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1.
《Bioscience, biotechnology, and biochemistry》2013,77(8):2224-2227
We isolated a cDNA clone with homology to known desaturase genes from Oblongichytrium sp., recently classified as a new genus of thraustochytrids (Labyrinthulomycetes), and found that it encoded Δ5-desaturase by its heterologous expression in yeast. The enzyme had higher activity toward 20:4n-3 than 20:3n-6, indicating that this Δ5-desaturase can be used in the production of n-3 polyunsaturated fatty acids in transgenic organisms. 相似文献
2.
The isolation of a brain peptide identical to the intestinal peptide PHI (peptide HI) is described. The peptide was isolated from porcine brain extract using a chemical assay method based on its C-terminal isoleucine amide structure. The complete amino acid sequence of the peptide was found to be: His-Ala-Asp-Gly-Val-Phe-Thr-Ser-Asp-Phe-Ser-Arg-Leu-Leu-Gly-Gln-Leu-Ser-Ala- Lys-Lys-Tyr-Leu-Glu-Ser-Leu-Ile-NH2. This sequence is identical to the intestinal peptide thus demonstrating PHI to be a brain-gut peptide. The role of PHI in the central nervous system as a neurotransmitter or neuromodulator is discussed. 相似文献
3.
A chemiosmotic molecular mechanism for proton-translocating adenosine triphosphatases 总被引:16,自引:0,他引:16
P Mitchell 《FEBS letters》1974,43(2):189-194
4.
Radiocarbon (14C) has been used to date carbon-rich objects in Earth science, archeology, and history since the 1940s. New methods, using spikes in 14C caused by solar proton events, can be used to annually date wood when crossdating is not possible, such as when sample size is low, samples are floating in time, or external disturbances lead to insecure dates. Here, we use a spike in radiocarbon during a solar energetic particle (SEP) event in 774/775 CE to confirm crossdating of a poorly-replicated King Billy pine (Athrotaxis selaginoides) chronology. Low sample depth between 1498 and 1523 CE (two trees) prevented confident dating of the early period of the chronology. Three core samples with strong correlation with the master chronology that likely included the 774/775 CE Miyake SEP event were identified for radiocarbon isotope analysis. We sectioned segments centered on the estimated 774/775 CE date and then isolated the holocellulose in each sample. Samples were sent to an accelerator mass spectrometry (AMS) for radiocarbon measurements. The AMS data confirmed the crossdating accuracy of the tree ring series and reinforces the applicability of this technique to anchor poorly dated tree ring series in time. In addition, we found sample processing with a microtome proved superior for holocellulose extractions and yielded more accurate 14C measurements. We recommend sampling with a microtome, processing at least three samples per year, and including sample masses greater than 100 ug C to confirm dating using radiocarbon spikes. 相似文献
5.
Electron transport, phosphorylation and internal proton concentration were measured in illuminated spinach chloroplast thylakoid membranes under a number of conditions. Regardless of the procedure used to vary these parameters, the data fit a simple chemiosmotic model. Protons from Photosystem II did not appear to be utilized differently from those derived from Photosystem I. The maximal phosphorylation efficiency () for photophosphorylation in washed thylakoids under oxidizing conditions is likely to be . This value is consistent with a proton-to-electron-pair ratio of 4 for electron flow through both photosystems and a proton-to-ATP ratio of 3 for the chloroplast proton-ATPase. 相似文献
6.
Expression of calf prochymosin in Saccharomyces cerevisiae 总被引:18,自引:0,他引:18
7.
8.
Mg2+ restores membrane potential in rat liver mitochondria deenergized by Ca2+ and phosphate movements 总被引:1,自引:0,他引:1
Cellular ornithine biosynthesis could be expected to play a significant role in putrescine formation and hence in growth. Two enzymes are involved in ornithine biosynthesis: arginase and transamidinase. These enzyme activities were studied in two human melanoma cell lines differing in their Km of diamine oxidase for putrescine and in their tumorigenicity in nude mice. Arginase activity accounts for the majority of ornithine formed in the highly tumorigenic cell line, while the majority of ornithine is derived from transamidinase action in the poorly tumorigenic cell line, with concomitant formation of methyl guanidine, a potent inhibitor of diamine oxidase. 相似文献
9.
Spondyloepiphyseal dysplasia, chondroitin sulfate type: a possible defect of PAPS--chondroitin sulfate sulfotransferase in humans 总被引:4,自引:0,他引:4
Paulo A.S. Mourão Setuko Kato Patricia V. Donnelly 《Biochemical and biophysical research communications》1981,98(2):388-396
Four patients with an unusual form of spondyloepiphyseal dysplasia excreted in the urine undersulfated chondroitin 6-sulfate (Biochem. Med. , 415–423, 1973). The sera of these patients show a low activity of PAPS — chondroitin sulfate sulfotransferase, while the undersulfated chondroitin sulfate present in their urine is a much better acceptor of than standard chondroitin sulfate when they are incubated with []PAPS and normal sulfotransferases. These results suggest that in these patients the skeletal lesions are secondary to a defect in the synthesis of chondroitin sulfate involving specifically the sulfotransferase activity. 相似文献
10.
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