Distribution of chondroitin sulfate in cartilage proteoglycans under associative conditions.
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Proteoglycan aggregates and proteoglycan subunits were extracted from bovine articular cartilage with guanidine-HC1 folowed by fractionation by equilibrium centrifugation in cesium chloride density gradients. The distribution of chondroitin sulfates (CS) in the cartilage proteoglycans was studied at the disaccharide level by digestion with chondroitinases. In the proteoglycan aggregate fraction, it was observed that the proportion of 4-sulfated disaccharide units to total CS increased from the bottom to the top fractions, whereas that of 6-sulfated disaccharide units was in the reverse order. Thus, the ratio of 4-sulfated disaccharide units to 6-sulfated disaccharide units increased significantly with decreasing density. The proportion of non-sulfated disaccharide units to total CS tended to increase with increasing density. These data indicate a polydisperse distribution of CS chains, under the conditions used here, in proteoglycan aggregates from bovine articular cartilage. (+info)
Complexes of aliphatic sulfates and human-serum albumin studied by 13C nuclear-magnetic-resonance spectroscopy.
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The interaction of human serum albumin and various long-chain sulfates has been studied. Binding of sodium octylsulfate to albumin increases in the concentration range studied as measured by equilibrium dialysis. In contrast, binding of the sodium salts of decylsulfate and dodecylsulfate is constant at a concentration of free ligand higher than 50 mM and 12 mM corresponding to binding of 110 and 83 sulfate molecules per albumin molecule, respectively. Viscosity measurements indicate that binding of decylsulfate and dodecylsulfate is associated with unfolding of the albumin molecule. In contrast, binding of octylsulfate does not cause gross conformation changes of albumin. However, the chemical shifts of bound octylsulfate obtained by natural abundance 13C nuclear magnetic resonance spectroscopy show significant changes at 80 mM and 150 mM free ligand. The spin-spin and spin-lattice relaxation times also show changes in the association between octylsulfate and albumin at 80 mM free sulfate. These observations indicate alterations in the binding properties at 10--11 and 20--21 bound ligand molecules, respectively. The relaxation times are considerably increased by binding to albumin, indicating less motional freedom of the molecules in the bound state. At high levels of sulfate binding the relaxation times of the terminal methyl group approach that of free ligand. The chemical shifts of all the bound carbon atoms studied, except the CH2 group nearest to the sulfate group (C1), are comparable to those observed in the micellar state indicating binding in a non-polar environment. However, the relaxation times indicate that the motional freedom of sulfates bound to albumin is much more restricted than in micelles. The shift of C1 indicates that this part of the ligand is situated in a polar environment. The following model for binding of high concentrations of aliphatic detergents is proposed. The sulfate group and the CH2 group nearest to it is situated in a polar medium caused by interaction between the sulfate group and a positive amino acid residue on albumin. The other CH2 groups interact with hydrophobic amino acid residues on albumin. The CH3 group does not interact with the albumin molecule but associates with other methyl groups of sulfates bound in the vicinity forming a hydrophobic medium. (+info)
Effect of cholesterol sulfate and sodium dodecyl sulfate on lecithin-cholesterol acyltransferase in human plasma.
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The effects of cholesterol sulfate and sodium dodecyl sulfate (SDS) on the esterification of cholesterol in sonicated dispersions of lecithin-cholesterol mixtures by lecithin-cholesterol acyltransferase [EC 2.3.1.43] (LCAT) in human plasma were studied in vitro. The acyltransferase activity was inhibited at concentrations of cholesterol sulfate higher than 1 X 10(-4) M. This inhibition was not eliminated by the addition of bovine serum albumin or CaC12. On the contrary, the acyltransferase activity was stimulated at concentrations of SDS ranging from 1 X 10(-5) M to 1 X 10(-3) M, and maximum stimulation was obtained at 5 X 10(-4) M. The maximum stimulation disappeared on the addition of bovine serum albumin (30 mg per ml of incubation medium), 1 X 10(-3) M CaC12 or 1 X 10(-4) M cholesterol sulfate. On the other hand, the extent of inhibition of the acyltransferase by cholesterol sulfate was not affected by the amount of lecithin in the dispersion added as a substrate, but the maximum stimulation (5 X 10(-4) M SDS) of the acyltransferase was interfered with when a large amount of lecithin was present in the dispersion. In addition, the amount of SDS required for maximum cholesterol esterification was not affected by the amount of lecithin present in the dispersion. These results suggest that the action of cholesterol sulfate on the acyltransferase is different from that of SDS. (+info)
Suspected nasopharyngeal carcinoma in three workers with long-term exposure to sulphuric acid vapour.
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Sulphuric acid vapour has been suspected of being an industrial carcinogen. In this study, a cluster is presented of three patients with nasopharyngeal carcinoma (NPC) who worked in the same building of a telecommunications conveyance station in southern Taiwan with long term exposure to sulphuric acid vapour concentrations as high as 0.18 mg/m3. All three workers were diagnosed with NPC within a 5 month period between September 1992, and March 1993. Compared with 19 other healthy workers from the same building, these three workers with NPC had worked significantly longer in this building than had the others (mean (SD) (years): 12.7 (0.6) v 7.4 (4.4); p = 0.01). With an in situ nucleic acid hybridisation and immunostaining method for colocalised Epstein-Barr virus (EBV) and secretory component (SC) protein among biopsy specimens of these three patients with NPCs, it was found that some tumour cells did not contain EBV and SC protein staining signals. These results indicate that EBV infection is not the only risk factor for NPC and long term exposure to relatively low concentrations of sulphuric acid vapour may be associated with the development of NPC. (+info)
Sulfuric acid on Europa and the radiolytic sulfur cycle.
