“Direct” synthesis of unsolvated aluminum hydride involving Lewis and Bronsted acids

Unsolvated aluminum hydride has been synthesized by the “direct” reaction of aluminum bromide or sulfuric acid with an alkali metal tetrahydroaluminate at 90–102°C in pure toluene or in toluene containing 5–10 wt % diethyl ether. The reaction involving aluminum bromide yields a mixture of unsolvated aluminum hydride phases of poor quality. The reaction with sulfuric acid affords a single-phase product as α-AlH₃ at ≤90°C.     

New fluorine-containing titanium bis(salicylideneimino) complexes in olefin polymerization

The titanium salicylideneimino complex TiCl₂{²-1-[NR=C(H)]-2-O-3,5-Bu^t ₂-C₆H₂}₂ (R = 2,3,5,6-F₄C₆H) was synthesized. In the presence of polymethylaluminoxane, the complex efficiently catalyzes polymerization of ethylene and, to a lesser degree, atactic propylene. The resulting polymers are characterized by high melting points, molecular weights, and polydispersity indices, as well as elastomeric (polypropylene) properties.     

Design,synthesis of novel quinazolin-4-one derivatives and biological evaluation against human MCF-7 breast cancer cell line

A new series of 6,8-dibromo-2-(4-chlorophenyl)quinazolin-4(3H)-one derivatives VI–XIII were synthesized. Their chemical structures were confirmed by spectral and elemental analysis. The cytotoxic effect of the newly synthesized compounds was tested in vitro against human breast cancer cell line (MCF-7). Most of the tested compounds have shown promising cytotoxic activity. Compounds X and XIIIb exerted a powerful cytotoxic effect against MCF-7 with a very low IC50 (0.0015 and 0.0047 µmol/ml), while compounds VI, VII, VIII, XIIb, XI, XIIIc and IX exerted a moderate cytotoxic effect (IC50 0.01523, 0.0213, 0.031, 0.0478, 0.049, 0.068 and 0.079 µmol/ml respectively), compared to doxorubicin (0.0025 µmol/ml). Exploring their apoptotic effect; interestingly,all compounds activated apoptotic cascade in MCF-7. Compounds VI, XIIIb, XIIb, XI, XIIa, VII, V and VIII showed potent effect even much more than doxorubicin by 12.87–5.91 folds, while compounds XIIIc, IX, XIIIa, XIIc and X showed moderate increase in CASP3 activity by 4.96–3.22 folds relative to untreated cells more or less similar to doxorubicin (5.57 folds).     

Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas

Obliquely propagating altra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized, two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfvén mode propagating parallel to the external magnetic field and dustmagnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that in parallel propagating dust-Alfvén mode these effects play no role, but in obliquely propagating dust-Alfvén mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays destabilizing role whereas the effect of dust/ion fluid temperature plays stabilizing role.     

Synthesis and biological activity of isoalantolactone—tryptamine conjugates

Previously unknown adducts of substituted tryptamines with sesquiterpene lactones, viz., isoalantolactone and its epoxy derivative, were synthesized by the Michael reaction. The compounds obtained were tested for various types of biological activity.     

Mechanochemical synthesis of poly(hydridocarbyne)

Poly(hydridocarbyne) was synthesized by the reaction of bromoform and magnesium metal under the mechanochemical activation conditions.     

Comparative study on photosynthetic activity of chloroplasts in acid and alkaline zones of Chara corallina

A novel experimental approach has been applied to investigate the relationship between pH banding in Chara cells and photosynthetic activity of chloroplasts located in cell regions adjacent to acid and alkaline bands. The combination of pH microelectrode technique with pulse amplitude modulation (PAM) microfluorimetry enabled parallel measurements of longitudinal pH profiles and chlorophyll fluorescence yield in acid and alkaline zones of individual Chara cells. The scanning with a pH-microelectrode along the cell length revealed the light-dependent pH pattern, i.e., alternating acid and alkaline bands with pH differences as large as 2 - 3 pH units. In parallel, measurements of chlorophyll fluorescence yield under actinic light were performed using PAM microfluorometry. It was found that the effective photochemical yield of photosystem II is substantially higher in acid than in alkaline zones. The results clearly show that the banding pattern is not confined solely to the plasmalemma but is also exhibited in alternating photosynthetic performance of the underlying chloroplast layer. Apparently, the acid regions enriched with CO2 ensure sufficient flow of this substrate to the Calvin cycle reactions, thus promoting the photosynthetic rate, whereas the alkaline zones devoid of CO2 favor radiative losses of absorbed solar energy in chloroplasts.     

