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Biomedical subjects

R Haselkorn

Publications and source records attributed to R Haselkorn.

At least 163 records · Page 9Linked to original sources
PubMed1968

Properties of ribulose-1,5-diphosphate carboxylase (carboxydismutase) from Chinese cabbage and photosynthetic microorganisms.

Ribulose-1,5-diphosphate carboxylase (carboxydismutase) was prepared from Chinese Cabbage [Brassica petsai (Parl)] and the K(m) values and molecular weight were determined. These parameters were found to be in good agreement with values reported for this enzyme from other higher plants. Investigation of carboxydismutase activity from the photosynthetic micro-organisms Chlamydomonas reinhardi (IU 89+), Plectonema boryanum (IU 594), and Chromatium strain D showed striking similarity to the higher plant enzyme, when the sedimentation coefficients were compared.

Carboxy-Lyases↗
PubMed1967

Morphology of a virus of blue-green algae and properties of its deoxyribonucleic acid.

The morphology of Safferman's virus of blue-green algae (phycovirus LPP-1) has been studied by electron microscopy and physicochemical methods. The virion has a short (100 to 200 A long, 150 A in diameter) forked tail, with an outer sheath, an inner core, and a capital attached to one of the vertices of a polyhedral head. The head capsid edge-to-edge distance is 600 A, based upon internal calibration of the magnification in electron micrographs by use of the line-line spacing of catalase crystals. Measurements of absorbancy and infectivity, and electron microscopy across the band of virus after zone centrifugation on a sucrose gradient, indicated that infectivity was correlated with the short-tailed particles described. The viral deoxyribonucleic acid (DNA) is linear, with a contour length of 13.2 +/- 0.5 mu, measured by the Kleinschmidt method. Its sedimentation coefficient, S(0) (20, w), is 33.4 +/- 0.7 S. These values are consistent with a molecular weight of 27 x 10(6) for the viral DNA. Based upon buoyant density in CsCl and thermal denaturation, the guanine-cytosine content of the DNA is 53%. The viral DNA was used as template for in vitro ribonucleic acid (RNA) synthesis by Escherichia coli RNA polymerase. This RNA annealed to 18% of the sequences in the viral DNA, 0.5% of the sequences in bacteriophage T7 DNA, and 0.25% of the sequences in Plectonema boryanum DNA, at saturating levels of RNA in the Hall-Nygaard hybridization assay. The lack of homology with T7 DNA is of interest because the two viruses are very similar morphologically. The lack of homology with host DNA suggests that this algal virus is a poor candidate for transduction.

Bacteriophages↗
PubMed1965

Electron microscopic and biochemical characterization of fraction I protein.

Electron micrographbs of high resolution have been obtained from fraction I protein of Chinese cabbage leaves. The protein, which has ribulose-1,5-diphosphate carboxylase activitY, appear to be a cube swth edge of about 120 angstroms. Substrtucture canl be seen in individual particles, conlsistent with a model having 24 subunits, the number prescribed by the available physical and chlemical data.

Biochemical Phenomena↗
PubMedDate not supplied

The ntr genes of Escherichia coli activate the hut and nif operons of Klebsiella pneumoniae.

Regulation of the synthesis of glutamine synthetase and of the arginine and glutamine transport systems (Ntr phenotype) in Salmonella have been shown to require two regulatory genes on the C-terminal side of the glnA gene (McFarland et al., 1981). We have cloned a HindIII-EcoRI DNA fragment from Escherichia coli coding for analogous properties with respect to the Ntr phenotype in E. coli. A plasmid containing this E. coli DNA fragment joined to another fragment carrying a cyanobacterial glnA gene (but no functional regulatory genes) was introduced into a Klebsiella pneumoniae mutant with a Gln-Ntr- phenotype, i.e., which could not derepress nitrogenase. The cyanobacterial gene made the Klebsiella strain Gln+ and the E. coli DNA fragment made the strain Ntr+, including the ability to derepress nitrogenase fully. Thus the products of the glnA-linked ntr genes of E. coli can regulate expression of the Ntr-dependent genes of Klebsiella.

Arginine↗