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51.
Anna Fietta Guido Grandi Massimo Malcovati Gianna Valentini Vittorio Sgaramella Antonio G. Siccardi 《Plasmid》1981,6(1):78-85
Plasmids S-a and Rts1 suppress the galactose-sensitive phenotype of galE mutants of Escherichia coli K-12, giving rise to both galactose-fermenting and nonfermenting strains. Fermenting strains produce normal inducible UDP-galactose epimerase. Plasmids extracted from either a fermenting or a nonfermenting strain are indistinguishable when examined by either measurements of length of relaxed circular molecules by electron microscopy or electrophoretic pattern of restriction endonuclease digestion products. The phenomenon could be explained by reversible recombination between a plasmid-borne epimerase gene and homologous chromosomal sequences. 相似文献
52.
Rhodopseudomonas palustris cells, characterized by a lamellar type intracytoplasmic chromatophore membrane system after phototrophic growth, yielded a crude supernatant cell-free fraction (S-144) after ultracentrifugation which retained the contents of both the cell compartments. After thiosulfate-dependent growth, a protein system was isolated from S-144 which catalyzed the thiosulfate-linked reduction of an endogenous c-type cytochrome. — The colorless oxidoreductase protein, after purification to homogeneity, revealed a molecular weight of 93,000 and, after SDS treatment, a particle weight of 48,000. It was focused at an average pI of 5.45. Apparent K
m values for several substrates were in the M range. The electron acceptor for thiosulfate oxidation was found to be a cytochrome c from S-144. The homogeneous acceptor protein, at liquid nitrogen temperature, exhibited absorption maxima at 549.0, 518.5 and 418.0 nm, and shoulders at 525.5, 512.0 and 508.0 nm. Its molecular weight was found to be 17,000 (gel filtration) and 16,000 (SDS gel electrophoresis). It was characterized by a pI of 10.0. Its midpoint redox potential of E
m,7.0=+228 mV was determined by redox titrations and the value of +205 mV by spectrophotometric calculations.Abbreviations BSA
bovine serum albumin
- HiPIP
high potential nonheme iron protein
- IEF
isoclectric focusing
- SDS
dodecylsulfate, sodium salt
- Temed
N,N,N,N-tetramethylethylenediamine 相似文献
53.
The effect of phenols on the hydrolysis of substituted phenyl β-d-gluco- and β-d-xylo-pyranosides by β-d-glucosidase from Stachybotrys atra has been investigated. Depending on the glycon part of the substrate and on the phenol substituent, the hydrolysis is either inhibited or activated. With aryl β-d-xylopyranosides, transfer of the xylosyl residue to the phenol, with the formation of new phenyl β-d-xylopyranosides, is observed. With aryl β-d-glucopyranosides, such transfer does not occur when phenols are used as acceptors, but it does occur with anilines. A two-step mechanism, in which the first step is partially reversible, is proposed to explain these observations. A qualitative analysis of the various factors determining the overall effect of the phenol is given. 相似文献
54.
Mario Maggi Guido Fantoni Alessandro Peri Stefano Giannini Maria Luisa Brandi Claudio Orlando Mario Serio 《The Journal of steroid biochemistry and molecular biology》1991,40(4-6):481-491
Oxytocin (OT) and V1 vasopressin (VP) receptors are present simultaneously in several tissues, including the uterus. In myometrium these receptors mediate contractility, while in endometrium they mediate the release of other uterotonic substances as endothelin (ET). In rabbit myometrium, estrogens increase, while progesterone blunts neurohypophysial hormone receptors. However, the action of sex steroids on OT and V1 VP receptors differs in terms of the ED50 and maximal effect. Therefore, at parturition, only OT receptors show a dramatic rise, while V1 VP receptors do not change, suggesting a major role for OT in labor. ET is a potent stimulator of uterine activity acting through specific receptors present on myometrial cells. These receptors as well as the endometrial localization of ET are modulated by sex steroids, indicating that ET might represent a paracrine regulator of uterine activity. In humans, OT but not V1 VP receptors increase as pregnancy progresses, confirming the primary relevance of OT in timing delivery. 相似文献
55.
56.
