Transmembrane electron transfer mediated by a viologen

A mechanism involving diffusion of doubly reduced viologen formed by disproportionation of viologen radical

Leif Hammarström, Mats Almgren, Thomas Norrby

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

A stopped-flow study of electron transfer (ET) through vesicle membranes composed of egg lecithin (phosphatidyl choline) was made. Cetylmethylviologen (N-methyl-N′-hexadecyl-4,4′-bipyridine, CMV) acted as transmembrane redox mediator by transferring electrons from dithionite in the bulk aqueous phase to CMV2+ or ferricyanide in the vesicle interior. Transmembrane ET was observed when viologen was bound only to the outer interface and the overall reaction was second order in viologen radical on the outside ([CMV+]out). Both facts exclude electron tunneling/self-exchange as mechanism. A mechanism is proposed where the rate-determining step is the disproportionation of two viologen radicals initially formed at the outer interface of the vesicle (2CMV+ = CMV0 + CMV2+). CMV0 diffuses rapidly through the membrane and is re-oxidized in the vesicle interior. A brief study of Ru(bpy)3 2+-sensitized, photoinduced transmembrane ET was made, giving further evidence for transmembrane viologen migration. Preliminary results from pulse-radiolytically induced transmembrane ET support the observation that the reaction is second order in [CMV+]out.

Original languageEnglish
Pages (from-to)5017-5024
Number of pages8
JournalJournal of Physical Chemistry
Volume96
Issue number12
Publication statusPublished - 1992

Fingerprint

Viologens
electron transfer
Electrons
membranes
choline
eggs
Dithionite
Membranes
Lecithin
electron tunneling
Electron tunneling
Lecithins
Phosphatidylcholines
pulses
electrons

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

@article{6a93c4c5a5304e34a99a1925f58ae8ad,
title = "Transmembrane electron transfer mediated by a viologen: A mechanism involving diffusion of doubly reduced viologen formed by disproportionation of viologen radical",
abstract = "A stopped-flow study of electron transfer (ET) through vesicle membranes composed of egg lecithin (phosphatidyl choline) was made. Cetylmethylviologen (N-methyl-N′-hexadecyl-4,4′-bipyridine, CMV) acted as transmembrane redox mediator by transferring electrons from dithionite in the bulk aqueous phase to CMV2+ or ferricyanide in the vesicle interior. Transmembrane ET was observed when viologen was bound only to the outer interface and the overall reaction was second order in viologen radical on the outside ([CMV+]out). Both facts exclude electron tunneling/self-exchange as mechanism. A mechanism is proposed where the rate-determining step is the disproportionation of two viologen radicals initially formed at the outer interface of the vesicle (2CMV+ = CMV0 + CMV2+). CMV0 diffuses rapidly through the membrane and is re-oxidized in the vesicle interior. A brief study of Ru(bpy)3 2+-sensitized, photoinduced transmembrane ET was made, giving further evidence for transmembrane viologen migration. Preliminary results from pulse-radiolytically induced transmembrane ET support the observation that the reaction is second order in [CMV+]out.",
author = "Leif Hammarstr{\"o}m and Mats Almgren and Thomas Norrby",
year = "1992",
language = "English",
volume = "96",
pages = "5017--5024",
journal = "Journal of Physical Chemistry",
issn = "0022-3654",
publisher = "American Chemical Society",
number = "12",

}

TY - JOUR

T1 - Transmembrane electron transfer mediated by a viologen

T2 - A mechanism involving diffusion of doubly reduced viologen formed by disproportionation of viologen radical

AU - Hammarström, Leif

AU - Almgren, Mats

AU - Norrby, Thomas

PY - 1992

Y1 - 1992

N2 - A stopped-flow study of electron transfer (ET) through vesicle membranes composed of egg lecithin (phosphatidyl choline) was made. Cetylmethylviologen (N-methyl-N′-hexadecyl-4,4′-bipyridine, CMV) acted as transmembrane redox mediator by transferring electrons from dithionite in the bulk aqueous phase to CMV2+ or ferricyanide in the vesicle interior. Transmembrane ET was observed when viologen was bound only to the outer interface and the overall reaction was second order in viologen radical on the outside ([CMV+]out). Both facts exclude electron tunneling/self-exchange as mechanism. A mechanism is proposed where the rate-determining step is the disproportionation of two viologen radicals initially formed at the outer interface of the vesicle (2CMV+ = CMV0 + CMV2+). CMV0 diffuses rapidly through the membrane and is re-oxidized in the vesicle interior. A brief study of Ru(bpy)3 2+-sensitized, photoinduced transmembrane ET was made, giving further evidence for transmembrane viologen migration. Preliminary results from pulse-radiolytically induced transmembrane ET support the observation that the reaction is second order in [CMV+]out.

AB - A stopped-flow study of electron transfer (ET) through vesicle membranes composed of egg lecithin (phosphatidyl choline) was made. Cetylmethylviologen (N-methyl-N′-hexadecyl-4,4′-bipyridine, CMV) acted as transmembrane redox mediator by transferring electrons from dithionite in the bulk aqueous phase to CMV2+ or ferricyanide in the vesicle interior. Transmembrane ET was observed when viologen was bound only to the outer interface and the overall reaction was second order in viologen radical on the outside ([CMV+]out). Both facts exclude electron tunneling/self-exchange as mechanism. A mechanism is proposed where the rate-determining step is the disproportionation of two viologen radicals initially formed at the outer interface of the vesicle (2CMV+ = CMV0 + CMV2+). CMV0 diffuses rapidly through the membrane and is re-oxidized in the vesicle interior. A brief study of Ru(bpy)3 2+-sensitized, photoinduced transmembrane ET was made, giving further evidence for transmembrane viologen migration. Preliminary results from pulse-radiolytically induced transmembrane ET support the observation that the reaction is second order in [CMV+]out.

UR - http://www.scopus.com/inward/record.url?scp=0002931686&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0002931686&partnerID=8YFLogxK

M3 - Article

VL - 96

SP - 5017

EP - 5024

JO - Journal of Physical Chemistry

JF - Journal of Physical Chemistry

SN - 0022-3654

IS - 12

ER -