全文获取类型
收费全文 | 126篇 |
免费 | 4篇 |
国内免费 | 3篇 |
出版年
2023年 | 2篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有133条查询结果,搜索用时 265 毫秒
91.
Markus J. Br?cker Sebastian Schomburg Dirk W. Heinz Dieter Jahn Wolf-Dieter Schubert Jürgen Moser 《The Journal of biological chemistry》2010,285(35):27336-27345
During (bacterio)chlorophyll biosynthesis of many photosynthetically active organisms, dark operative protochlorophyllide oxidoreductase (DPOR) catalyzes the two-electron reduction of ring D of protochlorophyllide to form chlorophyllide. DPOR is composed of the subunits ChlL, ChlN, and ChlB. Homodimeric ChlL2 bearing an intersubunit [4Fe-4S] cluster is an ATP-dependent reductase transferring single electrons to the heterotetrameric (ChlN/ChlB)2 complex. The latter contains two intersubunit [4Fe-4S] clusters and two protochlorophyllide binding sites, respectively. Here we present the crystal structure of the catalytic (ChlN/ChlB)2 complex of DPOR from the cyanobacterium Thermosynechococcus elongatus at a resolution of 2.4 Å. Subunits ChlN and ChlB exhibit a related architecture of three subdomains each built around a central, parallel β-sheet surrounded by α-helices. The (ChlN/ChlB)2 crystal structure reveals a [4Fe-4S] cluster coordinated by an aspartate oxygen alongside three cysteine ligands. Two equivalent substrate binding sites enriched in aromatic residues for protochlorophyllide substrate binding are located at the interface of each ChlN/ChlB half-tetramer. The complete octameric (ChlN/ChlB)2(ChlL2)2 complex of DPOR was modeled based on the crystal structure and earlier functional studies. The electron transfer pathway via the various redox centers of DPOR to the substrate is proposed. 相似文献
92.
Martin Schliep Ben Crossett Robert D. Willows Min Chen 《The Journal of biological chemistry》2010,285(37):28450-28456
The cyanobacterium Acaryochloris marina was cultured in the presence of either H218O or 18O2, and the newly synthesized chlorophylls (Chl a and Chl d) were isolated using high performance liquid chromatography and analyzed by mass spectroscopy. In the presence of H218O, newly synthesized Chl a and d, both incorporated up to four isotopic 18O atoms. Time course H218O labeling experiments showed incorporation of isotopic 18O atoms originating from H218O into Chl a, with over 90% of Chl a 18O-labeled at 48 h. The incorporation of isotopic 18O atoms into Chl d upon incubation in H218O was slower compared with Chl a with ∼50% 18O-labeled Chl d at 115 h. The rapid turnover of newly synthesized Chl a suggested that Chl a is the direct biosynthetic precursor of Chl d. In the presence of 18O2 gas, one isotopic 18O atom was incorporated into Chl a with approximately the same kinetic incorporation rate observed in the H218O labeling experiment, reaching over 90% labeling intensity at 48 h. The incorporation of two isotopic 18O atoms derived from molecular oxygen (18O2) was observed in the extracted Chl d, and the percentage of double isotopic 18O-labeled Chl d increased in parallel with the decrease of non-isotopic-labeled Chl d. This clearly indicated that the oxygen atom in the C31-formyl group of Chl d is derived from dioxygen via an oxygenase-type reaction mechanism. 相似文献
93.
