Comparative study of three methods for non-radioactive in vivo DNA Labeling in Escherichia coli using nucleoside analogs

In the present work, a comparative study of 5-FdUrd, thy(-), and metabolic in vivo labeling methods for plasmid and chromosomal DNA in E coli DH5alpha cells was performed in order to achieve the best thymidine substitution method by 5-BrdUrd. According to the colorimetric immunoenzymatic results, we found that the minimal detectable labeled DNA (MDLD) was 312 pg with the 5-FdUrd and thy(-) methods for 5-BrdUrd labeled plasmid DNA. 5-BrdUrd replaced about 96% of the total thymidine by 5-FdUrd methods; for the thy- and metabolic labeling methods, the MDLD value was 1,25 ng for denatured 5-BrdUrd chromosomal DNA. Pyrimidine nucleoside analogues were also evaluated as immunochemical markers for their in vivo introduction into DNA.