SYNTHESIS OF ELECTROPHORE-LABELED OLIGONUCLEOTIDES AND CHARACTERIZATION BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY

Recent work to apply mass spectrometric methods to DNA analysis has le d to the attachment of an electrophore to an oligonucleotide primer, w ith the purpose of investigating whether the advantages of electron ca pture ionization (increased ionization efficiency, reduced fragmentati on) could be extended to larger molecules, such as Sanger sequence lad ders. The stability of the electrophore-modified primers under conditi ons encountered during matrix-assisted laser desorption/ionization mas s spectrometry (MALDI-MS) was investigated. Four different electrophor e labels were successfully attached to the 5' terminus of a 17-base, s ingle-stranded oligodeoxyribonucleotide sequencing primer, The attache d electrophore tags are robust under conditions used for sample prepar ation and MALDIMS, and little or no fragmentation resulting from loss of the electrophore was observed. While no sensitivity enhancement was observed for the electrophore-labeled DNA, mass spectrometric conditi ons are discussed under which the electrophore labels could enhance th e detection of DNA sequencing ladders.