pH and Solvent titrations of enkephalins by carbon-13 nuclear magnetic resonance spectroscopy: complete assignments of resonances
- 1 January 1979
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 12,p. 1693-1699
- https://doi.org/10.1039/p29790001693
Abstract
Carbon-13 magnetic resonances of two enkephalins, [Met5]- and [Leu5]-enkephalin, have been assigned in water, dimethyl sulphoxide, and trifluoroethanol, and assignments of [D-Ala2]-enkephalin-amide have been made in water. The assignments of the Gly2 carbon atoms have been made by comparison with [D-Ala2]-enkephalin amide. pD Titrations were followed to assign all the carbon resonances in D2O first, and then the assignments of resonances in other solvents were obtained by solvent–solvent titrations. An unusual titration behaviour of the Tyr1 aromatic γ-atom at a higher pH was found, and this has been suggested to be due to a conformational change in the Tyr1 Cα–Cβ bond. Conformational features of enkephalins in solution are briefly considered in relation to previous studies.Keywords
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