title: Specific and nonspecific metal ion-nucleotide interactions at aqueous/solid interfaces functionalized with adenine, thymine, guanine, and cytosine oligomers.
abstract: This article reports nonlinear optical measurements that quantify, for the first time directly and without labels, how many Mg(2+) cations are bound to DNA 21-mers covalently linked to fused silica/water interfaces maintained at pH 7 and 10 mM NaCl, and what the thermodynamics are of these interactions. The overall interaction of Mg(2+) with adenine, thymine, guanine, and cytosine is found to involve -10.0 ± 0.3, -11.2 ± 0.3, -14.0 ± 0.4, and -14.9 ± 0.4 kJ/mol, and nonspecific interactions with the phosphate and sugar backbone are found to contribute -21.0 ± 0.6 kJ/mol for each Mg(2+) ion bound. The specific and nonspecific contributions to the interaction energy of Mg(2+) with oligonucleotide single strands is found to be additive, which suggests that within the uncertainty of these surface-specific experiments, the Mg(2+) ions are evenly distributed over the oligomers and not isolated to the most strongly binding nucleobase. The nucleobases adenine and thymine are found to bind only three Mg(2+) ions per 21-mer oligonucleotide, while the bases cytosine and guanine are found to bind eleven Mg(2+) ions per 21-mer oligonucleotide.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Holland
authors.forename: Jessica N
authors.initials: JN
authors.lastname: Malin
authors.forename: David S
authors.initials: DS
authors.lastname: Jordan
authors.forename: Esmeralda
authors.initials: E
authors.lastname: Morales
authors.forename: Franz M
authors.initials: FM
authors.lastname: Geiger
mesh_terms: D000225:Adenine / Q000737:chemistry*; D003596:Cytosine / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry*; D009711:Nucleotides / Q000737:chemistry*; D013816:Thermodynamics; D013941:Thymine / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D009711:Nucleotides; D014867:Water; D006147:Guanine; D003596:Cytosine; D008274:Magnesium; D000225:Adenine; D013941:Thymine