Radiolysis of chitosan derivatives exhibiting antimutagenic activity

The radiolysis of antimutagens extracted from natural biopolymer chitosan was studied by the EPR method. It was shown that addition of gallic acid (2 mol %) to quaternized chitosan results in a 2.5-fold decrease in the radiation-chemical yield of radicals and a nearly complete inhibition of the formation of ion radicals. Gallic acid units likely play the role of a stabilizer that protects the polycation from radiation damage and, hence, the structure of the cationogenic units from changes, thereby improving the antimutagenic properties of the system.     

Radiolysis of tetrachloromethane-water two-phase systems

The radiolysis of two-phase systems CCl₄-water proceeds in kinetical regime up to dose 12 kGy. Groos radiation yields of chloride ions are the same as the radiolysis of saturated solutions in this period. A two-phase rule of additivity is valid and the partial yields for both phases were calculated; G_CCl4(Cl^- = 5.61 ± 0.10 and G_H2O(Cl^-) = 8.29 ± 0.51 molecules/100 eV, respectively.The radiolysis proceeds in diffusional regime at the absorbed dose of more than 50 kGy. The gross radiation yield of chloride ions is determined by hydrolysis of molecular chlorine which is produced with G(Cl₂) = 0.68 ± 0.14 molecules/100 eV. An additional part of chloride ions is produced by radiolysis of substrates which diffuse into both phases with value G_dif(Cl^-) = 2.38 ± 0.31 molecules/eV. This value is approximately three times less than the gross radiation yields in kinetical regime of radiolysis of two-phase systems in saturated solutions of these substrates.     

Novel polycationic biocides: Synthesis and antibacterial activity of polymeric phosphonium salts

Various polymeric phosphonium salts and the corresponding low-molecular-weight model compounds were prepared and their antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell counting method in sterile distilled water. Antibacterial activity of the polymers was found to be higher than that of the corresponding model compounds, particularly against S. aureus. Furthermore, the polymeric phosphonium salt exhibited a higher activity by 2 orders of magnitude than the polymeric quaternary ammonium salt with the same structure except the cationic part. Compounds with the longest alkyl chain (octyl) studied were found to exhibit particularly high activity, and this finding may be ascribed to the contribution of the increased hydrophobicity of the compounds to the cidal activity. © 1993 John Wiley & Sons, Inc.     

Probing polyvalency in artificial systems exhibiting molecular recognition

An approach to the study of polyvalency-the interaction of polyvalent receptors with polyvalent ligands-in unnatural systems is outlined. In this study, the complexation of dibenzylammonium cations by dibenzo[24]crown-8 or benzometaphenylene[25]crown-8 is utilized as the component receptor-ligand interaction. Two analogous multivalent receptors-each containing either seven dibenzo[24]crown-8 (DB24C8 CLUSTER) or seven benzometaphenylene[25]crown-8 (BMP25C8 CLUSTER) moieties appended to a modified beta-cyclodextrin core-were prepared in moderate yields. For each of these multivalent receptors, complementary mono- and divalent ligands containing one or two dialkylammonium centers, respectively, were prepared in good yields. These ligands contained fluorine atom substituents to allow their interactions with crown ether compounds to be probed by (19)F NMR spectroscopy. The complexation of these monovalent ligands with the DB24C8 CLUSTER and the BMP25C8 CLUSTER was studied by determining the average binding constant (K(AVE)) between the receptors and ligands. The abilities of the crown ether clusters to complex with these monovalent ligands was compared with those of the monovalent crown ethers dibenzo[24]crown-8 and benzometaphenylene[25]crown-8. In both instances, it was found that clustering seven crown ethers together into one molecule is detrimental to the abilities of the crown ether moieties to complex with monovalent dialkylammonium ligands. The complexation of the divalent ligands by the DB24C8 CLUSTER and the BMP25C8 CLUSTER was then studied-again by determining K(AVE)-and their abilities to complex with these ligands was compared with those of their respective component interactions. By determining K(AVE) for the polyvalent interaction, it was possible to calculate an association constant, K(POLY), for the binding of the divalent ligands by the DB24C8 CLUSTER and the BMP25C8 CLUSTER compounds. In both instances K(POLY) for the polyvalent interaction was found to be approximately 2 orders of magnitude higher than the association constants, K(A), for the component interaction.     

