VACUUM ULTRAVIOLET CIRCULAR-DICHROISM SPECTRUM OF BETA-TURN IN SOLUTION

The vacuum ultraviolet circular dichroism spectrum of an isolated 4 → 1 hydrogen bonded β-turn is reported. The observed spectrum of N-acetyl-Pro-Gly-Leu-OH at - 40°C in trifluoroethanol is in good agreement with the theoretically calculated CD spectrum of the β-turn conformation. This spectrum, particularly the presence of a strong negative band around 180 nm and a large ratio [θ]201 [θ]225, can be taken as a characteristic feature of the isolated β-turn conformation. These CD spectral features can thus be used to distinguish the β-turn conformation from the β-structure in solution. © 1979.