Aquation

About: Aquation is a research topic. Over the lifetime, 1443 publications have been published within this topic receiving 17507 citations.

Binding Kinetics of Tetrachloro-1,2-diaminocyclohexaneplatinum(IV) (Tetraplatin) and cis-Diamminedichloroplatinum(II) at 37 °C With Human Plasma Proteins and With Bovine Serum Albumin. Does Aquation Precede Protein Binding?

Abstract: Experiments were conducted at 37 degrees C to study the kinetics of (a) binding of cis-diamminedichloroplatinum (II) (CDDP) and of a racemic mixture of d- and l-isomers of trans-tetrachloro-1,2-diaminocyclohexaneplatinum (IV) [or tetraplatin (TP)] to protein [human plasma proteins or bovine serum albumin (BSA)]; (b) aquation (acid hydrolysis) of CDDP and of TP; and (c) binding of charged (aquated) CDDP species to BSA. The experiments were performed at clinically relevant concentrations for CDDP, so that the proportional concentrations of platinum complexes relative to the concentrations of other chemical species in blood plasma were similar to those obtaining in the clinical use of the drug. "Free" (unbound) platinum complexes were separated from the protein-bound complexes were separated from the protein-bound complexes by gel filtration chromatography. By use of ion-exchange chromatography, charged platinum species were separated from the uncharged species and free charged platinum species of CDDP were separated from those bound to BSA. Platinum in various fractions was quantitated by atomic absorption spectrophotometry with electrothermal atomization; proteins were quantitated by te Bradford method with Coomassie blue dye. The kinetic data obtained by the application of these methods for CDDP are in good agreement with those obtained by other methods, e.g., binding rates based on separations by centrigugal ultrafiltration. The overall protein-binding reaction of CDDP was consistent with a binding process comprising two consecutive first-order reaction steps: the rate-controlling aquation reaction [half-life (t 1/2), approximately 2 hr] followed by a more rapid binding reaction of the charged (aquated) CDDP species to the protein (t 1/2, approximately 23 min). However, the results for TP indicated that prior aquation was not required for protein binding, and we could surmise that binding of TP to protein proceeds via a direct nucleophilic attack. An unexpected finding was the marked, reproducible difference in rates of aquation between the two lots of TP that we used; this finding suggests the need for cautions evaluation of pharmacokinetic data describing the behavior of TP.

Organoruthenium Prodrugs as a New Class of Cholinesterase and Glutathione-S-Transferase Inhibitors.

Abstract: A small library of 17 organoruthenium compounds with the general formula [RuII (fcl)(chel)(L)]n+ (in which fcl=face capping ligand, chel=chelating bidentate ligand, and L=monodentate ligand) were screened for inhibitory activity against cholinesterases and glutathione-S-transferases of human and animal origins. Compounds were selected to include different chelating ligands (i.e., N,N-, N,O-, O,O-, S,O-) and monodentate ligands that can modulate the aquation rate of the metal species. Compounds with a labile ruthenium chloride bond that provided rapid aquation were found to inhibit both sets of enzymes in reversible competitive modes and at pharmaceutically relevant concentrations. When applied at concentrations that completely abolish the activity of human acetylcholinesterase, the lead compound [(η6 -p-cymene)Ru(pyrithionato)Cl] (C1 a) showed no undesirable physiological responses on the neuromuscular system. Finally, C1 a was not cytotoxic against non-transformed cells at pharmaceutically relevant concentrations.

Kinetics of the aquation of amminepentacyanoferrate(ii). a volume profile analysis

Abstract: The kinetics of the aquation and reverse formation reactions of Fe(CN)5NH33- were studied in detail. The reported activation parameters and volume profile strongly support the operation of a limiting D substitution mechanism.