Nuclear magnetic resonance investigation of lysine–oligopeptides and a complex with d(pA)3pGpC(pT)3
✍ Scribed by Pari Davanloo; Donald M. Crothers
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1979
- Tongue
- English
- Weight
- 772 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
We report proton magnetic resonance studies of a series of lysine oligopeptides in HzO solution. At pH 5 the protonated €-amino groups are seen as broad resonances; the peptide NH proton resonances are split by spin-spin coupling with the Ca-H proton, and appear at positions which depend on position in the chain and on chain length. Assignments were made by the europium shift method, and we observed the expected effect of catalysis by the terminal -NHi of exchange of the adjacent peptide NH. Coupling constants and the temperature coefficient of chemical shift values were consistent with a non-hydrogen-bonded structure for the oligolysines. The rate and mechanism of NH hydrogen exchange were investigated by line-broadening measurements of the peptide protons as a function of pH. Exchange was found to be OH-catalyzed, with large differences in the rate depending on position in the chain. Preliminary studies of the complex between double-helical d(pA)3pGpC(pT)3 and tetra(L-lysine) were performed using 'H-and 31P-nmr techniques. Pmr spectra of the complex at pH values ranging from 3.98 to 8.15 showed very complicated patterns. Downfield shifts and reduction in exchange rates were observed for several tetra(L-lysine) protons. 31P-nmr spectra of the complex reveal an upfield shift of 1 ppm for 3'-5' phosphate diester resonances on complexation. 31P 2 ' 1 relaxation times change little on complex formation at low temperature but are altered a t higher temperature.