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At least 865 records · Page 48Linked to original sources
PubMed1990

Peculiar ultraviolet absorbing moieties of human osteoarthritic cartilage.

The ultraviolet absorbing components of human cartilage have been measured by microspectrophotometry. The characteristics of the chondrocytes appeared to be identical, irrespective of the pathology. However the matrix of osteoarthritis cartilage contained components that absorbed maximally in the region of 270 to 250 nm; such components were not found in the matrix of cartilage of non-arthritic joints. Substances that absorb maximally in this region of the ultraviolet could generate free radicals.

Aged↗
PubMed1976

Circular dichroism of rhodopsins and porphyropsins.

Circular dichroism and absorption spectra were determined for digitonin extracts of three rhodopsins: cattle, grass frog, and pigeon; and three porphyropsins: channel catfish, bluegill sunfish, and redear sunfish. A comparison of these spectra shows the following: (1) Porphyropsins, like rhodopsins, exhibit two positive CD peaks in the spectral region 320--700 nm: an alpha peak at about 520 nm and a small beta peak at about 355 nm. These peaks substantially diminish upon bleaching. (2) In the CD spectra the alpha peaks of the porphyropsins are larger than the alpha peaks of the rhodopsins, while the beta peaks are smaller than those of the rhodopsins. This is just the opposite of the corresponding relationship between the peaks in the absorption spectra. (3) The maxima of these peaks in the CD spectra of rhodopsins and porphyropsins are consistently blueshifted from corresponding maxima in absorption spectra. (4) Some of the visual pigments show additional positive CD peaks in the spectral region 250--320 nm. In all the visual pigments studied, the CD spectra in this region decrease on bleaching. No reciprocal relationship is observed between any of the CD bands in the visible and near ultraviolet region of the spectrum.

Animals↗
PubMed1978

Origin of the ribityl side-chain of riboflavin from the ribose moiety of guanosine triphosphate in Pichia guilliermondii yeast.

In wild-type cells and some riboflavin-deficient mutants of P. guilliermondii GTP is transformed to the ribitylated intermediates 2,5-diamino-6-hydroxy-4-ribitylaminopyrimidine and 5-amino-2,6-dihydroxy-4-ribitylaminopyrimidine of the riboflavin biosynthetic path. We were able to show that these compounds were formed in vitro as well as in permeabilized cells by reactions including a reductive conversion of the product of GTP cyclohydrolase II action upon GTP. In order to analyse the pyrimidine derivates, 6,7-dimethyl-8-ribitylpterin and 6,7-dimethyl-8-ribityllumazine were synthesized by reaction of pyrimidines with diacetyl. The formation of ribitylated pyrimidines was shown to be strictly dependent on the presence of NADPH2. The data obtained indicate that the reductive step is catalyzed by a 2,5-diamino-6-hydroxy-4-ribosylaminopyrimidine-reductase. 6,7-Dimethyl-8-ribitylpterin and 6,7-dimethyl-8-ribityllumazine isolated from the incubation mixtures have been identified by chromatography and by their ultraviolet and fluorescence spectra.

Diacetyl↗
PubMed1997

Isolation and structure elucidation of an intermediate in the photodegradation of ciprofloxacin.

Ciprofloxacin decomposes photochemically in aqueous solutions at acidic pH forming two major degradation products. One of the products, isolated from irradiated solutions by flash chromatography, was 7-[(2-aminoethyl)amino]-1-cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-3-quinoline carboxylic acid. The compound was an intermediate in the photochemical process, which degraded after longer exposure with a high-pressure mercury lamp to an aromatic amino-compound, 7-amino-1-cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-3-quinoline carboxylic acid. The structure of the intermediate was elucidated on the basis of information from ultraviolet, mass and nuclear magnetic resonance spectra.

Anti-Infective Agents↗
PubMed1976

Algal glyceraldehyde-3-phosphate dehydrogenase. Pyridine-nucleotide requirements of two enzymes purified from Scenedesmus obliquus.

Two enzymes with glyceraldehyde-3-phosphate dehydrogenase activity have been purified from heterotrophically grown Scenedesmus obliquus by ion-exchange chromatography and gel filtration. The D-enzyme has a molecular weight of 550000 and a VNADH: VNADPH ratio of 16 whereas the T-enzyme has a molecular weight of 140000 and a VNADH:VNADPH ratio of 0.15. The two enzymes, however, are very similar with regard to their Michaelis constants for the reduced pyridine nucleotides, pH optimum, subunit size and ultraviolet absorption.

Chlorophyta↗
PubMed1986

Isolation and partial characterization of a high molecular weight Cd/Zn-binding protein from the kidney of the scallop Placopecten magellanicus: preliminary studies.

Exposure of the scallop Placopecten magellanicus to 20 ppb Cd2+ in seawater for 7 weeks results in a 7-fold increase in the kidney cytosol content of Cd and 5-fold increase in Zn. Sephadex G-75 column chromatography of the kidney cytosol showed that most of the Cd and Zn were bound to a protein complex with an estimated molecular mass of 45,000 daltons. Further purification of this complex by DEAE A-25 column chromatography disclosed the presence of five peaks with varying degrees of affinity for the ion-exchange resin. One of these peaks (III) was successfully rechromatographed by ion-exchange chromatography and further purified by HPLC using a gel-permeation column. The resultant protein peak which was resistant to disaggregation by 20 mM dithiothreitol gave a preliminary amino acid composition with cysteine, glycine, alanine, and lysine as the major amino acids. The aromatic amino acid phenylalanine was also present. The ultraviolet absorption spectrum gave a 250/280 nm ratio of 2.5:1. Metal analysis of the purified protein showed that it contained Cd, Zn, and Cu in ratios of 1:1:1. Results of these studies indicate that scallop kidney produces a protein complex which appears to share both similarities with mammalian metallothionein with respect to the presence of both Cd and Zn but different with respect to apparent size, amino acid composition, and ultraviolet absorption spectrum.

Amino Acids↗