Reduction of the bis-pilocarpate-haemin complex at pH greater than or equal to 10 involves the simultaneous uptake of an electron by the Fe(III) ion and a proton by the pendant alkoxide group of an axial ligand. This provides a protein-free model for reactions such as the proton-coupled reduction of cytochromes which involve cooperative Coulombic interaction between two non-bonded sites. 相似文献
Wood samples, infested by fungi during storage, were shown to contain, besides the known 5-methyl-mellein, additional (3R)-8-hydroxy-3-methyl-3,4-dihydroisocoumarins substituted by 7-methyl, 5-formyl, 5-carboxy, 5-hydroxy, 5-methoxy, 6-methoxy-5-methyl and 6,7-dimethoxy-5-methyl groups, as well as 6-formyl-7-hydroxy-5-methoxy-4-methylphthalide. Several 2-methylchromanones were synthesized in order to show that this class of compounds can be distinguished from 3-methyl-3,4-dihydroisocoumarins by MS. 相似文献
The ammonification rates in surficial sediments of the Marica lagoon (Rio de Janeiro, Brazil) were estimated using two methods:
(1)
A direct evaluation of the ammonia productivity in sediments by means of an incubation procedure: the ammonia production rate is deduced from the difference in the ammonia concentrations in interstitial waters which were extracted directly after sampling and after incubation from two samples collected at the same point.
(2)
Since ammonia results essentially from the destruction of organic nitrogen, the ammonia productivity will be obtained by evaluating the nitrogen destruction rate: the amount of organic N mineralized is assumed to correspond to NH
inf4sup+
produced. The organic N destruction rate can be calculated by means of the matter balance equation provided the organic nitrogen profile and the sediment accumulation rate are known.
The sedimentation rate, evaluated by means of the 210Pb method, differed in various areas of the lagoon. It was 0.35 cm y–1 in the open area of the lagoon (at 1.6 m in water depth), near the mouth of the Mombuca river (site M2); and 0.27 to 0.28 cm y–1 at 1.6 to 1.7 m at a greater distance of the river mouth (site M4). In a confined part of the lagoon (Z1), surrounded by reeds (Typha dominguensis), the rate is lower: 1 to 1.4 mm y–1 in the upper level (from 0 to 4 cm) where the organic matter amount reaches 60 to 80% (dry w.), and 1.1 to 1.2 mm y–1 deeper (below 5 cm) where organic matter corresponds to less than 40% of the sediment. 相似文献
The aquatic fungus Blastocladiella emersonii provides a system for studying the regulation of expression of regulatory (R) and catalytic (C) subunits of cAMP-dependent protein kinase (PKA). Blastocladiella cells contain a single PKA with properties very similar to type II kinases of mammalian tissues. During development cAMP-dependent protein kinase activity and its associated cAMP-binding activity change drastically. We have previously shown that the increase in cAMP-binding activity during sporulation is due to de novo synthesis of R subunit and to an increase in the translatable mRNA coding for R (Marques et al., Eur. J. Biochem. 178, 803, 1989). In the present work we have continued these studies to investigate the mechanism by which the changes in the level of kinase activity take place. The C subunit of Blastocladiella has been purified; antiserum has been raised against it and used to determine amounts of C subunit throughout the fungus' life cycle. A sharp increase in C subunit content occurs during sporulation and peaks at the zoospore stage. Northern blot analyses, using Blastocladiella C and R cDNA probes, have shown that the levels of C and R mRNAs parallel their intracellular protein concentrations. These results indicate a coordinate pretranslational control for C and R subunit expression during differentiation in Blastocladiella. 相似文献
Summary Four siblings with the autosomal recessive Roberts syndrome are reported, and we discuss the phenotypic overlap of this syndrome with other similar radial, aplasia syndromes. 相似文献
Ascorbate oxidase is present in homogenates of the flesh of Cucurbita maxima fruits. Its activity is independent of ascorbate concentration over th 相似文献
Parkinson’s disease (PD) signs and symptoms regularly include tremor. Interestingly, the nucleoside guanosine (GUO) has already proven to be effective in reducing reserpine-induced tremulous jaw movements (TJMs) in rodent models, thus becoming a promising antiparkinsonian drug. Here, we aimed at revealing the mechanism behind GUO antiparkinsonian efficacy by assessing the role of adenosine A1 and A2A receptors (A1R and A2AR) on GUO-mediated anti-tremor effects in the reserpinized mouse model of PD. Reserpinized mice showed elevated reactive oxygen species (ROS) production and cellular membrane damage in striatal slices assessed ex vivo and GUO treatment reversed ROS production. Interestingly, while the simultaneous administration of sub-effective doses of GUO (5 mg/kg) and SCH58261 (0.01 mg/kg), an A2AR antagonist, precluded reserpine-induced TJMs, these were ineffective on reverting ROS production in ex vivo experiments. Importantly, GUO was able to reduce TJM and ROS production in reserpinized mouse lacking the A2AR, thus suggesting an A2AR-independent mechanism of GUO-mediated effects. Conversely, the administration of DPCPX (0.75 mg/kg), an A1R antagonist, completely abolished both GUO-mediated anti-tremor effects and blockade of ROS production. Overall, these results indicated that GUO anti-tremor and antioxidant effects in reserpinized mice were A1R dependent but A2AR independent, thus suggesting a differential participation of adenosine receptors in GUO-mediated effects.
Bioprocess and Biosystems Engineering - Unfortunately, in the “How to Cite as” section, the given and the family name of the author was incorrectly published, the correct name is... 相似文献