Reduction of trans-[Pt(CN)4Cl2]2- (as a model compound for antitumor-active platinum(IV) complexes) by thiols, RSH (thioglycolic acid, l-cysteine, dl-penicillamine, and glutathione), has been studied in 1.00 M aqueous perchlorate medium use stopped-flow spectrophotometry at 25 °C the interval 7.08 × 10-6 ≤ [H+] M. Time-resolved spectra show that redox takes place directly without initial substitution Pt(IV). The stoichiometry is [RSH]:[Pt(IV)] = 2:1. first-order with respect to [Pt(IV)]...

The reductions of Pt(iv) anticancer prodrugs [Pt(dach)Cl4] (ormaplatin/tetraplatin), cis-[Pt(NH3)2Cl4], and cis,cis,trans-[Pt(NH3)2Cl2Br2] by the several dominant reductants in human plasma have been characterized kinetically this work, including l-ascorbic acid (Asc), l-glutathione (GSH), l-cysteine (Cys), dl-homocysteine (Hcy), a dipeptide Gly-Cys. All follow an overall second-order kinetics, being first-order each [Pt(iv)] [reductant]. A general reactivity trend Asc < Hcy Cys-Gly GSH Cys...

The reduction of the platinum(IV) prodrug trans,trans,trans-[PtCl2(OH)2(c-C6H11NH2)(NH3)] (JM335) by L-cysteine, DL-penicillamine, DL-homocysteine, N-acetyl-L-cysteine, 2-mercaptopropanoic acid, 2-mercaptosuccinic and glutathione has been investigated at 25 degrees C in a 1.0 M aqueous perchlorate medium with 6.8 < or = pH 11.2 using stopped-flow spectrophotometry. stoichiometry Pt(IV):thiol is 1:2, redox reactions follow second-order rate law -d[Pt(IV)]/dt k[Pt(IV)][RSH]tot, where k denotes...

Staining of foods by toxic mycotoxins is a general severe problem in the world. To explore simple methods for effective monitoring mycotoxin-stained has extraordinary significance. Herein, we designed and prepared covalent organic framework (COF)-derived fluorescent composite (DhBd-PT-COF-FITC) anchoring continually utilized tag, fluorescein isothiocyanate (FITC), nanopore channel two-dimensional imine COF (DhBd-PT-COF) to detect major existent mycotoxin moldy sugar cane─3-nitropropionic...

Thioredoxins are small redox proteins and have the active sites of Cys-Xaa-Yaa-Cys; they overexpressed by many different cancer cells. Cisplatin Pt(II) analogues could bind to inhibit activities proteins, as demonstrated other researchers. Platinum(IV) anticancer drugs often regarded prodrugs, but their interactions with thioredoxins not been studied. In this work, 3,6-dioxa-1,8-octanedithiol (dithiol) was chosen a model compound for thioredoxins, its reactions cis-[Pt(NH(3))(2)Cl(4)]...

The development of Pt(IV) anticancer prodrugs to overcome the detrimental side effects Pt(II)-based drugs is current interest. kinetics and reaction mechanisms reductive activation carboplatin prodrug cis,trans-[Pt(cbdca)(NH3)2Cl2] (cbdca = cyclobutane-1,1-dicarboxylate) by major small-molecule reductants in human plasma were analyzed this work. included ascorbate (Asc), thiol-containing molecules L-cysteine (Cys), DL-homocysteine (Hcy), glutathione (GSH), dipeptide Cys-Gly. Overall...

Captopril, the first pharmaceutical drug designed, synthesized, and used primarily for treatment of hypertension congestive heart failure, is an angiotensin-converting-enzyme inhibitor also antioxidant. On other hand, kinetic mechanistic aspects oxidation captopril are not well understood. The by cisplatin prodrug a model compound, cis-[Pt(NH3)2Cl4] trans-[PtCl2(CN)4]2−, was thus investigated in this work. A stopped-flow spectrometer employed to follow kinetics over wide pH-range under...

L-Selenomethionine (SeMet), the predominant form of selenium acquired from diet by humans, has been used as a supplement, and exhibit some important functions like cancer prevention antioxidative defense. Its interactions with Pt(II) anticancer drugs have characterized, but its redox reactions platinum(IV) prodrugs not exploited. In this work, oxidation SeMet Pt(IV) model compounds trans-[PtX2(CN)4]2− (X = Cl, Br) was characterized. A stopped-flow spectrometer to record rapid scan spectra...

