Necessary conditions for absolute double matrix summability factors

We obtain necessary conditions for a doubly triangular matrix A to have the property that a double series ΣΣ λ _mn b _mn is summable |A| _k whenever the series ΣΣb _mn is bounded |A| _k .     

Targeted therapy vs. DNA-adduct formation-guided design: thoughts about the future of metal-based anticancer drugs

The development of metal-based anticancer drugs is mainly governed by the experience accumulated with cisplatin and its analogues. The synthesis is focused on adding appropriate leaving and non-leaving groups to a transition metal in order to get more favorable DNA binding properties, and the biological activity is tested in vitro, always in a second step, looking for the cell line that is killed at the lowest drug concentration. This strategy seems unproductive today for the area of new drug development where the knowledge on cancer genomics is suggesting the use of targets selectively expressed, or overexpressed by cancer cells. These targets almost always are proteins, constituting membrane receptors or components of crucial biochemical pathways. Some data indicate that the antitumor activity of cisplatin might also be due to the interaction with protein targets. This critical review examines the possibilities for metal-based drugs to challenge tumors with innovative strategies, based on genomic approaches, capitalizing on the chemical experiences with metals in medicine and focusing on the nature of the ligands which are added to a metal depending on the selected tumor cells and on their molecular targets.     

Validated LC Determination of the Piroxicam-β-Cyclodextrin Inclusion Complex in Tablets and in Human Plasma

A simple, rapid, specific, sensitive HPLC method has been developed for the determination of piroxicam in the tablet dosage form and in human plasma. The method totally eliminates solvent extraction and time-consuming separation procedures. Plasma proteins were precipitated by addition of 3:1 (v/v) acetonitrile-methanol, ZnSO₄, and MgSO₄ and the supernatant was injected directly on to a 250 mm × 4.6 mm, 5 μm particle Spherisorb analytical column. Acetonitrile-methanol-0.04 mol L^?1 KH₂PO_4, 40:10:50 (v/v); pH 3.8, was used as mobile phase. The drug was detected by UV detection at 330 nm. The response was linear over the range of 0.01–10 μg mL^?1 and 0.025–5 μg mL^?1 in mobile phase and human plasma samples, respectively. The proposed method was used without interference from the endogenous substances, for determination of piroxicam in plasma samples obtained from healthy volunteers. The results revealed that the method would be useful in monitoring plasma levels of the drug during pharmacokinetic studies. Assay of piroxicam in its dosage forms for quality-control purposes could also be performed successfully by use of this method.     

Complex formation and adsorption of V3+, Cr3+ and Fe3+ ions with poly(N-vinylimidazole)

The complex formation of soluble poly (N-vinylimidazole) (PVIm) with trivalent metal ions in aqueous solution was studied by using UV–vis spectroscopy. Formation constants of PVIm–metal complexes were calculated by applying the “molar ratio” method. It was found that the interaction between PVIm and trivalent metal ions follows 4(base unit):1(metal ion) stoichiometry. The stability constants for the complexes of PVIm with trivalent transition-metal ions were in agreement with the Irving– William series. The biggest formation constant was found for the PVIm–Fe³⁺ complex system. The capacity of adsorption for these metal ions was investigated using cross-linked PVIm. Cross-linked PVIm hydrogels were prepared by irradiating binary mixture of N-vinylimidazole–water with a ⁶⁰Co γ-ray source having a dose rate of 4.5 kGy/h. Adsorption studies were performed at different pH and metal ion concentrations at room temperature. It was observed that the same sequence for the metal ions was verified by adsorption studies. Received: 28 May 2001 Accepted: 29 July     

Novel platinum pyridinehydroxamic acid complexes: Synthesis,characterisation, X-ray crystallographic study and nitric oxide related properties

Herein, we describe the synthesis and characterisation of a novel class of Pt^II and Pt^IV pyridinehydroxamic acid (pyhaH) complexes of general formula cis-[Pt^IICl₂(x-pyhaH)₂] and cis-[Pt^IVCl₄(x-pyhaH)₂], respectively (where x = 3 or 4) in which the pyridinehydroxamic acid is coordinated to the platinum ion via the pyridine nitrogen only leaving the hydroxamic acid free to potentially release cytotoxic nitric oxide (NO). The crystal structure of the Pt^IV derivative, cis-[PtCl₄(4-pyhaH)₂] · 2CH₃OH is reported. To establish the biological effect of the uncoordinated hydroxamic acid moiety in the Pt^II compounds synthesised, the corresponding pyridinecarboxylic acid (pycaH) complexes of general formula cis-[Pt^IICl₂(x-pycaH)₂] (where x = 3 or 4) and the Pt^II pyridine (py) complex, cis-[Pt^IICl₂(py)₂] were synthesised and served as reference standards. The NO-releasing properties of each of the Pt^II compounds, the pyhaH and the pycaH ligands were studied. The Pt^II pyridinehydroxamic acid derivatives were found to induce potent in vitro effects attributable to either NO-release from the hydroxamic acid moiety and/or stimulation of inducible nitric oxide synthase of endothelial cells.     

