Proton magnetic resonance and optical spectroscopic studies of water-soluble polypeptides: Poly-L-lysine HBr, poly(L-glutamic acid), and copoly(L-glutamic acid42, L-lysine HBr28, L-alanine30)
✍ Scribed by E. M. Bradbury; C. Crane-Robinson; H. Goldman; H. W. E. Rattle
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1968
- Tongue
- English
- Weight
- 638 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The helix-coil transition has been studied by high-resolution NMR for three watersoluble polypeptides. Such systems are better models for protein behavior than those in TFA-CDC13 solvent. An upfield shift of ~7 cps is observed for the a-CH peak of poly(bg1utamic acid) and poly-clysine as the helix content increases over the transition. No such shift is found for copoly(L-glutamic acid42, L-lysine28, balanineao). The width of the a-CH peak for poly L-lysine increases rapidly as helix content rises but for poly L-glutamic acid and the copolymer, tlie width of this peak remains unchanged up to 60% helicity. This demonstrates a rapid rate of interconversion between helical and random conformations in partly helical polymer for the latter two polypeptides.
All three polymers however, show no apparent a-CH peak a t 100vo helicity. Sidechain resonance lines also broaden as helix content increases and, to a greater extent, the closer the proton is to the main chain.