Dc. Gale et Rd. Smith, CHARACTERIZATION OF NONCOVALENT COMPLEXES FORMED BETWEEN MINOR-GROOVEBINDING-MOLECULES AND DUPLEX DNA BY ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY, Journal of the American Society for Mass Spectrometry, 6(12), 1995, pp. 1154-1164
The noncovalent complex formed in solution between minor groove bindin
g molecules and an oligonucleotide duplex was investigated by electros
pray ionization-mass spectrometry (ESI-MS). The oligonucleotide duplex
formed between two sequence-specific 14-base pair oligonucleotides wa
s observed intact by ESI-MS and in relatively high abundance compared
to the individual single-stranded components. Only sequence-specific A
:B duplexes were observed, with no evidence of random nonspecific aggr
egation (i.e., A:A or B:B) occurring under the conditions utilized. Du
e to the different molecular weights of the two 14-base Fair oligonucl
eotides, unambiguous determination of each oligonucleotide and the seq
uence-specific duplex was confirmed through their detection at unique
mass-to-charge ratios. The noncovalent complexes formed between the se
lf-complementary 5'-dCGCAAA7TTTGCG-3' oligonucleotide and three minor
groove binding molecules (distamycin A, pentamidine, and Hoechst 33258
) were also observed. Variation of several electrospray ionization int
erface parameters as well as collision-induced dissociation methods we
re utilized to characterize the nature and stability of the noncovalen
t complexes. The noncovalent complexes upon collisional activation dis
sociated into single-stranded oligonucleotides and single-stranded oli
gonucleotides associated with a minor groove binding molecule. ESI-MS
shows potential for the study of small molecule-oligonucleotide duplex
interactions and determination of small molecule binding stoichiometr
y.