Detection of the conformational changes of Discosoma red fluorescent proteins adhered on silver nanoparticles-based nanocomposites via surface-enhanced Raman scattering

International audienc

Raman-Brillouin electronic density in short-period superlattices

International audienceWe analyze and interpret resonant Raman-Brillouin scattering by folded acoustic vibrations in short-period GaAs/AlAs superlattices. Analysis of the spectra and their resonance behavior is performed using a Raman-Brillouin electronic density constructed by combining thousands transitions between electronic eigenstates of the system according to their weight in the light-scattering process. We show that plots of this effective electronic density allow for capturing the essential physics of the electron-phonon interaction and of the resonant light-scattering process in a situation where complex effects are simultaneously present: electronic confinement in the quantum wells and wave-function delocalization due to interlayer coupling, folding of acoustic dispersion and symmetry changes in the deformation fields, resonant selection of optical transitions. Comparison between the measured spectra and those simulated using the Raman-Brillouin quantum model and the photoelastic model are presented. Activation and/or deactivation of the scattering by acoustic vibration doublets and changes in their intensity ratio with excitation energy are directly related to the Raman-Brillouin electronic density distribution along the superlattices axis. Limitations of the photoelastic model are discussed by comparing the steplike variation in the photoelastic coefficient to the Raman-Brillouin electronic density profiles

Physico-chemical characterization of the interaction of red fluorescent protein — DsRed with silica layers

The Discosoma Recombinant Red Fluorescent (DsRed) protein is the latest member of the family of fluorescent proteins. It holds great promise for applications in biotechnology and cell biology. However, before being used for rational engineering, knowledge on the underlying mechanisms relating the DsRed structural stability and adsorption properties on solid surfaces is highly demanded. The physico-chemical analysis performed in this study reveals that the interaction of DsRed with SiO2 surfaces does not lead to protein denaturation. The secondary structure of DsRed is preserved after adsorption and dehydration. The measured contact angles of sessile droplets with different DsRed concentrations determine the interaction as hydrophilic one. The photoluminescence emission of dehydrated DsRed droplets is found to be slightly red-shifted, peaking at 590 nm

Detection of the conformational changes of Discosoma red fluorescent proteins adhered on silver nanoparticles-based nanocomposites via surface-enhanced Raman scattering

Description of the relationship between protein structure and function remains a primary focus in molecular biology, biochemistry, protein engineering and bioelectronics. Moreover, the investigation of the protein conformational changes after adhesion and dehydration is of importance to tackle problems related to the interaction of proteins with solid surfaces. In this paper the conformational changes of wild-type Discosoma recombinant red fluorescent proteins (DsRed) adhered on silver nanoparticles (AgNPs)-based nanocomposites are explored via surface-enhanced Raman scattering (SERS). Originality in the present approach is to work on dehydrated DsRed thin protein layers in link with natural conditions during drying. To enable the SERS effect, plasmonic substrates consisting of a single layer of AgNPs encapsulated by an ultra-thin silica cover layer were elaborated by plasma process. The achieved enhancement of the electromagnetic field in the vicinity of the AgNPs is as high as 105. This very strong enhancement factor allowed detecting Raman signals from discontinuous layers of DsRed issued from solution with protein concentration of only 80 nM. Three different conformations of the DsRed proteins after adhesion and dehydration on the plasmonic substrates were identified. It was found that the DsRed chromophore structure of the adsorbed proteins undergoes optically assisted chemical transformations when interacting with the optical beam, which leads to reversible transitions between the three different conformations. The proposed time-evolution scenario endorses the dynamical character of the relationship between protein structure and function. It also confirms that the conformational changes of proteins with strong internal coherence, like DsRed proteins, are reversibl

Etude par spectrometrie Raman des contraintes, dopage et defauts associes dans GaAs heteroepitaxie

SIGLEINIST T 76523 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Etude par spectrometrie Raman des contraintes, dopage et defauts associes dans GaAs heteroepitaxie

SIGLEINIST T 76523 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Effect of substrate polarity on the optical and vibrational properties of (311)A and (311) B oriented InAlAs/InP heterostructures

International audienc

Raman-Brillouin electronic density in short-period superlattices

9 páginas, 8 figuras, 2 tablas.-- PACS number8s): 63.22.-m, 73.21.Cd, 73.22.Lp, 78.30.Fs.-- et al.We analyze and interpret resonant Raman-Brillouin scattering by folded acoustic vibrations in short-period GaAs/AlAs superlattices. Analysis of the spectra and their resonance behavior is performed using a Raman-Brillouin electronic density constructed by combining thousands transitions between electronic eigenstates of the system according to their weight in the light-scattering process. We show that plots of this effective electronic density allow for capturing the essential physics of the electron-phonon interaction and of the resonant light-scattering process in a situation where complex effects are simultaneously present: electronic confinement in the quantum wells and wave-function delocalization due to interlayer coupling, folding of acoustic dispersion and symmetry changes in the deformation fields, resonant selection of optical transitions. Comparison between the measured spectra and those simulated using the Raman-Brillouin quantum model and the photoelastic model are presented. Activation and/or deactivation of the scattering by acoustic vibration doublets and changes in their intensity ratio with excitation energy are directly related to the Raman-Brillouin electronic density distribution along the superlattices axis. Limitations of the photoelastic model are discussed by comparing the steplike variation in the photoelastic coefficient to the Raman-Brillouin electronic density profiles.The authors thank the Department of Industry of the Basque Government through ETORTEK for funding support.Peer reviewe

Photocatalytic activity of hybrid gold-titania nanocomposites

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Gold nanoring trimers: a versatile structure for infrared sensing

12 páginas, 6 figuras.-- et al.In this work we report on the observation of surface plasmon properties of periodic arrays of gold nanoring trimers fabricated by electron beam lithography. It is shown that the localized surface plasmon resonances of such gold ring trimers occur in the infrared spectral region and are strongly influenced by the nanoring geometry and their relative positions. Based on numerical simulations of the optical extinction spectra and of the electric near-field intensity maps, the resonances are assigned to surface plasmon states arising from the strong intra-trimer electromagnetic interaction. We show that the nanoring trimer configuration allows for generating infrared surface plasmon resonances associated with strongly localized electromagnetic energy, thus providing plasmonic nanoresonators well-suited for sensing and surface enhanced near-infrared Raman spectroscopy.This work was supported by CALMIP computing center at Paul Sabatier University and the ETORTEK project inano from the Department of Industry of the Basque Government.Peer reviewe