Tetraols, fluorescence

We find that the fluorescence yield of freshly prepared covalent (+)-anti-BaPDE-DNA adducts in oxygen-free solutions is 66+2 lower than the yield of the tetraol 7,8,9,10-tetrahydroxytetrahydro-benzo(a)pyrene (BaPT) in the absence of DNA. Since the fluorescence lifetime of BaPT under these conditions is 200ns, the mean fluorescence lifetime of the adducts (see reference T7) can be estimated to have a lower limit of 3ns, which is close to the mean value of 0.52x1.6 + 0.42x4.0 = 2.7 ns estimated from the two short fluorescence components of Undeman et al (10). 

An alternative approach used to investigate the covalent binding of B[a]P to mouse skin has been to release the hydrocarbon-DNA adducts from the isolated DNA by acid hydrolysis (60.61). Since, in the case of BPDE-DNA adducts, they are acid labile and the tetraols produced are not only more fluorescent than the adducts themselves but also more easily extracted from the large excess of unmodified bases, this provides a convenient approach. The method does, however, require the certainty that hydrolysis of the adducts will occur and that the products will be stable or, if degradation occurs, that they can still be recognized. 

Evidently, the synthesis of fluorescent photochrome 232 (Scheme 67) occurs through the formation of a keto bromide from ketone 231 (08OL1319). The reaction of thenoine and its brominated analog with tetraol gives dimer 233, although in very low yields (07JPOC960) (Scheme 67). 

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