laboratoire de physique statistique
 
 
laboratoire de physique statistique

Publications

Rechercher
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 


5
P U B L I C A T I O N S

S E L E C T I O N N E R
P A R M I :



 
2016
A Programmable DNA Origami Platform to Organize SNAREs for Membrane Fusion - Xu, Weiming and Nathwani, Bhavik and Lin, Chenxiang and Wan, Jing and Karatekin, Erdem and Pincet, Frederic and Shih, William and Rothman, James E.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 1384439-4447 (2016)

Abstract : Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes are the core molecular machinery of membrane fusion, a fundamental process that drives inter- and intracellular communication and trafficking. One of the questions that remains controversial has been whether and how SNAREs cooperate. Here we show the use of self-assembled DNA-nanostructure rings to template uniform-sized small unilamellar vesicles containing predetermined maximal number of externally facing SNAREs to study the membrane-fusion process. We also incorporated lipid-conjugated complementary ssDNA as tethers into vesicle and target membranes, which enabled bypass of the rate-limiting docking step of fusion reactions and allowed direct observation of individual membrane-fusion events at SNARE densities as low as one pair per vesicle. With this platform, we confirmed at the single event level that, after docking of the templated-SUVs to supported lipid bilayers (SBL), one to two pairs of SNAREs are sufficient to drive fast lipid mixing. Modularity and programmability of this platform makes it readily amenable to studying more complicated systems where auxiliary proteins are involved.
 
2014
A Half-Zippered SNARE Complex Represents a Functional Intermediate in Membrane Fusion - Li, Feng and Kuemmel, Daniel and Coleman, Jeff and Reinisch, Karin M. and Rothman, James E. and Pincet, Frederic
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 1363456-3464 (2014)

Abstract : SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins mediate fusion by pulling biological membranes together via a zippering mechanism. Recent biophysical studies have shown that t- and v-SNAREs can assemble in multiple stages from the N-termini toward the C-termini. Here we show that functionally, membrane fusion requires a sequential, two-step folding pathway and assign specific and distinct functions for each step. First, the N-terminal domain (NTD) of the v-SNARE docks to the t-SNARE, which leads to a conformational rearrangement into an activated half-zippered SNARE complex. This partially assembled SNARE complex locks the C-terminal (CTD) portion of the t-SNARE into the same structure as in the postfusion 4-helix bundle, thereby creating the binding site for the CTD of the v-SNARE and enabling fusion. Then zippering of the remaining CTD, the membrane-proximal linker (LD), and transmembrane (TMD) domains is required and sufficient to trigger fusion. This intrinsic property of the SNAREs fits well with the action of physiologically vital regulators such as complexin. We also report that NTD assembly is the rate-limiting step. Our findings provide a refined framework for delineating the molecular mechanism of SNARE-mediated membrane fusion and action of regulatory proteins.
 
2009
Local Membrane Mechanics of Pore-Spanning Bilayers - Mey, Ingo and Stephan, Milena and Schmitt, Eva K. and Mueller, Martin Michael and Ben Amar, Martine and Steinem, Claudia and Janshoff, Andreas
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 1317031-7039 (2009)

Abstract : The mechanical behavior of lipid bilayers; spanning the pores of highly ordered porous silicon substrates was scrutinized by local indentation experiments as a function of surface functionalization, lipid composition, solvent content, indentation velocity, and pore radius. Solvent-containing nano black lipid membranes (nano-BLMs) as well as solvent-free pore-spanning bilayers were imaged by fluorescence and atomic force microscopy prior to force curve acquisition, which allows distinguishing between membrane-covered and uncovered pores. Force indentation curves on pore-spanning bilayers attached to functionalized hydrophobic porous silicon substrates reveal a predominately linear response that is mainly attributed to prestress in the membranes. This is in agreement with the observation that indentation leads to membrane lysis well below 5\% area dilatation. However, membrane bending and lateral tension dominate over prestress and stretching if solvent-free supported membranes obtained from spreading giant liposomes on hydrophilic porous silicon are indented. An elastic regime diagram is presented that readily allows determining the dominant contribution to the mechanical response upon indentation as a function of load and pore radius.
Suppression of Proton Mobility by Hydrophobic Hydration - Bonn, Mischa and Bakker, Huib J. and Rago, Gianluca and Pouzy, Frederick and Siekierzycka, Joanna R. and Brouwer, Albert M. and Bonn, Daniel
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 13117070+ (2009)

Abstract : Fluorescence microscopy and conductivity measurements reveal a remarkably strong effect of hydrophobic groups on the mobility of protons in water. The addition of 5 M of tetramethylurea (4 methyl, groups per molecule) results in a reduction of the proton mobility by a factor of similar to 10: hydrophobic hydration strongly suppresses proton mobility. These observations demonstrate the collective nature of aqueous proton transport.
 
2007
Two-photon uncaging with fluorescence reporting: Evaluation of the o-hydroxycinnamic platform - Gagey, Nathalie and Neveu, Pierre and Benbrahim, Chouaha and Goetz, Bernard and Aujard, Isabelle and Baudin, Jean-Bernard and Jullien, Ludovic
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 1299986-9998 (2007)

Abstract : This paper evaluates the o-hydroxycinnamic platform for designing efficient caging groups with fluorescence reporting upon one- and two-photon excitation. The model cinnamates are easily prepared in one step by coupling commercial or readily available synthons. They exhibit a large one-photon absorption that can be tuned in the near-UV range. Uncaging after one-photon excitation was investigated by H-1 NMR, UV-vis absorption, and steady-state fluorescence emission. In the whole investigated series, the caged substrate is quantitatively released upon photolysis. At the same time, uncaging releases a strongly fluorescent coproduct that can be used as a reporter for quantitative substrate delivery. The quantum yield of double bond photoisomerization leading to uncaging after one-photon absorption mostly lies in the 10\% range. Taking advantage of the favorable photophysical properties of the uncaging coproduct, we use a series of techniques based on fluorescence emission to measure the action uncaging cross sections with two-photon excitation of the present cinnamates. Exhibiting values in the 1-10 GM range at 750 nm, they satisfactorily compare with the most efficient caging groups reported to date. Noticeably, the uncaging behavior with two-photon excitation is retained in vivo as suggested by the results observed in living zebrafish embryos. Reliable structure property relationships were extracted from analysis of the present collected data. In particular, the careful kinetic analysis allows us to discuss the relevance of the o-hydroxycinnamic platform for diverse caging applications with one- and two-photon excitation.