Detection of double-stranded DNA by IR- and UV-MALDI mass spectrometry.
Double-stranded DNA ranging from 9 kDa to over 500 kDa were desorbed and analyzed by MALDI TOF mass spectrometry. IR-MALDI with glycerol as matrix yielded excellent results for larger double-stranded DNA by adjustment of the ionic strength through the addition of salts. Very little fragmentation and a routine sensitivity in the subpicomole range were observed in IR-MALDI when double-stranded analytes harboring 70 base pairs or more were probed. In the lower mass range (up to approximately 70 base pairs), UV-MALDI with 6-aza-2-thiothymine as matrix was the ionization method of choice because it allowed specific double-stranded complexes containing relatively few base pairs to be desorbed intactly. In this mode, an essentially quantitative detection of the double-stranded form was observed for a 70-mer. The UV-MALDI was accompanied by a significant fragmentation and a resulting reduced sensitivity and mass resolution. The methods described open MALDI-MS for the analysis of large DNA-DNA and DNA-protein complexes.
Institute of Medical Physics and Biophysics, University of Münster, Germany. f.kir@PR-group.ou.dk
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Kirpekar
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Berkenkamp
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Hillenkamp
D004247:DNA / Q000032:analysis*; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
D004269:DNA, Bacterial; D004247:DNA