CHEMOENZYMATIC SYNTHESIS OF BIODEGRADABLE POLY(1’-O-VINYLADIPOYL-SUCROSE)

t A novel polymer containing the sucrose group was synthesized by radical polymerization from an enzymaticallyprepared monomer, l'-O-vinyledipoyl-sucrose (VAS). Transesterification reaction of sucrose with divinyl adipate inanhydrous pyridine catalyzed by an alkaline protease from Bacillus subtilis at 60℃ for 7 days gave VAS (yield 55%) withoutany blocking/deblocking steps. The vinyl sucrose ester could be polymerized with potassium persulfate and H_2O_2 as initiatorto give poly(l'-O-vinyladipoyl-sucrose) with M_n = 33,000 and M_w = 53,200, M_w/M_n = 1.61. The polymer was biodegradable.After 6 days in aqueous buffer (pH 7), this alkaline protease could degrade poly(l'-O-vinyladipoyl-sucrose) to M_n of ca.1080, M_w/M_n = 3.30 (37℃), and M_n of ca. 5200, M_w/M_n = 2.44 (4℃). The polymer containing the sucrose branch would be afunctional material in various application fields.     

Interaction of adenine and thymine with aqueous sugar solutions

The solubility of the nucleic acid bases, adenine and thymine, in aqueous erythritol, xylose, glucose, and sucrose solutions has been studied. The solubility of adenine increases linearly with glucose and sucrose concentration, whereas with the other reagents a nonlinear increase is observed. Below 1.5M reagent concentration, the solubility of adenine increases in the order erythritol < robose, xylose < glucose < sucrose. The solubility of thymine in these solutions, on the other hand, decreases, increases, or does not change depending upon the reagent. The effect of temperature on the solubility of adenine and thymine in sugar solution indicates that the transfer of these molecules from water to sugar solution is exothermic.Presented in part at the VIIth All-India Symposium in Biophysics held at Visva Bharati University during October 1976.     

Extraction of mercury from aqueous iodide solutions by trilaurylamine N-oxide and its subsequent determination by atomic absorption spectrometry

A solvent extraction technique using 0.01M solution of trilaurylamine N-oxide in benzene as extractant has been used to concentrate mercury efficiently from water solutions with or without the presence of 0.02M KI in weakly acidic media. In addition to unmodified aqueous solutions, mercury can be extracted quantitatively from aqueous iodide solutions that are up to 1M in HCl, H₂SO₄, and HNO₃ in a single equilibration. Distribution coefficients and separation factors of several elements relative to mercury(II) are reported for media that contain 0.1 M HCl and 0.02M KI. The reagent is superior to aliphatic amines and quaternary amines for the extraction of mercury from aqueous iodide solutions.     

Mechanism of oxidation of cyclohexanehexol (inositol) by quinquevalent vanadium

The oxidation of inositol by quinquevalent vandadium in acid medium is a first-order reaction both in vanadium (V) and inositol. The stoichiometry of the reaction is consistent with the use of two equivalents of vanadium (V) per mole of inositol with the formation of one mole of inosose. The reaction is catalyzed both by sulfuric and perchloric acid, but the rate is faster in sulfuric acid than in perchloric acid. In 1M–6M perchloric acid solutions the reaction has shown a variable order in H⁺, but in solutions of 2M–5M sulfuric and perchloric acid of constant ionic strength, the rate has a linear dependence on [H⁺]². There is also a linear correlation between the rate and bisulfate ions in sulfuric acid at constant hydrogen ion concentration. The energy of activation is found to be 19 kcal/mole and a negative entropy value of ? 14 e.u. A suitable mechanism, consistent with the kinetics in 2M–5M acid solutions, is suggested and the values of various rate constants are evaluated.     

