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13C- and 1H-nmr studies of cis-trans conformers of oligoprolines

✍ Scribed by Yen-Yau H. Chao; R. Bersohn

Publisher: Wiley (John Wiley & Sons)
Year: 1978
Tongue: English
Weight: 321 KB
Volume: 17
Category: Article
ISSN: 0006-3525
DOI: 10.1002/bip.1978.360171202

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✦ Synopsis

In aqueous solutions, 13C-and 'H-nmr studies show that the percentage of trans conformation of proline oligomers +H*N Pro-(Pro),-CO; increases substantially from n = 1 (65% trans) t o n = 2 (90% trans). The relatively low percentage of trans structure for the dimer ( n = 1) very likely is caused by the extra stability acquired by the end-to-end intramolecular H-bonding of the cis dimer. As n increases from 2 to 3 (or 5) in +HzN-Pro-(Pro),-CO;, the percentage of trans conformation stays more or less constant ( 4 . 9 ) . A high salt concentration (4M CaC12) causes a conformation randomization, so that the short-chain oligomers ( n = 1, 3,s) and the long-chain poly(L-proline) all show about the same fraction of trans conformation (0.7-0.8).

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