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Aquation

About: Aquation is a(n) research topic. Over the lifetime, 1443 publication(s) have been published within this topic receiving 17507 citation(s).


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TL;DR: It was concluded that the CBDCA ligand becomes a more labile leaving group once carboplatin has been monoaquated, and both chloro-ligands of cisplatin were shown to leave at similar rates, while certain cell lines were showed to be much more sensitive to DNA bound platinum.
Abstract: The kinetics of the aquation reactions of cisplatin and carboplatin and their subsequent reactions with DNA, both in vitro and in vivo, have been measured. The results have been extrapolated to indicate the expected cytotoxicity of these compounds in cells obtained from human cancer patients. Rate constants for the aquation at 37 degrees C of cisplatin and carboplatin of 8 X 10(-5) and 7.2 X 10(-7) s-1, respectively, were calculated from the half-life of these compounds in phosphate buffer, pH 7. This difference in their rate of activation was matched by their rates of binding to DNA. By use of a 14C-labeled ligand, carboplatin was shown to bind monofunctionally to DNA, after which there was a time-dependent formation of difunctional interstrand cross-links, formed from some of these initially monofunctional adducts. A similar, although faster, accumulation of cross-links was seen when cisplatin was bound to DNA. The loss of the 14C-CBDCA ligand of carboplatin was calculated to occur with a rate constant of 1.3 X 10(-5) s-1 which was similar to that for the rate of formation of interstrand cross-links and faster than that for the monofunctional reaction with DNA. It was concluded therefore that the CBDCA ligand becomes a more labile leaving group once carboplatin has been monoaquated. In contrast, both chloro-ligands of cisplatin were shown to leave at similar rates. The fact that other difunctional lesions were formed to the same extent, by equal bound doses of cisplatin or carboplatin, was indicated by the unwinding of supercoiled plasmid DNA. The effects of cisplatin and carboplatin on this DNA were the same once bound to the same extent. About a 100-fold larger dose of carboplatin was, as predicted by their rates of aquation, required to produce equivalent binding to plasmid DNA. In vivo, equal binding of the two drugs to DNA of various cell systems resulted in equal cytotoxicity. Again a much larger dose (20- to 40-fold) of carboplatin was required to produce this equal binding. In general a DNA bound platinum level of about 20 nmol/g reduced cell survival by 90%, although certain cell lines were shown to be much more sensitive to DNA bound platinum. Similar binding values, to those above, were obtained in the DNA extracted from cells of human cancer patients treated with cisplatin. It was inferred that the cytotoxic effect of this level of platinum on DNA would be (unless the cells were of a sensitive phenotype) about 90%.(ABSTRACT TRUNCATED AT 400 WORDS)

521 citations

Journal ArticleDOI
Abstract: Through spectroscopic (X-ray, Infrared, 1H-NMR, EPR, UV–vis) and electrochemical (cyclic voltammetry, differential pulse polarography) data and quantum mechanical calculations, the formulation [Ru(II)NO+] was attributed to a series of new ruthenium(II) amine compounds. A remarkable stability of the Ru(II) relative to Ru(III) was observed upon coordination to NO. The presence of nitrosyl in the coordination sphere results in dramatic implications in the lability, acidity and redox properties of the ligand trans to NO. These effects are higher than expected just on the basis of one unity increment in the metal center charge. Based on molecular orbital (MO) analysis and on reduction product analysis, the site of the reduction [Ru(NO)]3++e−→[Ru(NO)]2+ was assigned to the NO ligand. The dissociation of the coordinated NO0 is dependent on the trans effect and trans influence of the trans ligand L. Irradiation of the nitrosyl complexes with 300–350 nm light results in NO aquation and formation of the corresponding aquaruthenium(III) complex, i.e. trans-[ Ru ( NO )( NH 3 ) 4 L ] 3+ → H 2 O , H + hν trans-[ Ru ( NH 3 ) 4 ( H 2 O ) L ] 3+ + NO 0 Irradiation in the visible region (400–500 nm) did not result in any observable reaction in solution; however, at low temperature and in the solid state, evidence in favor of the formation of linkage isomers has been obtained. The hypotensive properties of trans-[Ru(NO)(NH3)4(P(OC2H5)3)](PF6)3 and trans-[Ru(NO)Cl(cyclam)](ClO4)2 have been demonstrated in mice and rats.

