Assessing the Utility of Infrared Spectroscopy as a Structural Diagnostic Tool for beta-Sheets in Self-Assembling Aromatic Peptide Amphiphiles

作者：Fleming Scott; Frederix Pim W J M; Sasselli Ivan Ramos; Hunt Neil T; Ulijn Rein V^*; Tuttle Tell

来源：Langmuir, 2013, 29(30): 9510-9515.

DOI：10.1021/la400994v

beta-Sheets are a commonly found structural motif in self-assembling aromatic peptide amphiphiles, and their characteristic %26quot;amide I%26quot; infrared (IR) absorption bands are routinely used to support the formation of supramolecular structure. In this paper, we assess the utility of IR spectroscopy as a structural diagnostic tool for this class of self-assembling systems. Using 9-fluorene-methyloxycarbonyl dialanine (Fmoc-AA) and the analogous 9-fluorene-methylcarbonyl dialanine (Fmc-AA) as examples, we show that the origin of the band around 1680-1695 cm(-1) in Fourier transform infrared (FTIR) spectra, which was previously assigned to an antiparallel beta-sheet conformation, is in fact absorption of the stacked carbamate group in Fmoc-peptides. IR spectra from C-13-labeled samples support our conclusions. In addition, DFT frequency calculations on small stacks of aromatic peptides help to rationalize these results in terms of the individual vibrational modes.

• 出版日期2013-7-30