DFT analysis of co-alkyl and co-adenosyl vibrational modes in B12-cofactors.

Pawel M Kozlowski, Tadeusz Andruniow, Andrzej A Jarzecki, Marek Z Zgierski, Thomas G Spiro

Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, USA. pawel@louisville.edu

Inorganic chemistry 2006 Jul 10

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Density functional theory (DFT)-based normal mode calculations have been carried out on models for B12-cofactors to assign reported isotope-edited resonance Raman spectra, which isolate vibrations of the organo-Co group. Interpretation is straightforward for alkyl-Co derivatives, which display prominent Co-C stretching vibrational bands. DFT correctly reproduces Co-C distances and frequencies for the methyl and ethyl derivatives. However, spectra are complex for adenosyl derivatives, due to mixing of Co-C stretching with a ribose deformation coordinate and to activation of modes involving Co-C-C bending and Co-adenosyl torsion. Despite this complexity, the computed spectra provide a satisfactory re-assignment of the experimental data. Reported trends in adenosyl-cobalamin spectra upon binding to the methylmalonyl CoA mutase enzyme, as well as on subsequent binding of substrates and inhibitors, provide support for an activation mechanism involving substrate-induced deformation of the adenosyl ligand.

Citation

Pawel M Kozlowski, Tadeusz Andruniow, Andrzej A Jarzecki, Marek Z Zgierski, Thomas G Spiro. DFT analysis of co-alkyl and co-adenosyl vibrational modes in B12-cofactors. Inorganic chemistry. 2006 Jul 10;45(14):5585-90