Theory of polydisperse reacting polymer systems

The kinetics of irreversible reactions between polymer chains of different molecular weights are studied, with emphasis on the case of highly reactive end groups. We calculate the rate constant k(N, M) for reaction between chains of lengths N and M respectively, in dilute and semi-dilute solutions and in the melt. In all cases, k(N, M) is dominated by the shortest chain: the limit k(N) ≡ k(N, ∞) is well-defined and scales as if both chains were of length N. In dilute solutions k(N, M) obeys mean field theory, being proportional to the equilibrium reactive group contact probability. For melts and concentrated solutions, k(N, M) follows diffusion-controlled laws: k(N, M) ≈ (R/τ_N)ƒ(M/N) where R_N and τ_N are the coil size and relaxation time of the shortest chain N, and ƒ(M/N) is a cross-over function describing the approach to the asymptotic form k(N) for M/N ≫ 1. We calculate the leading contributions to this cross-over function, which has universal forms depending on the concentration regime. The implications of these results for high-conversion free-radical polymerization are discussed.     

Hydraulic and osmotic permeabilities of water and water/sucrose solutions through cellophane membranes

Measurements were made of different transport phenomena in cellophane membranes, using a specially designed device. The aqueous, hydraulic permeability was studied over a range of temperatures between 30 and 50°C. The hydraulic permeability/temperature relationship was found to be linear. The use of sucrose solutions of equal concentration in the two phases on either side of the membrane produced a considerable variation in the hydraulic permeability when the solution concentrations were greater than 0.1 M. Osmotic flow experiments were carried out for sucrose/water solutions, and the coefficient of osmotic permeability was found to be independent of the solution concentrations separated by the membrane within the range of concentrations studied (up to 0.2 M). The equivalent pore radius was calculated for the membranes used; these values are higher than that of the molecular diameter of water. The reflection coefficient was calculated for one of the membranes used and a value of 0.077 was obtained.     

Entanglement properties of cellulose and amylose in an ionic liquid

Concentrated solutions of cellulose and amylose were prepared with an ionic liquid 1‐butyl‐3‐methylimidazolium chloride (BmimCl), which was chosen as a good solvent for these polysaccharides. Dynamic viscoelasticity of the concentrated solutions was examined to obtain the molecular weight between entanglements, M_e. The value of M_e in the molten state (M_e,melt), a material constant that reflecting the entanglement properties, was determined for cellulose and amylose by extrapolating M_e to the “melt.” A marked difference in M_e,melt was found: 3.2 × 10³ for cellulose and 2.5 × 10⁴ for amylose. The value of M_e,melt for cellulose, which is composed of β‐(1,4) bonding of D ‐glucose units, is very close to those for polysaccharides with a random‐coil conformation such as agarose and gellan in BmimCl. The much larger M_e,melt for amylose can be attributed to the helical nature of the amylose chain, α‐(1,4)‐linked D ‐glucose units. The effect of concentration on the zero‐shear viscosity for the solutions of cellulose and amylose was also examined. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

A study of shear-stress relaxation anomalies in binary mixtures of monodisperse polystyrenes

We report measurements of the nonlinear relaxation moduli after a step-shear strain of polystyrene solutions with nearly monodisperse and with bidisperse distributions of molecular weight. We find, as have others, that for monodisperse solutions with M/M_e > 60, there are anomalies, such as an unusually low nonlinear modulus and a kink in a plot of shear stress versus time after the step strain. Here M is the polymer molecular weight and M_e is the entanglement molecular weight. We find that in the bidisperse solutions the anomalies persist as long as M_w/M_e > 60, where M_w is the weight-averaged molecular weight of the bidisperse solution. The persistence of the anomalies in bidisperse solutions disagrees with a theory of Marrucci and Grizzuti that attributes the anomalies to strain inhomogeneities similar to shear banding. The Marrucci-Grizzuti theory predicts that as little as 10% short chains in the bidisperse mix should eliminate the anomalies, whereas in the experiments reported here at least 30% is required. Nevertheless the way in which the anomalies disappear at high strains when one increases the fraction of low-molecular-weight component is qualitatively similar to the theoretical predictions and supports the notion that strain inhomogeneities occur in these systems. © 1992 John Wiley & Sons, Inc.     

