Optical Spectra of Cu(II)−Azurin by Hybrid TDDFT-Molecular Dynamics Simulations

The ground state electronic structure of oxidized azurin from Pseudomonas aeruginosa and its optical response have been investigated by combining hybrid quantum mechanics/molecular mechanics simulations with time-dependent density functional theory. In agreement with experiment, we find that the unp...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2007-08, Vol.111 (34), p.10248-10252
Main Authors: Cascella, Michele, Cuendet, Michel A, Tavernelli, Ivano, Rothlisberger, Ursula
Format: Article
Language:English
Subjects:
Azurin - chemistry
Binding Sites
Copper - chemistry
Electrons
Hot Temperature
Optics and Photonics
Oxidation-Reduction
Protein Structure, Secondary
Pseudomonas aeruginosa - metabolism
Quantum Theory
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Summary:The ground state electronic structure of oxidized azurin from Pseudomonas aeruginosa and its optical response have been investigated by combining hybrid quantum mechanics/molecular mechanics simulations with time-dependent density functional theory. In agreement with experiment, we find that the unpaired electron spin density is mainly localized on the copper ion. The vertical absorption spectrum in the visible range is well reproduced, with the central band centered around 2.1 eV. The anisotropic dipolar field due to the extended α-helix polarizes the metal binding site and is responsible for a shift of the absorption bands by ±0.1−0.2 eV. At 300 K, the bond distances of the copper binding site undergo large fluctuations (∼0.3 Å). It is crucial to take these thermal fluctuations into account for a faithful description of the optical properties.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp071938i