MODIFICATION DE L'AMIDON PAR GREFFAGE DE DERIVES AROMATIQUES SOUS RAYONNEMENT IONISANT

The grafting of lignin onto starch using electron beam radiation was studied by analysing the reactivity of lignin models: cinamic alcohol, paramethoxybenzylic alcohol and p-benzenedimethanol on maltodextrins under electron beam activation. The products of the reaction were analysed by mass spectrometry MALDI-TOF & ESI as well as RMN spectrometry

Expression of pyrrothineN-acyltransferase activities inSaccharothrix algeriensisNRRL B-24137: new insights into dithiolopyrrolone antibiotic biosynthetic pathway

The hypothetical dithiolopyrrolone biosynthetic pathway includes a final step of pyrrothine nucleus acylation. The presence of an enzymatic activity catalysing this reaction was investigated in Saccharothrix algeriensis NRRL B‐24137. To understand the effect exerted by organic acids on the level of dithiolopyrrolone production, their influence on enzymatic expression was studied. Methods and Results: The transfer of acetyl‐CoA or benzoyl‐CoA on pyrrothine was assayed in the cell‐free extract of Sa. algeriensis NRRL B‐24137. This study reports the presence of an enzymatic activity catalysing this reaction that was identified as either pyrrothine N‐acetyltransferase or N‐benzoyltransferase. The stimulation of benzoyl‐pyrrothine (BEP) production by addition of benzoic acid at 1·25 mmol l−1 into the culture medium was demonstrated, and results showed that under the same conditions of growth, pyrrothine N‐benzoyltransferase specific activity was doubled. This study shows that BEP production is enhanced in the presence of benzoic acid partly because of an induction of pyrrothine N‐benzoyltransferase.

Pyridoacridines in the 21st Century

This minireview summarizes the work developed during this Century with compounds containing the pyridoacridine scaffold in its different isomeric forms. The isolation of natural products, syntheses, bioactivities, chelation capacity, and other properties of compounds containing this framework are discussed. For reasons of length, only compounds containing a maximum of seven condensed rings have been considered, with a few exceptions

Photosensibilisation de cibles biologiques (ADN, protéines) par des complexes polypyridiques de ruthénium(II)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Comment la réactivité photochimique de complexes de ruthénium avec l'ADN peut être modulée par une protéine

communication oral

Is the 3MLCT the only photoreactive state of polypyridyl complexes?

International audienceCharacterization of metal-centered triplet states with two monodentate ligands in [Ru(bpy)3]2+ and [Ru(bpz)3]2+ complexes has been achieved by using the density functional theory method. These states are quasi-degenerate with their corresponding 3MLCT states and can readily react with their environment

Amino acids and proteins in photochemistry

Photooxidation of proteins may result from a direct reactivity of the amino acids such as tyrosin or tryptophane with UV radiation. Recent data highlight the major role of the dissociative states of protonated aromatic amino acids in photofragmentation. This process can result from the loss of a hydrogen atom with formation of a radical cation. This will be a powerful tool to cleave selectively peptides. Proteins as DNA may also be the target of photosensitizers such as polyazaaromatic Ru-11 complexes. An important property of these compounds with very oxidative ligands is their very high oxidation power in the (MLCT)-M-3 (metal-to-ligand charge transfer) state. At the excited state, they are able to abstract an electron from electron donors such as the tryptophane. This reactivity can give rise to the formation of covalent photoadducts with the tryptophane. The formation of such damage displays a potent interest for the photodynamic therapy. Moreover, complex electron transfer reactions may also occur between ruthenium compounds under illumination and a metallo-protein such the superoxyde dismutase Cu/Zn leading to an inhibition of the enzymatic activity

Les acides aminés et les protéines en photochimie

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Photoelectron transfer processes with ruthenium(II) polypyridyl complexes and Cu/Zn superoxide dismutase.

The processes that are photoinduced by [Ru(bpz)(3)](2+) (bpz = 2,2'-bipyrazyl) in the presence of Cu/Zn superoxide dismutase (Cu/Zn SOD) are investigated by laser flash photolysis and electron paramagnetic resonance (EPR) spectroscopy; they are compared to those of the system [Ru(bpy)(3)(2+)-Cu/Zn SOD]. Although the mechanism is complicated, primary and secondary reactions can be evidenced. First, the excited [Ru(bpz)(3)](2+) complex is quenched reductively by Cu/Zn SOD with the production of a reduced complex and an oxidized enzyme. The oxidation site of Cu/Zn SOD is proposed to correspond to amino acids located on the surface of the protein. Afterward and only when this reductive electron transfer to the excited complex has produced enough oxidized protein, another electron-transfer process can be evidenced. In this case, however, the charge-transfer process takes place in the other direction, i.e. from the excited complex to the Cu(II) center of the SOD with the formation of Ru(III) and Cu(I) species. This proposed mechanism is supported by the fact that [Ru(bpy)(3)](2+), which is less photo-oxidizing than [Ru(bpz)(3)](2+), exhibits no photoreaction with Cu/Zn SOD. Because Ru(III) species are generated as intermediates with [Ru(bpz)(3)](2+), they are proposed to be responsible for the enhancement of [poly(dG-dC)](2) and [poly(dA-dT)](2) oxidation observed when Cu/Zn SOD is added to the [Ru(bpz)(3)](2+)-DNA system.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe