The chemical-transformation products of 1,6-dibromo-1,6-dideoxygalactitol and 1,2:5,6-dianhydrogalactitol in aqueous solution

After hydrolysis of 1,6-dibromo-1,6-dideoxygalactitol (1) and 1,2:5,6-dianhydrogalactitol (2), 11 compounds were isolated, three of them as tritylated derivatives. Their structures were established on the basis of chemical evidence and, for four compounds, by X-ray diffraction. The main product of the hydrolysis of 1 was 3,6-anhydro-1-bromo-1-deoxy-dl-galactitol; the end-products of the hydrolysis of 2 were 1,5-anhydro-dl-galactitol, 2,5-anhydro-dl-altritol, and galactitol.     

Somatic cell fusion of Trichoderma reesei resulting in new genetic combinations

Summary A selection method has been developed for the isolation of recombinant strains of Trichoderma reesei QM 9414. The method is based on somatic hybridization via anastomosis or protoplast fusion, and on the difference in growth rate of the resulting heterokaryons and synkaryons. The more intensive growth of the synkaryons as due to allelic complementation of adenine-requiring auxotrophic strains mutated in the adenylosuccinate synthetase gene. The synkaryons appeared is energetically growing spots in the heterokaryotic background. Stable diploids could not be isolated, which points to the transient nature of the diploid state in this species.     

Alga consumption of four dominant planktonic crustaceans in Lake Balaton (Hungary)

Between 1981–83 the gut contents ofDaphnia galeata, D. cucullata, Eudiaptomus gracilis, andCyclops vicinus were examined with light and scanning electron microscope to obtain information on the feeding of these species in Lake Balaton. The twoDaphnia species feed mainly on abioseston, and it is assumed that their primary nutrient source was organic matter adsorbed onto the surfaces of the abioseston granules plus bacteria and detritus.E. gracilis feeds on algae, showing a preference for green algae and diatoms.C. vicinus is also a prodigious consumer of algae in Lake Balaton, utilizing the whole size spectrum of phytoplankton. Concerning the trophic relationships between phytoplankton and zooplankton in Lake Balaton, that between diatoms and bothE. gracilis andC. vicinus is the most conspicouos. Convincing evidence for an extensive utilization of blue-green algae was not found. Though there is no firm evidence yet, it is likely that theDaphnia are dependent on organic matter adsorbed on the abioseston.     

Stirred fluidised-bed reactor developed for low-density biocatalyst supports

Summary A new type of multistage fluidised-bed reactor was constructed to avoid the fluidisation irregularities by slow stirring of the bed. Aminoacylase immobilized on a polyacrylamide type bead polymer was used as biocatalyst for resolution of racemic amino acids. The efficiency was considerably higher than that of a traditional packed-bed reactor.     

Effect of cooling rate,cryoprotectant and holding time at different transfer temperatures on the survival of cryopreserved cell suspension culture (Puccinellia distans (L.) Parl.)

Reflexed saltmarsh-grass suspension cultures produced by seed callus were frozen to the liquid nitrogen temperature. Cooling rates, cryoprotectants and holding times were taken as a function of transfer temperatures. The highest survival of cells (45%) was found at a freezing rate of 1°C min^-1, without cryoprotectant treatments. The cryoprotectants (proline, dimethyl sulphoxide, glycerol), used at different concentrations and transfer temperatures, increased the survival rate. The maximum value was 78% at 12.5% (w/v) of proline with –30°C transfer temperature. Considerable improvement of viability (from 0% to 95%) among the 12.5 and 15.0% (v/v) dimethyl sulphoxide cryopreserved cells was achieved by holding them at – 20°C for 10–30 min before plunging into the liquid nitrogen. A 20 min holding time at 15.0% (v/v) glycerol level and – 30°C transfer temperature significantly enhanced the viability of the explants from 42% to 92%. Plants were successfully regenerated from cells cryopreserved with proline (w/v) and dimethyl sulfoxide (v/v) levels of 12.5 and 15.0%, respectively.     