Aline P. Martins Nair S. Yokoya Maria Angela M. Carvalho Estela M. Plastino 《Journal of applied phycology》2008,20(5):767-773
Hypnea musciformis (Wulfen in Jacqu.) J.V. Lamour. is the main source for carrageenan production in Brazil and strains with selected characteristics
could improve the production of raw material. The effects of kinetin on growth rates, morphology, protein content, and concentrations
of pigments (chlorophyll a, phycoerythrin, phycocyanin, and allophycocyanin) were assessed in the wild strain (brown phenotype) and in the phycoerythrin-deficient
strain (green phenotype) of H. musciformis. Concentrations of kinetin ranging from 0 to 50 μM were tested in ASP 12-NTA synthetic medium with 10 μM nitrate (N-limited)
and 100 μM nitrate (N-saturated). In N-limited condition, kinetin stimulated growth rates of the phycoerythrin-deficient strain
and formation of lateral branches in both colour strains. Kinetin stimulated protein biosynthesis in both strains. However,
differences between both nitrogen conditions were significant only in the phycoerythrin-deficient strain. In the wild strain,
effects of kinetin on concentrations of phycobiliproteins were not significant in both nitrogen conditions, except for chlorophyll
content. However, the phycoerythrin-deficient strain showed an opposite response, and kinetin stimulated the phycobiliprotein
biosynthesis, with the highest concentrations of phycoerythrin in N-saturated medium, while the highest concentrations of
allophycocyanin and phycocyanin were observed in N-limited medium. These results indicate that the effects of kinetin on growth,
morphology, protein and phycobiliprotein contents are influenced by nitrogen availability, and the main nitrogen storage pools
in phycoerythrin-deficient strain of H. musciformis submitted to N-limited conditions were phycocyanin and allophycocianin, the biosynthesis of which was enhanced by kinetin. 相似文献
94.
Growth and pigment composition in the red alga <Emphasis Type="Italic">Halymenia floresii</Emphasis> cultured under different light qualities 总被引:1,自引:0,他引:1
José Luis Godínez-Ortega Pauli Snoeijs Daniel Robledo Yolanda Freile-Pelegrín Marianne Pedersén 《Journal of applied phycology》2008,20(3):253-260
Halymenia floresii is an edible species consumed in some Asian markets. In the Yucatan peninsula coast of Mexico, H. floresii dominates rocky substrata between 3 and 40 m where it grows up to 50 cm high. After analyzing the seasonal pattern of pigment
content on H. floresii, we evaluate if and how the spectral composition of light affects growth and pigment dynamics under laboratory cultivation.
Unialgal cultures were exposed to white, blue, red and green light in a 3-week experiment. Green light resulted in the highest
algal growth rates. Synthesis of chlorophyll a, α-carotene and lutein, but not of β-carotene, was induced by white or green light. Phycocyanin synthesis was stimulated by blue light and phycoerythrin synthesis
by blue or red light. Light quality treatments may be used to manipulate pigment composition in Halymenia floresii cultures. 相似文献
95.
Sorbus aucuparia and Sorbus aria as a Source of Antioxidant Phenolics,Tocopherols, and Pigments 下载免费PDF全文
Katarina P. Šavikin Gordana M. Zdunić Dijana B. Krstić‐Milošević Helena J. Šircelj Danijela D. Stešević Dejan S. Pljevljakušić 《化学与生物多样性》2017,14(12)
Due to its nutritive and medicinal properties, berries of some Sorbus species are used for the preparation of jams and jelly as well as in traditional medicine. On the other hand, their chemical composition is not much studied especially of those grown in Balkan Peninsula. We have analyzed individual phenolics, tocopherols, carotenoids and chlorophylls using HPLC in berries from Sorbus aucuparia and Sorbus aria collected in different localities in Serbia and Montenegro together with the amounts of total phenolics and proanthocyanidins as well as their radical scavenging activity against DPPH radical. Berries of S. aucuparia were richer source of polyphenolics in comparision with S. aria and, regardless the species and locality, caffeoylquinic acids such as neochlorogenic and chlorogenic acid were the most abundant compounds. Among analyzed tocopherols the most abundant in all samples was α‐tocopherol (0.48 – 19.85 μg/g dw) as it was β‐carotene among carotenoids (mean concentration of 0.98 μg/g dw in S. aucuparia and 0.40 μg/g dw in S. aria, respectively). Correlation between total phenolics and DPPH radical scavenging activity was noticed. Our study represents comprehensive report on chemical composition of S. aucuparia and S. aria which could contribute to a better understanding of their quality. 相似文献
96.
