Optical rotatory dispersion studies of poly-O-acetyl-γ-hydroxy-L-proline forms I and II

✍ Scribed by Gerald D. Fasman

• Publisher: Wiley (John Wiley & Sons)
• Year: 1966
• Tongue: English
• Weight: 524 KB
• Volume: 4
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1966.360040503

✦ Synopsis

Poly-0-acetyl-hydroxy-L-proline, forms I and I1 have been studied by optical rotatory dispersion (ORD) and ultraviolet spectrophotometry in solution and in the solid state.

Cotton effects of opposite sign, but not mirror images, were observed in the 250 mp region for the two forms (Form I, peak 278 mp; crossover, 254 mp; trough, 244 mp: Form 11, trough 270 mp; crossover, 248 mp; peak, 238 mp). Thus, the Cotton effects for a righehanded and left-handed helix have been shown to be opposite for the proline type helices I and 11. The ORD of films of form I was found to have a positive Cotton effect further into the ultraviolet region with peak at 218 mp. Absorption spectra showed a shift of 8 mp in the absorption peak in the 200 mp region for the two forms (form I, 211 mp; form 11, 203 mp). A shoulder was demonstrated in the f i l m absorption spectra in the 250 mp region where the Cotton effects are found. The mixing of the n, P* and P, P* states of the amide chromophore and n, P* state of the ester chromophore was suggested as being responsible for the Cotton effects in the 250 mp region.