Abstract:
Determination of protein structures has attracted extensive scientific attention. IR spectroscopy using traditional liquid cells has been reported to address the structure in a model peptide of sequence Ac-YAAKAAAKAAAAKAAH-NH<sub>2</sub> (pep17) with <super>13</super>C isotopic labels in deuterated water (D<sub>2</sub>O). Although similar to regular water, D<sub>2</sub>O is not physiologically equivalent to H<sub>2</sub>O in the aqueous matrix of cells and tissues. Therefore, peptide studies in D<sub>2</sub>O may not yield true peptide conformations. Here, <super>13</super>C isotope-edited FTIR was applied on pep17 in H<sub>2</sub>O using the Attenuated Total Reflection (ATR) technique. The peak of <super>13</super> C labeled residues in α-helix appears at 1602 cm<super>-1</super>, which can be used as a fingerprint peak of α-helix for the <super>13</super>C labeled residue. By the presence or absence of peak at 1602 cm<super>-1</super>, conformation of specific residues in the peptide was determined. For the first time, the elucidation of the secondary structure of the pep17 has been demonstrated in H<sub>2</sub>O.
