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Biomedical subjects

B L Jones

Publications and source records attributed to B L Jones.

At least 73 records · Page 4Linked to original sources
PubMed1982

A method for hydrolyzing and determining the amino acid compositions of picomole quantities of proteins in less than 3 hours.

A method is described for quantitatively hydrolyzing proteins in 45 min and for analyzing the hydrolysates by high-performance liquid chromatography in an additional 52 min. The alpha-amino acids were detected by the fluorescence of their omicron-phthaldialdehyde derivatives. Ten picomoles of each of the commonly occurring alpha-amino acids could be reliably determined. The method described yielded OPA-ethanethiolamino acid derivatives that were stable for 1 1/2 h and the HPLC method produced a better separation than previously published methods.

Amino Acids↗
PubMed1981

Purification and characterization of the entomocidal protoxin of Bacillus thuringiensis.

A procedure for purifying the insecticidal parasporal protoxin of Bacillus thuringiensis and a description of its biochemical and biophysical properties is provided. Mild alkali titration was necessary to generate a functional protoxin in a soluble form, and anion-exchange chromatography was used to remove contaminating cytoplasmic proteases that are nonspecifically bound to whole native parasporal crystals. Polyacrylamide gel electrophoresis, gel filtration chromatography, and meniscus depletion sedimentation equilibrium analysis revealed an apparent molecular weight for the protoxin of 1.34 x 10(5). The only NH2-terminal residue found was methionine. The soluble protoxin was 2.5 times more toxic to insect larvae than was the parasporal crystal. At alkaline pH the protoxin slowly converted to a low molecular weight toxin (apparent Mr = 6.8 x 10(4)). The molar specific toxicities of the protoxin and toxin were identical.

Amino Acid Sequence↗
PubMed1981

Distal common bile duct obstruction: an experimental study in monkeys.

Biliary obstruction was accomplished by surgically occluding the distal common bile duct in seven rhesus monkeys. Ultrasound scanning at 24-hour intervals showed that dilation of the common bile duct and gallbladder occurred before elevation of bilirubin or development of jaundice. The bile ducts expanded centrifugally from the obstructing point, with dilation of the intrahepatic ducts occurring several days after the onset of obstruction. After surgical release of the obstruction, the biliary ducts contracted centripetally, with the common bile duct requiring 30-50 days to return to normal size.

Animals↗
PubMed1979

Concentration of poliovirus from tap water using positively charged microporous filters.

Microporous filters that are more electropositive than the negatively charged filters currently used for virus concentrations from water by filter adsorption-elution methods were evaluated for poliovirus recovery from tap water. Zeta Plus filters composed of diatomaceous earth-cellulose-"charge-modified" resin mixtures and having a net positive charge of up to pH 5 to 6 efficiently adsorbed poliovirus from tap water at ambient pH levels 7.0 to 7.5 without added multivalent cation salts. The adsorbed virus were eluted with glycine-NaOH, pH 9.5 to 11.5. Electropositive asbestos-cellulose filters efficiently adsorbed poliovirus from tap water without added multivalent cation salts between pH 3.5 and 9.0, and the absorbed viruses could be eluted with 3% beef extract, pH 9, but not with pH 9.5 to 11.5 glycine-NaOH. Under water quality conditions in which poliovirus recoveries from large volumes of water were less than 5% with conventional negatively charged filters and standard methods, recoveries with Zeta Plus filters averaged 64 and 22.5% for one- and two-stage concentration procedures, respectively. Electropositive filters appear to offer distinct advantages over conventional negatively charged filters for concentrating enteric viruses from water, and their behavior tends to confirm the importance of electrostatic forces in virus recovery from water by microporous filter adsorption-elution methods.

Adsorption↗
PubMed1979

Glutamine as a feedback inhibitor of the Rhodopseudomonas sphaeroides nitrogenase system.

In whole cells of Rhodopseudomonas sphaeroides, nitrogen fixation, as measured by hydrogen production and acetylene reduction, was totally inhibited by micromolar concentrations of ammonia. This inhibition could not be duplicated by glutamate or glutamine alone. The inhibition by ammonia was abolished by methionine sulfoximine, a glutamine synthetase inhibitor. Inhibition by glutamine was complete in the presence of methionine sulfone, a preferential inhibitor of glutamate synthase, presumably by permitting a rise in the glutamine pool. The results indicated that the level of the glutamine pool controlled the activity of nitrogenase. None of these effects could be duplicated with cell-free nitrogenase, indicating there is probably a mediator which responds to the glutamine pool and inhibits nitrogenase, rather than glutamine itself being a direct inhibitor.

Ammonia↗
PubMed1977

A solvable selfreproductive hypercycle model for the selection of biological molecules.

By introducing a modified enzyme coupling in Eigen's hypercycle equations we have produced an exactly solvable selfreproductive hypercycle model. The model shows explicitly how collections of different macromolecular information carriers may coexist, through internal couplings, in the presence of constraints. We show how the "selective value" concept is manifested in the model and give simple criteria for selection among competing hypercycles.

Carrier Proteins↗
PubMed1977

A model for macromolecular selection in complementary instructing systems.

In this paper we consider a model for the selection and evolution of biological macromolecules when their reproduction is based on complementary instruction. The model is an extension of one of Eigen's models for selection and takes in account explicitly the formation of both single stranded and double stranded molecular complexes. We construct exact solutions to the rate equations for the case of constant rate parameters and error distributions. Criteria for selection are discussed.

Biological Evolution↗
PubMed1976

The amino acid sequence of wheat beta-purothionin.

The complete amino acid sequence of beta-purothionin, a low molecular weight, very basic, protein isolated from wheat endosperm material, has been determined. beta-purothionin is toxic to some bacteria, to yeasts, and to animals when injected. The protein contains 45 amino acid residues and has a molecular weight of 4913. The 8 cysteine and 10 basic residues are distributed throughout the molecule. The primary structure of the protein shows considerable homology to those of the viscotoxins, which are toxic, small, basic proteins found in the leaves and stems of European mistletoe (Viscum album L.).

Amino Acid Sequence↗