Circular dichroism and Fourier-transform infrared spectroscopic studies on T-cell epitopic peptide fragments of influenza virus hemagglutinin.

Epitopic peptides representing the C-terminal (HA1) region of cleaved hemagglutinin of influenza virus from different serotypes were synthesized. Circular dichroism and Fourier-transform infrared spectroscopic data showed that peptides HS2 and HS3 have a predominantly alpha-helical conformation in trifluoroethanol. Recently a component band appearing between 1640 and 1635 cm-1 in the amide I region of the Fourier-transform infrared spectra of polypeptides has been correlated with strongly H-bonded beta-turns (Ref. 8). Using this assignment, HS1 was found to contain less alpha-helix but have tendency to adopt beta-turn(s). Interestingly, fragment HS2 with the highest alpha-helix content proved to be the poorest T-cell epitope among serotypes HS1-HS3.