Radiolyse de l’ADN substitué au 5-bromouracile

Nous avons étudié la probabilité de coupure d'un ADN en double brin photosensibilisée et radiosensibilisée par le 5-Bromouracile (BrU). Sous irradiation ultraviolette, nous observons un point chaud de coupure au site nucléotidique en 5' du BrU. Sous irradiation X, l'augmentation de probabilité de coupure au même site est très modestement augmentée. Ce résultat laisse penser que la radiosensibilisation de l'inactivation cellulaire par le BrU ne peut pas simplement s'interpréter par une augmentation du nombre de coupures de chaînes

Clays and Health: Properties and Therapeutic uses

International audienceFirst book in English which describes the pharmaceutical and therapeutic benefits of clays in terms of their physical and physicochemical properties. Provides a concise history of the use of clay in human health practices. Unlike popular texts, this book describes the customary applications of clays and explains the mode of action causing the palliative effec

Determination of the DNA-interacting region of the archaebacterial chromosomal protein MC1. Photocrosslinks with 5-bromouracil-substituted DNA.

Protein MC1 is the major chromosomal protein in methanosarcinaceae. Using photochemical crosslinking on 5-bromouracil-substituted DNA, we identified the region of the protein that interacts with it. This region is located in the C-terminal part of the polypeptide chain, and the crosslinked amino-acids are in the region 74-86. Tryptophan 74 is one of the amino-acids crosslinked to DNA

Polymorphism of turnip yellow mosaic virus empty shells and evidence for conformational changes occurring after release of the viral RNA. A differential scanning calorimetric study.

Turnip yellow mosaic virus (TYMV) is a small isometric plant virus which decapsidates by releasing its RNA through a hole in the capsid, leaving behind an empty shell [R. E. F. Matthews and J. Witz, (1985) Virology 144, 318-327]. Similar empty shells (artificial top component, ATC) can be obtained by submitting the virions to various treatments in vitro. We have used differential scanning calorimetry, analytical sedimentation, and electron microscopy to investigate the thermodenaturation of natural empty shells (NTC, natural top component) present in purified virus suspensions, and of several types of ATCs. ATCs divided in two major classes. Those obtained by alkaline titration, by the action of urea or butanol behaved as NTC: their thermograms contained only one peak corresponding to the irreversible dissociation of the shells and the denaturation of the coat protein. The temperature of this unique transition varied significantly with pH, from 71 degrees C at pH 4.5 to 84 degrees C at pH 8.5. The thermograms of ATCs obtained by freezing and thawing, or by the action of high pressure, contained two peaks: shells dissociated first into smaller protein aggregates at 57 degrees C (at pH 5.0) to 61 degrees C (at pH 8.5), which denatured at the temperature of the unique transition of NTC. Shells obtained by heating virions to 55 degrees C at pH 7.6, changed conformation after the release of the viral RNA, as upon continuous heating to 95 degrees C, their thermograms were similar to those of the shells obtained by freezing and thawing, whereas after purification they behaved like NTC. Structural implications of these observations are discussed