Implications of the polymorphism of HLA-G on its function, regulation, evolution and disease association

The HLA-G gene displays several peculiarities that are distinct from those of classical HLA class I genes. The unique structure of the HLA-G molecule permits a restricted peptide presentation and allows the modulation of the cells of the immune system. Although polymorphic sites may potentially influence all biological functions of HLA-G, those present at the promoter and 3′ untranslated regions have been particularly studied in experimental and pathological conditions. The relatively low polymorphism observed in the MHC-G coding region both in humans and apes may represent a strong selective pressure for invariance, whereas, in regulatory regions several lines of evidence support the role of balancing selection. Since HLA-G has immunomodulatory properties, the understanding of gene regulation and the role of polymorphic sites on gene function may permit an individualized approach for the future use of HLA-G for therapeutic purposes

Single-crystal, polarized, Raman scattering study of the molecular and lattice vibrations for the energetic material cyclotrimethylene trinitramine

The single-crystal, polarized, Raman spectra for cyclotrimethylene trinitramine (RDX) have been studied at room temperature and pressure over the region of 5–3400 cm-1. While the observed Raman bands agree well with a previous Raman study, this work provides a consistent interpretation of the Raman spectra by assignment of fundamental modes, overtones, and combination bands. A total of 56 internal vibrations were observed, 36 of which were labeled as fundamental molecular vibrations. In addition, all 24 lattice optical phonons are identified. All six possible polarizations were probed to obtain the Ag, B1g, B2g, and B3g symmetry modes for both the lattice and molecular modes. Finally, the importance of these phonons for coupling with “doorway” Raman-active modes of RDX is discussed in relation to proposed mechanisms for detonation initiation

Microscopic ordering in smectic phases of liquid crystals

Orientational order in smectic phases of a ferroelectric liquid-crystalline material 4'-(2S, 3S)-2"-chloro-3"-methylpentanoyloxyphenyl-4-decyloxy thiobenzoate, abbreviated 10.S.C1Iso-leu, was examined by IR absorption spectroscopy. Oriented samples were prepared in both bookshelf and homeotropic alignment geometry. Several stronger IR vibrations were selected characterizing different parts and orientations of the molecules. Results show that the molecular tilt of the core parts of the molecules changes very little from the SA to the S* C phase implying that the core parts of the molecules are already tilted in the SA phase. Axes of the core parts, that are disordered on a cone in the SA phase, start to align with each other but remain on this cone on lowering the temperature into the S*C phase. The model agrees with some previous results.On a étudié par spectroscopie d'absorption infrarouge l'ordre orientationel dans les phases smectiques d'un matériau cristal liquide ferroélectri que, le décyloxy-4-thiobenzoate de [(2S, 3S)-chloro-2-méthyl-3-pentanoyloxy]-4'-phényle, en abrégé 10.S.C1Isoleu. Deux types d'échantillons orientés, l'un homéotrope, l'autre en configuration Clark-Lagerwall, ont été préparés et plusieurs bandes intenses en infrarouge, caractéristiques des différentes parties et orientations des molécules, ont été choisies. Les résultats montrent que l'inclinaison des parties centrales (cœurs) des molécules varie très peu de la phase SA à la phase S*C, ce qui implique que les cœurs des molécules sont déjà inclinés dans la phase SA. Leurs axes, qui sont désordonnés sur un cône dans la phase SA, s'alignent mais restent sur ce cône quand on passe en phase S*Cen abaissant la température. Ce modèle est en accord avec quelques résultats antérieurs

Thermotropic phase transitions in the bidimensional compound (C

The structural phase transitions in crystalline (n-C10H21NH3)2CuCl4 have been investigated by X-ray diffraction, IR spectroscopy and differential scanning calorimetry. The compound shows stepwise phase transitions with hysteresis, the heating and cooling cycles comprising three and four steps, respectively. Thus five phases are defined: [math]. The proposedmechanism of conformational transition for this compound ist8 or gt7 or tgt6 (Phases V & IV) → 2g-2k (..gt3g-..) (Phase III) → 2g-lk (..gtg-..) (Phases II & I

Photo-induced generation of the riboflavin-tryptophan adduct and a vibrational interpretation of its structure

A pure fraction of a riboflavin-tryptophan adduct was obtained for the first time from a mixture of products resulting from the anaerobic photoirradiation of riboflavin and tryptophan in solution. The procedure used to isolate the adduct is described. Characterization of the compound was performed by using absorption spectra and fluorescence measurements. A vibrational interpretation of the structure of this adduct was performed on the basis of its infrared spectrum. The vibrational assignment suggests an important electronic redistribution in the structure of riboflavin and tryptophan when the adduct is formed. From this fact can be inferred at least two ways of binding between the indole and isoalloxazine rings. Stability of the adduct is also discussed. © 1994

Vibrational study of N-phenyl-substituted hydroxynaphthylaldiminate copper(II) complexes

The infrared spectra of seven bis(N-phenyl-substituted hydroxynaphthylaldiminate) complexes of Cu(II) were scanned from 4000 to 100 cm-1. Particular emphasis is given to the low-energy region. The assignment of the chelate normal modes is supported by an approximate normal coordinate analysis based on a simplified general valence force field, and the geometrical parameters of the bis(N-phenylsalicylaldiminate)Cu(II) complex. The bands near 390 and 285 cm-1 are assigned to the CuO and CuN stretching vibrations, respectively. The corresponding force constants are estimated to be 1.37 and 0.88 mdyn Å-1. Influence of the nature of the different ligands on the structure of complexes is discussed. Similarity of the vibrational spectra for all the complexes suggests that they possess the same type of structure. © 1993

Apports de la spectroscopie vibrationnelle à l'étude des céramiques en hydroxyapatite phosphocalcique d'intérêt biologique

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