Guaraná (Paullinia cupana) as a commercial crop in Brazilian Amazonia

Guaraná (Paullinia cupana) is a woody vine or sprawling shrub native to the central Amazon Basin. The seeds are commercially produced on some 6,000 ha in the state of Amazonas near Manaus. The principal article of commerce is an amber-colored, carbonated soft drink. It is also widely used as a high caffeine stimulant and in local medicines. The plant is monoecious and is damaged by a number of diseases, the most severe being anthracnose. Prospects are excellent for greatly expanded international markets.     

Characteristics of alcohol/polyol dehydrogenases. The zinc-containing long-chain alcohol dehydrogenases

Sixteen characterized alcohol dehydrogenases and one sorbitol dehydrogenase have been aligned. The proteins represent two formally different enzyme activities (EC 1.1.1.1 and EC 1.1.1.14), three different types of molecule (dimeric alcohol dehydrogenase, tetrameric alcohol dehydrogenase, tetrameric sorbitol dehydrogenase), metalloproteins with different zinc contents (1 or 2 atoms per subunit), and polypeptide chains from different kingdoms and orders (mammals, higher plants, fungus, yeasts). Present comparisons utilizing all 17 forms reveal extensive variations in alcohol dehydrogenase, but with evolutionary changes that are of the same order in different branches and at different times. They emphasize the general importance of particular residues, suggesting related overall functional constraints in the molecules. The comparisons also define a few coincidences between intron positions in the genes and gap positions in the gene products. Only 22 residues are strictly conserved; half of these are Gly, and most of the remaining ones are Pro or acidic residues. No basic residue, no straight-chain hydrophobic residues, no aromatic residues, and essentially no branched-chain or polar neutral residues are invariable. Tentative consensus sequences were calculated, defining 13 additional residues likely to be typical of but not invariant among the alcohol dehydrogenases. These show a predominance of Val, charged residues, and Gly. Combined, the comparisons, which are particularly relevant to the data base for protein engineering, illustrate the requirements for functionally important binding interactions, and the extent of space restrictions in proteins with related overall conformations and functions.     

哈巴德布鲁克生态系统（H. B. E.）及其五号流域（W-5）研究

一、前言哈巴德布鲁克实验林(Hubbard Brook Experimental Forest)位于美国东北部新罕布什尔州中部的白山国家森林中。该地区位于典型温带湿润气候区内,年平均降水量为129.5cm,全年月平均降水量变化不大,冬雪夏雨。蒸发蒸腾量以每年6—9月为最大(Likens等,1977;Bormann等,1979)。该实验林为北美温带落叶阔叶林,属红果云杉(Picea rubens)-阔叶林。Hubbard Brook Ecosystem Study(HBES)是开始最     

Oxidation of Ferrous Iron and Elemental Sulfur by Thiobacillus ferrooxidans

The oxidation of ferrous iron and elemental sulfur by Thiobacillus ferrooxidans that was absorbed and unabsorbed onto the surface of sulfur prills was studied. Unadsorbed sulfur-grown cells oxidized ferrous iron at a rate that was 3 to 7 times slower than that of ferrous iron-grown cells, but sulfur-grown cells were able to reach the oxidation rate of the ferrous iron-adapted cells after only 1.5 generations in a medium containing ferrous iron. Bacteria that were adsorbed to sulfur prills oxidized ferrous iron at a rate similar to that of unadsorbed sulfur-grown bacteria. They also showed the enhancement of ferrous iron oxidation activity in the presence of ferrous iron, even though sulfur continued to be available to the bacteria in this case. An increase in the level of rusticyanin together with the enhancement of the ferrous iron oxidation rate were observed in both sulfur-adsorbed and unadsorbed cells. On the other hand, sulfur oxidation by the adsorbed bacteria was not affected by the presence of ferrous iron in the medium. When bacteria that were adsorbed to sulfur prills were grown at a higher pH (ca. 2.5) in the presence of ferrous iron, they rapidly lost both ferrous iron and sulfur oxidation capacities and became inactive, apparently because of the deposition of a jarosite-like precipitate onto the surface to which they were attached.     

