Physiological factors determining formation of plastocyanin and plastidic cytochrome c-553 in Scenedesmus

Physiological conditions necessary for the formation of plastocyanin and the concurrent cessation of cytochrome c-553 formation were studied in cells of copper-deficient Scenedesmus acutus after the addition of copper. Plastocyanin is formed after a lag-phase, leaving constant the content of plastidic cytochrome c-553. Therefore, the concentration of plastocyanin per cell increases and the concentration of cytochrome c-553 decreases during growth. Formation of plastocyanin during the induction period studied is dependent on light intensity. In the dark, there is a 90% inhibition, whereas under light intensities above 50 Wm^-2, a ratio of 1.3 molecules plastocyanin per 1,000 molecules chlorophyll is attained.Plastocyanin formations is inhibited by the uncoupler carbonylcyanide-p-trifluoromethoxy phenylhydrazone (FCCP), but not by moderate concentrations of 3-[3,4-dichlorophenyl]-1,1-dimethylurea (DCMU), and by keeping the algae under a nitrogen atmosphere without CO₂. Concurrently, the cultures treated with FCCP show a decreased endogenous ATP level. The ATP is necessary for plastocyanin formation.Abbreviations FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - DCMU 3-[3,4-dichlorophenyl]-1,1-dimethylurea - pcv packed cell volume     

Comparison of isolated peanut agglutinin receptor glycoproteins from human,bovine and porcine erythrocyte membranes

Affinity chromatography has been used to isolate and compare the peanut agglutinin receptors from neuraminidase-treated human, bovine and porcine erythrocyte membranes. Passage of Triton X-100-solubilised membrane material through either Sepharose- or acrylamide-based affinity columns resulted in the reversible binding of receptor molecules to the immobilised lectin. Elution with 0.2M galactose released specifically bound glycoprotein fractions, the composition and molecular weights of which were determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate.Carbohydrate analysis by gas chromatography identified these bound glycoprotein fractions as the major sources of the $\text{O-}\text{glycosidic-linked}$ disaccharide $\text{galactosyl}\text{-β-(1 → 3)-N-}\text{acetylgalactosamine}$ in these membranes. It is suggested that these isolated fractions represent a discrete population of glycoproteins within the membranes studied, which possess both $\text{O-}\text{glycosidic}$- and $\text{N-}\text{glycosidic-linked}$ carbohydrates.     

Conformation of sequential and random lysine–phenylalanine copolypeptides

The sequential copolypeptides (Lys-Phe-Lys)_n and (Lys₂-Phe-Lys)_n and a series of related random copolypeptides were investigated with respect of their ability to adopt the α-helix or β-conformation. Conformational transitions were induced by increasing the pH or by addition of NaClO₄ or methanol and were observed by recording the CD spectra. In contrast to the respective alternating copolypeptide (Phe-Lys)_n with its strong tendency for the β-structure reported previously, (Lys-Phe-Lys)_n can adopt either secondary structure, whereas (Lys₂-Phe-Lys)_n strongly favors the α-helix. Together with the random copolypeptides, whose composition varied from 20 to 50 mol % phenylalanine and whose average molecular weights ranged from 10,000 to 90,000, the influence of the phenylalanine content and of the chain length on conformational stability and the rotatory strength of the respective secondary structures were elaborated.     

A monoclonal antibody to viral glycoprotein blocks virus-immune effector T cells operating at H-2Dd but not at H-2Kd1.

A particular monoclonal antibody that binds to the influenza virus HA molecule inhibits HA-specific thymus-derived lymphocytes mediating cytotoxicity in the context of H-2Dd but not of H-2Kd. Another monoclonal antibody blocks both sets of HA-specific effector T cells. This observation, together with related findings from other laboratories, is considered to support the idea that T cell recognition is directed against some association of viral and H-2 glycoproteins, as proposed in the original formulation of the "altered self" concept.     

Dehalogenation of dichloromethane by cell extracts of hyphomicrobium DM2

A facultatively methylotrophic bacterium was isolated from enrichment cultures containing dichloromethane as the sole carbon source. It was identified as a Hyphomicrobium species. The organism grew exponentially in batch cultures with 10 mM dichloromethane at a specific growth rate of 0.07 h^-1. The release of Cl^- from dichloromethane and the disapperance of substrate paralleled growth. Resting dichloromethane-grown cells, in the presence of potassium sulphite as a trapping agent, converted cichloromethane methane quantitatively to formaldehyde. The conversion of dichloromethane to formaldehyde by cell extracts was stricly dependent on glutathione. Other thiols were inactive. Glutathione was not consumed in the course of the reaction. The specific activity of the enzymic dehalogenation of dichloromethane amounted to 3.8 mkat/kg protein in extracts of dichloromethane-grown cells and to less than 0.1 mkat/kg protein in extracts from cells grown on methanol.     

