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The TpG chelate of cis(diammineplatinum) forms two head-to-head rotamers in H2O solution (1998)

Elizondo-Riojas, M.-A. ; Gonnet, Florence ; Chottard, Jean-Claude ; [et al.]

Springer

JBIC 3 (1998), S. 30-43

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ISSN: 1432-1327

Keywords: Key words Cisplatin ; Antitumor drugs ; Nuclear magnetic resonance ; Molecular dynamics

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract d(TpG)– reacts with cis-[Pt(NH3)2(H2O)2]2+ in two steps to yield the platinum chelate cis-[Pt(NH3)2{d(TpG)-N3(1),N7(2)}]. In the latter, hindered rotation of the bases leads to an equilibrium between two rotamers interconverting slowly on the NMR time scale. The structure of the two rotameric chelates was studied by means of 1H NMR and molecular modeling techniques. The major and minor rotamers could be assigned unambiguously to the two head-to-head conformational domains which are characterized by syn/anti and anti/anti sugar-base orientations, respectively. Molecular models derived for both rotamers show that the orientations of the bases are mutually quasi-enantiomeric. The interconversion between the two rotamers (k ≈ 1 s–1 at 293 K) is approximately 104 times faster than the analogous rotamer interconversion observed in cis-[Pt(NH3)2{r(CpG)-N3(1),N7(2)}]+ [Girault J-P, Chottard G, Lallemand J-Y, Huguenin F, Chottard J-C (1984) J Am Chem Soc 106 : 7227–7232], suggesting that the steric clash of the exocyclic amino group of the platinum-bound cytosine with the ligands in cis position is more severe than that of the two thymine oxo groups.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s007750050205

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Reactions of the double-stranded oligonucleotide d(TTGGCCAA)2 with cis-[Pt(NH3)2(H2O)2]2+ and [Pt(NH3)3(H2O)]2+Kinetic Analysis of the Reactions Between GG-Containing Oligonucleotides and Platinum Complexes, Part II. Part I: Reactions of Single-Stranded Oligonucleotides with cis-[Pt(NH3)2(H2O)2]2+ and [Pt(NH3)3(H2O)]2+, ref.[15]. (1996)

Reeder, Franziska ; Gonnet, Florence ; Kozelka, JiřÍ ; [et al.]

Weinheim : Wiley-Blackwell

Chemistry - A European Journal 2 (1996), S. 1068-1076

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ISSN: 0947-6539

Keywords: antitumor agents ; DNA ; kinetics ; platinum complexes ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The kinetics of the reactions between the GG-containing double-stranded oligonucleotide d(TTGGCCAA)2 (II) and the platinum complexes cis-[Pt-(NH3)2(H2O)2]2+ (1) and [Pt(NH3)3-(H2O)]2+ (2) were studied and compared with those already determined for the reactions of the single-stranded octanucleotide d(CTGGCTCA) (I).[1] The results were as follows: i) Complex 1 reacted faster than 2 with both I and II. ii) Both complexes 1 and 2 reacted faster with II than with I. This acceleration was greater for 1 (x 13) than for 2 (x4) and only due to the increase of the platination rate of the 5′-G of the GG sequence. iii) For both I and II, the first platination by 1 and 2 was faster on the 5′-G than on the 3′-G. This difference was more significant for the platination of II (k5′/k3′ = 12 for 1 and 5 for 2) than of I (k5′/k3′ ≤ 2). iv) The cyclization reaction of the monoadducts (G*) of 1 to yield the GG cis-Pt(NH3)2+2 chelate (G*G*) was considerably slowed down in the duplex. This rate decrease was significantly larger for the chelation of the 5′-G* (factor of 16) than of the 3′-G* (factor of 4) monoadducts. v) The intrastrand chelation of the 3′-G* monoaducts (k3′c) was faster than that of the 5′-G* monoadducts (k5′c), both for I and II (k3′c/k5′c = 3 and 13, respectively). vi) In addition to the intrastrand G*G* crosslink, we also observed the interstrand crosslink d(GG*CC)-d(GG*CC) between the two 3′-Gs of the central tetranucleotide. The rate constant for the interstrand crosslinking (k3′i) was half that of the intrastrand chelation (k3′c). vii) The 5′ monoadduct, which was formed faster (k5′ 〈 k3′) and was chelated more slowly (k5′c 〉 k3′i 〈 k3′c), exhibited a half-life of 3.2 h under our experimental conditions.

Additional Material: 7 Ill.