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91.
The reactivities of anionic nitroalkanes with 2-nitropropane dioxygenase of Hansenula mrakii, glucose oxidase of Aspergillus niger, and mammalian d-amino acid oxidase have been compared kinetically. 2-Nitropropane dioxygenase is 1200 and 4800 times more active with anionic 2-nitropropane than d-amino acid oxidase and glucose oxidase, respectively. The apparent Km values for anionic 2-nitropropane are as follows: 2-nitropropane dioxygenase, 1.61 mm; glucose oxidase, 16.7 mm; and d-amino acid oxidase, 11.1 mm. Anionic 2-nitropropane undergoes an oxygenase reaction with 2-nitropropane dioxygenase and glucose oxidase, and an oxidase reaction with d-amino acid oxidase. In contrast, anionic nitroethane is oxidized through an oxygenase reaction by 2-nitropropane dioxygenase, and through an oxidase reaction by glucose oxidase. All nitroalkane oxidations by these three flavoenzymes are inhibited by Cu and Zn-superoxide dismutase of bovine blood, Mn-superoxide dismutases of bacilli, Fe-superoxide dismutase of Serratia marcescens, and other scavengers such as cytochrome c and NADH, but are not affected by hydroxyl radical scavengers such as mannitol. None of the scavengers tested affected the inherent substrate oxidation by glucose oxidase and d-amino acid oxidase. Furthermore, the generation of in the oxidation of anionic 2-nitropropane by 2-nitropropane dioxygenase was revealed by ESR spectroscoy. The ESR spectrum of anionic 2-nitropropane plus 2-nitropropane dioxygenase shows signals at g1 = 2.007 and g11 = 2.051, which are characteristic of . The generated is a catalytically essential intermediate in the oxidation of anionic nitroalkanes by the enzymes. 相似文献
92.
Measurement of Stomatal Aperture by Digital Image Processing 总被引:2,自引:0,他引:2
We developed a new digital image processing technique for exactlymeasuring the degree of stomatal opening, that is, the ratioof the width to the maximum length of a stomatal pore, and thepore area. We applied this technique to evaluate responses toSO2 of neighboring stomata in a small region of an intact attachedleaf, with the following results:
- The pore region could be exactly extracted even when the originaldigital image was of poor quality. The standard errors in theevaluation of the pore area, the pore length, and the pore widthwere 10 µm2, 0.3 µm and 0.3 µm, respectively.
- A wide variety of responses to SO2 was found among neighboringstomata in a small region of an attached leaf. The differenceswere especially remarkable before water-soaking and wilting.When these began, k1 showed a local maximum value, and thenall the stomata began to close. These results suggest that stomatalresponses of intact growing plants to air pollutants shouldbe examined from the standpoint of not only the average movementof many stomata but also the movement of each stoma and thatthe interrelationship among movements of neighboring stomatashould be investigated to clarify the mechanism of stomatalresponses to air pollutants.
93.
Treatment of Sendai virus with , followed by freezing and thawing resulted in a loss of hemolytic and cell fusion activities as well as infectivity without affecting hemagglutinating and neuraminidase activities. The anti-hemolytic activity of this compound was reversed by the addition of phosphatidyl choline to the virus samples. was successfully used for photoaffinity labeling of a specific virion site, and we confirmed the affected site of the glucoside to be the lipid components in the viral envelopes. 相似文献
94.
The development of intracytoplasmic membranes of Methanomonas margaritae cells grown under different culture conditions was studied. Growth on methane was strongly accelerated by the addition of copper ions. Acceleration by copper, however, was not observed in the case of growth on methanol. Cells grown on methane with copper possessed intracytoplasmic membranes along the cell periphery. When the organism was grown in a medium lacking copper, intracytoplasmic membranes appeared as large vesicles surrounded by a unit membrane at the periphery of the cell. The vesicles originated from paired membranes due to the absence of copper in the medium. Cells grown on methanol with or without copper possessed a number of vesicles of different sizes arranged in a chain along the cell periphery. The possible relationship between membrane arrangement and methane oxidation is discussed. 相似文献
95.
96.
