Ternary complex formation in aqueous solution between a beta-cyclodextrin polymer, a cationic surfactant and DNA

Polyelectrolyte complexes have been elaborated by mixing in water neutral poly(beta-CD), a cationic surfactant (DTAC) and herring sperm DNA fragments. The driving forces for the poly(beta-CD)/DTAC/DNA association in aqueous solution are, on the one hand, reversible inclusion interactions between the CD cavities of poly(beta-CD) and the alkyl group of DTAC, leading to the formation of a polycation and, on the other hand, electrostatic interactions between the opposite charges of the cationic surfactant and anionic DNA. Viscometry and SANS have been used to prove the occurrence of such ternary complexes in dilute aqueous solutions.     

Cation sensors based on terpyridine-functionalized boradiazaindacene

A new class of highly luminescent dyes is reported. The characteristic feature of these compounds is that a terpyridine fragment is closely appended to a boradiazaindacene moiety in such a way that cation binding to the vacant terpyridine causes strong perturbations of the photophysical properties of the boradiazaindacene unit. In particular, these sensors are especially applicable to the fluorescence detection of trace quantities of zinc(II) ions in solution. The mechanism of the cation-induced quenching process has been investigated by a combination of electrochemistry, UV/Vis absorption, emission, and NMR spectroscopy. Highly luminescent arrays can be formed by doping transparent polymers with low concentrations of these new dyes. In such materials, the change in photophysical properties upon cation binding is so marked that "cation writing" becomes feasible under routine conditions.     

Some Aspects on Preconcentration for Neutron Activation Analysis

A preconcentration method incorporated with neutron activation analysis was developed for the accurate determination of trace metals in biological and environmental samples. Bismuth diethyldithiocarbamate, thallium diethyldithiocarbarnate, and ammonium pyrrolidinedithiocarbamate were used as the preconcentration agents for three groups of metals. Trace metals were enriched and interfering elements such as Na, Br, P. K. etc. were removed simultaneously during the preconcentration process so that the sensitivity for each metal was greatly improved. Optimal conditions for sample digestion, group preconcentration of trace metals and neutron activation analysis of biological and environmental samples were discussed.     

Mass-variation and Darwin relativistic corrections in many-electron atoms

The formulation for the evaluation of the matrix elements over the relativisitic mass-variation and Darwin operators is presented. Calculations of these corrections have been carried out, using available analytical Hartree-Fock functions, for the positive ions, neutral systems, and negative ions for all the atoms from He to Kr.     

Lanthanide/ATP interaction in water mediated by luminescent hemispherical-shaped complexes

Ligand LH(2), composed of two bipyridylcarboxylate fragments linked to an amino butyl chain, reacts with europium and terbium to form luminescent complexes in water at neutral pH. When testing these unsaturated complexes as anion sensors with NO(3)(-), HPO(4)(2)(-), AMP, ADP, and ATP, a marked selectivity is observed for HPO(4)(2)(-) and ATP(4)(-) at pH = 7.0. The interaction of these anions with the complex was investigated by means of absorption and emission spectroscopies. With ATP(4)(-), ES-MS and (31)P NMR experiments revealed the formation of a [Ln.L.(ATP)](3)(-) ternary species.     

Relative viscosity and viscosity coefficients of aqueous azoniaspiroalkane bromides at 25°C

The relative viscosities η_r of dilute aqueous solutions of azoniaspiroalkane bromides, (CH₂) _n N⁺ (CH₂) _n Br^? (wheren=4, 5, and 6), have been measured at 25°C. The viscosityB _η andD _η coefficients were determined using the extended Jones-Dole equation $$\eta _r = 1 + A_\eta c^{1/2} + B_\eta c + D_\eta c^2$$ TheB _η coefficients obtained for the bicyclic azoniaspiroalkane bromides were compared with those of the corresponding homologous tetra-n-alkylammonium bromides. Based on the obtained sign and magnitude of (B _n ?0.0025ø _v ^° ) for the salts and for the bicyclic ions, the structural effects of cation geometry and alkyl group flexibility on water are discussed. The results indicate that the hydrophobic (clathrate hydrate-like) character of the larger tetra-n-alkylammonium ions is reduced significantly when cyclic groups are formed from the alkyl chains in symmetrical quaternary ammonium ions.     

