DNA Sequencing by a De-MALDI-TOF MS.
DNA sequencing by DE-MALDI-TOF MS. As we known, Sanger’s dideoxy termination method of DNA sequencing depends on high level of resolution to allow sequential distribution of the termination fragments of lengths ‘n’ and ‘n + 1’. The termination products of Sanger’s termination reactions however, can also be examined by delayed extraction MALDI-TOF MS. In this approach, mass spectra of each of the four specific dideoxy termination reactions generated from Sanger’s chemistry are overlaid and each sized product correlated to one of the four base termination reactions, since mass of each base is known. A major advantage of this approach is the fast acquisition of data by MALDI-TOF MS, which needs only minutes per sample.

DE-MALDI is coupled with high yield cycle sequencing protocol to make it suitable for analysis of sequencing mixtures of oligonucleotides, 40-50 bases long .

Diagram Showing Negative Ion Mass Spectra of Four Dideoxy Reactions Generated By Primer Extension on a 50-base Template. Numbers Indicate Peaks that correspond to expected size of termination products numbered according to the total DNA fragment length including primers:sequence deducted is given at the top of the figure.

Since fragments larger than 100 base cannot be utilized for sequencing, the technique can not be employed for genome sequencing, but can certainly be used for minisequencing required for single nucleotide polymorphism (SNP) genotyping.