Organic-inorganic hybrid hydrogels based on linear poly(N-vinylpyrrolidone) and products of hydrolytic polycondensation of tetramethoxysilane

The initial stage of gelation of organic-inorganic hybrid hydrogels based on poly(N-vinylpyrrolidone) and the products of hydrolytic polycondensation of tetramethoxysilane has been studied by capillary viscometry. The development of strong bonds between polymer molecules and silica particles in aqueous solutions is proved by the electrokinetic sonic amplitude method. The molecular mass of poly(N-vinylpyrrolidone), the concentration of starting components, and their total amount affect the onset time of gelation in poly(N-vinylpyrrolidone)—water—tetramethoxysilane systems. The general scheme of formation of three-dimensional networks in such systems under the conditions of mutual penetration of poly(N-vinylpyrrolidone) coils is suggested. According to this scheme, nanoparticles of the general formula SiO _x (OH) _y (OR) _z linking poly(N-vinylpyrrolidone) macromolecules serve as junctions of the gel network due to the formation of hydrogen bonds between hydrogens of silanol groups of organosilanes and oxygens of carbonyl groups of poly(N-vinylpyrrolidone).     

Effect of trimethylaluminum on the polymerization of ethylene with the catalytic system Bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride-methylaluminoxane

The effect of trimethylaluminum in commercial methylaluminoxane on the molecular-mass characteristics of polyethylene formed with the phenoxyimine titanium catalyst bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride activated by methylaluminoxane of varying purity is studied. It is shown that, all other conditions being equal, an increase in the content of trimethylaluminum in the reaction solution leads to an appreciable decrease in the molecular mass of the polymer. With an increase in the time of polymerization, the molecular mass tends to increase, while overall polydispersity indexes M _w/M _n remain substantially less than 2. The causes of the above effects are discussed.     

Outward photocurrent component in chloroplasts of Peperomia metallica and its assignment to the 'closed thylakoid' recording configuration

The photoinduced electrical events at energy-conserving chloroplast membranes can be studied in whole plastids using suction electrodes. In chloroplasts of Peperomia metallica the kinetic profile of photocurrent contains a minor outward component that occurs prior to and differs in polarity from the main component. The origin of this outward current was analyzed using single-turnover flashes in combination with prolonged light exposures and differential physicochemical treatments of tip-located (internal) and the exposed parts of a chloroplast. The outward current signal was higher after 10- to 20-s preillumination and gradually reduced in darkness. The relative amplitude of the outward peak current was enhanced when photosystem II (PS II) was excited by flashes given in the presence of far-red background light (lambda = 712 nm). The outward current was small or absent under conditions promoting activity of photosystem I (cyclic electron transport supported by artificial redox mediators in the presence of diuron) and was particularly high in the presence of PS II electron acceptors (e.g., p-phenylenediamine). This indicates the predominant association of the outward current with activity of PS II. The external application of diuron strongly inhibited the inward current, giving rise to a temporal increase in the outward current. On the contrary, when diuron was added into the suction pipette, the outward current was inhibited soon after sealing. The data suggest that the outward current originated in the tip-located portions of the thylakoid membrane that have orientation opposite to the exposed part of 'whole thylakoid'. These tip-located membrane portions are least accessible for inhibitors added into the outer medium and are highly sensitive to inhibitors (diuron), ionophores (gramicidin D), and detergents (Triton X-100) added into the pipette. Differential involvement of two photosystems in generation of the outward current may be caused by uneven structural distribution of photosystems I and II between appressed (granal) and nonappressed (stromal) thylakoids and by different recording configurations for these thylakoids.