title: Bridged cobalt amine complexes induce DNA conformational changes effectively.
abstract: Cobalt(III) hexaamine ion [Co(NH3)6]3+ is known to facilitate the transition of B- to Z-DNA or B- to A-DNA depending on the DNA sequences. Specific interactions are found between the amines of [Co(NH3)6]3+ and DNA atoms of A-DNA or Z-DNA. Bridged Co(III)pentaamine complexes, with multiple amine groups arranged in a rigid framework, may enhance the effectiveness of the conformational transition by occupying simultaneously two of the Co(III) hexaamine binding sites. Therefore, the imidazole-bridged Co(III)pentaamine complexes have been synthesized and their interactions with DNA oligonucleotides investigated by circular dichroism (CD) and NMR spectroscopy. CD studies of the titrations of d(A2C15G15T2) with [(NH3)5Co(Im)Co(NH3)5]Br5 and [(NH3)5Co(Im)2Co(NH3)4]Br7 showed that the former metal compound indeed is more effective than [Co(NH3)6]3+ in inducing the transition from B- to A-DNA. The conversion of B- to A-DNA was also supported by one- and two-dimensional NMR studies. Similarly for the titrations of poly(dC-dG). poly(dC-dG) and d(m5C-G)15 with these two bridged Co(III) complexes, efficient induction of Z-DNA was observed. Our studies suggest that bridged Co(III)pentaamine complexes may be useful agents for studying nucleic acid structures.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign 61801, USA.
authors.forename: C
authors.initials: C
authors.lastname: Bauer
authors.forename: A H
authors.initials: AH
authors.lastname: Wang
mesh_terms: D000588:Amines / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002942:Circular Dichroism; D003035:Cobalt / Q000737:chemistry* / Q000378:metabolism; D007093:Imidazoles / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry* / Q000378:metabolism; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000588:Amines; D007093:Imidazoles; C108979:N,N'-bis(pentaamminecobalt)imidazole; D009841:Oligonucleotides; D009942:Organometallic Compounds; D003035:Cobalt