Cluster Model of Aggregation of Epoxy-DPP Oligomers in Solutions. Structure of Coatings Based on Epoxy and Epoxy-Phenol Resins

The IR MATIR spectra in the 1535-1680 cm^-1 range were studied for epoxy-DPP resins (M _N = 1650-3400) in coatings on germanium substrate obtained from oligomer solutions in methylene chloride and Cellosolve with the concentration c = 10-50%. The concentration dependences of the relative viscosity of narrow-MWD fractions of epoxy oligomers (M _N = 1500-5300) in chloroform and Cellosolve solutions were studied. The structure of the network of cross-linked polymers based on epoxy (M _N = 2100-3400) and phenol-formaldehyde (M _N = 860) resins was studied by the electron-microscopic silver chloride decoration method. Based on the cluster lattice model, the optimal molecular weight and the concentration regimes were determined for epoxy oligomers in the lacquer composition for can protection.     

Dependence of viscosity of concentrated polymer solutions upon molecular weight and concentration

Molecular weight M and concentration c dependencies of the zero-shear viscosity (η) were measured over wide ranges of M and c for concentrated solutions of linear and branched poly(vinyl acetate) as well as of polystyrene under θ conditions. The log η versus log M and log η versus log c curves for a given system can be superposed by the horizontal shift along the abscissa, giving smooth master curves. From the shift factors the ratio of two exponents β and α, which appear in the following equation, can be evaluated: η = K′(cρ)^αM^β, where ρ is the density of the solution and K′ is a constant at constant temperature. The evaluated values of β/α for the systems under θ conditions are equal to or very close to 0.50 as was anticipated from the previous work. The above superposition method was also applied to available viscosity data, and it was found that β/α had a good correlation with a in [η] = KM^a. This indicates that the individual molecules in concentrated solutions maintain the same individuality as in dilute solutions, and might be a positive support to the packed sphere model proposed previously by the authors. The effect of solvent on the molecular weight and the concentration dependencies of viscosity was also discussed.     

Enthalpies of Dilution and Enthalpies of Mixing of Amino Acids with Sucrose in Aqueous Solutions at 298.15 K

The enthalpies of mixing of aqueous solutions have been determined for sucrose with six different amino acids (glycine, l-alanine, l-serine, l-valine, l-proline and l-threonine) at 298.15 K, by using a LKB-2277 flow microcalorimetric system. These results, along with the enthalpies of dilution of these solutes for the initial solutions, were used to determine the enthalpic interaction coefficients (h _xy, h _xyy, h _xxy) of the McMillan–Mayer Theory. The pair-wise cross interaction coefficients of amino acids and sucrose are discussed from the viewpoint of solute–solute interactions.     

Adiabatic compressibility of solutions of ethylene–propylene copolymers in hydrocarbon solvents

Adiabatic compressibility measurements are reported on solutions in hydrocarbon solvents of a low M_w high ethylene content, and of both high and low M_w low ethylene content ethylene–propylene copolymers. In all solutions the observed adiabatic compressibility was lower than the solvent value by an increment which was a function of the solvent type. Comparison of the data for a high and low molecular weight sample of the same copolymer indicates no molecular weight effects. Changes in the composition of the copolymer, as indicated by NMR spectroscopy, have only a slight effect on the adiabatic compressibility. The dominant feature of these studies is the apparent correlation of the chain length of the alkane solvent with the decrement in the compressibility.     

Soret Coefficients for Aqueous Polyethylene Glycol Solutions and Some Tests of the Segmental Model of Polymer Thermal Diffusion

A thermogravitational cell is used to measure Soret coefficients (s) for dilute binary aqueous solutions of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol (PEG) fractions with average molecular weights from 200 to 20,000 g-mol^–1. The cell design allows the top and bottom halves of the solution column to be withdrawn and injected into a high-precision HPLC differential refractometer detector for analysis. Previously reported mutual diffusion coefficients D and the measured Soret coefficients are used to calculate thermal diffusion coefficients D _T. s and D vary with the PEG molecular weight M as M ^+0.53 and M ^–0.52, respectively; hence, D _T = sD is essentially independent of M. The segmental model of polymer thermal diffusion predicts D _T = D_seg U _S/RT ², where D _seg is the segment diffusion coefficient, U _S the solvent activation energy for viscous flow, R the gas constant, and T the temperature. The predicted D _T values, although independent of M, are too large by a factor of five. Additional tests of the segmental model are provided using literature data for polystyrene + toluene, n-alkane + CCl₄, and n-alkane + CHCl₃ solutions. Agreement with experiment is not obtained. In particular, the measured D _T values for the alkane solutions are negative.     

