Inter-strand cross-linking of Vibrio cholerae DNA induced by furazolidone: a quantitative assay by four simple methods.

Four simple methods, i.e., (i) UV absorption spectrophotometry, (ii) hydroxyapatite chromatography, (iii) fluorescence analysis of ethidium bromide bound to DNA and (iv) assay of S1 endonuclease action, were used in parallel for the estimation of furazolidone-induced inter-strand cross-links in Vibrio cholerae DNA. The data produced by the four methods were in reasonable agreement with each other and provided similar linear dose-response relations, the correlation (between dose and response) coefficient being in any case numerically greater than 0.98. When the data obtained by four independent methods were plotted in a single graph, the resulting dose-response relation could be described by the equation log NR = 1.41 - 0.54 log D, where NR is the % non-reversible DNA remaining in the cells treated by furazolidone at dose D micrograms/ml x h. The correlation coefficient in this plot was -0.98 and significant to a level better than 0.1%. This study thus brings out that any one of these four methods can be used with reasonable confidence for the diagnosis and assay of inter-strand cross-links in DNA.