title: Direct observation of a DNA quadruplex by electrospray ionization mass spectrometry.
abstract: In 10 mM sodium phosphate, pH 7.6, containing 0.1 mM ethylenediaminetetraacetic acid, ions correspondings to the non-calent, four-stranded oligonucleotide, d(CGCG4GCG)4, were detected by negative ion electrospray ionization (ESI) mass spectrometry at a low nozzle-skimmer (delta NS) bias (-150 V), but not at a higher delta NS bias (> -250 V). In contrast, when the sample was desalted and analyzed by ESI mass spectrometry at a low delta NS bias only ions for the single-stranded d(CGCG4GCG) species were observed. These data agree with spectroscopic evidence which showed that oligonucleotides with the sequence motif 5'd(CGCGnGCG)3', where n = 2-5, formed stable four-stranded complexes in the presence of monatomic cations, like K+, Ca2+, Na+ and Li+, but not in their absence.
authors: Chemical Sciences Department, Pacific Northwest Laboratories, Richland, Washington 99352.
authors: D R
authors: DR
authors: Goodlett
authors: D G
authors: DG
authors: Camp
authors: C C
authors: CC
authors: Hardin
authors: M
authors: M
authors: Corregan
authors: R D
authors: RD
authors: Smith
mesh_terms: D001483:Base Sequence; D002942:Circular Dichroism; D004247:DNA / Q000032:analysis*; D004492:Edetic Acid; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000032:analysis; D013696:Temperature
chemical_list: D009841:Oligonucleotides; D004247:DNA; D004492:Edetic Acid