Conformational Mobility of the Pyrrolidine Ring of Proline in Peptides and Peptide Hormones as Manifest in Carbon 13 Spin-Lattice Relaxation Times

Abstract The spin-lattice relaxation times (T1) of carbon 13 in natural abundance were determined for proline, N-acetyl-prolineamide, glycylproline, cyclo(triprolyl), and a series of proline-containing peptide hormones. The data are interpreted in terms of rapid interconversion of proline between various ring-puckered forms. The nature of the puckering depends upon the type of group attached to proline. In proline, the β, γ, and δ carbon atoms are appreciably more mobile than the α carbon atom, suggesting rapid interconversion between a number of ring-puckered forms. In melanocyte-stimulating hormone release-inhibiting hormone (Pro-Leu-Gly-NH2) and its dimethylamido analog, the γ carbon atom has the greatest mobility, suggesting a rapid endo-exo interconversion at this position. In Gly-Pro and in acetyl-Pro-NH2, the cis and trans conformers of proline have very similar T1 values, indicating very little dependence of the dynamic proline ring conformation on the conformation at the peptide bond; in both isomers, the proline ring interconverts rapidly between half-chair conformers puckered at Cβ and Cγ. In thyrotropin-releasing hormone (lGlu-His-Pro-NH2), the proline ring conformation is similar to that in Gly-Pro, and independent of the state of ionization of the histidine residue. Oxytocin [see PDF for equation] , lysine-vasopressin [see PDF for equation] , [Ile5]angiotensin II (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe), and luteinizing hormone-releasing hormone ( lGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) all have proline in the trans conformation about the peptide bond, and the δ carbon atom has a mobility comparable to that of the α carbon atom. The latter reflects severe steric constraints at Cδ due to the neighboring residues. In oxytocin and angiotensin II, the β carbon atom is considerably more mobile than Cα or Cδ. In luteinizing hormonereleasing hormone, the proline ring apparently undergoes rapid interconversion between half-chair forms puckered at Cβ and Cγ, whereas in lysine-vasopressin, the mobility of Cγ is greatest

Intermittent antegrade warm cardioplegia reduces oxidative stress and improves metabolism of the ischemic-reperfused human myocardium

AbstractThe aim of this study was to compare the effect of intermittent antegrade warm blood cardioplegia and intermittent antegrade cold blood cardioplegia on myocardial metabolism and free radical generation of the ischemic-reperfused human myocardium. Thirty patients undergoing mitral valve procedures were randomly allocated to two groups: group 1 (15 patients) received warm blood cardioplegia and group 2 (15 patients), cold blood cardioplegia. Myocardial metabolism was assessed before aortic clamping, 1 minute after crossclamp removal, and after 20 minutes of reperfusion, by collecting blood simultaneously from the radial artery and coronary sinus. All samples were analyzed for lactate, creatine kinase, reduced and oxidized glutathione, ascorbic acid, fluorescent products of lipid peroxidation, and leukocyte activation (elastase). In all patients, early reperfusion was associated with significant coronary sinus lactate release. In group 2, but not in group 1, significant coronary sinus release of reduced and oxidized glutathione, fluorescent products of lipid peroxidation, and creatine kinase was also found; moreover, arterial-coronary sinus difference of ascorbic acid content was increased only in group 2, suggesting a transmyocardial consumption of this antioxidant vitamin. After 20 minutes of reperfusion, coronary sinus lactate release was no longer present in group 1, whereas significant production was still evident in group 2. In this group, significant coronary sinus release of fluorescent products of lipoperoxidation and reduced and oxidized glutathione was also observed at this time. No significant release of elastase from the coronary sinus was noted in the two groups throughout the study. The left ventricular stroke work index measured at the end of the study indicated a better functional recovery in group 1 than in group 2. In conclusion, intermittent antegrade warm blood cardioplegia protects the myocardium from ischemia-reperfusion injury better than intermittent antegrade cold blood cardioplegia; this phenomenon may be partly due to the decreased tissue oxidant burden mediated by intermittent warm blood cardioplegia. (J THORAC CARDIOVASC SURG 1995;109:787-95

Phasing spin-echo-acquired 31P spectroscopic images using complex conjugate data reversal

NRC publication: Ye

Intermittent warm blood cardioplegia: The biochemical background

NRC publication: Ye

CONFORMATIONAL HETEROGENEITY in LINEAR PEPTIDES in SOLUTION - A C-13 NMR-STUDY of [PRO3,PRO5]-ANGIOTENSIN-II

NATL RES COUNCIL CANADA,DIV BIOL SCI,OTTAWA K1A OR6,ONTARIO,CANADAFLORIDA ST UNIV,DEPT CHEM,TALLAHASSEE,FL 32306ESCOLA PAULISTA MED,04023 São Paulo,BRAZILESCOLA PAULISTA MED,04023 São Paulo,BRAZILWeb of Scienc

Three-dimensional 87Rb imaging of isolated pig hearts: Effects of regional ischemia

NRC publication: Ye

Evaluation of cardiac +31P magnetic resonance spectroscopy : Reviewing NMR principles

NRC publication: Ye