Vittoria Nuti Ronchi Lucia Giorgetti Mariagrazia Tonelli Guido Martini 《Plant Cell, Tissue and Organ Culture》1992,30(2):107-114
Cytological analysis of different carrot cell lines in culture has shown various cytogenetic anomalies generating new levels of ploidy and novel chromosome numbers. Polyploidy may be considered a reservoir of variability that can be released in the form of distinct new segregants of different ploidy. Mechanisms alternative to mitosis (reductional grouping, prophase chromosome reduction) operate from a polyploid state (possibly reached by means of endopolyploidy, endomitosis, nuclear fusion, or restitution nuclei) to generate new levels of ploidy and novel chromosome numbers necessary for selection to operate in vitro. The segregational phenomena require chromosome recognition in haploid set complements and abnormal behaviour of mitoses; the resulting chromosome variability suggests that chromosomes are arranged, in the resting nuclei, in an orderly and predictable manner.The knowledge of the molecular events governing these mechanisms, and how to control them, would be of great help for future applications of plant cell culture. 相似文献
57.
Aren van Waarde Guido van den Thillart Fred Dobbe 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1982,147(1):53-59
Summary Changes in the concentrations of ammonia, glutamate, alanine, aspartate, -ketoglutarate, oxaloacetate and succinate were measured in freeze-clamped lateralred muscle, dorsal white muscle and liver, and in rapidly cooled blood of goldfish after 12 h of anoxia. Alanine accumulation, succinate accumulation and aspartate depletion are observed in all tissues examined; in the liver the concentrations of glutamate increase and those of ammonia decrease. The mass-action ratio of the glutamate-pyruvate transaminase-catalyzed reaction stays within one order of magnitude from thermodynamic equilibrium in the direction of alanine formation. The mass-action ratio of the glutamate-oxaloacetate transaminase reaction is far from equilibrium when measured oxaloacetate concentrations are used. When levels of free oxaloacetate are calculated from LDH and MDH equilibrium constants, the mass-action ratio of glutamate-oxaloacetate transamination is close to equilibrium in the direction of aspartate formation. Since neither alanine nor glutamate decreases, and since ammonia gradients suggest a continuous ammonia production in all tissues examined, anaerobic proteolysis is assumed. A possible coupling between amino acid catabolism and ethanol production is discussed.Abbreviations
ALA
alanine
-
ASP
aspartate
-
EDTA
ethylene diamine tetraacetate
-
FP
ox
oxidated flavoprotein
-
FP
red
reduced flavoprotein
-
FUM
fumarate
-
GLU
glutamate
-
GOT
glutamate oxaloacetate transaminase
-
GPT
glutamate pyruvate transaminase
-
IMP
inosine monophosphate
- KG
-ketoglutarate
-
LDH
lactate dehydrogenase
-
MAL
malate
-
MAR
mass action ratio
-
MDH
malate dehydrogenase
-
OAA
oxaloacetate
-
PYR
pyruvate
-
sAMP
adenylosuccinate
-
SDH
succinate dehydrogenase
-
SUCC
succinate 相似文献
58.
Guido Chelazzi Stefano Focardi 《Journal of experimental marine biology and ecology》1982,65(3):263-273
Zonal oscillations of Monodonta turbinata (Born) were monitored with an actographic device which precluded clustering behaviour. Unfed snails maintained their cyclic pattern of behaviour for up to 8 days under a light-dark cycle which simulated the natural one. Under constant conditions of light or dark, however, the snails ceased migration and occupied a zonal position typical of day and night, respectively. Experiments in diffuse light and with light from below the floor of the experimental tank showed that the downward migration of M. turbinata in the daytime depends on positive geotaxis combined with negative phototaxis whilst the upward migration at night depends on a negative geotaxis. This mechanism is similar to that described in other littoral molluscs. There was no evidence of an endogenous control of rhythmic zonal activity. 相似文献
59.
Herman L. De Pooter Patrick J. Dirinck Guido A. Willaert Niceas M. Schamp 《Phytochemistry》1981,20(9):2135-2138
The headspace of whole Golden Delicious apples treated with propionic acid vapour, was analysed by means of GC, after enrichment on Tenax GC, and its c 相似文献
60.