Laboratoire P.A.S.T.E.U.R

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L'eau, une histoire trouble - Podcast France Culture

L’eau est un des éléments qui nous est le plus familier, mais recèle encore bien des mystères. Comment se sont construites les théories physiques et chimiques sur l’eau ? Quelles sont nos connaissances actuelles sur cette substance ?

Interview Arnaud GAUTIER, a chemical biologist !

Arnaud GAUTIER, Maître de Conférence au sein du Département de Chimie de l'École normale supérieure est lauréat du financement ERC Consolidator Grant 2016 et Médaille de Bronze du CNRS.

 

Visionnez son interview où il nous explique ce qu'est la chémobiologie et nous détaille ses projets à venir !

A Dual Functional Electroactive and Fluorescent Probe for Coupled Measurements of Vesicular Exocytosis with High Spatial and Temporal Resolution

Angew. Chem. Int. Ed. 2017, 56, 1 – 6

 

In this work, Fluorescent False Neurotransmitter 102 (FFN102), a synthesized analogue of biogenic neurotransmitters, was demonstrated to show both pH-dependent fluorescence and electroactivity. To study secretory behaviors at the single-vesicle level, FFN102 was employed as a new fluorescent/electroactive dual probe in a coupled technique (amperometry and total internal reflection fluorescence microscopy (TIRFM)). We used N13 cells, a stable clone of BON cells, to specifically accumulate FFN102 into their secretory vesicles, and then optical and electrochemical measurements of vesicular exocytosis were experimentally achieved by using indium tin oxide (ITO) transparent electrodes. Upon stimulation, FFN102 started to diffuse out from the acidic intravesicular microenvironment to the neutral extracellular space, leading to fluorescent emissions and to the electrochemical oxidation signals that were simultaneously collected from the ITO electrode surface. The correlation of fluorescence and amperometric signals resulting from the FFN102 probe allows realtime monitoring of single exocytotic events with both high spatial and temporal resolution. This work opens new possibilities in the investigation of exocytotic mechanisms.

 

 

‘Full fusion’ is not ineluctable during vesicular exocytosis of neurotransmitters by endocrine cells

Proc. R. Soc. A 473: 20160684.

 

Vesicular exocytosis is an essential and ubiquitous process in neurons and endocrine cells by which neurotransmitters are released in synaptic clefts or extracellular fluids. It involves the fusion of a vesicle loaded with chemical messengers with the cell membrane through a nanometric fusion pore. In endocrine cells, unless it closes after some flickering (‘Kiss-and-Run’ events), this initial pore is supposed to expand exponentially, leading to a full integration of the vesicle membrane into the cell membrane—a stage called ‘full fusion’.We report here a compact analytical formulation that allows precise measurements of the fusion pore expansion extent and rate to be extracted from individual amperometric spike time courses. These data definitively establish that, during release of catecholamines, fusion pores enlarge at most to approximately one-fifth of the radius of their parent vesicle, hence ruling out the ineluctability of ‘full fusion’.

Theory and Simulations for the Electron-Transfer/Ion-Transfer Mode of Scanning Electrochemical Microscopy in the Presence or Absence of Homogenous Kinetics

ChemElectroChem 2017

 

 

The electron transfer/ion transfer (ET/IT) mode of the scanning electrochemical microscopy (SECM) was developed recently and applied to studies of heterogeneous reactions at the substrate surface. The charged products or intermediates are detected by measuring the ion transfer current of this species across the liquid/liquid interface supported at the tip of a nanopipette. In this article, we developed the theory for this technique and explored its potential advantages and limitations. Using COMSOL Multiphysics package, the approach curves were simulated for three commonly encountered experimental situations, viz., the surface generated ionic species is either chemically stable or participates in a first or second order homogeneous reaction. The simulation results are generalized in the form of analytical approximations derived under limiting conditions.