English
 
User Manual Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
  Reaction coupling, acceptor pK, and diffusion control in light induced proton release of bacteriorhodopsin

Porschke, D. (2002). Reaction coupling, acceptor pK, and diffusion control in light induced proton release of bacteriorhodopsin. Journal of Physical Chemistry B, 106(39), 10233-10241. Retrieved from http://pubs.acs.org/doi/pdfplus/10.1021/jp0261004.

Item is

Basic

show hide
Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0012-F2C9-3 Version Permalink: http://hdl.handle.net/21.11116/0000-0002-01B7-E
Genre: Journal Article

Files

show Files
hide Files
:
16670.pdf (Publisher version), 0B
Name:
16670.pdf
Description:
-
Visibility:
Public
MIME-Type / Checksum:
application/pdf / [MD5]
Technical Metadata:
Copyright Date:
-
Copyright Info:
-
License:
-

Locators

show

Creators

show
hide
 Creators:
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 mechanism of proton release to the bulk during the photocycle of bacteriorhodopsin has been studied by absorbance measurements using pyranine as indicator. The initial absorbance change of the indicator is characterized by a sigmoidal shape, reflecting coupling of proton pumping with transfer of protons to the indicator. The time constants of pumping (tau(1) = 20 to 50 mus) and of transfer to the indicator (tau(2) = 0.4 to 1.5 ms) decrease with increasing pyranine concentration, consistent with coupling of an intra- and a bimolecular reaction step. Proton transfer by buffers is dependent on their pK value. The most efficient buffer in the test proved to be borate; in the presence of similar to1 m-M borate protons appeared in the bulk with a time constant of tau(2) approximate to 60 mus. The data are described by simple reaction mechanisms. The rate constants of proton transfer are consistent with a standard dependence on the pK difference between donor and acceptor, but apparently other factors like size and charge of the acceptor contribute as well. The rate constants of proton transfer from bacteriorhodopsin to acceptors with a favorable pK are at the limit of diffusion control. However, the data indicate the existence of a separate intramolecular reaction step for most acceptors, which seems to reflect proton transfer from the release cavity of bacteriorhodopsin to the periphery for acceptors, which cannot approach this cavity because of steric, electrostatic, and/or other factors. Crystal structures of bacteriorhodopsin support the interpretation that the release site is not directly accessible for acceptors such as pyranine. Proton transfer to borate is without barrier and, thus, there is no general diffusion barrier in the proton release of bacteriorhodopsin.

Details

show
hide
Language(s): eng - English
 Dates: 2002-10-03
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: Peer
 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: 106 (39) Sequence Number: - Start / End Page: 10233 - 10241 Identifier: -