Microbial communities occur throughout the cryosphere in a diverse range of ice-dominated habitats including snow, sea ice, glaciers, permafrost, and ice clouds. In each of these environments, organisms must be capable of surviving freeze-thaw cycles, persistent low temperatures for growth, extremes of solar radiation, and prolonged dormancy. These constraints may have been especially important during global cooling events in the past, including the Precambrian glaciations. One analogue of these early Earth conditions is the thick, landfast sea ice that occurs today at certain locations in the Arctic and Antarctic. These ice shelves contain liquid water for a brief period each summer, and support luxuriant microbial mat communities. Our recent studies of these mats on the Markham Ice Shelf (Canadian high Arctic) by high performance liquid chromatography (HPLC) showed that they contain high concentrations of chlorophylls a and b, and several carotenoids notably lutein, echinenone and beta-carotene. The largest peaks in the HPLC chromatograms were two UV-screening compounds known to be produced by cyanobacteria, scytonemin, and its decomposition product scytonemin-red. Microscopic analyses of the mats showed that they were dominated by the chlorophyte genera cf. Chlorosarcinopsis, Pleurastrum, Palmellopsis, and Bracteococcus, and cyanobacteria of the genera Nostoc, Phormidium, Leptolyngbya, and Gloeocapsa. From point transects and localized sampling we estimated a total standing stock on this ice shelf of up to 11,200 tonnes of organic matter. These observations underscore the ability of microbial communities to flourish despite the severe constraints imposed by the cryo-ecosystem environment. 相似文献
97.
98.
The compounds reported from the slime molds (myxomycetes) species are described. Almost 100 natural compounds including their chemical structures and biological activities are described in this review article. Only metabolites with a well-defined structure are included. 相似文献
99.
Karen Helen Wiltshire Claus Geisler Friedhelm Schroeder Doris Krogmann 《Aquatic Ecology》1995,29(3-4):303-314
The pigment fingerprints, determined by HPLC, of suspended matter from different areas of the German Bight and from the Elbe Estuary are presented. These include areas with suspended matter concentrations varying between 10 mg l–1 in the deeper waters in the middle of the Bight and 150 mg l–1 in the Elbe mouth. Pigment data allows the identification of three groups of suspended matter (marine, turbidity zone and Elbe) for the numerous different locations. The changes in pigment concentrations in the suspended matter over tidal cycles are considered. The presence of pigments and pigment breakdown productsi.e. lutein and chlorophyllides is used to assess the possible condition of the phytoplankton present in the suspended matter. These pigment characteristics are compared with the loading of the heavy metals cadmium, copper, manganese, iron, zinc and lead in the particulate matter. It has been demonstrated that the pigments of the planktonic material can be used very effectively to identify different types of suspended matter and that the heavy metal loadings of the suspended matter were significantly correlated with chlorophyll-a. 相似文献
100.
Summary A resting cell system was developed for the biosynthesis of soluble red pigments byMonascus. The medium contains glucose, glycine, ZnSO4 and MnSO4 in pH 7.0 MOPS buffer containing cycloheximide to prevent protein synthesis. The linear production observed over a period of at least four h was due to de novo polyketide synthesis and biological methylation, as shown by inhibition with cerulenin, iodoacetamide and ethionine. Production was inhibited by carbonyl reagents and stimulated by pyridoxamine suggesting that the conversion of endogenous intracellular orange pigments to extracellular red pigments involves Schiff base intermediates and vitamin B6 a cofactor. The resting cell system was used to study the mode of action of nutritional effectors previously pinpointed by experiments with growing cells. The negative effects of high concentrations of phosphate and Mg++ are due to inhibition of pigment synthase action, not to repression or inactivation of these enzymes. The positive effects of trace metals, especially Zn++, are due to stimulation of growth and enzyme action, not to induction or stabilization of the synthases. 相似文献