Showing papers by "National Chemical Laboratory published in 1978"

A determination of fundamental Zeeman parameters for the OH radical

Abstract: Measurements of the gas-phase E.P.R. spectra of OH in the J = 9/2 and 11/2 levels of the X2II state at 26 GHz and 35 GHz respectively are reported. Confocal and semi-confocal optical resonators have been used in place of the more conventional microwave cavities for these experiments. The data are analysed, together with previous measurements by Radford on other rotational levels in the determination of six independent g factors: These parameters are interpreted in terms of the electronic structure of the OH radical. In agreement with previous workers, it is found that the major contaminant of the X2II state is the A2Σ+ state and that this pair of states is a good example of Van Vleck's pure precession hypothesis.

Production, Purification and Partial Characterization of 1,4-β-Glucosidase Enzymes from Sporotrichum pulverulentum

Abstract: The production of 1,4-β-glucosidase activity by the rot fungus Sporotrichum pulverulentum has been investigated. It was found that cellobiose or cellulose is necessary to cause induction. With cellobiose as sole carbon source only cell-wall-bound enzymes are produced. For extracellular excretion cellulose seems to be a necessary carbon source. The purification procedures, for purification of enzyme activity in the culture solution, involve the following steps: (a) ultrafiltration, (NH4)2SO4 precipitation and dialyses; (b) preparative slab gel isoelectric focusing I, pH range 3–10; (c) phenyl-Sepharose chromatography; (d) preparative slab gel isoelectric focusing II, pH range 3–5. On the phenyl-Sepharose column the β-glucosidase activity was associated with two separable enzyme peaks, enzyme A and B. When these enzymes were subjected to further purification on preparative isoelectric focusing II, enzyme A was split into two peaks, A1 and A2, and enzyme B was split into three peaks, B1, B2 and B3. The significance of the separations is discussed. The isoelectric points of all the enzymes have been determined and found to vary between 4.52 to 5.15. The molecular weights, determined by dodecylsulphate-polyacrylamide gel electrophoresis, vary between 165000 and 182000. The kinetic constants Km and Ki have been determined for enzyme A and B as well as for the cell-bound β-glucosidase activity. Km for cellobiose was for both enzyme A and B higher than Km for p-nitrophenyl β-d-glucoside. Km/Ki of the free enzymes for gluconolactone is approximately 2500 (enzyme B) to 13000 (enzyme A) with cellobiose as substrate.

Conformation of amylose in water. I. Light‐scattering and sedimentation‐equilibrium measurements

Abstract: The conformation of amylose in aqueous solution has been found to be dependent on its molecular weight. When the molecular weight of amylose is outside of the so-called “dissolving gap” described by Burchard (6500

Molecular Weight and Intrinsic Viscosity of Konjac Gluco-mannan

Abstract: For the purpose of making clear the macromolecular chemical properties of konjac gluco-mannan, the light scattering and viscosity measurements were carried out for the aqueous solutions of the partially methylated derivatives, and following results were obtained: 1) The weight-average molecular weight, Mw, and the root mean square of radius of gyration, 1/2, were 100×l04~120×l04 and 1100~1300 A, respectively. 2) The versus Mw relationship was represented by the equation of =4.20×10−1 Mw1.08, and this fact suggested a random coil as a molecular form in the solution. 3) The intrinsic viscosity, [η], versus Mw relationship was represented by the equation of [η]=6.37×10−4 Mw0.74, which was considered to be useful for the purpose of estimating the molecular weight of konjac gluco-mannan by viscometric method.

Immobilization of β-Glucosidase in Fibroin Membrane

Abstract: Fibroin membrane was used as a support for immobilized β-gIucosidase. The immobilized enzyme was prepared by drying fibroin-enzyme solution on a horizontal plate, followed by ethyl alcohol treatment which was an essential process for immobilization. The immobilized β-glucosidase was characterized enzymatically compared with soluble enzyme, using p-nitrophenyl-β-D-glucopyranoside as a substrate. The immobilized enzyme showed 47% of the activity of soluble enzyme and little decrease of the activity was observed both on re-use and storage. There were no significant differences in pH dependency between immobilized and soluble enzyme activity. Activation energy was slightly larger with immobilized enzyme than soluble enzyme. The enzyme was considerably enhanced by immobilization in stabilities against heating, electrodialysis and protease treatment. Apparent affinity for the substrate decreased as membrane thickness increased. Enzyme affinity for substrate in the membrane was discussed.

Effective interfacial area in packed beds for absorption with chemical reaction

Abstract: The extended crossflow model is proposed and developed for describing gas absorption with chemical reaction in a packed bed operated in the trickle flow regime. The model involves the division of the total interfacial area into the interfacial area of the static hold-up and that of the dynamic hold-up. The concept of the effectiveness of the interfacial area of the static hold-up is presented. A procedure is developed for calculating the effectiveness, and consequently, the effective interfacial area for various different absorption processes with chemical reaction, both liquid phase controlled and gas phase controlled. The predictions based on the present model agree well with reported experimental data. The present model is shown to be simpler and more accurate than previous models. On propose et a mis au point un modele d'ecoulement transversal etendu pour decrire d'absorption de gaz accompagnee d'une reaction chimique dans un lit garni, lequel fonctionne dans un regime d'ecoulement a faible debit. Dans ledit modele, toute la zone interfaciale est divisee en deux secteurs, a savoir ceux de la retention statique et de la retention dynamique respectivement. On presente le concept de l'efficacite du secteur interfacial de la retention statique. On a mis au point une methode pour calculer l'efficacite, et par consequent le secteur interfacial effectif, dans le cas de differents procedes d'absorption impliquant une reaction chimique avec controle en phase liquide et en phase gazeuse. Les previsions obtenues avec le modele en question concordent bien avec Is resultats experimentaux qui ont ete publies. On indique que le modele actucl est plus simple et plus exact que les modeles anterieurs.

