Characterization of the pH-mediated solubility of Bacillus thuringiensis var. san diego native delta-endotoxin crystals.

Native crystals of Bacillus thuringiensis var. san diego, a coleopteran-specific delta-endotoxin, were metabolically labelled with [35S]methionine. Specific activity was 82,000 CPM/micrograms (2.44 Ci/mmol). Using a universal buffer formulated with the same ionic strength at every pH, we determined that native crystals dissolve above pH 10 and below pH 4. At the acidic pH, the rate of solubilization was substantially slower than at the alkaline pH. Recrystallization rates for the toxin were similar regardless of solubilization conditions. The banding patterns in denatured polyacrylamide gel electrophoresis were unaffected by solubilization conditions. Toxicity was higher for soluble toxin compared to crystal toxin, but virtually identical for the acidic and alkaline produced solutions. Acid solubilization is significant because of the acidic midgut of susceptible Coleoptera.     

Modulation of transient type K channel cloned from rat heart.

We have cloned a transient type K channel from rat heart (RH10) and coexpressed a metabotropic glutamate receptor (mGluR5) to study the functional modulation of RH10 coupled to the phosphatidylinositol (PI) hydrolysis. Stimulation of mGluR5 suppressed peak amplitude of RH10 current and affected voltage dependence of activation and inactivation of the channel.     

Effect of coenzymes on the quaternary structure conformation of glyceraldehyde-3-phosphate dehydrogenases of mung beans and rabbit muscle.

Kinetics of thermal inactivation of glyceraldehyde-3-phosphate dehydrogenases of mung beans and rabbit muscle have been studied under different pH conditions in the absence and presence of various concentrations of NAD+ and NADH. The data have been discussed with respect to the effect of the coenzymes on the quaternary structure symmetry of the two enzymes and their binding isotherms. Both the (homo-tetrameric) apo-enzymes exhibit biphasic kinetics of thermal inactivation, characteristic of C2 symmetry, at lower pH values and a single exponential decay of enzyme activity, characteristic of D2 symmetry, at higher pHs. In each case, NAD+ has no effect on the biphasic kinetic pattern of thermal inactivation at lower pH values, but NADH brings about a change to single exponential decay. At higher pH values, NADH does not affect the kinetic pattern (single exponential decay) of any enzyme, but NAD+ alters it to biphasic kinetics in each case. The data suggest that NAD+ and NADH have higher affinity for the C2 and D2 symmetry conformation, respectively. With mung beans enzyme, the effect of NAD+ on the two rate constants of biphasic inactivation at pH 7.3 is consistent with a Kdiss equal to 110 microM. The NAD(+)-dependent changes in the kinetic pattern of thermal inactivation of this enzyme at pH 8.6 suggest a positive cooperativity in the coenzyme binding (nH = 3.0). In the binding of NADH to the mung beans enzyme, a weak positive cooperativity is observed at pH 7.3.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bivariate flow cytometry of farm animal chromosomes: a potential tool for gene mapping

Bivariate flow karyotypes of chromosomes from sheep, cattle and pig lymphocytes and from a cattle-mouse somatic cell hybrid line were obtained using a dual laser fluorescence-activated cell sorter (FACS). Pig chromosomes were resolved into 19-20 peaks, indicating that most, if not all, pig chromosomes could be separated by this technique. Sheep chromosomes showed incomplete separation but three clear peaks, presumably representing the three large metacentric chromosomes, plus five other clusters were obtained. Cattle chromosomes showed poor separation but about four peaks could be distinguished, indicating that certain chromosomes could be sorted in this species. The use of cattle-mouse hybrids may enable other individual cattle chromosomes to be obtained. It is concluded that FACS separation will be a useful additional tool for gene mapping.     

Facile and stereoselective synthesis of 2'-5'-oligothioadenylate by UO2(2+) ion catalyst.

The synthesis and characterization of 2'-5'-oligothioadenylate by UO2(2+) ion catalyst are described. The polymerization of imidazole-activated thioadenylate or thioinosylate yielded oligomers containing mainly 2'-5'-internucleotidyl blond and Rp configuration at phosphorous atom.     

Electrostatic coupling of ion pumps.

In this paper the electrostatic interactions between membrane-embedded ion-pumps and their consequences for the kinetics of pump-mediated transport processes have been examined. We show that the time course of an intrinsically monomolecular transport reaction can become distinctly nonexponential, if the reaction is associated with charge translocation and takes place in an aggregate of pump molecules. First we consider the electrostatic coupling of a single dimer of ion-pumps embedded in the membrane. Then we apply the treatment to the kinetic analysis of light-driven proton transport by bacteriorhodopsin which forms two-dimensional hexagonal lattices. Finally, for the case of nonordered molecules, we also consider a model in which the pumps are randomly distributed over the nodes of a lattice. Here the average distance is equal to that deduced experimentally and the elemental size of the lattice is the effective diameter of one single pump. This latter model is applied to an aggregate of membrane-embedded Na, K- and Ca-pumps. In all these cases the electrostatic potential considered is the exact solution calculated from the method of electrical images for a plane membrane of finite thickness immersed in an infinite aqueous solution environment. The distributions of charges (ions or charged binding sites) are considered homogeneous or discrete in the membrane and/or in the external solution. In the case of discrete distributions we compare the results from a mean field approximation and a stochastic simulation.     

Life history patterns of river invertebrates

The initiation of invertebrate distribution patterns in rivers occurs by choice of oviposition sites and is influenced by the evolved reproductive strategies of the individual species. Subsequent redistribution by migration or drifting establishes patterns which are then modified by environmental influences on growth and mortality. Continuity of life cycles is sustained by variations on a number of defined life history strategies combined with evolved behavioural responses.