1H NMR studies at 360 Mhz of the methyl groups in native and chemically modified basic pancreatic trypsin inhibitor (BPTI)

In the ¹H NMR spectra obtained at 360 MHz after digital resolution enhancement, the multiplet resonances of the methyl groups in the basic pancreatic trypsin inhibitor (BPTI) were resolved. With suitable double irradiation techniques the individual methyl resonances were assigned to the different types of aliphatic amino acid residues. Furthermore, from pH titration and comparison of the native protein with chemically modified BPTI, the resonance lines of Ala 16 in the active site and Ala 58 at the C-terminus were identified. Potential applications of the resolved methyl resonances as natural NMR probes for studies of the molecular conformations are discussed.     

Properties of mammalian cells transformed by temperature-sensitive mutants of avian sarcoma virus.

Fibroblasts from European field vole (Microtus agrestis) and from normal rat kidney (NRK) have been infected by avian sarcoma virus mutants which are temperature-sensitive for the maintenance of transformation. These cells are transformed at 33 degrees C, but show normal cell characteristics in morphology, colony formation in agar, saturation density, sugar uptake and membrane proteins at 39 degrees C and 40 degrees C, the nonpermissive temperatures. Ts mutant virus was rescued from most of the ts transformed cell lines. NRK cells infected by avian sarcoma virus ts mutants and kept at the nonpermissive temperature can be transformed by wild-type avian sarcoma virus. The susceptibility of the temperature-sensitive NRK lines to this transformation is higher than the susceptibility of uninfected NRK at either permissive or nonpermissive temperature.     

Canarion,ein neues naphthochinon aus Usnea canariensis

The structure of canarione, a new naphthoquinone from the lichens Usnea canariensis and U. hookeri was elucidated by UV, ¹H-NMR, ¹³C-NMR, mass spectrometry, and chemical degradation as 5,8-dihydroxy-2-methyl-4H-naphtho [2,3b]-pyran-4,6,9 (6H, 9H)- trione.     

Immunohistochemische Lokalisierung der Isoenzyme der Creatinkinase im menschlichen Gewebe

Zusammenfassung In Gefrierschnitten lassen sich die Isoenzyme der Creatinkinase MM und BB durch spezifische Antikörper selektiv präzipitieren. Nach Sättigung der freien Antikörpervalenzen durch Zugabe von exogenem Antigen wird das im Schnitt fixierte Isoenzym durch eine histochemische Technik lokalisiert. Die Methode ermöglicht eine isoenzymspezifische Histochemie der Creatinkinase.Die Anwendung dieser Technik am menschlichen Gewebe führte zu folgenden Ergebnissen: CK-BB ließ sich sowohl in der Muskulatur als auch in der Mucosa des Colons nachweisen, während im Skelettmuskel zwischen cytoplasmatischer CK-MM und membrangebundenem Enzym im sarkoplasmatischen Reticulum und im Sarkolemm differenziert werdn konnte. In der Tonsille wurden CK-BB in epithelialem Gewebe, CK-MM in Muskelfasern lokalisiert. Das Isoenzymmuster von benachbarten einzelnen Schnitten wurde parallel immunologisch analysiert. Auf den Vorteil der Kombination von Immuntitration und Histchemie an gleichen Schnitten wird verwiesen.

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Immunohistochemical localization of creatinkinase isoenzymes in human tissue

Summary The use of an immunohistochemical method permits the localization of creatine kinase isoenzymes MM and BB in tissue sections. Frozen sections are first incubated with the specific antiserum and secondly with the soluble antigen under investigation. The antibody fixed creatine kinase can then be visualized by the tetrazolium-salt linked histochemical reaction.In this way CK-BB was found in the smooth muscle and the mucosa of the human colon. In sections of skeletal muscle CK-MM was predominantly localized in the intermyofibrillar space. Membrane bound activity could be demonstrated in the sarcoplasmic reticulum and the surface membrane after elution of the cytoplasmic enzyme.In the human tonsilla CK-BB was localized in lymphatic and epithelial tissues, CK-MM in the muscle fibers. The isoenzyme patterns in single sections of tonsilla were in parallel determined by the immunotitration assay. The results indicate the usefulness of the combined application of histochemistry and immunotitration in serial tissue sections.

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Unterstützt durch das Schwerpunktprogramm Enzymdiagnostik Pf 32/36 der Deutschen Forschungsgemeinschaft, 5300 Bonn-Bad Godesberg     

Quantitative analysis of activation and inactivation of asymmetry currents in biological membranes,based on a conformational transition model

Summary A basic voltage-dependent conformational transition mechanism is proposed. It comprises one relatively fast conversion between two individual states which are comparatively slowly coupled with a third state. Having introduced voltage as an additional parameter of state, standard methods of thermodynamics and rate theory are employed to describe the equilibrium and kinetic behavior of the system. In particular, a quantitative discussion is given regarding the asymmetrical displacement currents generated by switching on and off a voltage pulse. Effects of temperature pulse duration, and application of a conditioning prepulse are examined. The results provide a comprehensive basis for a quantitative analysis of pertinent experimental work. The so far presented measuring data can indeed be very well described along these lines.