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Toulouse, France

Jauvert E.,INSA Toulouse | Jauvert E.,Roche Holding AG | Jauvert E.,French National Center for Scientific Research | Jauvert E.,University Of Toulouse Laas | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2014

Immobilization of living micro-organisms on predefined areas of substrates is a prerequisite for their characterizations by atomic force microscopy (AFM) in culture media. It remains challenging since micro-organisms should not be denatured but attached strongly enough to be scanned with an AFM tip, in a liquid phase. In this work, a novel approach is proposed to electrostatically assemble biological objects of interest on 2 nm thick polyethylenimine (PEI) patterns fabricated by nanoxerography. This nanoxerography process involves electrostatic trapping of PEI chains on negatively charged patterns written on electret thin films by AFM or electrical microcontact printing. The capability of this approach is demonstrated using a common biological system, Pseudomonas aeruginosa bacteria. These negatively charged bacteria are selectively assembled on large scale arrays of PEI patterns. In contrast to other PEI continuous films commonly used for cell anchoring, these ultrathin PEI patterns strongly attached on the surface do not cause any denaturation of the assembled Pseudomonas aeruginosa bacteria. AFM characterizations of large populations of individual living bacteria in culture media can thus be easily performed through this approach, providing the opportunity to perform representative statistical data analysis. Interestingly, this process may be extended to any negatively charged micro-organism in solution. © 2014 American Chemical Society.

Formosa C.,CNRS Laboratory for Analysis and Architecture of Systems | Formosa C.,University Of Toulouse Laas | Formosa C.,CNRS Structure and Reactivity of Complex Molecular Systems | Lachaize V.,CNRS Laboratory for Analysis and Architecture of Systems | And 16 more authors.
Journal of Molecular Recognition | Year: 2015

We first described the interaction between hemagglutinin (HA) antibodies, immobilized on atomic force microscopy tips, and HA epitopes, immobilized on epoxy glass slides (model surface). Using our system, we then investigated the distribution of HA-labeled yeast cell wall protein covalently linked cell wall protein 12 over the cell surface of the yeast Saccharomyces cerevisiae during mating process. Finally, we could unfold multimers of HA-labeled β2-adrenergic receptors from the membrane of living transfected Chinese hamster ovary cells.Single-molecule force spectroscopy using atomic force microscopy (AFM) is more and more used to detect and map receptors, enzymes, adhesins, or any other molecules at the surface of living cells. To be specific, this technique requires antibodies or ligands covalently attached to the AFM tip that can specifically interact with the protein of interest. Unfortunately, specific antibodies are usually lacking (low affinity and specificity) or are expensive to produce (monoclonal antibodies). An alternative strategy is to tag the protein of interest with a peptide that can be recognized with high specificity and affinity with commercially available antibodies. In this context, we chose to work with the human influenza hemagglutinin (HA) tag (YPYDVPDYA) and labeled two proteins: covalently linked cell wall protein 12 (Ccw12) involved in cell wall remodeling in the yeast Saccharomyces cerevisiae and the β2-adrenergic receptor (β2-AR), a G protein-coupled receptor (GPCR) in higher eukaryotes. We first described the interaction between HA antibodies, immobilized on AFM tips, and HA epitopes, immobilized on epoxy glass slides. Using our system, we then investigated the distribution of Ccw12 proteins over the cell surface of the yeast S. cerevisiae. We were able to find the tagged protein on the surface of mating yeasts, at the tip of the mating projections. Finally, we could unfold multimers of β2-AR from the membrane of living transfected chinese hamster ovary cells. This result is in agreement with GPCR oligomerization in living cell membranes and opens the door to the study of the influence of GPCR ligands on the oligomerization process. Copyright © 2014 John Wiley & Sons, Ltd.

Laberdesque R.,Roche Holding AG | Laberdesque R.,University Of Toulouse Laas | Gauthier-Lafaye O.,Roche Holding AG | Gauthier-Lafaye O.,University Of Toulouse Laas | And 7 more authors.
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2015

Cavity-resonator-integrated guided-mode resonance filters (CRIGFs) are optical filters based on weak coupling by a grating between a free-space propagating optical mode and a guided mode, like guided-mode resonance filters (GMRFs). As compared to GMRFs they offer narrowband reflection with small aperture and high angular acceptance. We report experimental characterization and theoretical modeling of unexpected high-order reflected modes in such devices. Using coupled-mode modeling and moiré analysis we provide physical insight on key mechanisms ruling CRIGF properties. This model could serve as a simple and efficient framework to design new reflectors with tailored spatial and spectral modal reflectivities. © 2015 Optical Society of America.

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