We have discovered that trans-[Pt(en)2Cl2]2+ (en = ethylenediamine) is a highly selective and efficient reagent for the quantitative formation of intramolecular disulfide bonds in peptides. A series 14 dithiol peptides which form disulfide-containing rings ranging size from to 53 atoms were used characterize reagent. The are cleanly rapidly converted their forms by slight excess platinum complex under mild reaction conditions (slightly acidic neutral media). For all studied, including...

Acyclic dithiol and cyclic disulfide forms of the peptides Ac-Cys-Pro-Xaa-Cys-NH2 (Xaa = Phe, His, Tyr, Gly, Thr) Ac-Cys-Gly-Pro-Cys-NH2 peptide Ac-Ala-Gly-Pro-Ala-NH2 were synthesized characterized by mass spectrometry NMR spectroscopy. Rate constants kct ktc for cis-to-trans trans-to-cis isomerization, respectively, across Cys-Pro or Gly-Pro bonds determined magnetization transfer techniques over a range temperatures, activation parameters derived from temperature dependence rate...

A complex reaction mechanism of oxidation the anti-tubercular prodrug isoniazid (isonicotinic hydrazide, INH) by [IrCl6]2- as a model for redox processes such drugs in biological systems has been studied aqueous solution function pH between 0 and 8.5. Similar experiments have performed with its isomer nicotinic hydrazide (NH). All reactions are overall second-order, first-order observed second-order rate constants k' determined pH. Spectrophotometric titrations indicate stoichiometry...

Reduction of trans-[Pt(CN) 4 X 2 ] 2- (X = Cl or Br) [as model compounds for antitumour-active platinum(IV) pro-drugs] to [Pt(CN) by L-methionine, MeSR, has been studied at 25 °C in the range 0 < pH 12 Cl) and 6 use stopped-flow spectrophotometry. The stoichiometry is [Pt IV ]:[MeSR] ≈ 1: 1; reaction products are methionine S-oxide as identified NMR UV spectroscopies, respectively. kinetics first order with respect concentrations second-order rate constants have a small dependence. In...

cis persists: The population of the conformation Cys–Pro imide bond cyclic disulfide form peptides sequence Ac-Cys-Pro-(Xaa)m-Cys-NH2 (Xaa=Phe, Ala) ranges from 9.3 to 76.9 % and shows a striking periodic dependence on number residues in peptide.

Oxidation of cysteine thiol groups by trans-dichlorotetracyanoplatinate(IV) to form intramolecular peptide disulfide bonds has been studied for a series dithiol peptides ranging from 4 15 amino acid residues in length. The are rapidly and quantitatively transformed their forms slight excess [Pt(CN)(4)Cl(2)](2)(-), as shown HPLC. Quantitative analyses HPLC spectrophotometric titration confirm [Pt(IV)]:[dithiol peptide] stoichiometry 1:1. Under the low pH conditions used, oxidation 38-membered...

Efficient extractions of trace antibiotic residues in the environment are a key factor for accurate quantification residues. A new nanoporous material, namely, magnetically covalent organic polymer (MCOP, Fe 3 O 4 @SiO 2 ‐NH ‐COP) was synthesized this work and used magnetic solid‐phase extraction (MSPE). The combination MSPE with high‐performance liquid chromatography separation together ultraviolet detection (HPLC‐UV) established as an effective method determination four sulfonamide (SA)...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTIntramolecular Catalysis of the Cis−Trans Isomerization Proline Peptide Bonds in Cyclic Disulfide-Containing PeptidesDallas L. Rabenstein, Tiesheng Shi, and Stephen SpainView Author Information Department Chemistry, University California Riverside, 92521 Cite this: J. Am. Chem. Soc. 2000, 122, 10, 2401–2402Publication Date (Web):February 24, 2000Publication History Received3 November 1999Published online24 February 2000Published inissue 1...

Kinetics for complex formation between Pd(H2O)42+ and formic, butyric, dl-lactic, 2-methyllactic, methoxyacetic, malonic, succinic, oxydiacetic, l-malic, citric acids has been studied in an aqueous acidic medium by use of variable-temperature -pressure stopped-flow spectrophotometry. traces reactions the metal ion lactic, can be described single exponentials, which are assigned to monodentate complexes: + RCOOH ⇌ Pd(H2O)3OOCR+ H3O+ (k1, k-1). Equilibrium constants K1 acid calculated from...