First-Principle Calculations for the Active Centers in Vanadium-Containing Chloroperoxidase and its Functional Models:Geometrical and Spectral Properties

摘要

Vanadium-containing haloperoxidases (VXPOs) constitute a group of relatively newly discovered metalloenzymes catalyzing oxidation of halogen anions to hypohalous acids by hydrogen peroxide.The structures of their native and peroxide-bound forms as well as a reliable functional model system were characterized by X-ray diffraction crystallography methods.In this work,we focus on two well-characterized model systems and the active site itself of vanadium-containing chloroperoxidase from Curvularia inaequalis (VCPO).For the two model systems,we performed geometry optimization and frequency calculations at the B3LYP/LanL2DZ level of theory.In addition,the vertical energies and oscillator strengths for a few lowest electronic transitions were computed with TDDFT.The solvent effect on electronic transitions was modeled either by means of a few explicit water molecules hydrogen-bonded to studied complexes or by point charges representing them.As the active sites of VXPOs have to be modeled with additional charged groups of amino acids neutralizing the negative vanadium core,we restricted our calculations to DFT optimization and TDDFT calculations for excited states.In this paper,the results of these computations,namely,selected bond lengths and angles,vibrational frequencies,electronic transition energies,and oscillator strengths,are presented and compared with relevant literature data.This comparison,we believe,gives credits to the methodology and models used,which is also of importance for mechanistic considerations.