Genomic N(6)-methyladenine determination by MEKC with LIF

2'-Deoxy-N(6)-methyladenosine (N(6)mdA) is frequently found in prokaryotic and unicellular eukaryotic genomes. Although methylated bases represent only a minor fraction of the genome, they, however, exhibit strong biological effects. Here, we report a fast and sensitive method for the quantification of global adenine methylation in DNA. The method is based on a recently developed procedure consisting of fluorescence labeling of deoxyribonucleotides with BODIPY FL EDA and analysis by CE with LIF. An oligodeoxyribonucleotide site specifically modified with N(6)mdA was used for peak assignment, to establish separation conditions and to determine the LOD. The method yielded a LOD for N(6)mdA of 280 pM (1.4 amol), which is equivalent to ∼1 N(6)mdA per 10(4) normal nucleotides (0.01%) using 1 μg of DNA as the matrix. After calibration with completely dam methylated λ DNA, the assay was applied to the analysis of various DNAs.