The circular dichroism spectrum of poly‐ L ‐acetoxyproline

We report the circular dichroism (CD) spectrum of poly‐ L acetoxyproline in trifluoroethanol, a solvent in which the form I to form II conformational isomerization occurs slowly enough to permit observation of the spectral changes. A comparison is made to poly‐ L proline. As judged by the similarity of the CD spectra, the conformations of the corresponding forms of the two polymers must be nearly the same. Transition assignments are proposed; these are shown to agree with the theoretical calculations of Pysh. There is a serious unexplained discrepancy between our solution data and those of Fasman for poly‐ L acetoxyproline.