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Fourteen lichens, 10 green algal lichens and four cyanolichens, as well as a cyanobacterium emitted significant quantities of H2S (0.01–0.04 pmol g dw–1 s–1) and DMS (0.005–0.025 pmol g dw–1 s–1) but were sinks for COS (0.015–0.14 pmol g dw–1 s–1). In contrast, exchange of CH3SH and CS2 were sporatic and inconsistent. Although some interspecific variation occurred for the first three gases, exchange rates were relatively uniform and were not influenced by irradiance conditions. In contrast to DMS and H2S emission, COS uptake was strongly influenced by degree of thallus hydration. Because lichen dominated systems cover extensive terrestrial habitats, COS uptake is potentially important in the world's sulfur budget. 相似文献
4.
Kan Shida Kotaro Takamizawa Masato Nagaoka Takao Tsuji Toshiaki Osawa 《Microbiology and immunology》1994,38(4):273-279
The binding of Escherichia coli heat-labile enterotoxin (LT) type I to glycosylated proteins with lactose (Galβ1-4Glc) by amino carbonyl reaction was studied by the Western blot assay and by the microtiter well binding assay. LT bound to a lactose-α-lactalbumin amino carbonyl product (Lac-LA), whereas cholera toxin did not. The binding ability of Lac-LA was abolished by β-galactosidase treatment, indicating that the terminal galactose is essential for the binding of LT. The binding of LT to Lac-LA was inhibited by galactose and lactose, and most effectively inhibited by lactulose (Galβ1-4Fru), which is a structural analog of the Amadori rearrangement product of the amino carbonyl reaction between lactose and an ε-amino group of a lysine residue (lactuloselysine). The results suggest that LT recognizes the portion of lactuloselysine in Lac-LA. LT also bound to a melibiose (Galα1-6Glc)-α-lactalbumin amino carbonyl product (Mel-LA), but the binding ability of Mel-LA was weaker than that of Lac-LA, suggesting that the β1-4 linked terminal galactose is dispensable but preferable for the binding. Furthermore, LT bound to the amino carbonyl products of lactose with β-lactoglobulin, caseins, bovine serum albumin, and ovalbumin. These results indicate that LT binds to the amino carbonyl products between proteins and sugars containing the terminal galactose, such as lactose. 相似文献
5.
Membrane potential of Thermoplasma acidophila. 总被引:5,自引:0,他引:5
6.
Nicotinamide nucleotide transhydrogenase from beef heart mitochondria was purified to homogeneity and characterized. The enzyme is devoid of other respiratory chain activities as well as flavin. Reduction of NAD+ by NADPH catalyzed by reconstituted transhydrogenase generates an uncoupler-sensitive uptake of lipophilic anions, whereas the rate of reduction of NAD+ by NADPH is enhanced about 13 fold by uncouplers. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate reveales that the protein consists of a single polypeptide of a molecular weight of 97,000. 相似文献
7.
The role of oxidoreductases in reduction of carbonyl compounds was investigated by application of zymogram techniques. Eight bands were observed using ethanol with nicotinamide adenine dinucleotide (NAD) as coenzyme. Bands observed with lactic acid and (R)-(-)-phenyl-1,2-ethanediol with nicotinamide adenine dinucleotide phosphate (NADP) had similar R(m) values. 2-Hydroxyvalerate and malate manifested bands having similar R(m) values and were active with both NAD and NADP. Based on their structural similarity and identical R(m) values, oxidation of 1,4-cyclooctanediol (band #2) and cis-1,5-cyclooctanediol may be due to a common enzyme. The PAGE-zymogram technique may be used on a preparative scale to facilitate purification and full characterization on the observed stained bands. 相似文献
8.
Hajime Tokuda Tsutomu Unemoto 《Biochemical and biophysical research communications》1981,102(1):265-271
The membrane potential generated at pH 8.5 by K+-depleted and Na+-loaded is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na+-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na+ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na+-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na+ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na+ chemical gradient. 相似文献
9.
Relationships among several of the ion movements associated with the acrosome reaction of S. purpuratus were investigated. Egg jelly initiates 45Ca2+ and 22Na+ uptake, and K+ and H+ efflux. H+ efflux and 22Na+ uptake occur with approximately equivalent stoichiometries as rapidly as the appearance of acrosomal rods, perhaps reflecting a linked process. Most K+ loss, as measured either by 42K+ efflux or K+-ion-selective electrodes, occurs after the acrosome reaction is complete. Since an elevation of seawater K+ (from 10 to 15 mM) or the addition of 0.5 mM tetraethylammonium (TEA), an inhibitor of K+ channels, inhibits the acrosome reaction half-maximally, K+ movements or alterations of K+-dependent membrane potentials may regulate the triggering by jelly. Most, but not all, of the 45Ca2+ influx is inhibited with a mixture of 10 μM FCCP, 1 mM CN?, and 2 μg/ml oligomycin, suggesting that the mitochondria store most of the Ca2+. The extracellular Na+ concentration affects Ca2+ fluxes: sperm placed into 5 mM Na+ seawater have enhanced 45Ca2+ uptake, but do not undergo the acrosome reaction, unless 30 mM Na+ is also added. Low Na+ concentrations lead to spontaneous triggering, by allowing for both Ca2+ influx and Na+-dependent H+ efflux. At least one early Ca2+ requirement precedes the Na+ and H+ movements, as inferred from attempts at reversing the inhibitors of jelly induction of the acrosome reaction. When sperm are incubated with jelly in the absence of Ca2+, then washed and incubated with jelly in the presence of Ca2+, the acrosome reaction is triggered only upon the second incubation. However, when sperm are mixed with jelly in the presence of the other inhibitors (verapamil, TEA, 5 mM Na+ seawater, low pH, or elevated K+), they are altered so that even upon subsequent washing, jelly-mediated triggering is no longer possible. This suggests the existence of an intermediate state in the reaction pathway, that follows an event for which Ca2+ is required, but that precedes the Na+ and H+ movements, which are inhibited by all inhibitors of the acrosome reaction. These data are used to develop a partial sequence of ionic changes associated with the triggering mechanism. 相似文献
10.
U. Schreiber 《BBA》1980,591(2):361-371
Phycobilin fluorescence of Anacystis nidulans grown at 28°C increases substantially upon cooling below 10°C. A maximal increase is found around ?5°C and amounts to 300%, with almost complete reversibility upon re-warming. Illumination with actinic light leads to considerable stimulation of the cold-induced phycobilin fluorescence increase. Analysis of the light stimulation phenomenon reveals: (1) Actinic illumination shifts the fluorescence-temperature characteristic by about 3°C upwards on the T-axis. At temperatures below 5°C the light stimulating effect becomes smaller again and fluorescence-temperature characteristics measured at high and low light intensity converge around ?5°C. (2) In the 13-8°C region a large (up to 100%) light-induced phycobilin fluorescence increase is observed, while only negligible changes occur in the dark. (3) 3-(3,4-Dichlorophenyl)-1,1-dimethyl urea (DCMU) as well as uncouplers inhibit the light stimulation, which hence depends on coupled electron transport.In agreement with previous work (Schreiber, U. (1979) FEBS Lett. 107, 4–9) it is concluded that illumination enhances cold-induced phycobilisome detachment by increasing the net negative charge at the outer surface of the thylakoid membrane. The possible role of a fluid → ordered transition of membrane lipids (Murata, N. and Fork, D.C. (1975) Plant Physiol. 56, 791–796) is discussed. 相似文献