Study on the turn structure of polypeptides containing glycine and L-proline

Abstract

The formation of turn structure in peptide chains has direct relations with intramolecular hydrogen bonds, therefore the existence of this bond can be tested to research the turn structure. Herein, two tripeptides and three tetrapeptides are synthesized by using glycine and L-proline as raw materials, t-butoxycarbonyl and aniline as capping groups, and HBTU and HATU as condensation reagents. 1H NMR, IR and MS are adopted to characterize the structure of the products. Constant-gradient and variable-temperature 1H NMR spectra test is used to detect the intramolecular hydrogen bond of the synthesized polypeptides, and 1H-1H NOE is used for the speculation of the carbonyl group location of intramolecular hydrogen bond. The test illustrates that intramolecular hydrogen bond is found in three out of the five synthesized polypeptides, and it is not found in the other two. The polypeptides with intramolecular hydrogen bond formed all have the "-Gly-L-Pro-Gly-" segment, while the polypeptides with only "-L-Pro-Gly-" segment or "-Gly-L-Pro-" segment do not have intramolecular hydrogen bond formed. The carbonyl group forming of intramolecular hydrogen bond is attached to the amino group of the capping aniline, and amino group involved in hydrogen bond formation is linked to t-butoxycarbonyl.

Keywords

• bioorganic chemistry
• turn structure
• intramolecular hydrogen bond
• nuclear magnetic resonance spectroscopy
• -Gly-L-Pro-Gly- segment
• polypeptide