Inorganic pyrophosphate-driven ATP-synthesis in liposomes containing membrane-bound inorganic pyrophosphatase and F0-F1 complex from Rhodospirillum rubrum

PPi driven ATP synthesis has been reconstituted in a liposomal system containing the membrane-bound energy-linked PPiase and coupling factor complex, both highly purified from Rhodospirillum rubrum. This energy converting model system was made by mixing both enzyme preparations with an aqueous suspension of sonicated soybean phospholipids and subjecting to a freeze-thaw procedure. In the presence of ADP, Mg2+, Pi and PPi the system catalyzed phosphorylation by up to 25 nmol ATP formed X mg protein-1 X min-1, at 20 degrees C, which was sensitive to uncouplers and inhibitors of phosphorylation such as oligomycin, efrapeptin and N,N'-dicyclohexylcarbodiimide.     

Chronic toxicity of three insecticides (carbaryl,fenthion and lindane) in the freshwater snail Lymnaea stagnalis

A chronic intoxication with carbaryl, fenthion and lindane was induced in young snails. The parameter k of the von Bertalanffy's equation showed clearly the growth changes induced by these insecticides. In all cases the fecundity of intoxicated snails was reduced. Among these three insecticides, lindane was the most toxic, carbaryl the least.     

Toxicité aiguë d'un fongicide dithiocarbamate,le thirame,chez des larves de l'ephémère Cloeon dipterum: effets de divers paramètres

Acute toxicity and degradation of an aqueous suspension of Thiram were studied in Cloeon dipterum. Lethal concentrations for 50% of the larvae (LC 50) after 24 to 96 h of exposure and thresholds were calculated. LC 50 varied from 0.39 to 1.92 mg·l^?1 according to the time and the physiological state of the larvae. It was demonstrated that:

the sensitivity of the larvae increased with the time during which they were kept in the laboratory;

while the toxicity of the aqueous suspension (1 mg·l^?1) of Thiram decreased with time, another toxic product was formed.

     

Properties and function of the two hemes in Pseudomonas cytochrome c peroxidase

The oxidation-reduction potentials of the two c-type hemes of Pseudomonas aeruginosa cytochrome c peroxidase (ferrocytochrome c:hydrogen-peroxide oxidoreductase EC 1.11.1.5) have been determined and found to be widely different, about +320 and -330 mV, respectively. The EPR spectrum at temperatures below 77 K reveals only low-spin signals (gz 3.24 and 2.93), whereas optical spectra at room temperature indicate the presence of one high-spin and one low-spin heme in the enzyme. Optical absorption spectra of both resting and half-reduced enzyme at 77 K lack features of a high-spin compound. It is concluded that the heme ligand arrangement changes on cooling from 298 to 77 K with a concomitant change in the spin state. The active form of the peroxidase is the half-reduced enzyme, in which one heme is in the ferrous and the other in the ferric state (low-spin below 77 K with gz 2.84). Reaction of the half-reduced enzyme with hydrogen peroxide forms Compound I with the hemes predominantly in the ferric (gz 3.15) and the ferryl states. Compound I has a half-life of several seconds and is converted into Compound II apparently having a ferric-ferric structure, characterized by an EPR peak at g 3.6 with unusual temperature and relaxation behavior. Rapid-freeze experiments showed that Compound II is formed in a one-electron reduction of Compound I. The rates of formation of both compounds are consistent with the notion that they are involved in the catalytic cycle.     

In vitro cleavage specificity of the adenovirus type 2 proteinase

Two in vitro proteinase assay systems were developed and used to study the peptide bond specificity and substrate specificity of the adenovirus endoproteinase. Five adenovirus precursor proteins (PVI, PVII, PVIII, 87K, 11K), all found in the virion of the ts1 mutant grown at the nonpermissive temperature, were digested by the proteinase. All, except 11K, were cleaved to their mature counterparts. Some of the proteins, particularly the 87K terminal protein, were processed via cleavage intermediates similar to those found in vivo. The data suggest that the proteinase specifically hydrolyses Gly-Ala bonds. The high specificity for the natural substrates and the failure to cleave foreign proteins suggest that cleavage activity is determined not only by primary sequence but also by other physical features of the substrate. Enzyme activity was inhibited by diisopropylfluorophosphate, showing that it is a serine proteinase.     

The comparison of seed protein patterns within the genusArachis by polyacrylamide gel electrophoresis

The seed protein patterns of 12Arachis species were compared by polyacrylamide gel electrophoresis (PAGE), similarities between patterns were measured by the Jaccard index. Results obtained confirm the close relationships established between members of the genus on morphological grounds and support the more recent classification schemes.A. villosa andA. correntina could well be regarded as distinct species on grounds of protein differences whileA. macedoi andA. villosulicarpa (although members of the same section, Extranervosae) show considerable differentiation of their protein patterns. Surprisingly, the formA. ×batizogaea showed less similarity in protein pattern to those of its parental species than might have been expected. The principle value of seed protein pattern data appears to be in distinguishing species within sections.     

Electro-optical measurements on aqueous suspension of purple membrane from Halobacterium halobium

The permanent dipole moment, polarizability, and the retinal angle of Halobacterium halobium purple membranes were determined at different pH values. All of the parameters have a maximum between pH 5 and 6. There is a reversal in the direction of the permanent dipole moment near pH 5. The value of permanent dipole moment was determined to be 60 D/protein at pH 6.6, and the value obtained for polarizability was 3 X 10(-28) Fm2/membrane fragment. The retinal angle of all-trans retinal was 0.8 degrees smaller than that of the 13-cis conformation.     

Reaction of organocuprate reagents with protected 1,2-anhydro sugars. Stereocontrolled synthesis of 2-deoxy-C-glycosyl compounds

The reaction of protected 1,2-anhydro-α-d-gluco- and β-d-manno-pyranoses with alkyl and phenyl organocuprates afforded the corresponding C-glycosyl compounds in acceptable to high yield. Complete stereocontrol was obtained, leading respectively to the β-d or the α-d anomer. With the perbenzylated manno derivative, deoxygenation at C-2 was achieved in high yield, affording 2-deoxy-α-d-C-glycosyl compounds.     

New C-nucleoside analogs by dehydration of 1-benzyl-4,5,6,7-tetrahydro-6,6-dimethyl-2-(d-galacto-pentitol-1-yl)-indol-4-one

The reaction between 2-(benzylamino)-2-deoxy-d-glycero-l-gluco-heptose and 5,5-dimethyl-1,3-cyclohexanedione yields 1-benzyl-4,5,6,7-tetrahydro-6,6-dimethyl-2-(d-galacto-pentitol-1-yl)-indol-4-one (2). Acid-catalyzed, intramolecular dehydration of 2 under kinetically controlled conditions gives 1-benzyl-4,5,6,7-tetrahydro-2-α-d-lyxofuranosyl-6,6-dimethylindol-4-one; the anomeric configuration of this compound is only suggested. When the dehydration reaction is conducted under thermodynamically controlled conditions, it produces a 1:1 mixture of the α- and β-d-lyxopyranosyl compounds. The structures of the new compounds were elucidated by chemical and physical methods.