Preferred metabolic pathway of bovine muscle fibre revealed by synchrotron–deep ultraviolet fluorescence imaging

International audienceThe different bovine muscle fibre types I, IIA and IIX are characterised by their preferred metabolic pathway, either oxidative (I, IIA) or glycolytic (IIX), and their contraction speed, either slow-twitch (I) or fast-twitch (IIA, IIX). These physiological specificities are associated with variations in intracellular composition and their fluorescence spectra signatures. We hypothesised that these slight differences in autofluorescence responses could be used to discriminate the muscle fibre types by fluorescence imaging. Serial histological cross-sections of beef longissimus dorsi were performed: the start set was used to identify the metabolic and contractile type of muscle fibres by both immunohistoenzymology and immunohistofluorescence, and the following set was used to acquire synchrotron–deep ultraviolet (UV) autofluorescence images after excitation in the UV range (275 nm and 315 nm). This strategy made it possible to explore the label-free autofluorescence of muscle cells previously subtyped by histochemistry. Glycolytic cells (IIX) showed more intense fluorescence than oxidative cells (I and IIA) with near-90 % accuracy. This discrimination is more specifically assigned to the fluorescence of nicotinamide adenine dinucleotide. UV autofluorescence was unable to discriminate contractile type

DUV fluorescence bioimaging study of the interaction of partially reduced graphene oxide and liver cancer cells

The interaction of partially reduced graphene oxide (prGO) and Huh7.5.1 liver cancer cells was investigated by means of DUV fluorescence bioimaging. The prGO sample was obtained by the reduction (to a certain extent) of the initially prepared graphene oxide (GO) nanosheets with hydrazine. The fluorescence of the GO nanosheets increases with time of the reduction due to a change in ratio of the sp(2) and sp(3) carbon sites and the prGO sample was extracted from the dispersion after 6 min, when the intensity of the fluorescence reached its maximum. The reduction process was left to proceed further to saturation until highly reduced graphene oxide (denoted here as rGO) was obtained. GO, prGO and rGO samples were investigated by structural (scanning electron microscopy (SEM), scanning transmission electron microscopy coupled with energy dispersive spectrometry (STEM-EDS)) and spectroscopic (UV-vis, photoluminescence (PL), Raman) methods. After that, Huh7.5.1 cells were incubated with GO, prGO and rGO nanosheets and used in bioimaging studies, which were performed on DISCO beamline of synchrotron SOLEIL. It was found that the prGO significantly enhanced the fluorescence of the cells and increased the intensity of the signal by similar to 2.5 times. Time-lapse fluorescence microscopy experiments showed that fluorescence dynamics strongly depends on the type of nanosheets used. The obtained prGO nanostructure can be easily conjugated with aromatic ring containing drugs, which opens a possibility for its applications in fluorescence microscopy monitored drug delivery

Microspectroscopie infrarouge à transformée de Fourier avec source synchrotron et microscopie de fluorescence (application à la thérapie photodynamique de cellules cancéreuses)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Kerr-gated picosecond time-resolved resonance Raman spectroscopic probing of the excited states in lambda-[Ru(bipy)₂dppz](BF₄)₂

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Hybridization Kinetics of Oligodeoxyribonucleotides with a d(GCGAAGC) Hairpin at the 3′-End

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Opening of the extraordinarily stable mini-hairpin d(GCGAAGC)

International audienceFor the purposes of the antisense strategy oligodeoxyribonucleotides can be protected against serum and cell nuclease digestion by tagging at their 3′-end with a sequence naturally forming a very stable hairpin, d(GCGAAGC). This nuclease-resistant hairpin is also known for its high thermostability. We demonstrate in this study that attachment of d(GCGAAGC) at the 3′-end of an oligodeoxyribonucleotide does not hinder hybridization of the 5′-part of this oligonucleotide to a complementary DNA strand. Moreover, the hairpin is in equilibrium between a folded and an open structure, with an energy minimum in favor of pairing if it is possible, even with mismatches

Atmospheric pressure photoionization study of post-translational modifications: The case of palmitoylation

International audienceIn this work, atmospheric pressure photoionization was investigated for use in characterizing protein palmitoylation, which is a major post-translational modification of membrane proteins. The study focused on native and palmitoylated peptides originating from plasma membrane proteolipids, such as tetraspanins CD9 and CD151. Mass spectrometry experiments were performed using synchrotron radiation as a tunable UV source that provides optimal energy for photoionization (SR-APPI). In the positive ion mode, intense fragment ions corresponding to a. 6, candy ions were observed. Interestingly, these fragment ions conserved the palmitoyl modification, thus allowing for unambiguous structural characterization of the palmitoylated peptides. In-source fragmentation under APPI conditions offers a unique complement to conventional methods such as MS/MS, and the results demonstrate that APPI is a versatile and promising technique for the in-source characterization of post-translational modifications and top-down proteomics of membrane proteins. (C) 2012 Elsevier B.V. All rights reserved

Diffusion of Aromatic Solutes in Aliphatic Polymers above Glass Transition Temperature

The paper presents a harmonized description of the diffusion of solutes with repeated aromatic jumping units (JU) in entangled aliphatic polymers above their T-g, It is shown that the trace diffusion coefficients, D, are scaled with the number of JU or equivalently with solute molecular mass, M, as M-1M-Ku/(T-Tg + K beta), where K-alpha and K-beta are temperature-equivalent parameters related to Williams-Landel-Ferry (WLF) ones. The scaling of diffusion behaviors of linear aliphatic and aromatic solutes appear separated by a temperature shift, K-beta, of ca. 91 K. The effects of the number of JU and the distance between two JU were specifically probed in several aliphatic polymers (polypropylene, polylactide and polycaprolactone) at different temperatures above T-g with two homologous solute series: short oligophenyls and diphenylalkanes. An extended free-volume theory for many JU was accordingly inferred to account for the observed statistical independence between the fluctuations of the free volumes probed by each JU and the probability of the collective displacement of the center-of-mass of the solute. Outstanding properties of short oligophenyls series provided further insight on the underlying molecular mechanism of translation. Their activation energies grow differently according to the number of phenyl rings, N-ph, being odd or even. Constrained molecular dynamics demonstrated that such a parity effect could be remarkably reproduced when the translation of each JU (i.e., phenyl ring) was randomly controlled by a combination of short and long-lived contacts

A multiscalar photoluminescence approach to discriminate among semiconducting historical zinc white pigments

International audienceIn order to fully characterize the zinc white artists' pigment (ZnO), much used since the mid-nineteenth century, three samples collected in the early 20th century were studied using a combination of synchrotron and macroscopic photoluminescence spectroscopy and imaging. An improved microscope setup based on synchrotron microspectroscopy and microimaging was used to study the powders dispersed onto indium foil. The synchrotron setup offered a diffraction-limited resolution of 153 nm. The PL spectra of individual grains were measured and the distribution of particles' emission spectra was mapped at the nanoscale. The results revealed that while the samples have apparent homogeneous photoluminescence behavior at the macroscale (bulk), their PL signatures are inhomogeneous below 20 μm. At the nanoscale the three powder samples have quite different PL signatures. Different sources, perhaps even different batches, of zinc white might be readily differentiated using this method