Thermal and electrical properties of Ca5Mg4−xZnx(VO4)6 (0 ≤ x ≤ 4)

Calcium vanadates Ca₅Mg_4−xZn_x(VO₄)₆ (0 ≤ x ≤ 4) have been studied for the first time using a set of high-temperature methods of analysis. The onset of melting process determined from differential scanning calorimetry decreases from 1158 to 881 °C (± 1.5 °C) with increasing of x (dopant’s content). CTE temperature dependence is found to show a hysteresis. Electrical transport properties measured by impedance spectroscopy in air of different humidity are also discussed. The value of electrical conductivity does not depend on air humidity. It is found to equal to 1.5 × 10⁻⁶ S cm⁻¹ at 720 °C for Ca₅Mg₄(VO₄)₆ which is specific for garnet-related crystals.

     

Ferrocene‐modified thiopyrimidines: synthesis,enantiomeric resolution,antitumor activity

Ferrocenylalkyl thiopyrimidines ( 6a–d to 9a–d ) were prepared via the reaction of the α‐(hydroxy)alkyl ferrocenes, FcCHR(OH) ( 1a–d ; Fc = ferrocenyl; R = H, Me, Et, Ph), with 2‐thiopyrimidines ( 2 – 5 ) in acetone at room temperature in the presence of TFA, yielding 50–95%. The resulting enantiomers were resolved using HPLC on modified cellulose as chiral selector. The antitumor activities of S‐ferrocenylethyl 2‐thiopyrimidine ( 6b ) against two murine solid tumor models, carcinoma 755 (Ca755) and Lewis lung carcinoma (LLC) were evaluated in vivo. The strong antitumor effect of compound 6b on Ca755 and LLC was demonstrated. The index of tumor growth inhibition on Ca755 equaled 95% in comparison with control. Copyright © 2010 John Wiley & Sons, Ltd.     

Dependence of Total p-Electron Energy on the Number of Non-Bonding Molecular Orbitals

In recent work [Gutman et al. (2004) Chem Phys Lett 383: 171] a method was developed by means of which the influence of non-bonding molecular orbitals (NBMOs) on the value of total -electron energy (E) can be separated from the multitude of other molecular-structure-dependent effects. We now extend this method and establish the relation between E and the number n ₀ of NBMOs. It is shown that E (when computed within the HMO approximation, and expressed in the units of the HMO resonance integral ) is a decreasing function of n ₀, and that the dependence of E on n ₀ is almost perfectly linear.     

Observation of an unprecedented Cu Bis-His site: crystal structure of the H129V mutant of nitrite reductase

Copper nitrite reductases contain both an electron-transfer type 1 Cu site and a catalytic type 2 Cu site. We have mutated one of the type 2 copper ligating histidines to observe the effect on catalytic turnover. This mutation has created a unique site where Cu is ligated by 2 His Nepsilon2 atoms alone.     

Computational analysis of native and modified oligofructosides

This paper presents a quantum chemical calculation of native (2–7 fructoside residues) and chemically modified (2–4 fructoside residues) levan molecule models. A levan modification was carried out by oxidation and the following reduction or hyrdazonation of the fructoside rings. The conformational particularity and reaction ability was studied for the native and for the modified levan molecules.     

Platinum metallodrug-protein binding studies by capillary electrophoresis-inductively coupled plasma-mass spectrometry: characterization of interactions between Pt(II) complexes and human serum albumin

Characterizing how platinum metallocomplexes bind to human serum albumin (HSA) is essential in evaluating anticancer drug candidates. Using cisplatin as a reference complex, the application of capillary electrophoresis (CE) to reliably assess drug/HSA interactions was validated. Since this complex is small compared to the size of the protein, the binding response could only be recognized when applying CE coupled to a (platinum) metal-specific mode of detection, namely inductively coupled plasma-mass spectrometry (ICP-MS). This coupling allowed for confirmation of a specific affinity of cisplatin and novel Pt complexes to HSA, measurement of the kinetics of binding reactions, and determination of the number of drug molecules attached to the protein. As the cisplatin/HSA molar ratio increased, the reaction rate became faster with a maximum on the kinetic curve appearing at about 50 h of incubation at 20 times excess of cisplatin. The reaction was characterized as a pseudo-first order reaction with the rate constant k = 0.003 min(-1) at 37 degrees C. When incubated with a 20-fold excess of cisplatin, HSA bound up to 10 mol of Pt per mol of the protein. This is indicative for a strong metal-protein coordination occurring at several HSA sites other than the only protein cysteine residue. Structural analogs of cisplatin, bearing aminoalcohol ligands, showed comparable protein binding reactivity and stoichiometry but a common equilibrium was not reached even after one week of incubation. Also apparent was a two-step mechanism of the binding reaction. Results demonstrated the suitability of CE-ICP-MS as a rapid assay for high-throughput studying of drug/HSA interactions.     

