Studies on the protein-bound chondroitin sulphate of bovine cortical bone

A fraction containing chondroitin sulphate, isolated from bovine cortical bone under mild conditions, was separated by ion-exchange chromatography into three fractions with apparent homogeneity on electrophoresis and ultracentrifugation. Two of these appeared to consist of chondroitin sulphate bound to a glycoprotein ;core' that had similarities to the bone sialoprotein described previously. The differences in composition of the two fractions were considered to be due to variation in the number or lengths of the polysaccharide chains. The presence of xylose and the alkali-lability of the bond between protein and polysaccharide suggested the presence of a xylosylserine linkage. The third fraction had the properties of a relatively pure chondroitin sulphate which contained a small amount of peptide. These fractions differed considerably from the protein-polysaccharide complexes of epiphysial and other cartilages, and their relevance to the possible role of glycosaminoglycans is discussed.     

Comparison of antioxidant effectiveness of lipoic acid and dihydrolipoic acid

The abilities of dihydrolipoic acid (DHLA) to scavenge peroxynitrite (ONOO^?), galvinoxyl radical, 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate) cation radical (ABTS^+?), and 2,2′‐diphenyl‐1‐picrylhydrazyl radical (DPPH) were higher than those of lipoic acid (LA). The effectiveness of DHLA to protect methyl linoleate against 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH)‐induced oxidation was about 2.2‐fold higher than that of LA, and DHLA can retard the autoxidation of linoleic acid (LH) in the β‐carotene‐bleaching test. DHLA can also trap ～0.6 radicals in AAPH‐induced oxidation of LH. Moreover, DHLA can scavenge ～2.0 radicals in AAPH‐induced oxidation of DNA and AAPH‐induced hemolysis of erythrocytes, whereas LA can scavenge ～1.5 radicals at the same experimental conditions. DHLA can protect erythrocytes against hemin‐induced hemolysis, but accelerate the degradation of DNA in the presence of Cu²⁺. Therefore, the antioxidant capacity of –SH in DHLA is higher than S‐S in LA. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:216–223, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.20378     

Solvolytic reactions of Lewis acids in monobromoacetic acid and the nature of the solvolysed products

Solid compounds of composition SnCl₂(CH₂BrCOO)₂, Ti(CH₂BrCOO)₄, Zr(CH₂BrCOO)₄, Th(CH₂BrCOO)₄, Si₂O(CH₂BrCOO)₆ have been isolated when the respective tetrachlorides are refluxed with excess of monobromoacetic acid. Zirconylchloride forms the compound ZrO(CH₂BrCOO)₂. CH₂BrCOOH in a similar manner. These compounds have been characterized by their elemental analysis, molar conductance and by infrared studies, NMR and FAB mass spectrometry. In solution, the bromoacetate groups readily lost. Their Lewis acid character was established by isolating and characterizing their adducts with organic tertiary bases. Antimony pentachloride, aluminium trichloride and ferric chloride form compounds of composition SbCl₂(CH₂BrCOO)₃, Al(CH₂BrCOO)₃, FeCl(CH₂BrCOO)₂ and Fe(CH₂BrCOO)₃ when refluxed with excess of the solvent and these have been characterized by infrared studies.     

Chromatographic analysis of lipoic acid and related compounds

The analysis of lipoic acid and related compounds, such as its reduced form dihydrolipoic acid, its amide form lipoamide and other analogues, in biological and food samples is important in biochemistry, nutritional and clinical chemistry. This review summarizes the chromatographic methods for the determination of lipoic acid and related compounds, and their applications to various samples such as bacteria, tissues, drugs and food. Gas chromatographic methods with flame ionization detection and flame photometric detection are commonly used for the quantification of lipoic acid present as its protein-bound form, after acid or base hydrolysis of these samples. High-performance liquid chromatographic methods with ultraviolet, fluorescence and electrochemical detection are mainly used for the determination of free lipoic acid and related compounds, such as dihydrolipoic acid, lipoamide and other analogues. Moreover, gas chromatography–mass spectrometry and capillary electrophoresis methods are also developed.     

Atherosclerosis in Japanese quail and the effect of lipoic acid

The Japanese quail (Coturnix coturnix japonica) is a useful laboratory animal for the study of atherosclerosis. It is small, omnivorous, easy to maintain, and susceptible to either spontaneous or cholesterol-induced atherosclerosis, and it has a low feed consumption and short life cycle. It develops atheromatous lesions with the characteristic lipid deposition and myofibroblastic proliferation in the aorta and sometimes in the coronary artery. Japanese quail can be genetically bred into lines highly susceptible and resistant to atherosclerosis. A nutritional study has indicated that a high intake of soy protein prevents the disease in the quail. Contradictory results of studies with rabbits were reported in the early literature on the prevention of atherosclerosis by lipoic acid. Recently the effect of lipoic acid on atherosclerosis was reevaluated in the quail. A preventive effect of this compound was demonstrated when it was implanted s.c. and slowly released in the animal.     

Inhibitory effect of lipoic acid on firefly luciferase bioluminescence

Lipoic acid was found to inhibit the firefly luciferin-luciferase reaction. The inhibition is competitive and is the strongest known (Ki = 0.026 +/- 0.013 microM) compared with other reported inhibitors. Considering the structure-activity correlations, the mechanism of inhibition may originate from the sulfur atom and carboxyl moiety of lipoic acid giving it structural specificity. Subsequent addition of lipoic acid and nitric oxide accelerated the inhibition in vitro, suggesting that lipoic acid may have a functional role in regulating firefly bioluminescence.