N.M.R. studies on myelin basic protein. IV. ¹³C N.M.R. of the peptide encephalitogenic in the guinea pig

Abstract

The encephalitogenic nonapeptide Phe¹-Ser²-Trp³-Gly⁴-Ala⁵-Glu⁶-Gly⁷-Gln⁸- Lys⁹ and its [D-Ala⁵] analogue have been studied in aqueous solution by ¹³C n.m.r. spectroscopy. The resonances of all the carbons have been assigned and their pH profiles measured. The expected conformational differences are indicated by only subtle differences in long-range pH titration shifts. The spin-lattice relaxation times T₁ of all the protonated carbons of the [L-Ala⁵] nonapeptide have been measured at 25°C. Analysis of these data in terms of effective correlation times for side-chain mobilities suggests restricted motions for the side chains of Glu⁶ and Gln⁸ and the aromatic rings of Phe¹ and Trp³.