Radiolysis of chitosan

The γ-radiolysis of solid chitosan was studied. The radiolysis products hydrogen and ammonia were determined by chromatography and spectrophotometry (with Nessler’s reagent), respectively, and the amino groups were determined by potentiometic titration. The radiation-chemical yields were found to be G _{H 2} = 2.0 ± 0.3; G _{NH 3} = 5.8 ± 0.4 and G _{−NH 2} = 2.9 ± 0.8. The molecular mass of chitosan decreases with an increase in the absorbed radiation dose because of its degradation (G _D = 3.6 ± 0.4). A long-term posteffect was observed after irradiation. This is a preliminary report on the study concerning the search for optimal conditions of the synthesis of membranes from modified chitosan for removal of cadmium ions.     

Radiolysis of chloroalkanes

Radiolysis of chloroalkanes (from chloropropanes to chlorodecane) has been investigated. Hydrogen and hydrogen chloride are the main products of decomposition. Their concentrations linearly grow with the dose in the examined interval up to 150 kGy. The radiation-chemical yield of hydrogen increases from 0.72 for 1-chloropropane to 1.3 for 1-chlorodecane. The opposite trend is observed in the case of HC1: 3.7 for 1-chloropropane and 1.7 for 1-chlorodecane. Products of dechlorination, chlorination (di-and trichloroalkanes) with G 0.8–4.0, isomerization with G up to 90, as well as oligomerization products, have been identified in the liquid products.     

丝网印刷法制备高催化活性对电极

对电极在染料敏化太阳能电池（DSCs）中主要起催化氧化还原反应及收集电荷的作用,铂对电极常用的制备方法为磁控溅射法,但其成本较高,制备条件苛刻. 本文通过引入低成本的表面活性剂Span-85,所制得的铂对电极的附着力、透光率和均匀性显著改善,实现了面积可控,与两步浸泡法和旋涂热解法制备的对电极在DSCs中的光电转换效率分别为7.30%,6.96%和7.03%. 紫外-可见吸收光谱、扫描电镜和附着力测试等结果表明,（1）添加表面活性剂有利于增加附着力及改善透光率和均匀性;（2）使用该法制备的Pt/FTO对电极的透光率与两步浸泡法制作的相同,且铂粒子分布更加均匀. 电化学阻抗图谱、塔菲尔极化曲线和循环伏安曲线结果表明,丝网印刷方法制备的Pt/FTO对电极具有更加优异的催化性能,且该法更有利于降低其生产成本和大规模生产.     

Vibronic and spin-orbit splitting in spectra of systems exhibiting Jahn-Teller-Effect

Simple two- and three-dimensional models have been used to investigate the vibronic states of molecules exhibiting Jahn-Teller-Effect. According to the topology of the adiabatic potential surface, two cases have to be distinguished, which may (A) or may not (B) be treated in the Born-Oppenheimer approximation. In the latter case B strong Jahn-Teller coupling leads to a splitting of an A E absorption line into three peaks instead of the usual two ones. This additional splitting originates from transitions into the first and second metastable level of the upper potential well. However, the vibronic splitting will often be smeared out by coupling of the Jahn-Teller effect to a distortion of a Jahn-Teller inactive vibration. The effective spin-orbit splitting of an absorption band with unresolved vibrational structure is larger than in the case of vanishing Jahn-Teller coupling, contrary to the spin-orbit splitting of single vibronic levels. An experimental example of this effect is discussed. In Jahn-Teller case B it may be interpreted as a superposition of the vibronic and the spin-orbit splitting effects.

