Synthesis of N7-hydroxy- and N7-methoxycephalosporins.

Approximating the Permanent in O∗(n7) Time

The first polynomial-time algorithm to approximate (with arbitrary precision) the permanent of a non-negative matrix was presented by Jerrum, Sinclair and Vigoda. They designed a simulated annealing algorithm with a running time of O∗(n26) for 0/1 matrices. Subsequently, they improved their analysis, resulting in a O∗(n10) time algorithm. We present a O∗(n7) time algorithm. Our improvement come...

Fluorescence quantification of aflatoxin N7-guanine adducts.

Increasingly sensitive assays are needed to understand and evaluate the effects of chemical exposures on individuals and populations. Several assays have been developed to measure the environmental dietary carcinogen, aflatoxin, and its metabolites in biological specimens. One, the 8,9-dihydro-8-(N7-guanyl)-9-hydroxy-aflatoxin B1 nucleic acid adduct, has been shown to be both highly correlated ...

Base-boronated dinucleotides: synthesis and effect of N7-cyanoborane substitution on the base protons.

Boron-modified nucleic acids comprise a new set of DNA mimics that have potential biological and therapeutic applications. A series of nine dinucleotides containing N7-cyanoborane-2'-deoxyguanosine ((7b)dG) at the 3', 5' or both positions of the phosphodiester linkage have been synthesized using solution phase phosphoramidite chemistry. Fmoc was used as the 5'-protecting group because of incomp...

Biologically relevant chemical reactions of N7-alkylguanine residues in DNA.

DNA sequence selectivity of guanine-N7 alkylation by nitrogen mustards.

Nitrogen mustards alkylate DNA primarily at the N7 position of guanine. Using an approach analogous to that of the Maxam-Gilbert procedure for DNA sequence analysis, we have examined the relative frequencies of alkylation for a number of nitrogen mustards at different guanine-N7 sites on a DNA fragment of known sequence. Most nitrogen mustards were found to have similar patterns of alkylation, ...