Expression in Escherichia coli of hepatitis B virus DNA sequences cloned in plasmid pBR322

Fragments of hepatitis B virus DNA isolated from Dane particles have been inserted into the Escherichia coli plasmid pBR322 and cloned. Cells carrying the hybrid plasmid synthesise antigenic material that reacts specifically with antisera to hepatitis B viral antigens.

Absolute determination of dose rate from energetic electron beams

A method for absolute dose rate determinations in the range of 10(7) rad (Si) s(-1) to greater than 10(10) rad (Si) s(-1) is reported here. The method is useful in determining the simultaneous dose rate delivered to a device under test which is small enough that it does not significantly affect the beam current. The method requires (1) an instrument consisting of a Faraday cup, scattering plates, and collimators, (2) beam profile measurements, and (3) energy deposition calculations. The Faraday cup is designed for electron beams whose energy is in the range 5-50 MeV. This method is capable of providing dose rates accurate to 10% and total dose to 5%.

Packaging recombinant DNA molecules into bacteriophage particles in vitro

Recombinant phage genomes made in reactions with purified enzymes may be recovered directly by packaging into phage heads in vitro. The process is efficient and nonselective and offers containment in initial stages of handling recombinant DNA. Ligase [poly(deoxyribonucleotide):poly-(deoxyribonucleotide) ligase (AMP-forming), EC 6.5.1.1] reaction products can recombine with endogenous phage DNA during packaging, but UV-irradiation eliminates the biological activity of the endogenous DNA.

Lambdoid phages that simplify the recovery of in vitro recombinants

Derivatives of phage lambda are described for use as vectors for fragments of DNA generated with the HindIII and EcoRI restriction enzymes. With some vectors, hybrid molecules are recognised by a change from a turbid to a clear plaque morphology resulting from the insertion of a fragment of DNA into the lambda gene coding for the phage regressor. Other vectors contain a central, replaceable fragment of DNA which imparts a readily recognisable phenotype. This central fragment may include either a gene for a mutant transfer RNA (suppressor) or a part of the lacZ gene of E. coli able to complement a lacZ host. The appropriate lacZ host and indicator plates permit the ready distinction between recombinant and vector phages by the colour of the plaques.

Isolation and characterization of two sequence-specific endonucleases from Anabaena variabilis

Two endonucleases, AvaI and AvaII, were isolated from Anabaena variabilis on the basis of their ability to make a limited number of breaks at specific points in bacteriophage lambda DNA. Neither enzyme has cofactor requirements beyond Mg2+. Endonuclease AvaI makes eight breaks in the phage lambda chromosome at which the 5'-terminal sequence is pPy-C-G-N. AvaII endonuclease cuts phage lambda DNA more extensively, yielding fragments with the 5'-terminal sequence G-T-C-N or G-A-C-N. Neither enzyme generates cohesive ends.

Restriction and modification in B. subtilis. Purification and general properties of a restriction endonuclease from strain R

All Bacillus subtilis R-type strains showing the phenomena of restriction and modification contain an endonuclease that inactivates in vitro the biological activity of a variety of DNAs lacking R-specific modification, such as transfecting SPPI, SPO2 and phi105 DNA, and transforming B. subtilis 168-type DNA. The corresponding DNAs carrying R-specific modification are resistant to the enzyme. The enzyme has been purified approximately 400-fold and is essentially free from contaminating double strand-directed unspecific exo- or endonuclease activity. Only Mg2+ is required as cofactor. The substrate DNAs are cleaved at specific sites. The double-stranded fragments produced from SPP1 DNA (molecular weight 2.5 x 10(7)) have an average molecular weight of about 3 x 10(5).

Restriction and modification in B. subtilis. Nucleotide sequence recognised by restriction endonuclease R. Bsu R from strain R

Restriction endonuclease R from Bacillus subtilis strain R cleaves nonmodified SPP 1 DNA in approximately 80, and lambda DNA in about 200 different sites. DNA digests with this endonuclease and with endonuclease Hae III from Haemophilus aegyptius show identical fragmentation patterns on gel electrophoresis, indicating that the two enzymes recognise the same nucleotide sequence. The polynucleotide kinase reaction was used in conjunction with two-dimensional ionophoretic nucleotide mapping methods to identify the 5'-nucleotide sequences at the sites of cleavage by the B. subtilis restriction endonuclease. The results show that the recognition sequence is (see article) where arrows indicate the points of strand scission. Each of the four possible nucleotides can occur in the positions flanking the recognition site.

Microbial metabolism of aryl sulphonates a re-assessment of colorimetric methods for the determination of sulphite and their use in measuring desulphonation of aryl and alkylbenzene sulphonates

The reaction of 2,4-dinitroanilinomaleimide with sulphite which has been claimed as the basis of a suitable colorimetric assay for the anion was carefully re-examined. The sulphite-imide addition product provides a suitable and specific qualitative test for sulphite after separation by paper chromatography but the method as previously used is probably measuring the hydrolysis of the imide to 2,4-dinitroanilinomaleamic acid and cannot be used for sulphite determination either colorimetrically or in kinetic assays. A new colorimetric method for the determination of sulphite based on its reaction with Ellman's reagent, 5,5'-dithiobis(2-nitrobenzoic acid) is described and compared for sensitivity with the p-rosaniline-HCHO method. Both methods were used to show the formation of sulphite as the initial product of arylsulphonate metabolism by bacteria. The failure to find sulphite in similar cultures of a third organism was attributed to the very high activities of sulphite oxidase found in extracts. The Ellman reagent was examined as the basis of an indicator medium for the detection of sulphite-excreting colonies.

Metabolism of naphthalene, 2-methylnaphthalene, salicylate, and benzoate by Pseudomonas PG: regulation of tangential pathways

Naphthalene is metabolized by Pseudomonas PG through 1,2-dihydroxynaphthalene and salicylate to catechol, which is then degraded by the meta pathway. 2-Methylnaphthalene, but not 1-methylnaphthalene, also serves as a growth substrate and is metabolized by the same route, through 4-methylcatechol. The same nonspecific meta pathway enzymes appear to be induced by growth on either naphthalene or 2-methylnaphthalene. The level to which 2-hydroxymuconic semialdehyde hydrolase is induced is low and probably of no metabolic significance. Growth on salicylate or catechol, both intermediates of naphthalene degradation, or benzoate results in induction of the ortho pathway, the alternative route for catechol dissimilation. No induction of 1,2-dihydroxynaphthalene oxygenase was found in salicylate-grown cells. Anaerobic growth on a succinate-nitrate medium in the presence of various inducers indicates that cis, cis-muconate, or one of its metabolites is the inducer of the ortho pathway enzymes. The inducer or inducers of the early enzymes of naphthalene degradation and of the meta pathway enzymes must be an early intermediate of the naphthalene pathway above salicylate.

Pulmonary eosinophilia after substitution of aerosol for oral corticosteroid therapy

Three patients with chronic asthma developed pulmonary eosinophilia while oral prednisolone was being withdrawn after the introduction of treatment with beclomethasone dipropionate aerosol. These observations suggest that the development of pulmonary eosinophilia in patients with chronic asthma can be prevented by the systemic administration of corticosteroids, but not by a corticosteroid aerosol given by inhalation. It is considered that radiological examination of the chest should be carried out at frequent intervals during and for a few months after the substitution of corticosteroid aerosol therapy for oral corticosteroid therapy in order to ensure that those patients who are liable to develop pulmonary eosinophilia will be identified at an early stage. These precautions are even more essential when there is a previous history of pulmonary eosinophilia.