title: Proton magnetic resonance studies of angiotensin II conformation: cis-trans isomerism in sarcosine7-containing analogs.
abstract: 1H-NMR spectra for the angiotensin agonist sarcosine-(Sar)Arg-Val-Tyr-Ile-His-Sar-Phe [( Sar1,Sar7]Ang II) and the antagonist Sar-Arg-Val-Tyr-Ile-His-Sar-Ile in dimethylsulfoxide-d6 were examined at 400 MHz. Splitting of the resonances for Tyr, His, and Sar protons revealed that the His6-Sar7 peptide bond existed in both cis and trans forms, with one isomer predominating in the ratio 5:1 in both peptides. Comparison of the chemical shifts for the His6 and Phe8 ring protons in these peptides suggested a His/Phe stacking interaction in [Sar1,Sar7]Ang II which is important for agonist activity.
mesh_terms: D015059:1-Sarcosine-8-Isoleucine Angiotensin II / Q000031:analogs & derivatives*; D000804:Angiotensin II / Q000031:analogs & derivatives*; D006639:Histidine; D009682:Magnetic Resonance Spectroscopy; D010649:Phenylalanine; D011487:Protein Conformation; D013237:Stereoisomerism
chemical_list: D000804:Angiotensin II; D010649:Phenylalanine; D006639:Histidine; C049572:angiotensin II, 1-Sar-7-Sar-8-Ile-; C049573:angiotensin II, Sar(1,7)-; D015059:1-Sarcosine-8-Isoleucine Angiotensin II