Localization of the dominant non-enzymatic intermolecular cross-linking sites on fibrous collagen.

Previous studies have shown that fibrous collagen undergoes intermolecular cross-linking at multiple sites of the elongated triple-helical regions among adjacent juxtaposed collagen molecules on incubation with a very high concentration of reducing sugar such as 200 mM ribose, and the similarity of the changes in its physicochemical properties to that of senescent collagen aged in vivo has been emphasized. In the present study, however, it was found that when incubated with less than 30 mM ribose, fibrous collagen underwent intermolecular cross-linking primarily between the telopeptide region of a collagen molecule and the triple-helical region of another adjacent collagen molecule, and intermolecular cross-linking between the triple-helical regions of adjacent collagen molecules was very small. Physiological significance of the previous studies thus needs to be reevaluated.

Cloning and expression of soluble cytochrome c and its role in polyvinyl alcohol degradation by polyvinyl alcohol-utilizing Sphingopyxis sp. strain 113P3.

The gene encoding cytocrome c in the pva operon of Sphingopyxis sp. strain 113P3 was cloned, on the basis of the sequence of the gene for cytochrome c (GenBank accession no. AB190288). The deduced amino acid sequence of the gene showed homologies (37% and 47% identities) with two cytochromes c of different origins. The recombinant cytochrome c tagged with hexahistidines was expressed in the periplasm of Escherichia coli BL21(DE3) harboring pT-GroE, which was in accordance with the localization of cytochrome c in strain 113P3; the protein was purified to homogeneity. The purified recombinant cytochrome c was a monomeric protein with a molecular weight of 16.5 kDa. The oxidized and reduced forms of the protein showed absorption maxima at 409 nm and at 414, 520 and 550 nm, respectively. The recombinant cytochrome c was fully reduced by polyvinyl alcohol (PVA), coupled with a catalytic amount (1/10 molar concentration) of the recombinant PVA dehydrogenase (PVADH) of the same origin, suggesting that the cytochrome c involved in the pva operon is a physiological primary electron acceptor for PVADH and that PVA dehydrogenation is linked with the respiratory chain in Sphingopyxis sp. strain 113P3.

Color and chemical properties of oil used for deep frying on a large scale.

Acid value (AV), polar compound content (PC), carbonyl value (CV) and Gardner color of oil used for deep-frying in kitchens at a supermarket, lunch chain store, restaurant, eating house, and hospital were analyzed. All AVs obtained but one (3.38) were within the limit set by the Food Sanitation Act of Japan (AV ≤ 3, peroxide value ≤ 30). However, some oil samples had a PC over 25%, which is beyond the limit legislated by some European countries. When the relation between the Gardner color and the AV, PC, or CV of the oil was investigated, well correlated logarithmic regression curves were obtained from the oil of all kitchens except the hospital kitchen. However, the use of lard-containing canola oil without oil replenishment in the eating house increased color values rapidly. All of the values obtained from pure vegetable oil used almost daily were plotted on a graph. It was found that kitchen-by-kitchen differences in fryer, vegetable oil, frying temperature, heating time, and amounts and kinds of foods fried did not influence the relation between Gardner color value versus AV, PC or CV. In conclusion, frying vegetable oil used in large-scale kitchens without official inspection can be better controlled with Gardner color determination by the operators and administrators. This would improve the quality of the oil ingested by facility patrons.