Platination rate constants

Scheme 2. Mechanism of Formation of Cisplatin-DNA Adducts. kx, k2, k3 are aquation-rate constants (fcj and k2 are in Scheme l).kpl and kp2 are platination-rate constants, kc is the chelation-rate constant.

The platination-rate constants kp in Table 4 correspond to a bimolecu-lar one-step coordination of an N(7)-guanine to platinum via an associative... 

Table 5. First Platination Rate Constants. Influence of the nature of Y in cis-[PtY(NH3)2(H20)] and of the single- or double-stranded structure of the oligonucleotide...

The following conclusions can be drawn i) The platination-rate constants as well as the low AG kyc value agree with the lower nucleophilicity of A compared to G. ii) Considering the GA case (under study) one can expect a lower kyc for the less nucleophilic A in the geometrically unfavored 3,-position to the platinum atom of the monoadduct. This could account for the absence of GA adduct. 

The experimental determination of the rate constants for the platination of different oligonucleotides has turned out to be rather difficult. To avoid the complicacy due to the CL hydrolysis of the dichloro species,... 

Deposition of platinum metal In the case of platinum no solid product was found. The ionic liquid darkened more and faster the smaller the distance between the surface of the ionic liquid [EMIM][TfO] containing tetrabutylammonium hexachloro-platinate ([n-Bu4N]2[PtCl6]) and the Ar/H2-plasma (3 1, overall pressure 100 Pa) was chosen. So far no other ionic liquid has been tested. The rate constant for the reduction of the tetrabutylammonium ion with a hydrated electron is only 1.4 x 106 LmoH1 s 1, hence the main rival pathway for reduction of platinum(IV) is the reduction of the imidazolium ion of the ionic liquid. As in the case of copper, a suitable platinum salt - maybe made by electro-oxidation of metallic platinum in a suitable ionic liquid - has to be found. 

Platination Step, i) Starting from the dichloro complex, the first aquation (1) (Scheme 2) is rate-determining, but the kinetic data do not tell which is/are the actual DNA-platinating species in the various conditions, ii) The kpi rate constants differ by one order of magnitude from 0.3 to 2.5 m-1 s-1 [48] [78] [82], but the value of 2.08 0.07 m-1 s-1 that we have also deter-... 

The behaviour of hydrogen and methanol at constant oxidation rates can be compared in Fig. 2.1. Using platinized platinum anodes a constant current density was applied in a 0.5mol/L-1 H2S04 solution containing (a) H2 p — 1 bar) and (b) ImolL-1 CH3OH solution. While no more than 20 mV overpotential are... 

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