Author
Michel Vincent
Bio: Michel Vincent is an academic researcher from University of Paris-Sud. The author has contributed to research in topics: Fluorescence anisotropy & Quenching (fluorescence). The author has an hindex of 18, co-authored 33 publications receiving 800 citations.
Papers
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TL;DR: A set of n-(9-anthroyloxy) fatty acids has been studied by time-resolved and steady-state fluorescence anisotropy measurements in isotropic media and in vesicles of dipalmitoylphosphatidylcholine, showing the existence of structural lipid changes mainly localized in the hydrophobic core of the bilayer.
Abstract: A set of n-(9-anthroyloxy) fatty acids [2-, 7-, 9-, and 12-(9-anthroyloxy)stearic acid (AS) and 16-(9-anthroyloxy)palmitic acid (16-AP)] has been studied by time-resolved and steady-state fluorescence anisotropy measurements in isotropic media (ie, propylene glycol and a liquid paraffinic oil, Primol 342) and in vesicles of dipalmitoylphosphatidylcholine The two modes of rotation, "in-plane" and "out-of-plane", of the anthroyl ring can be detected by varying the excitation wavelength In both isotropic solvents, the value of the in-plane rotational rate is of the same order of magnitude as the out-of-plane rate for each one of the n-(9-anthroyloxy) fatty acids In propylene glycol, the anthroyl ring motions are similar for all derivatives except for the 16-AP for which the fluorophore rotates at a higher rate In the liquid paraffinic oil, identical motions of the fluorophore are observed for the 7-, 9-, and 12-AS; the motion for the 16-AP is again faster, while that for the 2-AS is slower Moreover, the fluorophore motion for each probe is faster in this solvent that in propylene glycol in conditions of identical viscosity When embedded in phospholipid bilayers, these probes report the microenvironment at a graded series of depths from the surface to the center of the bilayer [Haigh, E A, Thulborn, K R, & Sawyer, W H (1979) Biochemistry 18, 3525--3532] Studies in dipalmitoylphosphatidylcholine vesicles have been performed at three temperatures (21, 37, and 47 degrees C) corresponding to different lipid phases The out-of-plane mode of rotation is unhindered as demonstrated by an anisotropy decay profile asymptotic to zero Thus, evaluation of a membrane "fluidity" parameter at different depths of the bilayer is possible, even in the steady-state mode of observation When the in-plane mode of rotation contributes to the anisotropy decay, a hindrance to the motion is observed below the gel to liquid-crystalline transition Then information about lipid order can be obtained from the plateau value (r infinity) of the fluorescence anisotropy decay In the pretransition temperature range (37 degrees C), the results evidence the existence of structural lipid changes mainly localized in the hydrophobic core of the bilayer The main transition leads to a complete disappearance of the hindrances on the in-plane rotation
82 citations
TL;DR: It is shown that the FpvA-PaA complex adopts two different conformations depending on how it was prepared (formed in vitro or in vivo prior to purification), and the Förster resonance energy transfer kinetics from FpVA tryptophan residues to the PaA chromophore differs from one complex to the other, revealing differences in one or more of the donor-acceptor topologies.
Abstract: In iron limitation conditions, Pseudomonas aeruginosa secretes a major fluorescent siderophore named pyoverdin (PaA). PaA has an extremely high affinity for Fe3+ but also chelates other ions such as Al3+ and Ga3+ with a lower affinity. The transfer of PaA−Fe3+ across the outer membrane of the bacteria is mediated by the receptor FpvA, a TonB-dependent outer membrane transport protein. FpvA binds the iron-free and iron-loaded forms of pyoverdin with similar affinities, but only PaA−Fe3+ is taken up by the cell, suggesting that FpvA adopts different conformations depending on its loading status. We used time-resolved fluorescence spectroscopy to characterize the different forms of FpvA−PaA in vitro. We showed that the FpvA−PaA complex adopts two different conformations depending on how it was prepared (formed in vitro or in vivo prior to purification). The dihydroquinoline moiety of both conformers is fully protonated, or coordinated by protein charged groups, but the polarity of its environment, its solven...
60 citations
TL;DR: It is shown that the ability to bind aposiderophores is not specific to the OMTN subfamily but may be a more general feature of OMTs, and improved the understanding of the iron uptake mechanism via siderophore in Gram-negative bacteria.
58 citations
TL;DR: This study shows that the detergent-to-lipid ratio of the mixed micelles is an important parameter to control to limit the penetration and the mobility of water within the amphiphile aggregates and that laurdan is a nice tool to monitor this phenomenon.
54 citations
TL;DR: Comparison between BAT thermogenic activity and GDP binding and proportions of PE and PC showed a high correlation suggesting a change in the membrane occurring with the increase of mitochondrial activity that could be related to phospholipid composition rather than to membrane fluidity.
54 citations
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28 Jul 2005
TL;DR: PfPMP1）与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。
18,940 citations
TL;DR: The development of brown adipose tissue with its characteristic protein, uncoupling protein-1 (UCP1), was probably determinative for the evolutionary success of mammals, as its thermogenesis enhances neonatal survival and allows for active life even in cold surroundings.
Abstract: Cannon, Barbara, and Jan Nedergaard. Brown Adipose Tissue: Function and Physiological Significance. Physiol Rev 84: 277–359, 2004; 10.1152/physrev.00015.2003.—The function of brown adipose tissue i...
5,470 citations
TL;DR: Although annexins lack signal sequences for secretion, some members of the family have also been identified extracellularly where they can act as receptors for serum proteases on the endothelium as well as inhibitors of neutrophil migration and blood coagulation.
Abstract: Annexins are Ca2+ and phospholipid binding proteins forming an evolutionary conserved multigene family with members of the family being expressed throughout animal and plant kingdoms. Structurally,...
1,830 citations
TL;DR: The nature of detergent binding by the membrane from a noncooperative to a cooperative interaction already below the critical micellar concentration is considered and it is concluded that in general binding as a monolayer ring, rather than as a micelle, is the most probable mechanism.
985 citations
TL;DR: The results indicate that the size of the nanoparticle, perhaps because of the contributions of surface curvature, influences adsorbed protein structure and function.
Abstract: Adsorption of chicken egg lysozyme on silica nanoparticles of various diameters has been studied. Special attention has been paid to the effect of nanoparticle size on the structure and function of the adsorbed protein molecules. Both adsorption patterns and protein structure and function are strongly dependent on the size of the nanoparticles. Formation of molecular complexes is observed for adsorption onto 4-nm silica. True adsorptive behavior is evident on 20- and 100-nm particles, with the former resulting in monolayer adsorption and the latter yielding multilayer adsorption. A decrease in the solution pH results in a decrease in lysozyme adsorption. A change of protein structure upon adsorption is observed, as characterized by a loss in alpha-helix content, and this is strongly dependent on the size of the nanoparticle and the solution pH. Generally, greater loss of alpha helicity was observed for the lysozyme adsorbed onto larger nanoparticles under otherwise similar conditions. The activity of lysozyme adsorbed onto silica nanoparticles is lower than that of the free protein, and the fraction of activity lost correlates well with the decrease in alpha-helix content. These results indicate that the size of the nanoparticle, perhaps because of the contributions of surface curvature, influences adsorbed protein structure and function.
811 citations