title: Photoswitchable elements within a peptide backbone-ultrafast spectroscopy of thioxylated amides.
abstract: A series of thioxo compounds, thioacetamide, N-methylthioacetamide, a cyclic thioxoamide [(S)-5-thioxopyrrolidine-2-carboxylic acid ethyl ester], two thioxylated dipeptides (Ala-Psi[CS-NH]-Ala and Phe-Psi[CS-NH]-Ala) and a thioxylated dodecapeptide (Lys-Glu-Thr-Ala-Ala-Ala-Lys-Phe-Glu-Arg-Gln-His-Psi[CS-NH]-Nle-Asp-Ser-Ser-Thr-Ser-Ala-Ala, or [thioxo-His(12)]-S-peptide; Nle = norleucine) are investigated by ultrafast spectroscopy in the visible and near UV. The different molecules show very similar absorption dynamics featuring a rise of a strong visible absorption band on the subpicosecond and picosecond time scale. The decay of the visible absorption occurs within 150-600 ps. The observations are interpreted by the ultrafast formation of triplet states and their decay on the subnanosecond time scale. Comparison with published IR experiments on N-methylthioacetamide indicates that the cis-trans isomerization around the thioxopeptide bond is terminated within less than 1 ns.
authors.affiliation: BioMolekulare Optik, Department für Physik, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, D-80538 München, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Satzger
authors.forename: C
authors.initials: C
authors.lastname: Root
authors.forename: P
authors.initials: P
authors.lastname: Gilch
authors.forename: W
authors.initials: W
authors.lastname: Zinth
authors.forename: D
authors.initials: D
authors.lastname: Wildemann
authors.forename: G
authors.initials: G
authors.lastname: Fischer
mesh_terms: D000577:Amides / Q000737:chemistry*; D003627:Data Interpretation, Statistical; D010455:Peptides / Q000737:chemistry*; D010777:Photochemistry; D013056:Spectrophotometry, Ultraviolet; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013853:Thioacetamide / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D000577:Amides; C492098:N-methylthioacetamide; D010455:Peptides; D013438:Sulfhydryl Compounds; D013853:Thioacetamide