title: Influence of dT20 and [d(AT)10]2 on cisplatin hydrolysis studied by two-dimensional [1H,15N] HMQC NMR spectroscopy.
abstract: The influence of the presence of DNA on the kinetics of cisplatin (cis-[PtCl2(NH3)2]) aquation (replacement of Cl- by H2O) and anation (replacement of H2O by Cl-) involved in the hydrolysis of cisplatin have been determined by two-dimensional [1H,15N] HMQC NMR spectroscopy. Single-stranded dT20 and double-stranded [d(AT)10]2 oligonucleotides were used as DNA models, avoiding guanines which are known to react rapidly with aquated cisplatin forms. Reactions starting from cis-[PtCl2(15NH3)2], or from a stoichiometric mixture of cis-[Pt(15NH3)2(H2O)2]2+ and Cl- (all 0.5 mM Pt(II); in ionic strength, adjusted to 0.095 M or 0.011 M with NaClO4, pH between 3.0 and 4.0) were followed in an NMR tube in both the absence and presence of 0.7 mM dT20 or [d(AT)10]2. In the presence of dT20, we observed a slight and ionic-strength-independent decrease (15-20 %) of the first aquation rate constant, and a more significant decrease of the second anation rate constant. The latter was more important at low ionic strength, and can be explained by efficient condensation of cis-[Pt(15NH3)2(H2O)2]2+ on the surface of single-stranded DNA, in a region depleted of chloride anions. At low ionic strength, we observed an additional set of [1H,15N] HMQC spectral signals indicative of an asymmetric species of PtN2O2 coordination, and we assigned them to phosphate-bound monoadducts of cis-[Pt(15NH3)2(H2O)2]2+. Double-stranded [d(AT)10]2 slowed down the first aquation step also by approximately 15 %; however, we could not determine the influence on the second hydrolysis step because of a significant background reaction with cis-[Pt(NH3)2(H2O)2]2+.
authors.affiliation: Department of Chemistry, University of Bergen, Allégt. 41, 5007 Bergen, Norway. jo.vinje@kj.uib.no
authors.forename: Jo
authors.initials: J
authors.lastname: Vinje
authors.forename: Einar
authors.initials: E
authors.lastname: Sletten
authors.forename: Jirí
authors.initials: J
authors.lastname: Kozelka
mesh_terms: D000225:Adenine / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000737:chemistry; D002945:Cisplatin / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D015226:Dinucleoside Phosphates / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009587:Nitrogen Isotopes; D009841:Oligonucleotides / Q000737:chemistry*; D011071:Poly T / Q000737:chemistry*; D013816:Thermodynamics; D013936:Thymidine / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D015226:Dinucleoside Phosphates; D009587:Nitrogen Isotopes; D009841:Oligonucleotides; C028145:2'-deoxythymidylyl-(3'-5')-2'-deoxyadenosine; D011071:Poly T; D006859:Hydrogen; D004247:DNA; D000225:Adenine; D002945:Cisplatin; D013936:Thymidine