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A mixed matrix of 3-hydroxypicolinic acid (3-HPA) and pyrazinecarboxylic acid (PCA) was used for analysis of a variety of synthetic oligodeoxynucleotides ranging in length from 8-108-mers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The experimental results showed that DNA segments with masses in the range from 5000 to 10,500 Da can be analyzed with high resolution (isotopic peaks resolved) when 3-HPA/PCA was prepared by mixing saturated 3-HPA solution and saturated PCA solution (in 50% of a 0.5 mol/L solution of diammonium hydrogen citrate plus 50% acetonitrile) at the volume ratio of 4:1. Each component of a mixture of d(A)1-10 gave a well-resolved peak. Moreover, when 3-HPA/PCA was used to analyze two mixtures, one containing two 23-mer DNA segments with a 9 Da difference (A and T) and the other with a 7 Da difference (AA and TG), the two 23-mer ion peaks were well separated from each other and an isotopically resolved spectrum of each component was recorded. Under the identical experimental conditions, the sample-to-sample reproducibility, resolution, signal-to-noise ratio and the tolerance to metal salts, with 3-HPA/PCA, were superior to those observed using 3-HPA alone for analysis of DNA segments.

3-Hydroxycoumarin (3-HC) was designed, synthesized, and tested as a matrix for matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses of a variety of synthetic oligodeoxynucleotides ranging long from three to 70 bases. Using the matrix solution of 3-HC dissolved in a mixed solvent of acetone and diammonium hydrogen citrate, DNA segments over the mass range 800 Da to 6900 Da were isotopically resolved with high signal-to-noise (S/N) ratio. The individual isotopic molecular ion peaks of a group of 23-mer mixed-base oligomers differing by one or two bases with mass differences of 9 or 7 Da were recorded. Larger oligodeoxynucleotide segments of 34-mer, 50-mer, and 70-mer have also been analyzed effectively. Less than 250 attomol of a 10-mer DNA segment was clearly detected without any fragmentation. The new matrix can be used for the analysis of DNA segments in both positive-and negative-ion modes, and the quality of all negative-ion mode spectra are as good as that obtained in positive-ion mode shown in this paper. Compared with conventional matrices of 3-hydroxypicolinic acid (3-HPA) and 6-aza-2-thiothymine (ATT), 3-HC had noticeable improvement in resolution, S/N ratio, spot-to-spot-, and sample-to-sample reproducibility for analyzed DNA segments. (J Am Soc Mass Spectrom 2006Spectrom , 17, 1665Spectrom -1668

Six novel poly(phenylenevinylene) (PPV) derivatives carrying butoxy or myrtanyl groups, including poly(2-butoxy-m-phenylenevinylene) (Bu-MPV), poly(2,5-dibutoxy-p-phenylenevinylene-alter-p-phenylenevinylene) (Bu-PPPV), poly(2,5-dibutoxy-p-phenylenevinylene-alter-m-phenylenevinylene) (Bu-PMPV), poly(2-myrtanyl-m-phenylenevinylene) (Myr-MPV), poly(2,5-dimyrtanyl-p-phenylenevinylene-alter-p-phenylenevinylene) (Myr-PPPV), and poly(2,5-dimyrtanyl-p-phenylenevinylene-alter-m-phenylenevinylene) (Myr-PMPV), were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The repeat unit mass and the end-group structures of each sample were obtained. Distinctly different spectra with different ion series and/or different ion signal intensities were observed for the analytes Bu-MPV, Myr-MPV, Bu-PPPV, Myr-PPPV and Myr-PMPV when different matrices were used, and different ion series were acquired when different solvents were used for Myr-PPPV and Myr-PMPV. The results show that the PPV oligomers with different shapes and/or with different end groups can be selectively desorbed and ionized in MALDI by using different matrices.

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