Optimum conditions for transformed Panax ginseng hairy roots in flask culture

Panax ginseng hairy roots were transformed by Agrobacterium rhizogenes KTCT 2744. They showed an active branching pattern and fast growth in hormone-free medium, and good growth at 23°C, pH 5.8, 1/2 MS medium, and 3% sucrose. Sucrose provided the highest growth among seven carbon sources tested. Six complex media were also tested. In the combined sugar study, hairy roots grew better on sucrose without glucose or fructose than with glucose or fructose. In the 1/2 MS basal medium, 30 mM in nitrogen and 0.62 mM phosphate salt concentration was the optimum. The growth ratio was maximal at an inoculum size of 0.4% (w/v). Crude saponin and polysaccharide levels were also measured.     

DNA Computing of Bipartite Graphs for Maximum Matching

Let M be a matching in a graph G. It is defined that an M-augmenting path must obtain one element of M. In this paper, it is obtained that a matching M in a graph G is a maximum matching if and only if G contains no M-augmenting path and M is a maximal matching in G. It supplies a theoretical basis to DNA computing. A detailed discussion is given of DNA algorithms for the solutions of the maximal matching problem and maximum matching one in a bipartite graph.     

Study of the Solid Solutions of LiNbO3and LiTaO3with Mn

Two unusual, extensive new solid solutions of LiNbO₃and LiTaO₃with MnO have been prepared, where 4Mn²⁺replace a combination of 3Li⁺and a pentavalent cation: Nb⁵⁺or Ta⁵⁺. The formulas are Li_1−xM_1−xMn_4xO₃, 0<x<0.13, forM=Nb and 0<x<0.23 forM=Ta. The solid solutions were characterized by X-ray powder diffraction and density measurements. The manganese oxidation states were determined by X-ray photoelectron spectroscopy.     

Solubility of methane in aqueous solutions of triethylenediamine

The solubilities of methane were measured in water and aqueous solutions of triethylenediamine (TED), triethylenediamine hydrochloride (TED·HCl), and HCl at several concentrations up to 1M at 5° intervals from 5 to 25°C. Methane solubilities in solutions of TED·HCl and HCl are lower than those in water and decrease with increasing cosolute concentration. In contrast, the solubilities in TED solutions are greater than those in water and increase with increasing TED concentration. The order of methane solubilities at 25°C in water and in 0.5M aqueous solutions is TED>H₂O>HCl>TED·HCl with Ostwald coefficients of 3.57×10^–2, 3.44×10^–2, 3.26×10^–2, and 3.19×10^–2, respectively, and with an experimental precision of about ±0.2×10^–3. Thermodynamic functions for the transfer of methane from water to 0.25, 0.50, and 0.75M aqueous solutions have been calculated on the molar concentration scale. The free energies of transfer are compared with previous results for methane in aqueous solutions of tetraalkylammonium halides.     

The adsorption behaviour of99Mo(VI),238U(VI),95Zr(IV) and95Nb(V) on alumina

The distribution of Mo(VI) and the interfering radiocontaminants U(VI), Zr(IV) and Nb(V) have been investigated between chromatographic alumina and aqueous hydrochloric acid solutions of concentrations ranging from 0.5M to 11M. At low acidities (less than 1M HCl) the distribution coefficients increase with the decrease of acid concentration, while in the region of 2–4M they increase with the increase of the acid concentration. Above 4M HCl, the increase inK _D continues with the acid concentration for both Zr(IV) and Nb(V), but constant values are reached for U(VI) and Mo(VI).