title: Structural varieties of selectively mixed G- and C-rich short DNA sequences studied with electrospray ionization mass spectrometry.
abstract: Short guanine(G)-repeat and cytosine(C)-repeat DNA strands can self-assemble to form four-stranded G-quadruplexes and i-motifs, respectively. Herein, G-rich and C-rich strands with non-G or non-C terminal bases and different lengths of G- or C-repeats are mixed selectively in pH 4.5 and 6.7 ammonium acetate buffer solutions and studied by electrospray ionization mass spectrometry (ESI-MS). Various strand associations corresponding to bi-, tri- and tetramolecular ions are observed in mass spectra, indicating that the formation of quadruplex structures is a random strand by strand association process. However, with increasing incubation time for the mixtures, initially associated hybrid tetramers will transform into self-assembled conformations, which is mainly driven by the structural stability. The melting temperature values of self-assembled quadruplexes suggest that the length of G-repeats or C-repeats shows more significant effect on the stability of quadruplex structures than that of terminal residues. Accordingly, we can obtain the self-associated tetrameric species generated from the mixtures of various homologous G- or C-strands efficiently by altering the length of G- or C-repeats. Our studies demonstrate that ESI-MS is a very direct, fast and sensitive tool to provide significant information on DNA strand associations and stoichiometric transitions, particularly for complex mixtures. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012, China.
authors.forename: Yanwei
authors.initials: Y
authors.lastname: Cao
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012, China.
authors.forename: Shang
authors.initials: S
authors.lastname: Gao
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012, China.|State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012, China.
authors.forename: Caijin
authors.initials: C
authors.lastname: Li
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012, China.
authors.forename: Yuting
authors.initials: Y
authors.lastname: Yan
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.affiliation: College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012, China. guoxh@jlu.edu.cn.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Guo
mesh_terms: D001483:Base Sequence; D003596:Cytosine / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry*; D044367:Phase Transition; D021241:Spectrometry, Mass, Electrospray Ionization; D013053:Spectrophotometry / Q000379:methods
chemical_list: D006147:Guanine; D003596:Cytosine; D004247:DNA
keywords: DNA conformation transition; ESI-MS; G-quadruplex; i-motif; strand random associations