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Zusammenfassung Mittels einfacher zwei- und dreidimensionaler Modelle wurden die vibronischen Zustände von Molekülen untersucht, die einen Jahn-Teller-Effekt zeigen. Entsprechend der Topologie der adiabatischen Potentialfläche sind zwei Fälle A und B zu unterscheiden, die im Rahmen der Born-Oppenheimer-Näherung behandelt werden können bzw. wo dies nicht möglich ist. Im letzteren Falle B führt eine sehr starke Jahn-Teller-Kopplung zur Aufspaltung einer AE Absorptionslinie in drei statt wie üblich in zwei Peaks. Diese zusätzliche Aufspaltung rührt her von Übergängen in die ersten beiden metastabilen Resonanzzustände der oberen Potentialmulde. In vielen Fällen wird mit einer Jahn-Teller-Kopplung der asymmetrischen Schwingung eine Verschiebung der Gleichgewichtslage einer Jahn-Teller inaktiven Schwingung einherlaufen: Die vibronischen Aufspaltungen sollten daher durch Schwingungsverbreiterung teilweise verschmiert sein. Während die Spin-Bahn-Aufspaltung einzelner vibronischer Niveaus durch Jahn-Teller-Kopplung verringert wird, wird die effektive Spin-Bahn-Aufspaltung einer Absorptionslinie mit nichtaufgelöster Schwingungsstruktur vergrößert. Ein experimentelles Beispiel für diesen Effekt wird diskutiert. Im Jahn-Teller-Fall B kann er als Überlagerung der vibronischen und der Spin-Bahn-Aufspaltung interpretiert werden.

     

Radiolysis and variation of anti-microbial activity of gamma-irradiated acrinol aqueous solution on radiosterilization

The investigations about the radiolysis materials and their quantities, and, anti-microbial activities of gamma-irradiated (in the ranges of 0.516-2.064 kC/kg (2-8 MR] acrinol on liquid dosage form have been carried out to study the application of radiosterilization. About nine components were found as radiolysis materials. Most of them were also found in the UV-irradiated of Fenton's reagent-treated acrinol solution. Increase of anti-microbial activity was observed with gamma-irradiated acrinol solutions, but this phenomenon was not long-lasting. The micro-organism such as Pseudomonas aeruginosa or Staphylococcus aureus that infect at the lips of wound are highly sensitive to the gamma-irradiation. They are almost sterilized by the irradiation of 10 kGy (1.0 Mrad). At a low acrinol concentration, the decomposition rate of acrinol by the irradiation was relatively high. When 1.0% of acrinol solution was irradiated at a dose of 10 kGy (1.0 Mrad), the decomposition of the drug was less than 2% and the variation of anti-microbial activity was negligible.     

Radiolysis of p-benzoquinone solutions

The products of the continuous radiolysis of p-benzoquinone (Q) at different concentrations of H₂SO₄, Q and Cl^– are p-hydroquinone (H₂Q) and 2-hydroxy-p-benzoquinone (2-Q-OH). In the presence of some alcohols, a carbonyl compound is produced in addition to H₂Q and 2-Q-OH. The dependence of G values of the products on these factors is described. The material balance between G(-Q) and G(H₂Q)+G(2-Q-OH) is maintained. The experimental results indicate the occurrence of the following reaction: . By competition studies, it was possible to evaluate the rate coefficients for the following reactions: .     

Radiolysis of alkylnaphthalene oils

Radiolysis of alkylnaphthalene oils was studied. It was shown that the radiation-chemical yield of hydrogen grows linearly (from 0.26 for KR-007A oil to 0.78 for KR-019 oil) with an increase in the average (with allowance for the composition) length of the alkyl chains. A number of liquid alkanes and alkenes (C₅–C₁₂) along with naphthalene were identified in the radiolysis products. Dimers and polymers make 2–10% depending on the radiation dose. Alkylnaphthalene oils used as additives for synthetic oils of the WM-5 type substantially improve the radiation resistance of these oils.     

