Random fields and quantum effects in proton glasses

The effects of quantum fluctuations on the proton glass phase in mixed hydrogen-bonded ferro-antiferroelectric systems are considered. The system is described in terms of the infinite-ranged Ising pseudospin glass model in a transverse tunneling field in the presence of random parallel fields. The stability limit of the high-temperature proton glass phase is determined within the thermofield dynamic approach, and the behavior or linear and nonlinear susceptibility is evaluated.     

Modification of solids with volatile organics III: Natural zeolites

Summary The effect of pre-adsorbed benzene and ethanol on the adsorptive properties of natural zeolite (clinoptilolite) has been studied by gas-solid chromatography. It has been shown that modification of the solid surface by volatile organics has a significant influence on the adsorptive properties. The modification is of the same order as the more difficult modification by inorganics, as illustrated here by clinoptilolite modification with Co²⁺. Energy distribution of surface adsorptive sites appears to be continuous and confirms previous finding that only a small proportion of active sites is responsible for most adsorbate retention. Part II reference [4]     

Excess and partial excess molar volumes of mixing of N,N-dibutyl-2-ethylhexamide with dodecanol

Excess and excess partial molar volumes of mixing of the system N,N-dibutyl-2-ethylhexylamide (DBEHA) + dodecanol (DDA) were determined at 25, 35, 45, 55 and 65°C. The excess molar volumes exhibit a maxima at each temperature at approximatelyx _DBEHA = 0.3 and a minima close tox _DBEHA = 0.9. The values of the excess volumes in general increase with the temperature. The partial excess molar volumes are calculated from the smoothed data and the results are discussed in the light of postulated amide-alcohol interactions.     

Carbamoylimidazolium and thiocarbamoylimidazolium salts: novel reagents for the synthesis of ureas, thioureas, carbamates, thiocarbamates and amides

Carbamoylimidazolium salts act as efficient N,N-disubstituted carbamoylating reagents. These salts are readily prepared by the sequential treatment of secondary amines with N,N′-carbonyldiimidazole (CDI) and iodomethane. The carbamoylimidazolium salts are more efficient carbamoyl transfer reagents than the intermediate carbamoylimidazoles, as a result of the ‘imidazolium’ effect. Kinetic studies on the base promoted hydrolysis of both carbamoylimidazoles and carbamoylimidazolium salts reveal over a hundred-fold rate acceleration. The salts react with amines, thiols, phenols/alcohols, and carboxylic acids in high yields, without the need for subsequent chromatographic purification of the products, producing ureas, thiocarbamates, carbamates, and amides, respectively. Analogous thiocarbamoylimidazolium salts were also synthesized from secondary amines and N,N′-thiocarbonyldiimidazole (TCDI), followed by methylation with iodomethane.     

Development of a fibrinolytic surface: specific and non-specific binding of plasminogen

Plasminogen is the primary zymogen in the fibrinolytic pathway, and its primary function involves degradation of fibrin. Biomaterials often show adsorption of fibrinogen and subsequent formation of fibrin. Plasminogen's function in vivo could be adapted to facilitate its activation and fibrinolytic function on a biomaterial surface. In order to elucidate plasminogen function adsorbed to a model fibrinolytic surface ligands known to affect plasminogen properties in solution were attached to model silica surfaces to study the effects of immobilized ligands as fibrinolytic activators. Model silica surfaces were synthesized which contained covalently attached lysine moieties (surface I), sulfonate moieties (surface II) or a combination of both (surface III). Lysine moieties on these model surfaces interact specifically with multiple lysine-binding sites of plasminogen and induce a number of changes in conformation and function. Sulfonate moieties interact non-specifically with accessible lysine and arginine residues of plasminogen and also affect the function of plasminogen. Inherent physico-chemical properties monitored following plasminogen adsorption were activation to plasmin, enzymatic activity, fluorescent intensity, and fluorescent polarization, monitored by total internal reflection fluorescence, each of which are affected by plasminogen conformation.

