7 research outputs found
Titre en anglais non fourni.
Ce travail de thĂšse a portĂ© sur lâĂ©tude structurale de peptides urotensinergiques humains par DC, RMN etmodĂ©lisation molĂ©culaire. LâhUII (11 aa) et son analogue lâURP (8 aa) sont considĂ©rĂ©s comme les peptides vasoactifs les plus puissants connus Ă ce jour et sont impliquĂ©s dans divers systĂšmes biologiques, notamment le systĂšme cardiovasculaire et la prolifĂ©ration des cellules tumorales. Ces deux peptides sont des ligands endogĂšnes d'un RCPG, lâUT. Ils peuvent exercer des actions physiologiques communes mais aussi divergentes. Afin dâapporter des Ă©lĂ©ments permettant une meilleure comprĂ©hension de leurs activitĂ©s biologiques, nous avons, dans un premier temps, dĂ©terminĂ© la structure 3D de trois agonistes (hUII4-11, URP,P5U) et dâun antagoniste (urantide) dans un milieu micellaire mimant les membranes des cellules eucaryotes, le DPC. Dans les quatre peptides, nous avons observĂ© la prĂ©sence de deux conformations majoritaires du pont disulfure, RHStaple et LHHook, qui sont connues pour ĂȘtre essentielles Ă lâactivitĂ© biologique. Nous avons mis en Ă©vidence une diffĂ©rence de nature de coude entre les agonistes (coude ÎČ de type I) et lâantagoniste (coude ÎČ de type IIâ). Nos analyses ont Ă©galement permis de montrer lâexistence de variations dâorientation des chaĂźnes latĂ©rales des rĂ©sidus F6, Y9 et plus spĂ©cialement celle de W7 entre les agonistes etlâantagoniste. Le groupe indole du D-W7 prĂ©sente ainsi une rotation de 180°. Dans un deuxiĂšme temps, nous avons mis en Ă©vidence un impact de la concentration sur la conformation de lâhUII qui nâest pas observĂ© pour lâURP. Ce phĂ©nomĂšne dâauto-association pourrait avoir une influence sur lâinteraction avec le rĂ©cepteur et ĂȘtre Ă lâorigine des divergences dâactivitĂ©s biologiques entre lâhUII et lâURP.This work aims to characterize the structure of human urotensinergic peptides by CD, NMR and molecular modelling. hUII (11 aa) and its analogue URP (8 aa) are considered as the most potent vasoactive peptides known so far and are involved in various biological systems, including the cardiovascular system and tumor cell proliferation. These two peptides are endogenous ligands of a GPCR, UT, and exert common but also divergent physiological actions. In order to gain a better understanding of their biological activities, we determined the structures of three agonists (hUII4-11, URP, P5U) and one antagonist (urantide), in DPC micelles, a cellular eukaryotic mimetic membrane. For all peptides, we observed the presence of two major forms of the disulfide bridge, RHStaple and LHHook, which are known to be essential for biological activity. We showed a difference in the turn nature between agonists (type I ÎČ turn) and the antagonist (type IIâ ÎČ turn). Our analyses also revealed that, in agonists and antagonist, the side chain orientations of residues F6, Y9 and more specifically W7 were different. Indeed, the indole group of D-W7 exhibited a 180° rotation. Secondly, we showed that, contrary to URP, the conformation of hUII was dependent on concentration. This selfassembly phenomenon may impact the interaction with the receptor and be responsible for the differential biological activities of hUII and URP
Conformational studies of urotensinergic peptides using NMR and molecular modelling, in DPC micelles
National audienc
Conformational studies of urotensinergic peptides using NMR and molecular modelling, in DPC micelles
National audienc
Comparative structural analyses of urotensinergic peptides by CD spectroscopy, NMR and Molecular Modelling
International audienc
Comparative structural analyses of urotensinergic peptides by CD spectroscopy, solution NMR and molecular modelling
International audienc
SiteâSelective PdâCatalysed FujiwaraâMoritani type Reaction of N,S âHeterocyclic Systems with Olefins
International audienceAbstract Dihydroâ1,4âthiazine skeletons bearing olefin fragment at their αâposition were prepared through a Pd(OAc) 2 âcatalysed FujiwaraâMoritani type reaction via CâH alkenylation with olefins. This approach is selective, generalizable to a wide range of olefins and requires only 1â
eq. of Ag 2 CO 3 without the need of coâoxidant. The CâH bond activation proved to be strongly dependent on the olefin's substitution while unfused dihydroâ1,4âthiazines seemed to be affected by the oxidation state of the sulfur atom. The utility of olefins obtained was demonstrated by their implication in the dipolar cycloaddition reaction with a nonâstabilized azomethine ylide. magnified imag