A ¹³C spin‐lattice relaxation study of dipeptides containing glycine and proline: Mobility of the cyclic proline side chain

Abstract

Abstract Molecular dynamics of the cyclic dipeptides cyclo (Gly‐ L ‐Pro), cyclo ‐(L‐Pro‐ L ‐Pro), and cyclo (L‐Pro‐D‐Pro) and the linear dipeptides L‐Pro‐Gly and cis and trans Gly‐ L ‐Pro were studied in neutral aqueous solution by 13 C nuclear magnetic resonance. Spinlattice relaxation times ( T 1 ) were determined for each individual carbon atom. The correlation times, τ, were derived from a semiquantitative analysis of the T 1 data. The correlation times of the proline ring carbons, β, γ, and δ suggest that the cyclic dipeptides have more restriction of conformational freedom in the proline ring than the linear dipeptides. This effect is most pronounced on the γ carbon.