262 citations

Journal ArticleDOI
TL;DR: The ability to tune the chemical reactivity of this class of organometallic ruthenium arene compounds should be useful in optimizing their design as anticancer agents.
Abstract: Organometallic compounds offer broad scope for the design of therapeutic agents, but this avenue has yet to be widely explored. A key concept in the design of anticancer complexes is optimization of chemical reactivity to allow facile attack on the target site (e.g., DNA) yet avoid attack on other sites associated with unwanted side effects. Here, we consider how this result can be achieved for monofunctional “piano-stool” ruthenium(II) arene complexes of the type [(η6-arene)Ru(ethylenediamine)(X)]n+. A potentially important activation mechanism for reactions with biomolecules is hydrolysis. Density functional calculations suggested that aquation (substitution of X by H2O) occurs by means of a concerted ligand interchange mechanism. We studied the kinetics and equilibria for hydrolysis of 21 complexes, containing, as X, halides and pseudohalides, pyridine (py) derivatives, and a thiolate, together with benzene (bz) or a substituted bz as arene, using UV-visible spectroscopy, HPLC, and electrospray MS. The x-ray structures of six complexes are reported. In general, complexes that hydrolyze either rapidly {e.g., X = halide [arene = hexamethylbenzene (hmb)]} or moderately slowly [e.g., X = azide, dichloropyridine (arene = hmb)] are active toward A2780 human ovarian cancer cells, whereas complexes that do not aquate (e.g., X = py) are inactive. An intriguing exception is the X = thiophenolate complex, which undergoes little hydrolysis and appears to be activated by a different mechanism. The ability to tune the chemical reactivity of this class of organometallic ruthenium arene compounds should be useful in optimizing their design as anticancer agents.

251 citations

Journal ArticleDOI
TL;DR: The first structurally characterized examples of the 1,2,3-triazole motif employed in a terdentate ligand display enhanced steric freedom and a facile receptivity towards a reversible aquation in the case of an electrogenerated Fe(III) state.
Abstract: The first structurally characterized examples of the 1,2,3-triazole motif employed in a terdentate ligand display enhanced steric freedom and a facile receptivity towards a reversible aquation in the case of an electrogenerated FeIII state.

232 citations

Journal ArticleDOI
TL;DR: The aqua adducts of the anticancer complexes (X=biphenyl (Bip) 1, X=5,8,9,10-tetrahydroanthracene (THA) 2, X-DHA and THA 3; en=ethylenediamime) were separated by HPLC and characterised by mass spectrometry as the products of hydrolysis in water.
Abstract: The aqua adducts of the anticancer complexes [(eta(6)-X)Ru(en)Cl][PF(6)] (X=biphenyl (Bip) 1, X=5,8,9,10-tetrahydroanthracene (THA) 2, X=9,10-dihydroanthracene (DHA) 3; en=ethylenediamime) were separated by HPLC and characterised by mass spectrometry as the products of hydrolysis in water. The X-ray structures of the aqua complexes [(eta(6)-X)Ru(en)Y][PF(6)](n), X=Bip, Y=0.5 H(2)O/0.5 OH, n=1.5 (4), X=THA, Y=0.5 H(2)O/0.5 OH, n=1.5 (5 A), X=THA, Y=H(2)O, n=2 (5 B), and X=DHA, Y=H(2)O, n=2 (6), are reported. In complex 4 there is a large propeller twist of 45 degrees of the pendant phenyl ring with respect to the coordinated phenyl ring. Although the THA ligand in 5 A and 5 B is relatively flat, the DHA ring system in 6 is markedly bent (hinge bend ca. 35 degrees ) as in the chloro complex 3 (41 degrees ). The rates of aquation of 1-3 determined by UV/Vis spectroscopy at various ionic strengths and temperatures (1.23-2.59x10(-3) s(-1) at 298 K, I=0.1 M) are >20x faster than that of cisplatin. The reverse, anation reactions were very rapid on addition of 100 mM NaCl (a similar concentration to that in blood plasma). The aquation and anation reactions were about two times faster for the DHA and THA complexes compared to the biphenyl complex. The hydrolysis reactions appear to occur by an associative pathway. The pK(a) values of the aqua adducts were determined by (1)H NMR spectroscopy as 7.71 for 4, 8.01 for 5 and 7.89 for 6. At physiologically-relevant concentrations (0.5-5 microM) and temperature (310 K), the complexes will exist in blood plasma as >89 % chloro complex, whereas in the cell nucleus significant amounts (45-65 %) of the more reactive aqua adducts would be formed together with smaller amounts of the hydroxo complexes (9-25 %, pH 7.4, [Cl(-)]=4 mM).

212 citations

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202111
202010
201914
20187
201713
20168