Toward the clinical application of time-domain fluorescence lifetime imaging

High-speed (video-rate) fluorescence lifetime imaging (FLIM) through a flexible endoscope is reported based on gated optical image intensifier technology. The optimization and potential application of FLIM to tissue autofluorescence for clinical applications are discussed. (c) 2005 Society of Photo-Optical Instrumentation Engineers

Real-time time-domain fluorescence lifetime imaging including single-shot acquisition with a segmented optical image intensifier

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Self refractive non-linearities in chalcogenide based glasses

We report third order non-linear absorption and refraction measurements at 1.20µm and 1.52µm on selected gallium–Lanthanum sulfide-based glasses (Ga:La:S) showing negligible non-linear absorption and a refractive non-linearity close to one hundred times that of SiO2. Their potential use in telecommunication as base materials for all-optical switching practical devices is evaluated resulting in large figures of merit. The addition of a glass modifier to the Ga:La:S matrix has improved thermal and optical properties, resulting in ease of fibre drawing. The non-linear optical response of this new variant of the Ga:La:S family is studied

Cholesterol-dependent membrane fusion induced by the gp41 membrane-proximal external region-transmembrane domain connection suggests a mechanism for broad HIV-1 neutralization.

UNLABELLED: The HIV-1 glycoprotein 41 promotes fusion of the viral membrane with that of the target cell. Structural, biochemical, and biophysical studies suggest that its membrane-proximal external region (MPER) may interact with the HIV-1 membrane and induce its disruption and/or deformation during the process. However, the high cholesterol content of the envelope (ca. 40 to 50 mol%) imparts high rigidity, thereby acting against lipid bilayer restructuring. Here, based on the outcome of vesicle stability assays, all-atom molecular dynamics simulations, and atomic force microscopy observations, we propose that the conserved sequence connecting the MPER with the N-terminal residues of the transmembrane domain (TMD) is involved in HIV-1 fusion. This junction would function by inducing phospholipid protrusion and acyl-chain splay in the cholesterol-enriched rigid envelope. Supporting the functional relevance of such a mechanism, membrane fusion was inhibited by the broadly neutralizing 4E10 antibody but not by a nonneutralizing variant with the CDR-H3 loop deleted. We conclude that the MPER-TMD junction embodies an envelope-disrupting C-terminal fusion peptide that can be targeted by broadly neutralizing antibodies. IMPORTANCE: Fusion of the cholesterol-enriched viral envelope with the cell membrane marks the beginning of the infectious HIV-1 replicative cycle. Consequently, the Env glycoprotein-mediated fusion function constitutes an important clinical target for inhibitors and preventive vaccines. Antibodies 4E10 and 10E8 bind to one Env vulnerability site located at the gp41 membrane-proximal external region (MPER)-transmembrane domain (TMD) junction and block infection. These antibodies display broad viral neutralization, which underscores the conservation and functionality of the MPER-TMD region. In this work, we combined biochemical assays with molecular dynamics simulations and microscopy observations to characterize the unprecedented fusogenic activity of the MPER-TMD junction. The fact that such activity is dependent on cholesterol and inhibited by the broadly neutralizing 4E10 antibody emphasizes its physiological relevance. Discovery of this functional element adds to our understanding of the mechanisms underlying HIV-1 infection and its blocking by antibodies

Large enhancement of the third order optical susceptibility in Cu-silica composites produced by

No description supplie

Large Enhancement of the Third-order Optical Susceptibility in Cu-silica Composites Produced by Low-Energy High-Current Ion Implantation

3 pages, 3 figures, 1 table.-- PACS: 61.46.+w; 78.67.Bf; 42.65.An; 42.65.Hw; 61.72.Ww; 61.80.Jh; 73.22.LpLow-energy high-current ion implantation in silica at a well-controlled substrate temperature has been used to produce composites containing a large concentration of spherical Cu clusters with an average diameter of 4 nm and a very narrow size distribution. A very large value for the third-order optical susceptibility, (3) = 10–7 esu, has been measured in the vicinity of the surface plasmon resonance by degenerate four-wave mixing at 585 nm. This value is among the largest values ever reported for Cu nanocomposites. Additionally, the response time of the nonlinearity has been found to be shorter than 2 ps. The superior nonlinear optical response of these implants is discussed in terms of the implantation conditions.This work has been partially supported by the EU under the BRPR-CT98-0616 project, by CAM, Spain, under the 075/0038/1998 project, and by the CSIC-CNRS 2000FR0026 agreement for traveling funding. J.O. wishes to thank CSIC for funding his position. A.L.S. gratefully acknowledges the Alexander von Humboldt foundation and RFBR 99-02-17767 for financial support.Peer reviewe

The Bilayer Collective properties govern the interaction of an HIV-1 antibody with the viral membrane

Efficient engagement with the envelope glycoprotein membrane-proximal external region (MPER) results in robust blocking of viral infection by a class of broadly neutralizing antibodies (bnAbs) against human immunodeficiency virus (HIV). Developing an accommodation surface that engages with the viral lipid envelope appears to correlate with the neutralizing potency displayed by these bnAbs. The nature of the interactions established between the antibody and the lipid is nonetheless a matter of debate, with some authors arguing that anti-MPER specificity arises only under pathological conditions in autoantibodies endowed with stereospecific binding sites for phospholipids. However, bnAb-lipid interactions are often studied in systems that do not fully preserve the biophysical properties of lipid bilayers, and therefore, questions on binding specificity and the effect of collective membrane properties on the interaction are still open. Here, to evaluate the specificity of lipid interactions of an anti-MPER bnAb (4E10) in an intact membrane context, we determine quantitatively its association with lipid bilayers by means of scanning fluorescence correlation spectroscopy and all-atom molecular dynamic simulations. Our data support that 4E10 establishes electrostatic and hydrophobic interactions with the viral membrane surface and that the collective physical properties of the lipid bilayer influence 4E10 dynamics therein. We conclude that establishment of peripheral, nonspecific electrostatic interactions with the viral membrane through accommodation surfaces may assist high-affinity binding of HIV-1 MPER epitope at membrane interfaces. These findings highlight the importance of considering antibody-lipid interactions in the design of antibody-based anti-HIV strategies

An electronically tunable ultrafast laser source applied to fluorescence imaging and fluorescence lifetime imaging microscopy

We demonstrate that spectral selection from a supercontinuum generated in a microstructured fibre can provide a continuously electronically tunable ultrafast spatially coherent source for confocal microscopy and both scanning and wide field fluorescence lifetime imaging. © 2005 Optical Society of America