Singlet molecular oxygen quenching by the antioxidant dimethylmethoxy chromanol in solution and in ex vivo porcine skin.

Singlet-oxygen is a non-radical reactive oxygen species believed to play a major role in many photooxidation processes in connection with diverse photo-biological processes such as skin ageing or photocarcinogenesis. Dimethylmethoxy chromanol (3,4-dihydro-6-hydroxy-2,2-dimethyl-7-methoxy-1(2H)-benzopyran) is a potent antioxidant used in cosmetic and pharmaceutical formulations. We have assessed the singlet oxygen quenching ability of dimethylmethoxy chromanol, by monitoring the near-IR phosphorescence of singlet-oxygen in solution and in ex vivo porcine skin samples.

[Leiomyosarcoma of the larynx. Based on one case].

Leiomyosarcoma is a malignant tumour of smooth muscle cells. Usually is found in the gastrointestinal and female genital tracts, but is extremely rare in the larynx. Diagnosis is based in immunohistochemical studies.

Long-lived glycosyl-enzyme intermediate mimic produced by formate re-activation of a mutant endoglucanase lacking its catalytic nucleophile.

The mutant E134A 1,3-1,4-beta-glucanase from Bacillus licheniformis, in which the catalytic nucleophilic residue has been removed by mutation to alanine, has its hydrolytic activity rescued by exogenous formate in a concentration-dependent manner. A long-lived alpha-glycosyl formate is detected and identified by (1)H-NMR and matrix-assisted laser desorption ionization-time-of-flight-MS. The intermediate is kinetically competent, since it is, at least partially, enzymically hydrolysed, and able to act as a glycosyl donor in transglycosylation reactions.

Expeditious synthesis of a new hexasaccharide using transglycosylation reaction catalyzed by Bacillus (1-->3),(1-->4)-Beta-D-glucan 4-glucanohydrolase.

Enzymatic hydrolysis of barley (1-->3),(1-->4)-beta-D-glucan using a recombinant (1-->3),(1-->4)-beta-glucanase from Bacillus licheniformis gives Glc beta 4Glc beta 3Glc isolated after acetylation in 49% yield. Conventional treatment produced the corresponding beta-fluoride which was carefully de-O-acetylated. A transglycosylation reaction with this substrate, catalyzed by the title enzyme, gave Glc beta 4Glc beta 3Glc beta 4Glc beta 4Glc beta 3Glc in 20% yield.

Synthesis of aryl 3-O-beta-cellobiosyl-beta-D-glucopyranosides for reactivity studies of 1,3-1,4-beta-glucanases.

A series of substituted aryl beta-glycosides derived from 3-O-beta-cellobiosyl-D-glucopyranose with different phenol-leaving group abilities as measured by the pKa of the free phenol group upon enzymatic hydrolysis has been synthesised. Aryl beta-glycosides with a pKa of the free phenol leaving group > 5 were prepared by phase-transfer glycosidation of the per-O-acetylated alpha-glycosyl bromide with the corresponding phenol, whereas the 2,4-dinitrophenyl beta-glycoside was obtained by condensation of 1-fluoro-2,4-dinitrobenzene with the partially acetylated trisaccharide followed by acid de-O-acetylation. The aryl beta-glycosides have been used for reactivity studies of the wild-type Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase.