Although X-ray crystallography can determine the structure of peptides/proteins in atomic level, lots of proteins do not form single crystal structure. NMR is another powerful technique for structural biology. However, the measurement of NMR spectra of peptides/proteins is usually long, making it difficult for NMR to determine the structure of transition state of peptides/proteins with short life-time. Recently, 13C isotope edited ATR-FTIR spectroscopy has been shown to be able to determine peptides/proteins structure in residue level in D2O with quick performance. Since peptides/proteins reside in H2O (not D2O), application of 13C isotope edited FTIR spectroscopy in H2O will be interesting. The major challenge of the measurement of FTIR spectra of peptides/proteins in H2O is the strong background absorption of H2O around 1610 cm-1, which will cover the amide I band of peptides/proteins. In this paper, a model a-helical peptide YAAK(AAAAAK)2AAH (referred as Pep17 in the following) was synthesized and 13C isotopic labels were introduced into Pep17 at different positions. Attenuated total reflection (ATR) technique was used to avoid the H2O background absorption and detect the FTIR spectra of Pep17. The 13C amide I band was successfully detected at 1602 cm-1, which can be used as a finger-print peak to determine the conformation of specific residues. For example, residues 6, 7, 11, 12, 15, and 16 were found to be in helix. However, residues 2 and 3 were in unstructured conformation. Thus, the conformation of specific residues has been determined in H2O

Determination of the conformation of specific residues in model a-helix peptide by <sup>13</sup>C labeled carbonyls

248th National Meeting (2014)

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Determination of the conformation of specific residues in model a-helix peptide by 13C labeled carbonyls

Determination of the conformation of specific residues in model a-helix peptide by ¹³C labeled carbonyls