- β-D-ribosidase activity indicators with a chromogenic substrate
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This invention provides a method of detecting enzyme activity on a solid medium. The enzyme substrate has a chromogenic portion comprising a catechol residue, in which a derivitising moiety is linked to the aromatic ring of the catechol via a bond, and an enzyme cleavable group which is attached via an ester or ether linkage to the oxygen atom derived from a hydroxyl group of the catechol residue. If the enzyme substrate contacts an enzyme capable of cleaving the enzyme cleavable groups and the cleaved compound contacts a chelatable metal ion, a substantially non-diffusable coloured precipitate is formed.
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Page/Page column 32
(2009/05/29)
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- Determination of the sequential order of acidity in a polyhydroxylated benzophenone series. Consequence on the oxidation reaction in relation to hepatotoxicity
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The pKa values of successive acid-base equilibria involved in the pyrogallol ring ionisation of exifone, 2,3,4-trihydroxybenzophenone 1, and related methoxy derivatives were determined by UV-VIS absorption spectrometry and potentiometric titration.Due to strong intramolecular hydrogen bonding, the sequential order of acidity of the three hydroxy groups of 1 was found to be 4-OH > 3-OH > 2-OH.The polyhydroxylated benzophenones were oxidized to 3,4-quinone only in a narrow range of acidity in which the monoanionic 4-olate species predominated in solution.The attachment of an amino-alcohol residue resulted in the trapping of the transient 3,4-quinone and provided a convenient route to novel 1,4-benzoxazine derivatives.Cytotoxicity experiments in rat hepatocytes indicated that some of these compounds were significantly less toxic than the parent exifone.
- Largeron, Martine,Langevin-Bermond, Dominique,Fleury, Maurice-Bernard
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p. 893 - 900
(2007/10/03)
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