Summary The leucine genes of Bacillus subtilis have been cloned directly from the chromosomal DNA into Escherichia coli leuB cells by selection for the Leu+ phenotype using RSF2124 as a vector plasmid. The hybrid plasmid designated RSF2124-B·leu contained a 4.2 megadalton fragment derived from B. subtilis DNA, including the leu genes. The fragment had one site susceptible to EcoRI* and another site susceptible to BamNI endonuclease. Among the three fragments produced by EcoRI* and BamNI endonucleases, the 1.2 megadalton fragment had the ability to transform B. subtilis leuA, leuB and leuC auxotrophs to leu
+. However, B. subtilis ilvB and ilvC auxotrophs were not rescued even by the whole 4.2 megadalton fragment present in the hybrid plasmid. -Isopropylmalate dehydrogenase (leuB gene product) activity found in E. coli cells containing the hybrid plasmid was about 60% of that in E. coli wild type cells, despite the high copy number (7.8) of the plasmid per chromosome observed. 相似文献
97.
Masayasu Inoue Kenji Okajima Kazunobu Ito Kozo Utsumi Satimaru Seno 《生物化学与生物物理学报:生物膜》1977,467(2):130-136
The effect of concanavalin A and its succinylated derivative on cell agglutination and potassium compartmentation of mature and immature erythrocytes was observed. The binding of tetravalent concanavalin A to the surface glycoproteins of rabbit erythrocytes leads to a change in the properties of the surface membrane, which results in an induction of cell agglutination and concomitant release of potassium from the cells. Both of the phenomena induced by concanavalin A are temperature dependent, and observed at above 15°C.Divalent succinylated concanavalin A, lacking the inducing activity of surface glycoprotein cross-linking into patches and caps, caused neither cell agglutination nor change in the potassium compartmentation of erythrocytes and reticulocytes.In the case of immature reticulocytes, however, remarkable agglutination of the cells was induced without a change in the potassium compartmentation after treatment with tetravalent concanavalin A.It is suggested that changes in the molecular organization of the surface membrane occur in which potassium compartmentation of the reticulocytes becomes more susceptible to surface glycoprotein cross-linking during cellular maturation. 相似文献
98.
The surface pressures of α-tocopherol analogs, fatty acids, and their mixtures were measured in their spread monolayers at an air—water interface. The surface pressure—area isotherms for the mixed monolayers of α-tocopherol and either stearic acid, oleic acid or linoleic acid deviated positively from those calculated on the basis of the additivity rule, and the magnitude depended on the length of the phytyl side chain in α-tocopherol and on the degree of unsaturation of the fatty acid chains. Lysosome membranes of mouse liver were stabilized by addition of α-tocopherol. A decrease in the length of the phytyl side chain in α-tocopherol reduced its ability to stabilize lysosome membranes. A good correlation was obtained between the extent of stabilizing activity of α-tocopherol analogs on lysosome membranes and the degree of positive deviation of the surface pressure for their mixtures with fatty acids. 相似文献
99.
Kohei Kawashima Eiji Watanabe Ken-ichi Isobe Michinori Ogura Ei-ichi Nagura Kazumasa Yamada Itsuro Sobue Kenji Mizoguchi Yasuhiko Ito Yoshiyuki Nagai Izumi Nakashima 《Cellular immunology》1982,67(2):279-286
During the course of immunization of (C3H × DBA/2)F1 mice (genotype H-2k/b) with L cell (H-2k/k)/L1210 leukemia cell (H-2d/d) hybrids and L1210 leukemia cells, some of them produced a good titer of anti-self-H-2 (H-2d) antibodies. Antigens recognized by this anti-self-H-2 antiserum were shown to be controlled by the H-2K-IA-IB-IJ-IE subregions of the H-2d but not H-2k nor H-2b haplotypes of parental as well as F1 origins and to have a tissue distribution identical to that of class 1 H-2 (H-2K/D) antigens. 相似文献
100.
Eisuke Mekada Kenji Kohno Masahiro Ishiura Tsuyoshi Uchida Yoshio Okada 《Biochemical and biophysical research communications》1982,109(3):792-799
We have measured the specific uptake of 125I-labelled diphtheria toxin in the presence of methylamine by a number of cell lines with different sensitivities to diphtheria toxin. The results show a strong correlation between the toxin sensitivities of the cell lines and the amount of specific uptake. The specific association of labelled toxin with cells was clearly demonstrated even with CHO cells, a cell line with relatively low sensitivity. Thus, CHO cell mutants that are resistant to diphtheria toxin could be classified as toxin-binding or non-binding cells by this method. 相似文献