title: Loss of Hoogsteen pairing ability upon N1 adenine platinum binding.
abstract: Chloroform- and Freon-soluble mixed thymine, adenine complexes trans-[Pt(MeNH(2))(2)(ChmT-N3)(ChmA-N1)]NO(3) (2) and trans-[Pt(MeNH(2))(2)(ChmT-N3)(TBDMS-ado-N1)]BF(4) (3) (ChmT = anion of 1-cyclohexylmethylthymine ChmTH, ChmA = 9-cyclohexylmethyladenine, TBDMS-ado = 2',3',5'-tri-tert-butyldimethylsilyladenosine) have been prepared and characterized to study their propensity to undergo Hoogsteen and/or reversed Hoogsteen pairing in solution with free ChmTH and free 3',5'-diacetyl-2'-deoxyuridine, respectively. No Hoogsteen or reversed Hoogsteen pairing between 2 and ChmT takes place in CDCl(3). In Freon, partial H bonding between N1 platinated TBDMS-ado and 3',5'-diacetyl-2'-deoxyuridine as well as its [3-(15)N] labeled analogue is unambiguously observed only below 150 K. Comparison of (1)J ((15)N-(1)H) coupling constants of 3',5'-diacetyl-2'-deoxyuridine involved in Hoogsteen pairing with free and N1 platinated adenine suggests that the interaction is inherently weaker in the case of platinated adenine. To better understand the complete absence of hydrogen bonding between the ChmA ligand in 2 and free ChmTH, ab initio calculations (gas phase, 0 K) have been carried out for Hoogsteen pairs involving adenine (A) and thymine (T), as well as simplified analogues of 2 and T, both in the presence and absence of counteranions. The data strongly suggest that reduction of the effective positive charge of the heavy metal ion Pt(2+) by counterions diminishes interaction energies. With regard to mixtures of 2 and ChmTH in chloroform, this implies that ion pair formation between the cation of 2 and NO(3)(-) may be responsible for the lack of any measurable Hoogsteen pairing in this solvent.
authors.affiliation: Fachbereich Chemie, Universität Dortmund, 44221 Dortmund, Germany.
authors.forename: Kathrin S
authors.initials: KS
authors.lastname: Schmidt
authors.forename: Jan
authors.initials: J
authors.lastname: Reedijk
authors.forename: Klaus
authors.initials: K
authors.lastname: Weisz
authors.forename: Eline M
authors.initials: EM
authors.lastname: Basilio Janke
authors.forename: Judit E
authors.initials: JE
authors.lastname: Sponer
authors.forename: Jiri
authors.initials: J
authors.lastname: Sponer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lippert
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry*; D001665:Binding Sites; D002725:Chloroform; D002851:Chromatography, High Pressure Liquid; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D009944:Organoplatinum Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D012821:Silanes / Q000138:chemical synthesis / Q000737:chemistry; D013237:Stereoisomerism; D013696:Temperature; D013941:Thymine / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: C465243:(Pt(MeNH(2))(2)(ChmT-N3)(ChmA-N1))NO(3); C465245:(Pt(MeNH(2))(2)(ChmT-N3)(TBDMS-ado-N1))BF(4); D009942:Organometallic Compounds; D009944:Organoplatinum Compounds; C465244:Pt(MeNH(2))(2)(ChmT-N3); D012821:Silanes; D010984:Platinum; D002725:Chloroform; D000225:Adenine; D013941:Thymine