Radiolysis of water-nitrobenzene-carbon tetrachloride and water-chlorobenzene-carbon tetrachloride two-phase systems. Radiation yields of chloride ions

The influence of nitrobenzene and chlorobenzene on the total radiation yield of chloride ions in the -irradiation of water-carbon tetrachloride two-phase systems has been determined. Nitrobenzene at small concentrations shows a pronounced protective influence on the radiation destruction of carbon tetrachloride. Similar protective effect on the destruction of carbon tetrachloride is shown by chlorobenzene, too, but the decrease of radiation yields of chloride ions is smoother, which is explained by radiation decomposition of chlorobenzene itself. Protective effect of nitrobenzene and chlorobenzene on the radiation destruction of carbon tetrachloride is explained by transfer of energy from carbon tetrachloride molecules to the aromatic molecules.     

Total synthesis of indole-derived allocolchicine analogues exhibiting strong apoptosis-inducing activity

A series of novel pyrrolo-allocolchicine derivatives (containing a 1-methyl-1H-indol-5-yl moiety replacing ring?C) was synthesized. The tetracyclic ring system was constructed by Suzuki-Miyaura cross-coupling of a 1-methylindole-5-boronate with an ortho-iodo-dihydrocinnamic acid derivative and subsequent intramolecular Friedel-Crafts acylation. After reduction of the resulting ketone, the nitrogen functionality was introduced in a Mitsunobu-type reaction by using zinc azide followed by LiAlH(4) reduction. Structural assignments were supported by X-ray crystallography. The compounds synthesized were then tested against BJAB tumor cells and found to exhibit pronounced cytotoxic activity (proliferation inhibition and apoptosis induction). The ketone 24?b was even active at sub-nanomolar concentration. In addition, the antitumor potential of the compounds was confirmed by using B lymphoid cell lines.     

Dielectric studies on binary mixtures of systems exhibiting intermediate nematic phase

Two binary phase diagrams of the liquid crystals (4-n-pentylphenyl-4-n-hexyloxybenzoate (PPHB) with 4-nitrophenyl-4-n-pentylbenzoate (NPPB) and 4-n-hexyloxyphenyl-4-n-decyloxybenzoate (HPDB) with NPPB) have been studied. PPHB shows only a nematic phase where as for HPDB trimorphism, with the SmC, SmA and nematic phases, was observed. Substance NPPB which has a strong polar nitro group is non-mesogenic one. Both the phase diagrams show an induction and stabilization of SmA phase and appearance of the nematic state in the high concentration range of polar component. The dielectric measurements confirm the phase transition temperatures and show changes in the short range interaction at the phase transitions.     

Radiolysis of L- and D-Monosaccharides

The effects of ⁶⁰Co -radiation on D-glucose, L-glucose, D-galactose, L-galactose, D-mannose, and L-mannose were studied. The yields of gaseous radiolysis products were determined. The curves of radical buildup and decay in crystalline samples were obtained. Conclusions on the relative radiation stability of these D- and L-monosaccharides to the action of nonpolarized radiation were drawn.     

The Radiolysis of Pyrogallol Red

 The radiolysis of pyrogallol red solution (PGR) by gamma radiation has been studied spectrophotometrically. The decrease in absorbance of the characteristic band of pyrogallol red at 490 nm and pH 4 gives a reproducible response and an accurate means of dosimetry for the dose ranges 0.02–1.5 kGy. Received January 3, 2001. Revision June 15, 2001.     