Release of 6-KETO-PGF1α and thromboxane B2 in late appearing cardioprotection induced by the stable PGI analogue: 7-OXO-PGI

We have shown earlier that prostacylin (PGI₂) and its stable analogue: 7-oxo-prostacyclin(7-OXO) may induce a prolonged, late appearing (24–48 h after drug administration), dose dependent protection of the heart from harmful consequences of a subsequent severe ischaemic stress, such as myocardial ischaemia, life-threatening ventricular arrhythmias and early ischaemic morphological changes. In an other study we observed that a similar but shortlived (less than 1 h) cardioprotection, induced by preconditioning brief coronary artery occlusions, is greatly reduced by blockade of the cyclooxygenase pathway, suggesting that prostanoids might play a role in this shortlasting protection.Objective of our present study was to elucidate the importance of some arachidonic acid (AA) metabolites, such as PGI₂ and thromboxane A₂ (TXA₂) in the mechanism of the late appearing, prolonged cardioprotection. Estimation of the metabolites: 6-keto-PGF₁ (6-KETO) and thromboxane B₂ (TXB₂) was made from the perfusate of isolated Langendorff hearts of guinea-pigs pretreated with 50 g/kg 7-OXO, 24 and 48 h before preparation. Pretreatment alone produced a slight, but significant elevation of 6-KETO (from 206±11 to 284±19 pg/ml/min after 24 h, and to 261±18 pg/ml/min after 48 h). No change was seen in TXB₂ production. Global ischaemia for 25 min (followed by 25 min reperfusion) markedly increased the release of both AA metabolites; maximal values were observed in the third min of reperfusion (6-KETO from 206±11 to 1275±55 pg/ml/min and TXB₂ from 29±4 to 172±12 pg/ml/min). All values returned to the preischaemic level by the 25th min of reperfusion. Ischaemic increase in 6-KETO level was significantly higher in the perfusate of hearts from pretreated animals (1507±73 pg/ml/min after 24 h, and 1398±54 pg/ml/min after 48 h) that in those of untreated controls. There was no difference in TXB₂ values. Thus both basal and ischaemic release of PGI₂ increased 24 and 48 h after pretreatment with 7-OXO but not TXA₂ production. Results suggest that endogenous prostanoids might play a role in late appearing cardioprotection.     

The IleL229 → Met mutation impairs the quinone binding to the QB-pocket in reaction centers of Rhodobacter sphaeroides

A spontaneous mutant (R/89) of photosynthetic purple bacterium Rhodobacter sphaeroides R-26 was selected for resistance to 200 M atrazin. It showed increased resistance to interquinone electron transfer inhibitors of o-phenanthroline (resistance factor, RF=20) in UQ_o reconstituted isolated reaction centers and terbutryne in reaction centers (RF=55) and in chromatophores (RF=85). The amino acid sequence of the Q_B binding protein of the photosynthetic reaction center (the L subunit) was determined by sequencing the corresponding pufL gene and a single mutation was found (Ile^L229 Met). The changed amino acid of the mutant strain is in van der Waals contact with the secondary quinone Q_B. The binding and redox properties of Q_B in the mutant were characterized by kinetic (charge recombination) and multiple turnover (cytochrome oxidation and semiquinone oscillation) assays of the reaction center. The free energy for stabilization of Q_AQ_B ^– with respect to Q_A ^–Q_B was G_AB=–60 meV and 0 meV in reaction centers and G_AB=–85 meV and –46 meV in chromatophores of R-26 and R/89 strains at pH 8, respectively. The dissociation constants of the quinone UQ_o and semiquinone UQ_o ^– in reaction centers from R-26 and R/89 showed significant and different pH dependence. The observed changes in binding and redox properties of quinones are interpreted in terms of differential effects (electrostatics and mesomerism) of mutation on the oxidized and reduced states of Q_B.Abbreviations BChl bacteriochlorophyll - Ile isoleucine - Met methionin - P primary donor - Q_A primary quinone acceptor - Q_B secondary quinone acceptor - RC reaction center protein - UQ_o 2,3-dimethoxy-5-methyl benzoquinone - UQ₁₀ ubiquinone 50 This work is dedicated to the memory of Randall Ross Stein (1954–1994) and is, in a small way, a testament to the impact which Randy's ideas have had on the development of the field of competitive herbicide binding.