THE FAR ULTRAVIOLETABSORPTIONSPECTRAOF POLYPEPTIDE AND PROTEINSOLUTIONSAND THEIRDEPENDENCE ON CONFORMATION

Summary.-The absorption spectra of polypeptides and proteins in aqueoussolution in the region 185-240 muhave been investigated, andthe various factors contributingtothis absorption havebeen analyzed. In polypeptides inthea-helicalform,a largehypochromic effect is observed, aswellasanewfeatureintheformof a shoulder at205 mu., whichis not present inthespectrumof therandomcoil confor- mation. The absorption spectrum associated with the 3-form has also been re- corded andis shownto differ fromeachof the othertwo. The hypochromic effectis also observed in proteins, and by applying a correction for the absorption of chromophoric side chains, it is possible to arrive at a value for the helical contentof the protein, which agrees moderately well with data derived from optical rota- tory dispersion measurements. We have greatly benefited from discussion with W. B. Gratzer andM.Kashathroughout thecourse of this investigation. Thiswork was supportedby the Office of Naval Research (N5 ori- 07654.)