Diffusion de neutrons aux petits angles : application à l'étude des macromolécules biologiques en solution

Lairez, D.; Pelta, Juan

doi:10.1051/jp4:2005130003

Cited by 5 publications

(6 citation statements)

References 19 publications

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“…It is useful to compute partial structure factors defined as the separate contributions to S(q) of only the H or only the P monomers. This is eventually to be compared with experiments using labelled chains 43 .…”

Section: Structure Factormentioning

confidence: 99%

Micelle formation, gelation and phase separation of amphiphilic multiblock copolymers†

2011

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The phase behaviour of amphiphilic multiblock copolymers with a large number of blocks in semidilute solutions is studied by lattice Monte Carlo simulations. The influence on the resulting structures of the concentration, the solvent quality and the ratio of hydrophobic to hydrophilic monomers in the chains has been assessed explicitely. Several distinct regimes are put in evidence. For poorly substituted (mainly hydrophilic) copolymers formation of micelles is observed, either isolated or connected by the hydrophilic moieties, depending on concentration and chain length. For more highly substituted chains larger tubular hydrophobic structures appear which, at higher concentration, join to form extended hydrophobic cores. For both substitution ratios gelation is observed, but with a very different gel network structure. For the poorly substituted chains the gel consists of micelles cross-linked by hydrophilic blocks whereas for the highly substituted copolymers the extended hydrophobic cores form the gelling network. The interplay between gelation and phase separation clearly appears in the phase diagram. In particular, for poorly substituted copolymers and in a narrow concentration range, we observe a sol-gel transition followed by an inverse gel-sol transition when increasing the interaction energy. The simulation results are discussed in the context of the experimentally observed phase properties of methylcellulose, a hydrophobically substituted polysaccharide.

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Section: Structure Factormentioning

confidence: 99%

Micelle formation, gelation and phase separation of amphiphilic multiblock copolymers†

2011

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“…3). When there are no density 01004-p.7 fluctuations within the ES, in the case of crystals or amorphous solids, this parameter is the coherent scattering length density (SLD) usually designed by (or sometimes by N b in neutron reflectivity) that writes: (12) where the b i are the respective coherent scattering length off the constitutive atoms of the elementary scatterer and v is its molar volume.…”

Section: Notion Of Elementary Scatterer/scattering Length Densitymentioning

confidence: 99%

“…Let us now consider the case where the objects are rigid and centro-symmetrical. In this case, and only in this case, the amplitudes and form factors are independent from the orientation and positions of objects and the intra and inter can be decoupled (see (12) by choosing the origin of the objects in their center of mass. Let us consider the respective centers of mass and of objects: .…”

Section: Case Of Rigid Centro-symmetrical Objectsmentioning

confidence: 99%

Small-Angle Neutron Scattering

Dasannacharya¹,

Goyal

2016

Encyclopedia of Nanotechnology

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Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ∼ 1 nm up to ∼ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ∼ 1 cm 3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area.. .) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2 nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer configurations, optimization of sample characteristics prior to measurements (thickness, volume, hydrogen content.. .), standards measurements to be made and principle of data reduction. Résumé. (La Diffusion de Neutrons aux petits angles (DNPA) est une technique permettant de sonder la structure 3-D de matériaux sur une gamme typique de taille comprise entre ∼1 nm) et ∼ quelques 100 nm, les informations obtenues étant statistiquement moyennées sur la taille de l'échantillon dont le volume est d'environ 1 cm 3. C'est une technique très puissante car elle permet de faire une caractérisation complète de la structure d'un objet donné de dimensions nanométriques (rayon de giration, forme, volume, masse, dimension fractale, surface spécifique.. .) grâce à la détermination du facteur de forme, ainsi que la détermination de la manière dont les objets sont organisés au sein d'un milieu continu, et donc de décrire les interactions entre les objets, par la détermination du facteur de structure. Les propriétés spécifiques de neutrons (possibilité de moduler le contraste pa...

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“…In this case, and only in this case, the amplitudes and form factors are independent from the orientation and positions of objects and the intra and inter can be decoupled (see (12) by choosing the origin of the objects in their center of mass. Let us consider the respective centers of mass and of objects:…”

Section: Case Of Rigid Centro-symmetrical Objectsmentioning

confidence: 99%

“…It is more convenient to express it considering the distances from the gravity center of the object ( N i r i = 0) (12). It comes then:…”

Section: Guinier Regimementioning

confidence: 99%

Small-angle neutron scattering

Modern Techniques for Characterizing Magnetic Materials

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Abstract. Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ∼ 1 nm up to ∼ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ∼ 1 cm 3 . This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area. . . ) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2 nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer configurations, optimization of sample characteristics prior to measurements (thickness, volume, hydrogen content. . . ), standards measurements to be made and principle of data reduction.Résumé. (La Diffusion de Neutrons aux petits angles (DNPA) est une technique permettant de sonder la structure 3-D de matériaux sur une gamme typique de taille comprise entre ∼1 nm) et ∼ quelques 100 nm, les informations obtenues étant statistiquement moyennées sur la taille de l'échantillon dont le volume est d'environ 1 cm 3 . C'est une technique très puissante car elle permet de faire une caractérisation complète de la structure d'un objet donné de dimensions nanométriques (rayon de giration, forme, volume, masse, dimension fractale, surface spécifique. . . ) grâce à la détermination du facteur de forme, ainsi que la détermination de la manière dont les objets sont organisés au sein d'un milieu continu, et donc de décrire les interactions entre les objets, par la détermination du facteur de structure. Les propriétés spécifiques de neutrons (possibilité de modul...

show abstract

Diffusion de neutrons aux petits angles : application à l'étude des macromolécules biologiques en solution

Cited by 5 publications

References 19 publications

Micelle formation, gelation and phase separation of amphiphilic multiblock copolymers†

Micelle formation, gelation and phase separation of amphiphilic multiblock copolymers†

Small-Angle Neutron Scattering

Small-angle neutron scattering

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