Production of specific copolymers of polyhydroxyalkanoates from industrial waste

Polyhydroxyalkanoates, biodegradable plastics with the desired physical and chemical properties of conventional synthetic plastics, are extensively investigated. In this study, specific bacterial strains produced specific copolymers from food waste. Copolymers of HB and HV (poly[3-hydroxybutyrate-co-3-hydroxyvalerate]) were obtained using various ratios of butyric acid (C₄) and valeric acid (C₅) as carbon sources. The C₄ to C₅ ratio affected the melting points of the copolymers. Melting and glass transition temperatures and many other thermal properties are important parameters relative to in-service polymer applications. Higher ratios of butyrate to valerate gave higher melting points. When a mixed culture of activated sludge was employed to produce copolymers using food wastes as nutrients, the obtained copolymers showed various monomer compositions. Copolymers with a higher portion of HV were obtained using soy waste; copolymers with less HV were obtained using malt wastes. Pure strains, (i.e., Alcaligenes latus DSM 1122, and DSM 1124, Staphylococcus spp., Klebsiella spp.) produced specific copolymers from food waste. Only Klebsiella spp. produced different copolymers; the ratios of HB:HV were 93:7 and 79:21 from malt waste and soy waste, respectively. The other strains produced polymers of 100% HB. Selecting industrial food wastes as carbon sources can further reduce the cost of producing copolymers. Open Laboratory of Chirotechnology of the Institute of Molecular Technology for Drug Discovery and Synthesis The University Grants Committee Area of Excellence Scheme, Hong Kong     

An alternative intraarterial therapeutic agent for hepatic tumors:131I lipiodol/histoacryl mixture

Lipiodol has excellent retainable ability in hepatoma cells. This agent can be labeled with radioisotope (¹³¹I) and mixed with tissue adhesive (Histoacryl), and then alttached on the lesion of liver by intrahepatic arterial administration. In this study, we attempt to obtain the optimal ratio of Lipiodol to Histoacryl and evaluate the consolidation of blood in vitro and toxicity and biodistribution in vivo. The ratio of¹³¹I Lipiodol/Histoacryl mixture (L/H), concentration of heparin and flow rate of blood are varied by simulating the installation of bloodstream to test the time of consolidation. In addition, the optimal ratios of the L/H mixtures are assessed in vitro in heparinized human blood. According to those results, Lipiodol and Histoacryl mixed with 1∶1 or 2∶1 ratio have an ideal time of 13 to 15 seconds in vitro; in addition, 1.2∶1 ratio is an optimal ratio in the biodistribution study. Interestingly, heparin and acetic acid does not alter the consolidation time, in addition, no variation occurs when varying the flow rate of blood. The consolidation of L/H mixture with blood is incubated in the 37°C, normal saline bath for 24 hours. No dissociation of free¹³¹I is found. The optimal mixture is also injected into the hepatic artery of the Sprague-Dawley rats carrying for 24 hours. No dissociation of free¹³¹I is found. The optimal mixture is also injected into the hepatic artery of the Sprague-Dawley rats carrying hepatocellular carcinoma (NIS1 cell line). Radioactive consolidate is well confined in the tumor without evidence of leakage of the mixture to the lung or distribution of free¹³¹I in the thyroid. In conclusion, this mixture has the merits of both irradiation and embolization of the tumor. The¹³¹I Lipiodol/Histoacryl mixture (1.2∶1) is a promising alternative for intrahepatic arterial administration to treat hepatic tumors. Histoacryl can confine the¹³¹I and, also, embolize the tumor vessels.     

The preparation, characterization, and thermal behaviour of some lithium aluminum oxides: Li3AlO3 and Li5AlO4

The purpose of this research was to study the best conditions for the synthesis of the double oxides Li₅AlO₄ and Li₃AlO₃ in the solid state starting from the simple oxides, and to determine their heats of formation.Li₅AlO₄ was obtained from Li₂O₂ or Li₂O and -Al₂O₃ in a Li/Al molar ratio of 51, and was characterized by X-ray methods. Lithium orthoaluminate, Li₃AlO₃, was obtained from Li₂O₂ and -Al₂O₃ in a molar ratio 31. The postulated formula, Li₃AlO₃, was confirmed by chemical analysis.The temperature ranges in which the compounds are stable were established by the DTA method, and were found to be very limited for Li₃AlO₃ (400–430°) but greater for Li₅AlO₄ (440 — more than 600°).The heats of formation of Li₅AlO₄ and Li₃A10₃, also determined by means of the DTA method, were found to be –552.3 ± 0.8 kcal/mole and –416.8 ± 2 kcal/mole, respectively.

