Unusual hydrogen bonding patterns of N7metallated, N1deprotonated guanine nucleobases: acidity constants of cis-[Pt(NH3)2(Hegua)2]2+and crystal structures of cis-[Pt(NH3)2(egua)2]·4H2O and cis-[Pt(NH3)2(egua)2]· Hegua·7H2O (Hegua = 9-ethylguanine)
- 1 January 1995
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 23,p. 3767-3775
- https://doi.org/10.1039/dt9950003767
Abstract
Three closely related complexes of cis-PtII(NH3)2 with neutral 9-ethylguanine (Hegua) and anionic (N1 deprotonated) 9-ethylguanine (egua), respectively, have been prepared and studied: cis-[Pt(NH3)2(Hegua)(egua)]CIO4·2H2O 1, cis-[Pt(NH3)2(egua)2]·4H2O 2 and cis-[Pt(NH3)2(egua)2]·Hegua·7H2O 3. The crystal structures of complexes 2 and 3 have been determined. Platinum co-ordination in all cases is through N7 of neutral (1) or anionic (1–3) guanine. The PtII electrophile co-ordinated at N7 acidifies the N1 proton of neutral 9-ethylguanine (pKa= 9.57 ± 0.04), giving pKa1= 8.02 ± 0.01 and pKa2= 8.67 ± 0.01 for the two Hegua ligands in cis-[Pt(NH3)2(Hegua)2]2+. All three compounds display interesting hydrogen-bonding patterns either in the solid state and/or in solution. According to 1H NMR interaction shifts of guanine NH and NH2 resonances of complex 1 in Me2SO solution, this compound forms three intermolecular hydrogen bonds between neutral and deprotonated guanine ligands. For complex 2, hydrogen bonding between two deprotonated guanines in the solid state is via N1 and N2H2. In complex 3, the neutral 9-ethylguanine is hydrogen bonded to one of the two anionic guanine ligands through three hydrogen bonds, involving N1, N2H2 and O6. This pattern represents a mismatch between two guanines, brought about by initial co-ordination of a PtII electrophile to N7 and subsequent deprotonation of the N1 position of the metallated nucleobase. The model character of these compounds with regard to metal-induced mutagenicity is briefly discussed.Keywords
This publication has 92 references indexed in Scilit:
- Intramolecular triple-helix formation at (PunPyn).cntdot.(PunPyn) tracts: recognition of alternate strands via Pu.cntdot.PuPy and Py.cntdot.PuPy base tripletsBiochemistry, 1992
- Comments on potentiometric pH titrations and the relationship between pH-meter reading and hydrogen ion concentrationAnalytica Chimica Acta, 1991
- Stereochemically controlled ligands influence atropisomerization of platinum(II) nucleotide complexes. Evidence for head-to-head and stable .LAMBDA. head-to-tail atropisomersJournal of the American Chemical Society, 1990
- Platinum(II) binding to N7 and N1 of guanine and a model for a purine-N1,pyrimidine-N3 cross-link of cisplatin in the interior of a DNA duplexInorganic Chemistry, 1990
- Adducts of the antitumor drug cis-diamminedichloroplatinum(II) with DNA: formation, identification, and quantitationBiochemistry, 1985
- Self base pairing in a complementary deoxydinucleoside monophosphate duplex: crystal and molecular structure of deoxycytidylyl-(3'-5')-deoxyguanosineBiochemistry, 1983
- Infrared and Raman spectroscopic study of 15N and D-substituted guaninesSpectrochimica Acta Part A: Molecular Spectroscopy, 1978
- Raman spectral studies of nucleic acids and related molecules—I Ribonucleic acid derivativesSpectrochimica Acta Part A: Molecular Spectroscopy, 1967
- A study of some problems in determining the stoicheiometric proton dissociation constants of complexes by potentiometric titrations using a glass electrodeAnalytica Chimica Acta, 1967
- Polynucleotides II : The X-ray diffraction patterns of solutions of the randomly coiled and helical forms of polyriboadenylic acidJournal of Molecular Biology, 1959