Determination of the Kinetic Profile of a Dinuclear Platinum Anticancer Complex in the Presence of Sulfate: Introducing a New Tool for the Expedited Analysis of 2D [¹H, ¹⁵N] HSQC NMR Spectra

Abstract

Two-dimensional (2D)[1H, 15N] heteronuclear single-quantum coherence (HSQC) NMR experiments of the kinetics of aquation and sulfation of the dinuclear platinum anticancer complex [{trans-PtCl(NH3)2}2(μ-NH2(CH2)6NH2)]2+ (1,1/t,t, 1) in 15 mM sulfate solution are reported using conditions (298 K, pH 5.4) identical to those previously used for other anionic systems (phosphate and acetate), allowing for a direct comparison. Sulfate is the fourth most abundant anion in human plasma. The rate constant for the aquation step (kH) is higher than that previously found in the presence of phosphate, but the anation rate constants are similar. The rate constant for sulfate displacement of the aqua ligand (kL) is approximately three times higher than that of phosphate, and a further major difference between these two anions is the very high k−L for loss of sulfate, suggesting that when formed in plasma the sulfato species will be substitution labile. We also introduce a novel (free) plug-in, ‘2D NMR analysis’, developed for the expedited integration and analysis of 2D [1H, 15N] HSQC NMR spectra. We have found that this plug-in significantly reduces the amount of time taken in the analysis of experiments with no loss to the quality of the data.

Solution studies of dinuclear polyamine-linked platinum-based antitumour complexes

“…43 Peak volumes were converted into concentrations relative to the initial concentration of the dichloro species of 1 or 1′ . The concentrations of 1 and 2 (and 1′ and 2′ ) at each time point were derived based on the relative volumes of the Pt– 15 NH 3 crosspeaks after correcting for peak overlap, according to the single aquation model, as described previously.…”

Antiangiogenic platinum through glycan targeting

“… 15 In the case of glycans, formation of a Pt–sulfate bond may be preceded by a pre-association through the proposed sulfate clamp, a concept strictly analogous to the reactions observed in the kinetics of DNA binding by these compounds. 16 – 18 In this paper we examine the effects of the two principal compounds, Triplatin and TriplatinNC, on limiting aspects of HS function. We show that the biological consequences of metalloshielding extend to modulation of HPSE activity and HS–fibroblast growth factor interactions leading to inhibition of cell invasion and angiogenesis.…”

A new approach to glycan targeting: enzyme inhibition by oligosaccharide metalloshielding

“…In agreement, we note that the aquation kinetics in 15 mM sulphate of the prototypical dinuclear compound [{ trans -PtCl(NH 3 ) 2 } 2 (μ-NH 2 (CH 2 ) 6 NH 2 )] 2+ (structurally analogous to BBR3464) confirmed covalent binding to SO 4 2− . 16 The major difference between binding of phosphate and sulfate is the very high k −L for loss of sulphate, suggesting that when formed the sulphato species will be substitution-labile. Incubation of the platinum compounds with the enzyme prior to addition of Fondaparinux does not affect the assay results, indicating that there is no direct action of the compounds on the enzyme.…”