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A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes. (+info)
Biosynthesis of heparin/heparan sulfate: kinetic studies of the glucuronyl C5-epimerase with N-sulfated derivatives of the Escherichia coli K5 capsular polysaccharide as substrates.
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The D-glucuronyl C5-epimerase involved in the biosynthesis of heparin and heparan sulfate was investigated with focus on its substrate specificity, its kinetic properties, and a comparison of epimerase preparations from the Furth mastocytoma and bovine liver, which synthesize heparin and heparan sulfate, respectively. New substrates for the epimerase were prepared from the capsular polysaccharide of Escherichia coli K5, which had been labeled at C5 of its D-glucuronic and N-acetyl-D-glucosamine moieties by growing the bacteria in the presence of D-[5-(3)H]glucose. Following complete or partial ( approximately 50%) N-deacetylation of the polysaccharide by hydrazinolysis, the free amino groups were sulfated by treatment with trimethylamine.SO(3)complex, which yielded products that were recognized as substrates by the epimerase and released tritium from C5 of the D-glucuronyl residues upon incubation with the enzyme. Comparison of the kinetic properties of the two substrates showed that the fully N-sulfated derivative was the best substrate in terms of its K(m)value, which was significantly lower than that of its partially N-acetylated counterpart. The V(max)values for the E.coli polysaccharide derivatives were essentially the same but were both lower than that of the O-desulfated [(3)H]heparin used in our previous studies. Surprisingly, the apparent K(m)values for all three substrates increased with increasing enzyme concentration. The reason for this phenomenon is not entirely clear at present. Partially purified C5-epimerase preparations from the Furth mastocytoma and bovine liver, respectively, behaved similarly in terms of their reactivity towards the various substrates, but the variation in apparent K(m)values with enzyme concentration precluded a detailed comparison of their kinetic properties. (+info)
A habitat for psychrophiles in deep Antarctic ice.
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Microbes, some of which may be viable, have been found in ice cores drilled at Vostok Station at depths down to approximately 3,600 m, close to the surface of the huge subglacial Lake Vostok. Two types of ice have been found. The upper 3,500 m comprises glacial ice containing traces of nutrients of aeolian origin including sulfuric acid, nitric acid, methanosulfonic acid (MSA), formic acid, sea salts, and mineral grains. Ice below approximately 3,500 m comprises refrozen water from Lake Vostok, accreted to the bottom of the glacial ice. Nutrients in the accretion ice include salts and dissolved organic carbon. There is great interest in searching for living microbes and especially for new species in deepest Antarctic ice. I propose a habitat consisting of interconnected liquid veins along three-grain boundaries in ice in which psychrophilic bacteria can move and obtain energy and carbon from ions in solution. In the accretion ice, with an age of a few 10(4) years and a temperature a few degrees below freezing, the carbon and energy sources in the veins can maintain significant numbers of cells per cubic centimeter that are metabolizing but not multiplying. In the 4 x 10(5)-year-old colder glacial ice, at least 1 cell per cm(3) in acid veins can be maintained. With fluorescence microscopy tuned to detect NADH in live organisms, motile bacteria could be detected by direct scanning of the veins in ice samples. (+info)
Oxidized low density lipoproteins regulate synthesis of monkey aortic smooth muscle cell proteoglycans that have enhanced native low density lipoprotein binding properties.
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Oxidized low density lipoproteins (Ox-LDL) affect several biological processes involved in atherogenesis. However, it is not known whether Ox-LDL can regulate proteoglycan expression and thus affect arterial wall lipoprotein retention. This study evaluated whether Ox-LDL, as compared with native LDL, regulates proteoglycan expression by monkey arterial smooth muscle cells in vitro and whether proteoglycans synthesized in the presence of Ox-LDL exhibit altered lipoprotein binding properties. Ox-LDL stimulated glycosaminoglycan synthesis, as measured by (35)SO(4) incorporation, by 30-50% over that of native LDL. The effect was maximal after 72 h of exposure to 5 microg/ml of Ox-LDL. The molecular sizes of versican, biglycan, and decorin increased in response to Ox-LDL, as indicated by size exclusion chromatography and SDS-polyacrylamide gel electrophoresis. These effects could be mimicked by the lipid extract of Ox-LDL. These size increases were largely due to chain elongation and not to alterations in the ratio of (35)SO(4) to [(3)H]glucosamine incorporation. Affinity chromatography indicated that Ox-LDL stimulated the synthesis of proteoglycans with high affinity for native LDL. Ox-LDL also specifically stimulated mRNA expression for biglycan (but not versican or decorin), which was correlated with increased expression of secreted biglycan. Thus, Ox-LDL may influence lipoprotein retention by regulating synthesis of biglycan and also by altering glycosaminoglycan synthesis of vascular proteoglycans so as to enhance lipoprotein binding properties. (+info)