Frequency analysis of time-varying elastance model of the left ventricle

Zadeh's transfer function method for linear time-variable systems is used to apply frequency-domain analysis to a periodically time-varying elastance model of the left ventricle. Left ventricular pressure computed from the system function of the time-varying elastance and the phasors of aortic flow shows a typical waveform of the measured ventricular pressure.     

Bacteriophage MS2 RNA: A correlation between the stability of the codon: Anticodon interaction and the choice of code words

Summary The non-random distribution of degenerate code words in Bacteriophage MS2 RNA can be explained partially by considerations of the stability of the codon-anticodon complex in prokaryotic systems. Supporting this hypothesis we note that wobble codons are positively selected in codons having G and/or C in the first two positions. In contrast, wobble codons are statitically less likely in codons composed of A and U in the first two positions. Analyses of nucleotides adjacent to 5 and 3 ends of codons indicate a nonrandom distribution as well. It is thus likely that some elements of RNA evolution are independent of the structural needs of the RNA itself and of the translated protein product.This work was supported by grants from the Belgian Government Actions concertées - Gekon-certéerde Acties, N.F.W.O. and F.K.F.O. as well as from le Ministère de l'éducation du Québec. A preliminary report of this work was given at the EMBO ribosome workshop, Brussels 1976     

Modeling enzyme immobilization in porous solid supports

Enzymes are often immobilized on the internal surfaces of porous solid by immersing enzyme-free particles in a well mixed solution of enzyme. The ensuing impregnation process involves coupled transient mass transfer and surface attachment of enzyme. A mathematical model is employed to explore the influences of process parameters on the amount of enzyme loaded and the distribution of immobilized enzyme within the support particles. Nonuniform loading of the support occurs under some conditions. This is significant since the distribution of enzyme within the support particle influences the overall activity and stability of the immobilized enzyme catalyst. The model developed here may also be used to describe removal of reversibly immobilized enzyme during washing or utilization of the immobilized enzyme catalyst.     

A semimechanistic mathematical model for growth of Rhizopus oligosporus in a model solid-state fermentation system

A Semimechanistic mathematical model is developed which describes the growth of Rhizopus oligosporus in a model solid-state fermentation system. Equations are presented for the release of glucoamylase, the diffusion of glucoamylase, the hydrolysis of starch, the generation and diffusion of glucose, and the uptake of glucose and conversion into new biomass. Good agreement of the model with the experimental data was obtained only after the glucoamylase diffusivity and the maximum specific glucose uptake rate were altered from their originally determined values. The model recognizes the distributed nature of the solid-state fermentation and therefore is able to predict the concentration profiles of the system components within the substrate. The model provides an insight into the possible rate-limiting steps in solid-state fermentation-the generation of glucose within the substrate and the resulting availability of glucose at the surface.     

Determination of total and active immobilized enzyme distribution in porous solid supports

The total and active immobilized enzyme (IME) distributions in porous supports are studied both theoretically and experimentally. In order to determine experimentally the enzyme distribution profiles within a single particle, we construct a diffusion cell containing controlled-pore glass particles such that the cell would mimic a large pellet support. Our purpose is to study the interplay between the diffusion process within the interparticle void space and immobilization process in the controlled-pore glass particles onto the evolution of the (total and active) enzyme distributions. A mathematical model is developed to describe the interaction of various processes within the diffusion cell. The immobilized enzymes are determined for a system of trypsin and controlled-pore glass particles. The total amount of enzymes are determined by the amino acid analysis, and the active fraction is obtained by an active-site titration. The experimentally measured total IME profiles compare very well with that predicted by the model. The determined active enzyme profile is found to be nonuniform one, and it represents about 40% of the total enzyme immobilized in the support particles.     

Purification and some properties of an extracellular l-amino acid oxidase from Cellulomonas cellulans AM8 isolated from soil

Summary The soil isolate Cellulomonas cellulans AM8 produces an extracellular l-amino acid oxidase (L-AAO) with broad substrate specificity. The strain produced up to 0.35 unit (U)/ml of the extracellular L-AAO in a simple medium containing glycerol and yeast extract. The enzyme was easily purified up to 30 U/mg protein using Phenyl-Sepharose fast flow. The purified enzyme migrated as single band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) with a molecular mass of 55 kDa. On native PAGE the molecular mass was approx. 300 000 kDa, which may be due to aggregation. With the exception of glycine, proline, and threonine, all the amino acids normally constituting proteins were oxidized. The V _max values from 0.7 to 35.2 U/mg for aspartic acid and lysine, respectively, and the K _m values from 0.007 to 7.1 mm for cysteine and valine, respectively, were obtained at 25° C and pH 7.0 in oxygen-saturated solutions. The L-AAO had a pH optimum of 6.5–7.5. It was stable for several months at — 30° C and for some days at 35° C. Ferricyanide served as an electron acceptor with a V _max of 50 U/mg and K _m for 0.3 mm with phenylalanine as the substrate. Correspondence to: R. D. Schmid     

Flavonoids of Derris araripensis

Nineflavonoids: a dihydrochalcone,a flavone,four 3-methylflavonols,a flavanone, a 3-methylflavanonol and a flavan were isolated from the roots of Derris araripensis. Eight of these compounds are reported for the first time. Structures were established by spectral analysis and chemical degradation.     

Inhibition of Ouabain-binding to (Na+ + K+)ATPase by antibody against the catalytic subunit but not by antibody against the glycoprotein subunit

Antibodies against purified ($\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)}\text{ATPase}$ from the rectal gland of Squalus acanthias, as well as against its catalytic subunit, inhibited ouabain binding by as much as 50%. However, antibodies against the glycoprotein subunit did not inhibit ouabain binding. These data suggest that binding of antibody against the catalytic subunit to the enzyme either covers the ouabain binding site or destroys its conformation, while binding of antibody against the glycoprotein has no such effect.