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Determination of the Relationship between the Geometric Structure of a Model Peptide and Its 13C Isotope-Edited FTIR Spectroscopy by ATR in H2O

(Middle Tennessee State University, 2015-02-15) Alharbi, Olaa Eid ; Wang, Chengshan ; Wang, Chengshan ; Ding, Keying ; Kong, Jing ; Chemistry

Determination of protein structures (such as α-helix, β-sheet, unstructured conformation, and so on) is important to correlate the function of a protein with its structure.1 X-ray crystallography is a powerful technique but it requires proteins to form single crystal structure. However, lots of proteins do not meet this requirement. NMR can determine the structure of peptides/proteins in aqueous environment but the measurement is time-consuming. Thus, determination of the structure of proteins/peptides with short life-time (such as one hour) in aqueous solution is challenging for NMR. Recently, IR spectroscopy has been reported to be able to address the geometric structure of peptide with 13C isotopic labels in deuterated water (D2O) in residue level.2 Although similar to regular water, D2O is not physiologically approved.3 On the other hand, H2O has intensive absorption around 1620 cm-1 (this will cover the IR absorption of proteins/peptides) in IR spectroscopy. Thus, traditional transmission measurement of IR spectra of proteins/peptides in H2O will fail, because the thickness of normal liquid FTIR cell is in millimeter level.