title: Silver (I) as DNA glue: Ag(+)-mediated guanine pairing revealed by removing Watson-Crick constraints.
abstract: Metal ion interactions with DNA have far-reaching implications in biochemistry and DNA nanotechnology. Ag(+) is uniquely interesting because it binds exclusively to the bases rather than the backbone of DNA, without the toxicity of Hg(2+). In contrast to prior studies of Ag(+) incorporation into double-stranded DNA, we remove the constraints of Watson-Crick pairing by focusing on homo-base DNA oligomers of the canonical bases. High resolution electro-spray ionization mass spectrometry reveals an unanticipated Ag(+)-mediated pairing of guanine homo-base strands, with higher stability than canonical guanine-cytosine pairing. By exploring unrestricted binding geometries, quantum chemical calculations find that Ag(+) bridges between non-canonical sites on guanine bases. Circular dichroism spectroscopy shows that the Ag(+)-mediated structuring of guanine homobase strands persists to at least 90 °C under conditions for which canonical guanine-cytosine duplexes melt below 20 °C. These findings are promising for DNA nanotechnology and metal-ion based biomedical science.
authors.affiliation: Department of Chemistry and Biochemistry, UCSB.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Swasey
authors.affiliation: Department of Applied Physics, Aalto University, 00076 Aalto, Finland.
authors.forename: Leonardo Espinosa
authors.initials: LE
authors.lastname: Leal
authors.affiliation: Department of Applied Physics, Aalto University, 00076 Aalto, Finland.
authors.forename: Olga
authors.initials: O
authors.lastname: Lopez-Acevedo
authors.affiliation: Department of Chemistry and Biochemistry, UCSB.
authors.forename: James
authors.initials: J
authors.lastname: Pavlovich
authors.affiliation: Department of Physics, UCSB, Santa Barbara, CA 93117.
authors.forename: Elisabeth G
authors.initials: EG
authors.lastname: Gwinn
mesh_terms: D020029:Base Pairing / Q000235:genetics*; D002942:Circular Dichroism; D003596:Cytosine / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry; D008958:Models, Molecular; D036103:Nanotechnology; D009690:Nucleic Acid Conformation; D012834:Silver / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013816:Thermodynamics
chemical_list: D012834:Silver; D006147:Guanine; D003596:Cytosine; D004247:DNA