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Multireference Ab Initio Calculations of g tensors for Trinuclear Copper Clusters in Multicopper Oxidases.

Vancoillie, Steven; Chalupský, Jakub; Ryde, Ulf LU ; Solomon, Edward I; Pierloot, Kristine; Neese, Frank and Rulíšek, Lubomír (2010) In The Journal of Physical Chemistry Part B 114(22). p.7692-7702
Abstract
EPR spectroscopy has proven to be an indispensable tool in elucidating the structure of metal sites in proteins. In recent years, experimental EPR data have been complemented by theoretical calculations, which have become a standard tool of many quantum chemical packages. However, there have only been a few attempts to calculate EPR g tensors for exchange-coupled systems with more than two spins. In this work, we present a quantum chemical study of structural, electronic, and magnetic properties of intermediates in the reaction cycle of multicopper oxidases and of their inorganic models. All these systems contain three copper(II) ions bridged by hydroxide or O(2-) anions and their ground states are antiferromagnetically coupled doublets.... (More)
EPR spectroscopy has proven to be an indispensable tool in elucidating the structure of metal sites in proteins. In recent years, experimental EPR data have been complemented by theoretical calculations, which have become a standard tool of many quantum chemical packages. However, there have only been a few attempts to calculate EPR g tensors for exchange-coupled systems with more than two spins. In this work, we present a quantum chemical study of structural, electronic, and magnetic properties of intermediates in the reaction cycle of multicopper oxidases and of their inorganic models. All these systems contain three copper(II) ions bridged by hydroxide or O(2-) anions and their ground states are antiferromagnetically coupled doublets. We demonstrate that only multireference methods, such as CASSCF/CASPT2 or MRCI can yield qualitatively correct results (compared to the experimental values) and consider the accuracy of the calculated EPR g tensors as the current benchmark of quantum chemical methods. By decomposing the calculated g tensors into terms arising from interactions of the ground state with the various excited states, the origin of the zero-field splitting is explained. The results of the study demonstrate that a truly quantitative prediction of the g tensors of exchange-coupled systems is a great challenge to contemporary theory. The predictions strongly depend on small energy differences that are difficult to predict with sufficient accuracy by any quantum chemical method that is applicable to systems of the size of our target systems. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part B
volume
114
issue
22
pages
7692 - 7702
publisher
The American Chemical Society
external identifiers
  • wos:000278301000033
  • pmid:20469875
  • scopus:77953154132
ISSN
1520-5207
DOI
10.1021/jp103098r
language
English
LU publication?
yes
id
0b48b76d-f9e8-41df-8534-7a59e24add9f (old id 1610251)
date added to LUP
2010-06-10 16:24:53
date last changed
2018-05-29 11:11:41
@article{0b48b76d-f9e8-41df-8534-7a59e24add9f,
  abstract     = {EPR spectroscopy has proven to be an indispensable tool in elucidating the structure of metal sites in proteins. In recent years, experimental EPR data have been complemented by theoretical calculations, which have become a standard tool of many quantum chemical packages. However, there have only been a few attempts to calculate EPR g tensors for exchange-coupled systems with more than two spins. In this work, we present a quantum chemical study of structural, electronic, and magnetic properties of intermediates in the reaction cycle of multicopper oxidases and of their inorganic models. All these systems contain three copper(II) ions bridged by hydroxide or O(2-) anions and their ground states are antiferromagnetically coupled doublets. We demonstrate that only multireference methods, such as CASSCF/CASPT2 or MRCI can yield qualitatively correct results (compared to the experimental values) and consider the accuracy of the calculated EPR g tensors as the current benchmark of quantum chemical methods. By decomposing the calculated g tensors into terms arising from interactions of the ground state with the various excited states, the origin of the zero-field splitting is explained. The results of the study demonstrate that a truly quantitative prediction of the g tensors of exchange-coupled systems is a great challenge to contemporary theory. The predictions strongly depend on small energy differences that are difficult to predict with sufficient accuracy by any quantum chemical method that is applicable to systems of the size of our target systems.},
  author       = {Vancoillie, Steven and Chalupský, Jakub and Ryde, Ulf and Solomon, Edward I and Pierloot, Kristine and Neese, Frank and Rulíšek, Lubomír},
  issn         = {1520-5207},
  language     = {eng},
  number       = {22},
  pages        = {7692--7702},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part B},
  title        = {Multireference Ab Initio Calculations of g tensors for Trinuclear Copper Clusters in Multicopper Oxidases.},
  url          = {http://dx.doi.org/10.1021/jp103098r},
  volume       = {114},
  year         = {2010},
}