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Browning cross-linking

Uvarova and Gorshkova131 reported the thermal polymerization of 2-furfuryl vinyl ether and of a series of vinyl ethers of alkyl-1-(2-furyl) eaibinols. Treatment of these compounds at 150 °C for 24 hours produced brown cross-linked products with 2-furfuryl vinyl ether, and soluble, low molecular-weight polymers with the others. It seems likely that in all these systems the ring participated in the growth of the chains, but the lack of experimental details and of structural determination makes it difficult to assess the results. [Pg.79]

Pirie (Pll) was the first to investigate the yellow-brown pigment in nuclear cataracts. Examination of 660 cataractous lenses (B37, D12, Pll) revealed 25% to be uniformly pale yellow and a further 29% with a hazel to deep brown nucleus. She isolated a fraction of insoluble crystallin protein held together by covalent cross-links that were not disulfides. A brown cross-linked material was isolated that appeared to contain some nonprotein mate-... [Pg.42]

Ionic cross-linking can be achieved in a number of systems and different microstructures result. For rigid chains it is possible for the ion to coordinate in a specific manner with the chain. Alginates are a good example of this. These are natural polymers derived from a brown macro-algae. The method of extraction and the species of the algae influences the chemistry and hence the rheology of these polymers. There... [Pg.210]

It is noteworthy that, unlike the previously described induces of PTPC opening, GD3 is able to exert its effect on mitochondria even in the presence of submicromolar calcium concentration (Kristal and Brown, 1999a), a property shared only by the most potent PT inducers, such as the thiol cross-linking agent phenylarsine oxide and by the peptide mastoparan. This low calcium requirement is important because intracellular calcium concentration during CD95-mediated apoptosis was not described to rise above 0.4 pM (Oshimi and Miyazaki, 1995). [Pg.299]

The initial products of the reactions between sugars and proteins may enter a cascade of reactions yielding fluorescence, browning, and polymerization of proteins ("cross-linking"). The brown pigments, so-called melanoidins, are polymers whose composition has not yet been established completely. Melanoidins bind calcium and may thus interfere with de- and remineralization in caries. [Pg.34]

Armstrong attributed the increased resistance of dentin matrix to proteolysis to the blockage of susceptible sites by covalently bound carbohydrate. Later it became clear that the Maillard reaction induces the formation of covalent bonds (cross-links) between protein molecules, accounting for such resistance as well. The presence of non-degradable matrix proteins inhibits mineral dissolution (Chapter 2). In addition, both brown pigments and cross-linked proteins inhibit the production of extracellular polysaccharides by cariogenic streptococci (Kobayashi et al., 1990). [Pg.34]

It is noteworthy that several of fhe above-mentioned mediators of discoloration have been found fo inhibif sfrepfococcal proliferation. In addition, collagen cross-linking caused by enzymatic and non-enzymat-ic browning or by tannage with tannins might render dentin less susceptible to proteolytic degradation. [Pg.38]

The first attempts to use macroporous polystyrene supports for onium ion catalysts were reported in the early papers of Brown and Jenkins 54) and of Regen 89). The lightly cross-linked macroporous Rohm and Haas XE-305, 46 % RS as spacer chain catalyst 15, gave O- and C-alkyl products from 2-naphthoxide ion and benzyl bromide... [Pg.77]

Like as2-casein, /e-casein has two disulfide bonds which can form cross-links with /3-lactoglobulin. The N-terminal two-thirds of the molecule is hydrophobic and contains the two disulfide bonds. The C-termi-nal end is hydrophilic, polar, and charged. It varies in the number of attached carbohydrate moieties and has only one phosphate group. These characteristics make /c-casein ideal for the surface of casein micelles, where it is most often found. It is not susceptible to calcium ion binding, as the other caseins are, and when present on the surface of micelles, it protects the other caseins from calcium (McMahon and Brown 1984A Swaisgood 1982). [Pg.586]

Cross-linking using diazonium compounds usually creates deeply colored products characteristic of the diazo bonds. Occasionally, the conjugated molecules may turn dark brown or even black. The diazo linkages are reversible by addition of 0.1 M sodium dithionite in 0.2 M sodium borate, pH 9. On cleavage, the color of the complex is lost. [Pg.182]

Reported applications of EGS include cross-linking studies of cytochrome P-450 (Baskin and Yang, 1980a), conjugation of tumor necrosis factor with lymphotoxin (Browning and Ribolini, 1989), the conversion of a gonadotropin-releasing hormone... [Pg.220]

Brown-Augsburger, P., Tisdale, C., Broekelmann, T., Sloan, C., and Mecham, R. P. (1995). Identification of an elastin cross-linking domain that joins three peptide chains. Possible role in nucleated assembly./. Biol. Chem. 270, 17778-17783. [Pg.454]


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See also in sourсe #XX -- [ Pg.35 , Pg.274 , Pg.275 ]




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