The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Jeanphilippe Demaret - One of the best experts on this subject based on the ideXlab platform.
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structure determination of a Tetradecapeptide mimicking the rxvrg consensus sequence recognized by a xenopus laevis skin endoprotease an approach based on simulated annealing and 1 h nmr
Journal of Computer-aided Molecular Design, 1995Co-Authors: Francoisregis Chalaoux, Daniel Baron, Sonja Meddeb, Jeanpierre Ballini, P Vigny, Jeanphilippe DemaretAbstract:The Tetradecapeptide of sequence H-Asp-Val-Asp-Glu-Arg 5-Asp-Val-Arg-Gly9-Phe-Ala-Ser-Phe-Leu-NH2 is recognized by a putative maturation endoprotease of the Xenopus laevis skin, which cleaves between Arg8 and Gly9. A conformational search has been performed on this peptide by simulated annealing calculations. Two different models in agreement with the NMR data were found. The conformational difference between the two types of model is located in the consensus sequence, i.e., from Arg5 to Gly9.
Berta Ponsati - One of the best experts on this subject based on the ideXlab platform.
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a Tetradecapeptide somatostatin dicarba analog synthesis structural impact and biological activity
Bioorganic & Medicinal Chemistry Letters, 2014Co-Authors: Pablo Martingago, Rosario Ramon, Eric Aragon, Jimena Fernandezcarneado, Pau Martinmalpartida, Xavier Verdaguer, Pilar Lopezruiz, B Colas, Maria Alicia Cortes, Berta PonsatiAbstract:We described here the first Tetradecapeptide somatostatin-analogue where the disulfide bridge has been replaced by a carbon-carbon double bond. This analogue was prepared using microwave assisted ring closing metathesis (RCM) using the 2nd generation Grubbs as catalyst. Under our optimized conditions the cyclization between allylGly 3 and 14 proceeded in moderate yield, excellent cyclic/linear ratio and very high Z-double bond selectivity. NMR studies also demonstrated that the conformational flexibility of this peptide is increased in comparison to that of the natural hormone. Remarkably, this alkene-bridged somatostatin analog is highly selective against somatostatin receptors 1 and 5, suggesting that conformational rigidity is not required for the efficient interaction of somatostatin analogues with these two receptors.
Daniel Baron - One of the best experts on this subject based on the ideXlab platform.
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nmr conformational study of a model Tetradecapeptide mimicking the rxvrg consensus cleavage site of a xenopus luevis skin endoprotease
International Journal of Peptide and Protein Research, 2009Co-Authors: Francoisregis Chalaoux, Jacques Riand, Annemarie Leseney, Daniel BaronAbstract:A model Tetradecapeptide, used for the purification of the RXVRG-endoprotease from Xenopus laevis skin exudate, has been studied by two-dimensional NMR, correlation (COSY) and NOE (NOESY) spectroscopy. This peptide has the 5-9 consensus sequence (RXVRG), along with an acidic moiety (1-4) and a hydrophobic domain (10-14). Variations with temperature of NH chemical shifts in a dimethyl sulfoxide solution (low thermal coefficients at residues 6, 7 and 8) and quantified NOE values from four spectra at different mixing times clearly showed a structural organization in the consensus domain with psi-angles around [-40, -10 degrees] for residues 7 and 8, and two NOE correlations of alpha HiNHi + 2 type (5-7 and 6-8). Moreover, a privileged rotamer in the side chain is established for three residues (Val2, Asp3 and Val7) and limited possibilities are discussed for seven others. Most of the folding trends were not observed in the [Ser7] derivative, underlying the relationship between the conformations and a full consensus sequence. In the model Tetradecapeptide an equilibrium between two beta-turns of type I, fragments 4-7 and 5-8, seems the most probable. Comparison between this Tetradecapeptide and its 4-14 fragment, also a substrate for RXVRG-endoprotease, shows that the 1-3 moiety (DVD) influences the consensus domain structure(s) and clearly stabilizes the folded one(s). Finally, two analytical methods are developed in order to determine: (1) the trifluoroacetic acid content of the peptide samples, on the basis of 19F NMR spectroscopy; (2) the mean phi- and psi-angles of each residue, from the whole set of NH/alpha H coupling constants (3JN alpha) and NOE data at a local level.
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two dimensional 1h nmr study of a Tetradecapeptide with the consensus sequence arg5 asp val arg gly9 structural effects of the outside substitution ser12 by ala12
Journal of Biomolecular Structure & Dynamics, 1995Co-Authors: Jacques Riand, Francoisregis Chalaoux, Annemarie Leseney, Daniel BaronAbstract:Conformation of a Tetradecapeptide with a RXVRG consensus sequence, Arg5-Asp-Val-Arg-Gly9, found in several precursors of antibacterian peptides, was investigated in dimethylsulfoxide solution by proton NMR spectroscopy. Complete resonance assignments and conformational parameters were obtained through correlated (COSY) and nuclear Overhauser (NOESY) techniques. The 3J(alpha H, beta H) coupling constants and the intramolecular NOE, NH...beta H, were used to analyse the conformers around the C alpha-C beta bond and, in four cases, to obtain stereospecific assignments. Use of restraints derived from NOE connectivities and 3J(NH, alpha H) coupling constants allows the determination of a range of phi and psi dihedral angles for all the residues in the sequence. The present NMR results provide favourable evidence for the formation of two bends in the consensus sequence of the Tetradecapeptide. The first one has most of the features of a Glu4-Val7 beta-turn (low temperature coefficient of the Val7NH chemical shift, Arg5 alpha H...Val7NH and Asp6NH...Val7NH NOE correlations). The second one exhibits only the Asp6 alpha H...Arg7NH and Val7NH...Arg8NH NOE interactions. These consensus sequence organizations proposed were confirmed by molecular modeling based on low potential energy structure on the [4-9] fragment with high agreement of NOE data. Overall, the substitution of Ser12 by Ala12 shifts the conformation of the hydrophobic moiety [10-14] towards a quite random coil structure in this fragment and strongly destabilizes the folded structures of the consensus domain where only one NH (Val7) is solvent-shielded opposed to three (Asp6 to Arg8) in the [Ser12] Tetradecapeptide. These conformational changes could be related to the processing enzyme activities on these model oligopeptides.