Correlations were as follows: increased fluorescent intensity and decreased fluorescent polarization were indicative of plasminogen conformational changes and are correlated to increased enzymatic activity of plasmin. Surfaces I and III showed a 20% increase in fluorescent intensity, and a 25% and 8% decrease in fluorescent polarization, respectively, in comparison to surface II. The specific activity for surfaces I and III was increased 11.3 and 1.8 fold above that found for surface II. Plasminogen incubated with sulfonate groups in solution resulted in no increase in fluorescent intensity and a slight decrease in fluorescent polarization as compared with plasminogen alone and reduced specific activity of plasmin in the presence of sulfonate as compared with plasmin alone. Lysine or ε-aminocaproic acid (ACA) incubated with plasmin in solution showed a 30% and 10% increase in fluorescent intensity, a 24% and 5% decrease in fluorescent intensity, and maximum specific activity increased 3.6 and 2.5 fold, respectively, over plasminogen alone.

Interactions of plasminogen with ligands for its lysine-binding sites produced dramatic effects both in solution and adsorbed to model fibrinolytic surfaces. The characterization of these interactions along with known fibrin interactions will allow selection of appropriate surface modifications to enhance the fibrinolysis of thrombus formed at a biomaterial interface. These modifications may lead to a native-like surface structure to protein and cellular components of blood and create a more biocompatible surface.     

Radical polymerization of n-substituted methacrylamides

The relationship between the structure of monomer and kinetics of the radical polymerization of N-ethylmethacrylamide, N-butylmethacrylamide and N-phenylmethacrylamide in methanol and in dimethylsulphoxide was investigated. The reaction order with respect to initiator is 0·5 in all cases; the order with respect to monomer is independent of the type of substituent but depends on the solvent and on the viscosity of the reaction mixture. The polymerization rate, the value of $\text{κ}{}_{\mathrm{p}}\text{/κ}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and the initiator efficiency decrease in the series N-phenylmethacrylamide, N-ethylmethacrylamide and N-butylmethacrylamide. The overall activation energy of polymerization for the monomers lies between 16 and 20 kcal/mol.     

On the modification of solid adsorbents with volatile organics II. The role of the layer adsorbed

Summary This paper presents a continuation of our research dedicated to solid-adsorbent surface modification with what are commonly regarded as volatile and easily eluted organic compounds. Two porous adsorbents were used: natural zeolite (clinoptilolite) and alumina, while the adsorbates employed were n-hepatane and benzene. The results show that a simple injection of volatile adsorbate greatly alters the solid surface adsorption properties. The consequences of volatile modifier application are discussed on the grounds of adsorption isotherms determined at 313K. Possible implications to the tailor made adsorbents are outlined as well.Part I, J. Chromatogr.442, 105 (1988)     

pH-dependent electrochemical behaviour of hydrophilic ampholytic membranes

Ampholytic membranes were synthesized by copolymerizing (2-hydroxyethyl)methacrylate as the hydrophilic component, methacrylic acid and (N,N-diethylaminoethyl)methacrylate as ionogenic components (both ionogenic monomers in amounts 2.5 mol% or 10 mol%), and ethylenedimethacrylate as the crosslinking agent (3,5 or 10 mol%). The effects of pH on the swelling and membrane potentials of the membranes were investigated. The dependence of the membrane potentials on pH is characterized by the position of the isoelectric point and by the slope of the straight part of the dependence. This slope reflects the attained degree of ideality of the membrane. By varying the degree of cross linking and the content of ionogenic components, it is possible to vary the pH-dependent response of the membranes.     

Synthesis and evaluation of the catalytic properties of semicarbazides derived from N-triphenylmethyl-aziridine-2-carbohydrazides

A straightforward synthesis of a series of new catalysts derived from N-triphenylmethyl-aziridine-2-carbohydrazides is described. The new compounds have been tested for the enantioselective addition of diethyl- and phenylethynylzinc to aryl and alkyl aldehydes, which afforded the corresponding chiral alcohols in high chemical yields (up to 92%) and with excellent ee’s of approximately 90%.