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1.
Background
Chow and Liu showed that the maximum likelihood tree for multivariate discrete distributions may be found using a maximum weight spanning tree algorithm, for example Kruskal's algorithm. The efficiency of the algorithm makes it tractable for high-dimensional problems. 相似文献2.
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Mark L. Paddock Scott H. Rongey Edward C. Abresch George Feher Melvin Y. Okamura 《Photosynthesis research》1988,17(1-2):75-96
Many herbicides that inhibit photosynthesis in plants also inhibit photosynthesis in bacteria. We have isolated three mutants of the photosynthetic bacterium Rhodobacter sphaeroides that were selected for increased resistance to the herbicide terbutryne. All three mutants also showed increased resistance to the known electron transfer inhibitor o-phenanthroline. The primary structures of the mutants were determined by recombinant DNA techniques. All mutations were located on the gene coding for the L-subunit resulting in these changes Ile229 Met, Ser223 Pro and Tyr222 Gly. The mutations of Ser223 is analogous to the mutation of Ser264 in the D1 subunit of photosystem II in green plants, strengthening the functional analogy between D1 and the bacterial L-subunit. The changed amino acids of the mutant strains form part of the binding pocket for the secondary quinone, Q
b
. This is consistent with the idea that the herbicides are competitive inhibitors for the Q
b
binding site. The reaction centers of the mutants were characterized with respect to electron transfer rates, inhibition constants of terbutryne and o-phenanthroline, and binding constants of the quinone UQ0 and the inhibitors. By correlating these results with the three-dimensional structure obtained from x-ray analysis by Allen et al. (1987a, 1987b), the likely positions of o-phenanthroline and terbutryne were deduced. These correspond to the positions deduced by Michel et al. (1986a) for Rhodopseudomonas viridis.Abbreviations ATP
adenosine 5-triphosphate
- Bchl
bacteriochlorophyll
- Bphe
bacteriopheophytin
- bp
basepair
- cyt c2+
reduced form of cytochrome c
- DEAE
diethylami-noethyl
- EDTA
ethylenediamine tetraacetic acid
- Fe2+
non-heme iron atom
- LDAO
lauryl dimethylamine oxide
- Pipes
piperazine-N,N-bis-2-ethane-sulfonic acid
- PSII
photosystem II
- RC
reaction center
- SDS
sodium dodecylsulfate
- Tris
tris(hydroxy-methyl)aminomethane
- UQ0
2,3-dimethoxy-5-methyl benzoquinone
- UQ10
ubiquinone 50 相似文献
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R C Frankis M J Weise R M Nair G V Paddock 《Archives of biochemistry and biophysics》1985,238(1):178-186
The red blood cells of normal adult ducks contain two main hemoglobins. The most abundant type, HbA, comprises approximately 80% of the total, with the remaining 20% being made up of HbD. An attempt was made to determine whether during hemolytic anemia a special alpha globin chain (alpha s) replaces the alpha chain of HbA found in normal animals. This special stress alpha globin, whose existence has been seriously questioned, was originally postulated to explain the sequence discrepancies obtained between alpha chains of normal and anemic chickens and ducks. Using gel electrophoresis, isoelectric focusing, and HPLC peptide mapping techniques no qualitative differences between the alpha A globins of normal and anemic animals were found. The nature of the beta globin chains present in adult ducks has also never been rigorously established. In this work, a variety of techniques, including HPLC, gel electrophoresis, and microcolumn amino acid analysis, were used to examine the beta chains from each hemoglobin. Using these methods, no differences were found between the beta globin chains of the two hemoglobins. 相似文献
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Stephen W. Paddock 《BioEssays : news and reviews in molecular, cellular and developmental biology》1994,16(5):357-365
The laser scanning confocal microscope (LSCM) 1 LSCM: laser scanning confocal microscope; FISH: fluorescence in situ hybridisation; DiO6: 3,3′-dihexyloxacarbocyanine iodide; NBD-ceramide: 6-((N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-caproyl)sphingosine; DiO: 3,3′-dioctadecyloxacarbocyanine perchlorate; DiI: 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl-indocarbocyanine perchlorate; CCD: charge-coupled device; DIC: differential interference contrast; FURA2: (-(2-(5-carboxyoxazol-2-yl)-6-aminobenzofuran-5-oxy)-2-)2′-amino-5′-methylphenoxy)-ethane-N,N,N′,N′-tetraacetic acid, sodium salt);BCECF: 2′,7′-bis-(carboxyethyl)-5-(and-6-)-carboxyfluorescein;fluo-3: 1-(2-amino-5-(2,7-dichloro-6-hydroxy-3-oxo-3H-xanthen-9-yl)-2-(2′amino-5′-methylphenoxy)-ethane-N,N,N′,N′,-tetraacetic acid, ammonium salt; DAPI: 4′,6-diamidino-2-phenylindole, dihydrochloride; PET: positron emission tomogrophy; CT: computer-assisted tomogrophy; CiD: cubitus interruptus dominus; MRC: Medical Research Council; TOTO-1: benzothiazolium-4-quinolinium dimer; YOYO-1: benzoxazolium-4-quinolinium dimer; ex.: excitation wavelength; em.: emission wavelength. is now established as an invaluable tool in developmental biology for improved light microscope imaging of fluorescently labelled eggs, embryos and developing tissues. The universal application of the LSCM in biomedical research has stimulated improvements to the microscopes themselves and the synthesis of novel probes for imaging biological structures and physiological processes. Moreover the ability of the LSCM to produce an optical series in perfect register has made computer 3-D reconstruction and analysis of light microscope images a practical option. 相似文献
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