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Zusammenfassung Es wurden die Bildungsverhältnisse der doppelten Oxide Li₅AlO₄ und Li₃AlO₃ in fester Phase ausgehend von den einfachen Oxyden geprüft und ihre Bildungswärmen bestimmt. Li₅AlO₄ wurde aus Li₂O₂ oder Li₂O und -Al₂O₃ beim Molverhältnis von Li/Al 5 1 erhalten und röntgenographisch identifiziert. Das Orthoaluminat Li₃AlO₃ erhielt man beim Molverhältnis 3 1 von Li₂O₂ und -Al₂O₃. Die Zusammensetzung von Li₃AlO₃ wurde durch chemische Analyse nachgewiesen. Die DTA-Prüfung zeigte, daß Li₃AlO₃ nur im sehr kleinen Temperaturgebiet (400–430°), Li₅AlO₄ hingegen im weiteren Bereich zwischen 440–600° stabil ist. Die Bildungswärmen betrugen für Li₅AlO₄ –552.3±0.8, für Li₃AlO₃ –416.8±2 kcal/Mol.

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Résumé On a recherché les meilleures conditions pour réaliser la synthèse à l'état solide des oxydes doubles Li₅AlO₃ et Li₃AlO₃ en partant des oxydes individuels et pour déterminer leur chaleur de formation. Li₅AlO₄ a été obtenu en partant de Li₂O₂ (ou Li₂O) et de -Al₂O₃ dans le rapport molaire Li/Al=5/1; il a été caractérisé par étude aux rayons X. L'orthoaluminate de lithium, Li₃AlO₃, a été obtenu en partant de Li₂O₂ et de -Al₂O₃ mélangés dans le rapport 3/1. L'analyse chimique a confirmé la formule présumée Li₃AlO₃. L'ATD a permis de déterminer le domaine de stabilité thermique de ces composés: très restreint pour Li₃AlO₃ (400–430°), plus grand pour Li₅AlO₄ (440-plus de 600°), ainsi que leurs chaleurs de formation: –416.8±2 kcal/mole et –552.3±0.8 kcal/mole, respectivement.

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— Li₅AlO₄ Li₃AlO₃ . Li₅AlO₄ Li₂O₂ Li₂O -l₂₃ Li/Al 51, . , Li₃AlO₃, Li₂O₂ -l₂₃ 31. . , , , Li₃AlO₃ (400—430 °?) Li₅AlO₄ (440- 600 °?). Li₅AlO₄ Li₃AlO₃ 552.3 ± 0.8 416.8 ± 2 /, .

     

Progress in the understanding of drug-receptor interactions, Part 1: experimental charge-density study of an angiotensin II receptor antagonist (C30H30N6O3S) at T = 17 K

An experimental study of the electron-density distribution rho(r) in an angiotensin II receptor antagonist 1 has been made on the basis of single-crystal X-ray diffraction data collected at a low temperature. The crystal structure of 1 consists of infinite ribbons in which molecules are connected by an N-H...N hydrogen bond and several interactions of the C-H...O, C-H...N, and C-H...S type. The molecular conformation, characterized by the syn orientation of a tetrazole and a pyrimidinone ring with respect to a phenyl spacer group, is stabilized by two short SO and SN intramolecular contacts between a substituted thiophene fragment and the other two heterocycles of 1. The electrostatic nature of these interactions is documented. Furthermore, the Laplacian of rho(r) in the plane defined by the sulfur, oxygen, and nitrogen atoms involved in these interactions shows their strongly directional character as the regions of charge concentration on the valence shell of the nitrogen and oxygen atoms directly face the regions of charge depletion on the valence shell of the sulfur atom. All the chemical bonds and the relevant intra- and intermolecular interactions of 1 have been quantitatively described by the topological analysis of rho(r). Simple relationships between the bond path lengths (R(b)) and the values of rho at the bond critical points (rho(bcp)) have been obtained for the 28 C-C bonds, the seven N-C bonds, and the four O-C bonds. For the first two classes of bonds the relationship is in the form of a straight line, whose parameters, for the C-C bonds, agree, within experimental uncertainty, with those previously derived in our laboratory from a 19 K X-ray diffraction study of crystals of a different compound. Maps of the molecular electrostatic potential phi(r) derived from the experimental charge density display features that are important for the drug-receptor recognition of 1.