research Group of Biomolecular Dynamics, MPI for biophysical chemistry, Max Planck Society, ou_578610              

Content

show
hide
Free keywords: -
 Abstract: The electrostatics of purple membranes has been analyzed by measurements of the electric dichroism in dc and ac fields in a broad pH range. The dc data are mainly used to characterize the permanent dipole, whereas the ac data serve as control for changes of global structure and of the induced dipole. At pH values from 8 to 3.5, the dc dichroism is negative at low field strengths and turns to positive values at higher field strengths, in qualitative agreement with the orientation function for disks having a permanent dipole moment perpendicular to the plane and an induced dipole moment in the plane. The minimum value of the dichroism, ξmin/dc , indicates the permanent dipole and shows a complex dependence on the pH but does not approach zero at any pH between 3.5 and 8, which would be expected for a simple reversal of the permanent dipole. However, the dependence of ξmin/dc on pH shows a λ point at pH 4.9, which reflects reversal of the dipole. Fitting of the stationary dichroism for E smaller or equal to 12 kV m-1 to the orientation function shows a decrease of the permanent dipole λ in the pH range 5 to about 50% of the value found at pH 7. In the same pH range, the limit dichroism, ξdc/infinity, derived from dc data also decreases to about 50% of the value at pH 7, whereas parallel measurements of the ac dichroism show almost constant ξac/infinity values. The combined observations indicate reversal of the permanent dipole, changes of disk bending, and the existence of a fluctuating dipole moment, probably resulting from bending fluctuations. Reversal of the dipole moment at pH 4.9 is confirmed by combined pH and field jump experiments. The direction of the dipole is reverted in the same pH range as the direction of stationary pH changes upon illumination, indicating an important function of the dipole for vectorial proton transfer. Comparison of experimental data with simple calculations of the protein dipole from the crystal structure indicates the existence of a large dipole component, which is directed opposite to the protein dipole at pH 7 and is probably due to a nonsymmetric distribution of charges on lipid residues. The results indicate a high degree of compensation in the electric asymmetry, which seems to be necessary for stability of purple membranes.

Details

show
hide
Language(s): eng - English
 Dates: 2004-07-282003-05-15
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: eDoc: 123979
URI: http://pubs.acs.org/doi/pdfplus/10.1021/jp027510v
 Degree: -

Event

show

Legal Case

show

Project information

show

Source 1

show
hide
Title: Journal of Physical Chemistry B
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: -
Pages: - Volume / Issue: 107 (19) Sequence Number: - Start / End Page: 4632 - 4638 Identifier: -