title: Template-directed assembly and characterization of metallosalen-DNA conjugates.
abstract: Nucleic acid template-directed synthesis represents a powerful method for the encoded synthesis of new bioconjugates. Our laboratory previously reported a strategy for the synthesis of a new metal-DNA hybrid, metallosalen-DNA, by the DNA or RNA template-directed cross-linking of two salicylaldehyde-modified DNA oligonucleotides. The current manuscript describes the optimal assembly requirements and biophysical characterization of metallosalen-DNA conjugates containing nickel and manganese ions. Competitive assembly reactions demonstrated the template-directed nature of metallosalen-DNA formation. A single metallosalen-DNA conjugate was assembled selectively in the presence of two pairs of salicylaldehyde precursor strands and a single DNA template. Assembly reactions were sensitive to base pair mismatches in the pairing arms. Single base mismatches resulted in a loss of metallosalen-DNA conjugate yield. Metallosalen-DNA assembly yields depended on the identity and length of the template spacer, the reaction pH, and the type of metal and diamine utilized in the assembly reaction. Metallosalen-DNA conjugates were stable to a variety of conditions, including extended incubation at 50 degrees C. Nickel metallosalen-DNA remained unchanged after incubation at 80 degrees C for 24 h, while decomposition of manganese metallosalen-DNA was observed under the same conditions. Circular dichroism (CD) spectroscopy indicated that DNA duplexes containing internal metallosalen moieties adopted B-form double helices. UV thermal denaturation analysis demonstrated that 32-nucleotide duplexes containing internal metallosalen modifications displayed melting temperatures approximately 5 degrees C less than unmodified DNA duplexes.
authors.affiliation: Department of Chemistry, The Robert H. Lurie Comprehensive Cancer Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Czlapinski
authors.forename: Terry L
authors.initials: TL
authors.lastname: Sheppard
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D020137:Base Pair Mismatch; D001483:Base Sequence; D002614:Chelating Agents / Q000138:chemical synthesis*; D002942:Circular Dichroism; D003432:Cross-Linking Reagents; D004247:DNA / Q000737:chemistry*; D005029:Ethylenediamines / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008345:Manganese / Q000737:chemistry; D009532:Nickel / Q000737:chemistry; D009691:Nucleic Acid Denaturation; D009841:Oligonucleotides / Q000138:chemical synthesis; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D012313:RNA / Q000737:chemistry; D013696:Temperature; D013698:Templates, Genetic
chemical_list: D000447:Aldehydes; D002614:Chelating Agents; D003432:Cross-Linking Reagents; D005029:Ethylenediamines; D009841:Oligonucleotides; D009942:Organometallic Compounds; C013243:salicylaldehyde; D008345:Manganese; D012313:RNA; D009532:Nickel; D004247:DNA; C011452:disalicylaldehyde ethylenediamine