7-DEAZA PURINE-BASES OFFER A HIGHER ION STABILITY IN THE ANALYSIS OF DNA BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY

Oligodeoxynucleotides which contain 7-deaza analogues of the normal pu rine nucleotides have been synthesized both enzymatically and chemical ly. When subjected to matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis, the modified samples offer both hig her stability and increased sensitivity compared to otherwise identica l unmodified oligodeoxynucleotides. In view of these observations, mod els for the fragmentation of oligodeoxynucleotides in MALDI-MS with po sitive ion detection mode are presented. Additionally, the potential u se of 7-deaza purine nucleotides in the MALDI-MS analysis of DNA seque ncing reactions is discussed.