A COMPARISON OF THERMALLY INDUCED CHANGES IN SONICATED PHOSPHOLIPID AND SURFACTANT VESICLES BY MEANS OF INTRA-MOLECULAR EXCIMER-FORMING PROBE

Abstract The molecule (1,l'-dipyrenyl)-methyl ether (dipyme) was used for monitoring the bilayer fluidity of surfactant and sonicated phospholipid vesicles. In the latter systems, the observed transition temperatures ( Tc ) are identical with those found by different methods. Surfactant vesicles prepared from dioctadecyldimethylammonium bromide (DODAB) and dihexadecylphosphate (DHP) molecules manifest a similar fluidity of their bilayers as those of sonicated phospholipid vesicles below their Tc. However, unlike in phospholipid vesicles, there was no significant change of the bilayer structure above Tc observed in surfactant vesicles. DHP vesicles formed in pure water provide a different solubilization site for dipyme than those prepared in a buffer solution. Such sites are characterized by a relatively high local concentration of the probe and the appearance of the blue shifted spectrum of the excimer.     

Adsorption and kinetic studies of cationic and anionic dyes on pyrophyllite from aqueous solutions

The adsorption of cationic Methylene Blue (MB) and anionic Procion Crimson H-EXL (PC) dyes from aqueous medium on pyrophyllite was studied. Changes in the electrokinetics of pyrophyllite as a function of pH were investigated in the absence and presence of multivalent cations. The results show that pyrophyllite in water exhibits a negative surface charge within the range pH 2-12. Pyrophyllite is found to be a novel adsorbent for versatile removal of cationic and anionic dyes. The negative hydrophilic surface sites of pyrophyllite are responsible for the adsorption of cationic MB molecules. The adsorption of anionic PC dye is possible after a charge reversal by the addition of trivalent cation of Al. Nearly 2 min of contact time are found to be sufficient for the adsorption of both dyes to reach equilibrium. The experimental data follow a Langmuir isotherm with adsorption capacities of 70.42 and 71.43 mg dye per gram of pyrophyllite for MB and PC, respectively. For the adsorption of both MB and PC dyes, the pseudo-second-order chemical reaction kinetics provides the best correlation of the experimental data.     

Validated method for the determination of the novel organo-ruthenium anticancer drug NAMI-A in human biological fluids by Zeeman atomic absorption spectrometry

NAMI-A is a novel ruthenium-containing experimental anticancer agent. We have developed and validated a rapid and sensitive analytical method to determine NAMI-A in human plasma, plasma ultrafiltrate and urine using atomic absorption spectrometry with Zeeman correction. The sample pretreatment procedure is straightforward, involving only dilution with an appropriate hydrochloric acid buffer-solution. Because the response signal of the spectrometer depended on the composition of the sample matrix, in particular on the amount of human plasma in the sample, all unknown samples were diluted to match the matrix composition in which the standard line was prepared (plasma-buffer 1:10 v/v). This procedure enabled the measurement of samples of different biological matrices in a single run. The validated range of determination was 1.1-220 microM NAMI-A for plasma and urine, and 0.22-44 microM for plasma ultrafiltrate. The lower limit of detection was 0.85 microM in plasma and urine and 0.17 microM in plasma ultrafiltrate. The lower limit of quantitation was 1.1 and 0.22 microM, respectively. The performance of the method, in terms of precision and accuracy was according to the generally accepted criteria for validation of analytical methodologies. The applicability of the method was demonstrated in a patient who was treated in a pharmacokinetic phase I trial with intravenous NAMI-A.     

Synthesis of triazene-substituted homoconjugated push-pull chromophores by formal [2 + 2] cycloadditions

1-(4-Ethynylphenyl)-3,3-dialkyltriaz-1-enes, well-known building blocks for branched dendrimer syntheses, were utilized as a new type of electron-donor component in formal [2 + 2] cycloadditions. The click-type, atom-economic reactions proceed efficiently under ambient conditions without any catalyst. The resulting products are structurally interesting push-pull chromophores and were investigated in the context of optoelectronic properties using UV/Vis spectroscopy, NMR studies, and computational chemistry.