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31.
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33.
Effects of variation in the structure of spermine on the association with DNA and the induction of DNA conformational changes. 总被引:3,自引:0,他引:3 下载免费PDF全文
Manganese shares the uniport mechanism of mitochondrial calcium influx, accumulates in mitochondria and is cleared only very slowly from brain. Using dual-label isotope techniques, we have investigated both Mn2+ and Ca2+ mitochondrial efflux kinetics. We report that (1) there is no significant Na(+)-dependent Mn2+ efflux from brain mitochondria; (2) Mn2+ inhibits both Na(+)-dependent and Na(+)-independent Ca2+ efflux in brain, in a mode that appears to be primarily competitive and with apparent Ki values of 5.1 and 7.9 nmol/mg respectively; and (3) Ca2+ does not appear to inhibit Mn2+ efflux from brain mitochondria. Findings (1) and (2) suggest the possibility of mitochondrial accumulation of both Mn2+ and Ca2+ in Mn2(+)-intoxicated brain. 相似文献
34.
Manju Basu Shu-Ai Weng Hongyu Tang Farhat Khan Federica Rossi Subhash Basu 《Glycoconjugate journal》1996,13(3):423-432
The galactosyltransferase, GalT-4, which catalyses the biosynthesisin vitro of neolactotetraosylceramide, nLcOse4Cer (Gal1-4GleNAc1-3Gal1-4Glc-Cer) from lactotriaosylceramide, LcOse3Cer (GlcNAc1-3Gal1-4Glc-Cer), and UDP-galactose has been purified 107 500-fold from a mineral oil induced mouse T-lyphoma P-1798, using affinity columns. The purified enzyme is partially stabilized in the presence of phospholipid liposomes. Two closely migrating protein bands of apparent molecular weights 56 kDa and 63 kDa were observed after sodium dodecyl sulfate polyacrylamide gel electrophoresis of highly purified mouse GalT-4. These two protein bands, when subjected to limited proteolysis, resulted in three peptides with identical mobilities indicating amino acid sequence identity between the proteins. Both protein bands from P-1798 gave a positive immunostain when tested with polyclonal antibody against bovine lactose synthetase (UDP-Gal:Glc 4-galactosyltransferase) following Western blot analysis on nitrocellulose paper. The enzyme has a pH optimum between 6.5 and 7.0 and like all other galactosyltransferases, GalT-4 has absolute requirements for divalent cation (Mn2+). TheK
m values for the substrate LcOse3Cer and donor UDP-galactose are 110 and 250 µm, respectively. Substrate competition studies with LcOse3Cer and either asialo-agalacto-1-acid glycoprotein orN-acetylglucosamine revealed that these reactions might be catalysed by the same protein. The only other glycolipid which showed acceptor activity toward the purified GalT-4 was iLcOse5Cer (GlcNAc1-1-3Gal1-4Lc3), the precursor for polylactosamine antigens. However, competition studies with these two active substrates using the most purified enzyme fraction, revealed that these two reactions might be catalysed by two different proteins since the experimental values were closer to the theoretical values calculated for two enzymes. Interestingly however, it seems that the GalT-4 from P-1798 has an absolute requirement for anN-acetylglucosamine residue in the substrate since the lyso-derivative (GlcNH21-3Gal1-4Glc-sphingosine) of the acceptor glycolipid LcOse3Cer is completely inactive as substrate while theK
m andV
max of the reacetylated substrate (GlcNac1-3Gal1-4Glc-acetylsphingosine) was comparable with LcOse3Cer. Autoradiography of the radioactive product formed by purified P-1798 GalT-4 confirmed the presence of nLcOse4Cer, as the product cochromatographed with authentic glycolipid. The monoclonal antibody IB-2, specific for nLcOse4Cer, also produced a positive immunostained band on TLC as well as giving a positive ELISA when tested with radioactive product obtained using a highly purified enzyme from mouse P-1798 T-lymphoma.Abbreviations EDTA
ethylenediamine tetraacetate
- ME
-mercaptoethanol
- PEG
polyethylene glycol
- PBS
phosphate buffered saline
- Suc
sucrose
- Mn2+
manganese
- Gal
galactose
- GlcNAc
N-acetylglucosamine
- UDP-Gal
Uridine diphosphate galactose
- Ab
antibody
- SDS
sodium dodecyl sulphate
- PAGE
polyacrylamide gel electrophoresis
- ECB
embryonic chicken brain
- Cer
ceramide
- nLc4 or NlcOse4Cer
Gal1-4GleNac1-3Gal1-4Glc-Cer, neoLactotetraosylceramide
- Lc3 or LcOse3Cer
GlcNac1-3Gal1-4Glc-Cer, lactotriaosylceramide
- iLc5
iLcOse5Cer, GlcNAc1-3nLcOse4Cer
- nLc6
nLcOse6Cer, Gal1-4iLcOse5Cer
- SA–Gal–1AGP
asialo-agalacto1-acid glycoprotein
- TLC
thin layer chromatography 相似文献
35.
