Femtosecond two-dimensional infrared (2D IR) spectroscopy is applied to the amide I modes of the terminally protected homo-octapeptide Z-[L-(alpha Me)Val](8)-OtBu in CDCl3, 2,2,2-trifluoroethanol (TFE), and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solutions to acquire 2D spectral signatures that distinguish between 3(10)- and alpha-helix structures. Suppression of diagonal peaks by controlling polarizations of IR pulses clearly reveals cross-peak patterns that are crucial for structural determination. A doublet feature is observed when the peptide ester forms a 3(10)-helix in CDCl3 and TFE and when it is at the initial stage of 3(10)- to alpha-helix transition in HFIP.
Different spectral signatures of octapeptide 3(10) and alpha-helices revealed by two-dimensional infrared spectroscopy
TONIOLO, CLAUDIO;MORETTO, ALESSANDRO;
2006
Abstract
Femtosecond two-dimensional infrared (2D IR) spectroscopy is applied to the amide I modes of the terminally protected homo-octapeptide Z-[L-(alpha Me)Val](8)-OtBu in CDCl3, 2,2,2-trifluoroethanol (TFE), and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solutions to acquire 2D spectral signatures that distinguish between 3(10)- and alpha-helix structures. Suppression of diagonal peaks by controlling polarizations of IR pulses clearly reveals cross-peak patterns that are crucial for structural determination. A doublet feature is observed when the peptide ester forms a 3(10)-helix in CDCl3 and TFE and when it is at the initial stage of 3(10)- to alpha-helix transition in HFIP.Pubblicazioni consigliate
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