title: Fragmentation of isomeric intrastrand crosslink lesions of DNA in an ion-trap mass spectrometer.
abstract: The collision-induced dissociation pathways of isomeric cytosine-guanine and cytosine-adenine intrastrand crosslink-containing dinucleoside monophosphates were investigated with the stable isotope-labeled compounds to gain insights into the effects of chemical structure on the fragmentation pathways of these DNA modifications. A Dimroth-like rearrangement, which was reported for protonated 2'-deoxycytidine and involved the switching of the exocyclic N4 with the ring N3 nitrogen atom, was also observed for the cytosine component in the protonated ions of C[5-8]G, C[5-2]A, and C[5-8]A, but not C[5-N(2)]G or C[5-N(6)]A. In these two sets of crosslinks, the C5 of cytosine is covalently bonded with its neighboring purine base via a carbon atom on the aromatic ring and an exocyclic nitrogen atom, respectively. On the contrary, the rearrangement could occur for the deprotonated ions of C[5-N(2)]G, C[5-N(6)]A, and unmodified cytosine, but not C[5-8]G, C[5-2]A, or C[5-8]A. In addition, ammonia could be lost more readily from C[5-N(2)]G and C[5-N(6)]A than from C[5-8]G, C[5-2]A, and C[5-8]A. The results from the present study afforded important guidance for the application of mass spectrometry for the structure elucidation of other intrastrand/interstrand crosslink lesions.
authors.affiliation: Department of Chemistry, University of California at Riverside, Riverside, California 92521-0403, USA.
authors.forename: Huachuan
authors.initials: H
authors.lastname: Cao
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D001973:Bromodeoxyuridine / Q000737:chemistry; D002247:Carbon Isotopes / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D003596:Cytosine / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D015226:Dinucleoside Phosphates / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000737:chemistry; D011522:Protons; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002247:Carbon Isotopes; D003432:Cross-Linking Reagents; D015226:Dinucleoside Phosphates; D009587:Nitrogen Isotopes; D011522:Protons; D003596:Cytosine; D004247:DNA; D001973:Bromodeoxyuridine