Phyllosphere micro-organisms of Brassica napus were isolated and their antagonism against Leptosphaeria maculans , causal agent of blackleg disease, was tested in vitro . In paired culture, Erwinia herbicola was found to be highly antagonistic to L. maculans. Bioassay of the culture filtrate of the bacterium against the test fungus revealed that Erw. herbicola secretes an antifungal substance into the culture medium. This substance was partially thermolabile and markedly reduced the germination and germ tube length of L. maculans . Aqueous bacterial suspensions and cold-sterilized culture filtrates, when applied to the seedlings prior to inoculation, significantly reduced the severity of blackleg disease. 相似文献
36.
Suresh Chand Purnima Basu Neeti Maheshwari 《Journal of plant biochemistry and biotechnology.》1994,3(1):53-54
Somatic embryogenesis and regeneration of plantlets was achieved In callus cultures derived from cotyledonary leaf pieces of Hyoscyamus muticus L on MS medium enriched with 2 mg/l 2,4–0 and 0.5 mg/l BAP. For embryogenesis and organogenesis varying concentrations of NAA with or without BAP were added In the medium. Organogenesis was also achieved when callus was transferred to the hormone free medium. 相似文献
37.
38.
Preparation of surface glycoproteins from human fetal brain cells by affinity chromatography on Con A-Sepharose 4B was a problematic endeavor due to leaching of Con A from the matrix. Dissociation of Con A from the matrix took place irrespective of the presence of lipid and/or detergent and the buffer composition during chromatography and was apparently related to the nature of the protein under study. Pretreatment of Con A-Sepharose with 6 M guanidine or 8 M urea reduced Con A leaching. The Con A eluate also contained noncovalently associated glycolipid. Elution at 25 degrees C rendered fractions containing a higher degree of Con A and glycolipid contamination compared to the negligible contamination by these two components when elution was carried out at 4 degrees C. This phenomenon was attributed to the formation of heterogeneous mixed micelles of glycoprotein. 相似文献
39.
Summary The presence of ethanol (5 % v/v), in nutrient medium, ehanced DNA synthesis per E. coli cell nearly 2.8-fold compared to that in control cells. At this concentration, the derepressed synthesis of -galactosidase per bacterium also increased about 3-fold. We, therefore, propose that the ethanol-mediated gene-amplification proportionately elevated the induced synthesis of -galactosidase. 相似文献
40.
A comparative account of the microbiological characteristics of soils under natural forest,grassland and cropfield from Eastern India 总被引:4,自引:0,他引:4
Microbiological and physico-chemical characteristics of tropical forest, grassland and cropfield soils from India were investigated.
The study revealed that the conversion of natural forest led to a reduction of soil organic C (26–36%), total N (26–35%),
total P (33–44%), microfungal biomass (44–66%) and total microbial biomass C, N and P (25–60%) over a period of 30–50 years.
Comparative analysis of microbial activity in terms of basal soil respiration revealed maximum activity in the forest and
minimum in the cropfield soil. Analysis of microbial metabolic respiratory activity (qCO2) indicated relatively greater respiratory loss of CO2-C per unit microbial biomass in cropfield and grassland than in forest soil. Considering the importance of the microbial
component in soil, we conclude that the conversion of the tropical forest to different land uses leads to the loss of biological
stability of the soil. 相似文献