Photoswitchable elements within a peptide backbone-ultrafast spectroscopy of thioxylated amides.
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.
Satzger
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BioMolekulare Optik, Department für Physik, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, D-80538 München, Germany.
Root
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C
Gilch
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Zinth
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Wildemann
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D
Fischer
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G
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
D000577:Amides; C492098:N-methylthioacetamide; D010455:Peptides; D013438:Sulfhydryl Compounds; D013853:Thioacetamide