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structure determination of a Tetradecapeptide mimicking the rxvrg consensus sequence recognized by a xenopus laevis skin endoprotease an approach based on simulated annealing and 1 h nmr
Journal of Computer-aided Molecular Design, 1995Co-Authors: Francoisregis Chalaoux, Daniel Baron, Sonja Meddeb, Jeanpierre Ballini, P Vigny, Jeanphilippe DemaretAbstract:The Tetradecapeptide of sequence H-Asp-Val-Asp-Glu-Arg 5-Asp-Val-Arg-Gly9-Phe-Ala-Ser-Phe-Leu-NH2 is recognized by a putative maturation endoprotease of the Xenopus laevis skin, which cleaves between Arg8 and Gly9. A conformational search has been performed on this peptide by simulated annealing calculations. Two different models in agreement with the NMR data were found. The conformational difference between the two types of model is located in the consensus sequence, i.e., from Arg5 to Gly9.
Carolyn J. Cassady - One of the best experts on this subject based on the ideXlab platform.
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negative ion matrix assisted laser desorption ionization time of flight post source decay calibration by using fibrinopeptide b
Journal of the American Society for Mass Spectrometry, 1998Co-Authors: Jaran Jainhuknan, Carolyn J. CassadyAbstract:Fibrinopeptide B (Mr 1552.58) was employed as a calibration compound for matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) post-source decay (PSD) fragment ion analysis in the negative mode. Experiments were performed by using both continuous and delayed extraction, with the maximum reflectron voltages being 30 and 21 kV, respectively. For comparison, a common positive ion PSD calibrant, ACTH(18–39) (Mr 2466.7), was also employed with positive ion calibration constants being applied to negative ion spectra. Using fibrinopeptide B as the calibrant, the negative ion PSD results for angiotensin II (Mr 1046.2), renin substrate Tetradecapeptide (horse) (Mr 1759.0), and the custom-synthesized peptide (K2G4)2 (Mr 987.1) showed a factor of 1.5–2 improvement in absolute mass accuracy. Typical absolute mass-to-charge ratio accuracies were within ±1 Thomson and were achieved even when the peptide being analyzed was more massive than fibrinopeptide B. In addition, both calibrants showed increased accuracy when experiments were conducted in the delayed extraction mode. Other advantages of using fibrinopeptide B are its moderate cost and the ability to perform calibration and sample analysis for negative ion PSD under the same instrumental conditions.
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anion and cation post source decay time of flight mass spectrometry of small peptides substance p angiotensin ii and renin substrate
Rapid Communications in Mass Spectrometry, 1996Co-Authors: Jaran Jainhuknan, Carolyn J. CassadyAbstract:Substance P, angiotensin II and renin substrate Tetradecapeptide were used to compare post-source decay (PSD) fragmentation of positive and negative peptide ions in a reflectron time-of-flight mass spectrometer. The peptides readily produced both [M+H]+ and [M−H]− ions by matrix-assisted laser desorption/ionization (MALDI). Dissociation of the protonated molecules yielded primarily a+n and b+n fragment ions and low-mass ions characteristic of individual amino acid residues. In contrast, the distinguishing feature of the anion spectra is a complete, or almost complete, series of y+n ions. In addition, b−n, c−n, x−n, and [yn18]− fragment ions are found in the anion spectra. Anion formation from substance P is particularly interesting, because this peptide contains no acidic carboxyl groups to act as a charge site. In general, peptide cations produced predominantly fragment ions from the N-terminus, while anion dissociation gave primarily C-terminal fragment ions. The results suggest that cation and anion PSD yield complementary information on peptide primary structures.
Sonja Meddeb - One of the best experts on this subject based on the ideXlab platform.
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structure determination of a Tetradecapeptide mimicking the rxvrg consensus sequence recognized by a xenopus laevis skin endoprotease an approach based on simulated annealing and 1 h nmr
Journal of Computer-aided Molecular Design, 1995Co-Authors: Francoisregis Chalaoux, Daniel Baron, Sonja Meddeb, Jeanpierre Ballini, P Vigny, Jeanphilippe DemaretAbstract:The Tetradecapeptide of sequence H-Asp-Val-Asp-Glu-Arg 5-Asp-Val-Arg-Gly9-Phe-Ala-Ser-Phe-Leu-NH2 is recognized by a putative maturation endoprotease of the Xenopus laevis skin, which cleaves between Arg8 and Gly9. A conformational search has been performed on this peptide by simulated annealing calculations. Two different models in agreement with the NMR data were found. The conformational difference between the two types of model is located in the consensus sequence, i.e., from Arg5 to Gly9.
