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Title: Cleavage of [4Fe-4S]-Type Clusters: Breaking the Symmetry

Abstract

The cleavage of [4Fes4S]-type clusters is thought to be important in proteins such as FesS scaffold proteins and nitrogenase. However, most [4Fes4S]2+ clusters in proteins have two antiferromagnetically coupled high-spin layers in which a minority spin is delocalized in each layer, thus forming a symmetric Fe2.5+sFe2.5+ pair, and how cleavage occurs between the irons is puzzling because of the shared electron. Previously, we proposed a novel mechanism for the fission of a [4Fes4S] core into two [2Fes2S] cores in which the minority spin localizes on one iron, thus breaking the symmetry and creating a transition state with two Fe3+sFe2+ pairs. Cleavage first through the weak Fe2+sS bonds lowers the activation energy. Here, we propose a test of this mechanism: break the symmetry of the cluster by changing the ligands to promote spin localization, which should enhance reactivity. The cleavage reactions for the homoligand [Fe4S4L4]2- (L ) SCH3, Cl, H) and heteroligand [Fe4S4(SCH3)2L2]2- (L ) Cl, H) clusters in the gas phase were examined via broken-symmetry density functional theory calculations. In the heteroligand clusters, the minority spin localized on the iron coordinated by the weaker electron-donor ligand, and the reaction energy and activation barrier of the cleavage were lowered, which ismore » in accord with our proposed mechanism and consistent with photoelectron spectroscopy and collision-induced dissociation experiments. These studies suggest that proteins requiring facile fission of their [4Fes4S] cluster in their biological function might have spin-localized [4Fes4S] clusters.« less

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1001532
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry A, 113(19):5710-5717
Additional Journal Information:
Journal Volume: 113; Journal Issue: 19; Journal ID: ISSN 1089-5639
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ACTIVATION ENERGY; BINDING ENERGY; BIOLOGICAL FUNCTIONS; CLEAVAGE; DISSOCIATION; ELECTRONS; FISSION; FUNCTIONALS; IRON; NITROGENASE; PHOTOELECTRON SPECTROSCOPY; PROTEINS; SPIN; SYMMETRY; VALENCE; Environmental Molecular Sciences Laboratory

Citation Formats

Niu, Shuqiang, and Ichiye, Toshiko. Cleavage of [4Fe-4S]-Type Clusters: Breaking the Symmetry. United States: N. p., 2009. Web. doi:10.1021/jp900402y.
Niu, Shuqiang, & Ichiye, Toshiko. Cleavage of [4Fe-4S]-Type Clusters: Breaking the Symmetry. United States. https://doi.org/10.1021/jp900402y
Niu, Shuqiang, and Ichiye, Toshiko. 2009. "Cleavage of [4Fe-4S]-Type Clusters: Breaking the Symmetry". United States. https://doi.org/10.1021/jp900402y.
@article{osti_1001532,
title = {Cleavage of [4Fe-4S]-Type Clusters: Breaking the Symmetry},
author = {Niu, Shuqiang and Ichiye, Toshiko},
abstractNote = {The cleavage of [4Fes4S]-type clusters is thought to be important in proteins such as FesS scaffold proteins and nitrogenase. However, most [4Fes4S]2+ clusters in proteins have two antiferromagnetically coupled high-spin layers in which a minority spin is delocalized in each layer, thus forming a symmetric Fe2.5+sFe2.5+ pair, and how cleavage occurs between the irons is puzzling because of the shared electron. Previously, we proposed a novel mechanism for the fission of a [4Fes4S] core into two [2Fes2S] cores in which the minority spin localizes on one iron, thus breaking the symmetry and creating a transition state with two Fe3+sFe2+ pairs. Cleavage first through the weak Fe2+sS bonds lowers the activation energy. Here, we propose a test of this mechanism: break the symmetry of the cluster by changing the ligands to promote spin localization, which should enhance reactivity. The cleavage reactions for the homoligand [Fe4S4L4]2- (L ) SCH3, Cl, H) and heteroligand [Fe4S4(SCH3)2L2]2- (L ) Cl, H) clusters in the gas phase were examined via broken-symmetry density functional theory calculations. In the heteroligand clusters, the minority spin localized on the iron coordinated by the weaker electron-donor ligand, and the reaction energy and activation barrier of the cleavage were lowered, which is in accord with our proposed mechanism and consistent with photoelectron spectroscopy and collision-induced dissociation experiments. These studies suggest that proteins requiring facile fission of their [4Fes4S] cluster in their biological function might have spin-localized [4Fes4S] clusters.},
doi = {10.1021/jp900402y},
url = {https://www.osti.gov/biblio/1001532}, journal = {Journal of Physical Chemistry A, 113(19):5710-5717},
issn = {1089-5639},
number = 19,
volume = 113,
place = {United States},
year = {Thu May 14 00:00:00 EDT 2009},
month = {Thu May 14 00:00:00 EDT 2009}
}