The comparison of sample extraction procedures for the determination of cations in soil by IC and ICP-AES

This paper presents the extraction of cations from a soil sample, type ranker on serpentinite, in deionized water, by use of three different extraction techniques. The first extraction technique included the use of a rotary mixer, the second technique involved the use of a microwave digestion system with different extraction temperatures, and the third technique employed an ultrasonic bath with different extraction times. Ion chromatography was used for determining the concentration of Li, Na, K, Ca, Mg and ammonium ions in soil extracts with subsequent determination of concentrations for all cations, except for ammonium ion extraction, conducted by Inductively Coupled Plasma-Atomic Emission Spectrometry. The results of cation extractions showed that microwave assisted extraction was most efficient for the Li, Na, K, Ca, Mg, Co, Mn, Ni, Pb and ammonium ions. Use of a rotary mixer for extraction was most efficient for Cd and Zn ions, while use of ultrasound bath was most efficient for Cr, Cu, Fe and Al ions. Several times higher amount of cations extracted by the most efficient, compared to the second best technique, under optimal conditions, were noticed in the case of: Ca, Mg, Co, Mn, Fe, Al, and Zn ions.     

Reaction of primary phosphines with elemental sulfur and alkali metal hydroxides (MOH, M = Na, K, Cs): a novel and facile three-component synthesis of trithiophosphonates

Primary phosphines readily react with elemental sulfur and alkali metal hydroxides (MOH, M = Na, K, Cs) in the molar ratio 1:3:2 under mild conditions (70 °C, 0.5 h, ethanol) to afford alkali metal trithiophosphonates in good to high yields (72-90%).     

Differential SERS activity of gold and silver nanostructures enabled by adsorbed poly(vinylpyrrolidone)

We report that poly(vinylpyrrolidone) (PVP), a common stabilizer of colloidal dispersions of noble metal nanostructures, has a dramatic effect on their surface-enhanced Raman scattering (SERS) activity and enables highly selective SERS detection of analytes of various type and charge. Nanostructures studied include PVP-stabilized Au-Ag nanoshells synthesized by galvanic exchange reaction of citrate-reduced Ag nanoparticles (NPs), as well as solid citrate-reduced Ag and Au NPs, both before and after stabilization with PVP. All nanostructures were characterized in terms of their size, surface plasmon resonance wavelength, surface charge, and chemical composition. While the SERS activities of the parent citrate-reduced Ag and Au NPs are similar for rhodamine 6G (R6G) and 1,2-bis(4-pyridyl)ethylene (BPE) at various pH values, PVP-stabilized nanostructures demonstrate large differences in SERS enhancement factors (EFs) between these analytes depending on their chemical nature and protonation state. At pH values higher than BPE's pK(a2) of 5.65, where the analyte is largely unprotonated, the PVP-coated Au-Ag nanoshells showed a high SERS EF of >10(8). In contrast, SERS EFs were 10(3)- to 10(5)-fold lower for the protonated form of BPE at lower pH values, or for the usually highly SERS-active cationic R6G. The differential SERS activity of PVP-stabilized nanostructures is a result of discriminatory binding of analytes within-adsorbed PVP monolayer and a subsequent increase of analyte concentration at the nanostructure surface. Our experimental and theoretical quantum chemical calculations show that BPE binding with PVP-stabilized Au-Ag nanoshells is stronger when the analyte is in its unprotonated form as compared to its cationic, protonated form at a lower pH.