| MS method development for the determination of oligodeoxynucleotides (ODNs) and their carcinogen adducts is required to pursue studies of estrogen-quinone-induced DNA modification. Our goal is to develop specific MS methods not only for the structure determination of DNA materials that are modified by estrogen metabolites, but also for model ODNs and other DNA modifications.;Because the matrix plays an important role in ionization for matrix assisted laser desorption/ionization (MALDI) analysis, our first goal is the development of new matrices to give improved detection limits, quantification, and sequencing for the determination of ODNs (Chapter II). We evaluated a combination matrix of anthranilic acid (AA), nicotinic acid (NA) with a trace of sodium citrate for ODNs and, with collaborators from Iowa State University, a series of ionic liquid matrices for the determination of peptides, proteins, and synthetic polymers (Chapter III).;Applying the optimized matrix described in Chapter II, we successfully located the abasic site in ten 6 to 18-base modified single-stranded ODNs. Moreover, we applied an enzymatic digestion and MALDI MS to sequence and detect the modified sites in longer ODNs (Chapter IV).;Evidence is beginning to emerge that abasic sites are intermediates in mutagenesis. Thus, we successfully developed tandem mass spectrometry to determine abasic sites in modified ODNs (Chapter V). We also demonstrated that MALDI and ESI MS of products formed by a chemical cleavage initiated by an unusual reaction of the analyte with the AA of the matrix gives information to locate abasic sites in larger ODNs (Chapter VI).;The high sensitivity of the improved matrix of AA/NA allowed us to study ODNs containing estrogen-quinone-induced adducts directly by MALDI-TOF MS (Chapter VII). To complement the MALDI studies in Chapter VII, we also applied HPLC/MS/MS to identify and quantify catechol-estrogen adducts and conjugates from cancer-cell cultures and mouse-skin tissue (Chapter VIII).;Using the method developed in Chapter IV, we also determined a series of photomodified ODNs by exonuclease digestion, MALDI and post-source decay MS of the product "ladders" (Chapter IX). |
