title: The stability of Cα peptide radicals: why glycyl radical enzymes?
abstract: The conformational space of dipeptide models derived from glycine, alanine, phenylalanine, proline, tyrosine, and cysteine has been searched extensively and compared with the corresponding C(α) dipeptide radicals at the G3(MP2)-RAD level of theory. The results indicate that the (least-substituted) glycine dipeptide radical is the thermochemically most stable of these species. Analysis of the structural parameters indicates that this is due to repulsive interactions between the C(α) substituents and peptide units in the radical. A comparison of the conformational preferences of dipeptide radicals and their closed-shell parents also indicates that radical stability is a strongly conformation-dependent property.
authors.affiliation: Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377 München, Germany.
authors.forename: Johnny
authors.initials: J
authors.lastname: Hioe
authors.forename: Gökcen
authors.initials: G
authors.lastname: Savasci
authors.forename: Harald
authors.initials: H
authors.lastname: Brand
authors.forename: Hendrik
authors.initials: H
authors.lastname: Zipse
mesh_terms: D004151:Dipeptides / Q000737:chemistry*; D004798:Enzymes / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D004151:Dipeptides; D004798:Enzymes; D005609:Free Radicals; D010455:Peptides; D005998:Glycine