Fig 5.

Calculated coupled-oscillator LD for the peptide π→π* transition of gramicidin in different possible conformations: α-helix (solid line; α), a parallel intertwined double β-helix (long dash; β DH), and a HD of β-helices (short dash; β HD). (Inset) The calculated absorption for the same structures. The π→π* transition moment was taken to be directed along a line connecting the middle of the carbonyl bond and the nitrogen of the amide group (16). An alternative polarization with the transition moment directed between the carbonyl carbon and the nitrogen (17) gave a similar result. The values for the LD and absorption are relative, with the maximal absorbance set to 1.