Electron transfer through vesicle membranes: Effects of reactant compartmentalization and intervesicle migration on the reaction kinetics

Leif Hammarström, Mats Almgren

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Abstract

The kinetics of electron transfer through vesicle membranes mediated by viologen was considered in detail. In previous studies, the rate-determining step of the reaction has been found to be the disproportionation of two viologen radicals: 2CnV+ ⇔ CnV2+ + CnV0. The effect of reactant compartmentalization was demonstrated by both experiments and simulations. Second-order fits to the kinetic data showed that disregarding compartmentalization is a good approximation for the major part of the observed reaction when the initial average occupancy number 〈n0〉 ≥ 10. The value for the rate constant obtained from a "good" fit was unaffected by compartmentalization. Both simulations and experiments showed that when 〈n0〉 ≥ 5, it was not possible to obtain a satisfactory second-order fit over the same interval. Experiments showed that migration of CnV2+ between vesicles was rapid (1/k- <1 ms), but migration of CnV+ was slow on the time scale of the experiments. The effect of viologen migration was demonstrated by simulations. The simulation results are general for compartmentalized reactions described by 2A → A + B, with and without the possibility of intercompartment exchange of A during the reaction.

Original languageEnglish
Pages (from-to)11959-11966
Number of pages8
JournalJournal of Physical Chemistry
Volume99
Issue number31
Publication statusPublished - 1995

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Viologens
Reaction kinetics
electron transfer
reaction kinetics
membranes
Membranes
Electrons
simulation
Experiments
Kinetics
kinetics
Rate constants
intervals
approximation

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

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abstract = "The kinetics of electron transfer through vesicle membranes mediated by viologen was considered in detail. In previous studies, the rate-determining step of the reaction has been found to be the disproportionation of two viologen radicals: 2CnV+ ⇔ CnV2+ + CnV0. The effect of reactant compartmentalization was demonstrated by both experiments and simulations. Second-order fits to the kinetic data showed that disregarding compartmentalization is a good approximation for the major part of the observed reaction when the initial average occupancy number 〈n0〉 ≥ 10. The value for the rate constant obtained from a {"}good{"} fit was unaffected by compartmentalization. Both simulations and experiments showed that when 〈n0〉 ≥ 5, it was not possible to obtain a satisfactory second-order fit over the same interval. Experiments showed that migration of CnV2+ between vesicles was rapid (1/k- <1 ms), but migration of CnV+ was slow on the time scale of the experiments. The effect of viologen migration was demonstrated by simulations. The simulation results are general for compartmentalized reactions described by 2A → A + B, with and without the possibility of intercompartment exchange of A during the reaction.",
author = "Leif Hammarstr{\"o}m and Mats Almgren",
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TY - JOUR

T1 - Electron transfer through vesicle membranes

T2 - Effects of reactant compartmentalization and intervesicle migration on the reaction kinetics

AU - Hammarström, Leif

AU - Almgren, Mats

PY - 1995

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N2 - The kinetics of electron transfer through vesicle membranes mediated by viologen was considered in detail. In previous studies, the rate-determining step of the reaction has been found to be the disproportionation of two viologen radicals: 2CnV+ ⇔ CnV2+ + CnV0. The effect of reactant compartmentalization was demonstrated by both experiments and simulations. Second-order fits to the kinetic data showed that disregarding compartmentalization is a good approximation for the major part of the observed reaction when the initial average occupancy number 〈n0〉 ≥ 10. The value for the rate constant obtained from a "good" fit was unaffected by compartmentalization. Both simulations and experiments showed that when 〈n0〉 ≥ 5, it was not possible to obtain a satisfactory second-order fit over the same interval. Experiments showed that migration of CnV2+ between vesicles was rapid (1/k- <1 ms), but migration of CnV+ was slow on the time scale of the experiments. The effect of viologen migration was demonstrated by simulations. The simulation results are general for compartmentalized reactions described by 2A → A + B, with and without the possibility of intercompartment exchange of A during the reaction.

AB - The kinetics of electron transfer through vesicle membranes mediated by viologen was considered in detail. In previous studies, the rate-determining step of the reaction has been found to be the disproportionation of two viologen radicals: 2CnV+ ⇔ CnV2+ + CnV0. The effect of reactant compartmentalization was demonstrated by both experiments and simulations. Second-order fits to the kinetic data showed that disregarding compartmentalization is a good approximation for the major part of the observed reaction when the initial average occupancy number 〈n0〉 ≥ 10. The value for the rate constant obtained from a "good" fit was unaffected by compartmentalization. Both simulations and experiments showed that when 〈n0〉 ≥ 5, it was not possible to obtain a satisfactory second-order fit over the same interval. Experiments showed that migration of CnV2+ between vesicles was rapid (1/k- <1 ms), but migration of CnV+ was slow on the time scale of the experiments. The effect of viologen migration was demonstrated by simulations. The simulation results are general for compartmentalized reactions described by 2A → A + B, with and without the possibility of intercompartment exchange of A during the reaction.

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