title: DFT analysis of co-alkyl and co-adenosyl vibrational modes in B12-cofactors.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, USA. pawel@louisville.edu
authors.forename: Pawel M
authors.initials: PM
authors.lastname: Kozlowski
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Andruniow
authors.forename: Andrzej A
authors.initials: AA
authors.lastname: Jarzecki
authors.forename: Marek Z
authors.initials: MZ
authors.lastname: Zgierski
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Spiro
mesh_terms: D003038:Cobamides / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D008765:Methylmalonyl-CoA Mutase / Q000737:chemistry* / Q000378:metabolism; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman
chemical_list: D003038:Cobamides; D008765:Methylmalonyl-CoA Mutase; C000913:cobamamide