Electronic Spectra of N-(P-Methoxybenzylidene)-P-N-Butylaniline (MBBA)

Abstract: The ultraviolet absorption spectra of MBBA in the metastable and stable solids, the nematic, and the isotropic liquid states have been measured. Furthermore the spectra of dilute solutions and the linear dichroism spectra of nematic single liquid crystal in a homogeneous orientation have also been observed.

Effect of immobilized enzyme deactivation in fixed- and fluid-bed reactors

Abstract: A two-parameter theoretical model is developed to evaluate the effect of immobilized enzyme deactivation on substrate conversion in fixed- and fluid-bed reactors under diffusion-free conditions. The method describes a simple reaction in which three different immobilized enzyme deactivation forms are considered, and an expression is developed to evaluate the effect of immobilized enzyme deactivation on yield in a consecutive reaction. Comparison of reactor performances for the two reactor types reduces to a comparison of the appropriate dimensionless parameters. The practical implications of the development are illustrated through an example.

Preparation of carboxylic acids from hydroxy compounds by oxidation with ozone

Abstract: Various mono- and dicarboxylic acids were obtained with appreciable yields from saturated hydroxy compounds by oxidation in aqueous acetic acid with a mixture of ozone and oxygen followed with oxygen. The starting materials and the mono- and dicarboxylic acids obtained were as follows: Primary alcohols RCH2OH → RCOOH; α,ω-glycols HOCH2(CH2)nCH2OH → HOOC(CH2)nCOOH; secondary alcohols and 12-hydroxyoctadecanoic acid R1CH2CH(OH)CH2R2 → R1COOH + R2CH2COOH + R1CH2COOH + R2COOH; alicyclic alcohols CH2(CH2)nCHOH → HOOC(CH2)nCOOH; 9,10-dihydroxyoctadecanoic acid CH3(CH2)7CH(OH)CH(OH) (CH2)7COOH → CH3(CH2)7COOH + HOOC(CH2)7COOH. Small amounts of aldehydes, ketones, and carboxylic acids having fewer carbon atoms than those of the carboxylic acids formed as main products were also detected from some of the oxidation products.

Diffusional influences on the parametric sensitivity of immobilized enzyme catalysts

Abstract: Immobilization of an enzyme within an insoluble material permeable to substrate can change the apparent behavior of the enzyme. In particular, external mass transfer and intraparticle diffusion effects can significantly influence the dependence of observed reaction rate on operating parameters such as temperature and pH. This analysis shows that, under very general conditions, the influence of diffusion alone is to diminish the sensitivity of the observed rate to any parameter that is uniform throughout the catalyst particle. However, the optimal value of the parameter is not changed because of intrapellet diffusional effects.

Gas liquid reactions in a packed bed: Some implications of the extended crossflow model

Abstract: The extended crossflow model was proposed earlier5 to account for the role of the stagnant zones of liquid in a packed trickle bed during absorption with a chemical reaction. Here the model is applied to a second order reaction to investigate the behaviour of the effectiveness f of the interfacial area of the static hold-up during absorption with a chemical reaction. General criteria are developed which give conditions for the limiting behaviour of f for reaction kinetics of any form. Finally, a possible pitfall is described in detail which must be avoided in conducting kinetic experiments in a packed trickle bed. Une extension du modele d'ecoulement croise a ete proposee anterieurement5 pour repreenter le role des zones de liquide stagnant dans une colonne a garnissage au cours d'une absorp tion avec reaction chimique. Ce modele est applique ici a une reaction d'ordre deux pour analyser le comportement du facteur d'efficacite f de l'interface du volume de retention durant une absorption avec reaction chimiqne. On a etabli des criteres generaux qui indiquent les conditions du comportemeut limite de f quelle que soit la cinetique de la reaction. Enfin, on decrit en detail un piege possible dans lequel il faut eviter de tomber en faisant des experiences impliquant la cinetique dams un lit garni de faible debit.

The permeation behavior of metal complex solutions through cellulose acetate membranes

Abstract: Transport phenomena of several kinds of metal complexes were investigated with cellulose acetate membranes annealed at 65°–76°C. In reverse osmosis experiments, the rejections of metal complexes involving organic sequestering agents such as EDTA or citric acid were much higher than those of the corresponding metal ions. While, in the case of metal complexes involving small inorganic ligands such as NH3 or SCN-, their rejections did not necessarily increase with the increase in the coordination numbers of the metal ions. To more precisely understand such transport behaviors, the distribution and the diffusion coefficients of metal complexes were obtained by desorption-rate measurements with dense cellulose acetate membranes. The results revealed that the distribution of a metal ion to the membrane was largely depended on the coexisting ligands. Attempts were also made to explain the distribution coefficient from the microscopic point of view by using Glueckauf's equation.

Chemistry of lac resin. viii. synthesis of jalaric ester‐i, possible key compound in the elaboration of lac resin by laccifer lacca kerr

Abstract: Preparation of (E)- and (Z)-16-hydroxy-9-hexadecenoic acids and erythro-aleuritic acid starting from naturally occurring aleuritic acid, is described. 16-Hydroxy-(Z)-9-hexadecenoic acid and jalaric acid have been selectively condensed to furnish the naturally occurring jalaric xxxter-I. The possible importance of this compound in the elaboration of lac resin by the insect is pointed out.