Radiolysis of polychlorodibenzodioxins in hexane

In the radiolysis of 2,3,7,8-tetrachlorodibenzodioxin in n-hexane (dose 6.5 Mrad), the degree of its decomposition according to data of chromatographymass spectrometry is not less than 99.99995 rel. % (detection limit 2· 10^–10 mass %). In this case, the less-chlorinated dibenzodioxins formed at lower irradiation doses are not detected.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 786–790, April, 1991.     

Radiolysis of aqueous cesium iodide

In hypothetical accident scenarios for Light Water reactors, the extent of release of iodine upon irradiation needs to be assessed for the purpose of evaluation of the applicable source term. In this context, an understanding of the behaviour of aqueous cesium iodide solutions subjected to high gamma-ray fluxes acquires significant importance. In the present work, gamma radiolysis of a cesium iodide solution (10^–2M I^–) with and without boron additive is investigated by irradiating with⁶⁰Co source at ambient temperature. Upon irradiation of the CsI solution, iodine is liberated, and the concentration of iodide in the KOH trap present in the radiolysis vessel increases with dose. The radiolytic products I ₃ ^– , IO ₃ ^– and H₂O₂ formed in the irradiated solution are also estimated and G values obtained are reported. G(I ₃ ^– ) and G(IO ₃ ^– ) are of the order of 10^–3 and 10^–4, respectively. G(H₂O₂) decreases with increase in dose. Addition of boron up to 200 ppm, does not appear to alter significantly the release fraction of iodine.     

New polymer systems exhibiting microphase separation transition with the formation of nano-microstructures

The concept of microphase separation was up to now widely applied mainly to the conformational transitions in block-copolymer solutions and melts. However, recently it became obvious that this concept has a much more general meaning. It was shown that microphase separation transition can be observed in random copolymers, interpenetrating polymer networks, polyelectrolyte mixtures, poor solvent polyelectrolyte solutions, ionomer solutions and melts, polymer blends and solutions with nonlocal entropy of mixing. In all these examples the emerging microdomain structures correspond to the nanometer scale, therefore the study of these effects can lead to the new ways of obtaining polymer materials with controlled nano-microstructure. In this presentation the review of our recent findings on microphase separation in some of the above-mentioned systems will be presented. 1. The problem of microphase separation in the systems containing weakly charged polyelectrolytes (polyelectrolyte mixtures and poor solvent polyelectrolyte solutions) will be considered. From the methodic point of view, it will be shown that this problem can be solved by direct minimization of the free energy, without the use of “weak segregation” or “strong segregation” assumptions which are common in the theory of block-copolymers. The final phase diagrams exhibit wide macroscopic phase separation regions, which is their main difference from the corresponding phase diagrams for block-copolymer systems. The formation of microdomains is thus coupled with macroscopic phase separation: in most of the cases microdomain structure is formed in one of the coexisting phases after macroscopic phase separation takes place [1] - [2]. 2. The formation of the multiplet structure in ionomer melts and solutions can be also considered as the microphase separation in the random copolymer system with the formation of the “micelles” (or clusters) of ionic links. The parallels with micelle formation in block-copolymer systems can be established if one considers a new “superstrong segregation regime” for block-copolymer microstructures. This regime can be indeed observed for diblock copolymers with one ionomeric and one neutral block [3]. 3. The microphase separation transition in ordinary polymer blends and solutions is also possible. The conditions for this effect are: (i) significant entropic contribution to polymer/polymer or polymer/solvent miscibility, (ii) the nonlocal character of this contribution with a high value of the nonlocality radius. It is argued that one can expect that the entropy nonlocality radius increases in the vicinity of the glass transition for the blend or polymer solutions (in the latter case solvent molecules act like “poor solvent plasticisers”). Computer simulation data supporting the theoretical prediction of microphase separation transition in these systems will be presented [4] - [5].     

Surface immobilization of indometacin for preparing polypropylene materials exhibiting biological activity

Russian Journal of Applied Chemistry - A procedure was proposed for the modification of the manganese-oxide catalyst hopcalite GFG allowing the new quality, water resistance of granules, to be...