Purification and Kinetic Mechanism of Human Brain Soluble Catechol-O-Methyltransferase

The soluble form of human brain catechol-O-methyltransferase (EC 2.1.1.6, COMT) has been purified approximately 4,000-fold from a 250,000 X g supernatant solution. The purified enzyme exhibits a molecular weight near 27,500 and a pI value equal to approximately pH 5.0. Initial velocity and product inhibition studies are consistent with an ordered reaction mechanism for soluble COMT. Tropolone, a dead-end inhibitor, exhibited a competitive pattern of inhibition when dopamine (DA) was the varied substrate and an uncompetitive pattern when S-adenosyl-L-methionine (SAM) was the varied substrate. These observations strongly suggest that the soluble form of COMT from human brain catalyzes the O-methylation of catecholamines via an ordered reaction mechanism in which SAM is the leading substrate. Since the membrane-bound form of COMT catalyzes the O-methylation of catecholamines through an identical reaction mechanism, these data provide further evidence that two forms of COMT, while being localized in distinct subcellular compartments, are quite similar in their molecular structure.     

Characterization of Membrane-Bound and Soluble Catechol-O-Methyltransferase from Human Frontal Cortex

Abstract: Catechol- O -methyltransferase (COMT; E.C. 2.1.1.6) from human frontal cortex occurs in both a soluble and membrane-bound form. Attempts to solubilize the membrane-bound transferase by repeated washing or by extraction into solutions of high ionic strength were unsuccessful. The finding that Triton X-100 was capable of solubilizing membrane-bound COMT suggested that the membrane-bound transferase is an integral membrane protein. The membrane-bound and soluble enzymes did not differ in their requirements for magnesium ions or in their pH-activity profiles; both enzymes showed an optimum near pH 8.0 when assayed in phosphate buffer. In addition, the two enzymes did not differ in the degree of inhibition caused by CaCl₂, both enzymes displaying 65% inhibition at 2.5 m M CaCl₂. The competitive inhibitors tropolone and nordihydroguaiaretic acid displayed K _i values for the membrane-bound transferase five- to 10-fold lower than those observed for the soluble transferase. Solubilization of membrane-bound COMT in Triton X-100 resulted in an increase in the apparent K _m value of the membrane-bound transferase for dopamine. The increase in K _m appeared to be due to apparent competitive inhibition by Triton X-100 and reached a limiting value of approximately 80 μM. These results confirm that membrane-bound COMT is an integral membrane protein that may be structurally distinct from soluble COMT.     

Yeasts in molecular biology. Spheroplast preparation withCanadida utilis,Schizosaccharomyces pombe andSaccharomyces cerevisiae

Efficient preparation of spheroplasts fromCandida utilis, Saccharomyces cerevisiae, andSchizosaccharomyces pombe, using a purified mixture of enzymes fromTrichoderma harzianum, is described. Limitations of other methods, and differences between yeasts are demonstrated.     

Kidney transplantation in Canada, 1981-84.

The Canadian Renal Failure Register was established in 1980. Data have been collected annually for all Canadian patients in whom irreversible kidney failure developed and who required dialysis or transplantation. The authors present actuarial patient and graft survival rates for 1981-84. In 1984, patients with a functioning renal graft accounted for 43.9% of the patients with end-stage renal disease. The number of transplants performed increased from 482 in 1981 to 662 in 1984; however, 1,022 patients undergoing dialysis (25.2%) were on an active waiting list for a transplant at the end of 1984. Greater effort is needed to increase the transplantation rate.     

Interaction of medroxyprogesterone acetate with cytosol androgen receptors in the rat hypothalamus and pituitary

The binding of medroxyprogesterone acetate (MPA) with cytosol androgen receptors from rat pituitary and hypothalamus was studied. The pituitary and hypothalamic cytosol androgen receptors from adult castrated female rats were in vitro labeled using 3H natural (testosterone (T) and 5 alpha-dihydrotestosterone (DHT] and [3H]synthetic (methyltrienolone) androgens as radioligands. The [3H]androgen-receptor complexes sedimented with a coefficient of 8S in linear sucrose gradients. When incubated with an excess of radioinert MPA, specific binding was abolished indicating interaction of MPA with androgen receptors. Furthermore specific [3H]MPA-androgen cytosol receptor complexes could be identified in these neuroendocrine tissues when a post-gradient receptor labeling technique was used in the absence or presence of radioinert MPA, DHT, and triamcinolone acetonide. A study of binding kinetics disclosed that the equilibrium dissociation constant and saturation binding capacity for the MPA binder, were similar to those exhibited by DHT binding to androgen receptors in both studied tissues under identical experimental conditions. The overall results were interpreted as demonstrating that MPA interacts with cytosol steroid receptors other than those of progesterone in the rat hypothalamus and anterior pituitary. The data are consistent with MPA binding to androgen receptors.