title: Charge effects for differentiation of oligodeoxynucleotide isomers containing 8-oxo-dG residues.
abstract: Dissociation reactions of a series of multiply charged oligodeoxynucleotide (ODN) 12-mer anions were studied using an ion trap mass spectrometer. These mixed nucleobase 12-mers fragment first by loss of a neutral nucleobase (A, G, C, and/or 5-methyl-cytosine) followed by cleavage at 3' C-O bond of the sugar from which the base is lost to produce the complementary sequence ions, i.e., [a - B] and w type of ions. No detectable loss of 8-oxo-guanine and/or thymine from these 12-mers is observed under gentle collision conditions in the ion trap. The primary loss of a nucleobase and the subsequent backbone cleavage to generate sequence ions strongly depend on the charge state of the parent molecular ion. For low charge states (2- and 3-), product ions due to the loss of a neutral guanine base and related sequence ions are dominant in the tandem mass spectra. However, preferential loss of a neutral adenine becomes the primary reaction channel from the 5- charge state of the molecular ion. Such charge state dependent fragmentation behavior was utilized to determine the site of 8-oxo-dG residue in a series of structural isomers. The position of 8-oxo-dG residue can be simply determined from the fragmentation pattern of 3- charge state, but not of 5- charge state. It is suggested that in addition to specific modification that affects the N-glycosidic bond strength, total charge content of an ODN is an important factor for determining the differential fragmentation behavior.
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Hai
authors.initials: H
authors.lastname: Luo
authors.forename: Mary S
authors.initials: MS
authors.lastname: Lipton
authors.forename: Richard D
authors.initials: RD
authors.lastname: Smith
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D007536:Isomerism; D009841:Oligonucleotides / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D009841:Oligonucleotides; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine