Proc. Nat. Acad. Sci. USA

Vol. 72, No. 12, pp. 4948-4952, December 1975 Biophysics

13C-nuclear magnetic resonance study of [85% 13C-enriched proline]thyrotropin releasing factor: 13C-13C vicinal coupling constants and conformation of the proline residue (hypothalamic hormone/13C labeling/pH effects/angular dependence/pyrrolidine ring puckering)

WOLFGANG HAAR*, SERGE FERMANDJIAN*§, JAROSLAV VICARt, KAREL BLAHAf, AND PIERRE FROMAGEOT* * Service de Biochimie, Centre d'Etudes Nucleaires de Saclay, B.P. no. 2, 91190-GIF-sur-Yvette, France; t Institute of Organic Chemistry and Biochemistry, Flemingoro Namesti 2, Prague, Czechoslovakia; and * Institute for Medical Chemistry, Palacky University, Olomouc, Czechoslovakia

Communicated by Irvtine H. Page, September 22, 1975

To understand fully interactions between ABSTRACT peptides and cellular receptors, peptide side chain conformation must be defined. In many cases the complexity of proton nuclear magnetic resonance (NMR) prevents this but the present work demonstrates this problem can be solved by using 13C enrichment. Selective '3C enrichment of a natural peptide hormone has been achieved by preparing [85% '3C enriched prolinelthyrotropin releasing factor which was examined by '3C NMR spectroscopy at various pH values. Because of the '3C enrichment, one-bonded and three-bonded (vicinal) "3C-'3C coupling constants have been determined. The latter vary from 0 to 5 Hz and show bond angle dependence. These data indicate that in this hormone the pyrrolidine ring is not free but fixed in the Cl-endo puckered conformation. It has also been possible to assign chemical shift values for a second order 13C NMR spectrum.

Thyrotropin releasing factor (TRF) is a hypothalamic, tripeptide hormone with sequence

13C-nuclear magnetic resonance study of [85% 13C-enriched proline]thyrotropin releasing factor: 13C-13C vicinal coupling constants and conformation of the proline residue.

Proc. Nat. Acad. Sci. USA Vol. 72, No. 12, pp. 4948-4952, December 1975 Biophysics 13C-nuclear magnetic resonance study of [85% 13C-enriched proline...
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