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221.
Larry U. L. Tan Ernest K. C. Yu Nancy Campbell John N. Saddler 《Applied microbiology and biotechnology》1986,25(3):250-255
Summary The use of a column cellulose hydrolysis reactor with continuous enzyme recycling was demonstrated by incorporating a continuous ultrafiltration apparatus at the effluent end of the column reactor. Using this setup, over 90% (w/v) cellulose hydrolysis was achieved, resulting in an average sugar concentration of 6.8% (w/v) in the effluent stream. The output of the system was 1.98 g of reducing sugar/l/h with a ratio of 87% (w/v) of the reducing sugars being monomeric sugars. Batch hydrolysis reactors were less effective, resulting in 57% (w/v) of the cellulose being hydrolyzed. The output of the batch reactor was 1.33 g of reducing sugar/l/h with similar product concentrations and percentage of monomeric sugars. The ratio of reducing sugar/filter paper unit of cellulase activity for the column method was 69.1 mg/U as compared to only 21.2 mg/U for the batch reactor. 相似文献
222.
Structural basis of the polymorphism of human complement components C4A and C4B: gene size, reactivity and antigenicity. 总被引:14,自引:1,他引:13
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The human complement components C4A and C4B are highly homologous proteins, but they show markedly different, class-specific, chemical reactivities. They also differ serologically in that C4A generally expresses the Rodgers (Rg) blood group antigens while C4B generally expresses the Chido (Ch) blood group antigens. C4A 1 and C4B 5 are exceptional variants which possess their class-specific chemical reactivities, but express essentially the reversed antigenicities. The genes encoding the typical Rg-positive C4A 3a and Ch-positive C4B 3 allotypes and the interesting variants C4A 1 and C4B 5 have been cloned. Characterization of the cloned DNA has revealed that the genes encoding the A 3a, A 1 and B 3 allotypes are 22 kb long, but that encoding B 5 is only 16 kb long. Comparison of derived amino acid sequences of the polymorphic C4d fragment has shown that C4A and C4B can be defined by only four isotypic amino acid differences at position 1101-1106. Over this region C4A has the sequence PCPVLD while C4B has the sequence LSPVIH, and this presumably is the cause of their different chemical reactivities. Moreover, the probable locations of the two Rg and the six Ch antigenic determinants have been deduced. Our structural data on the C4A and C4B polymorphism pattern suggests a gene conversion-like mechanism is operating in mixing the generally discrete serological phenotypes between C4A and C4B. 相似文献
223.
毛叶丁香罗勒精油的化学成分分析 总被引:1,自引:0,他引:1
西双版纳引种栽培的毛叶丁香罗勒精油用Finnigan-4510型毛细管色谱/质谱/计算机联用方法进行了化学成分分析,共分离了26个成分,鉴定了其中的16个成分,占全精油含量的98.5%。主要成分是:丁香酚(80.33%);罗勒烯(12.80%);β-毕橙茄烯(4.24%)。 相似文献
224.
Yuri Yu. Gleba Ivan F. Kanevsky M. V. Skarzhynskaya I. K. Komarnitsky N. N. Cherep 《Plant cell reports》1986,5(5):394-397
Protoplast fusion of Nicotiana tabacum (B6S3) crown gall cells and Atropa belladonna leaf mesophyll cells was carried out. Hybrids were selected for their capacity to grow on hormone-free media and to green in light. Shoots incapable of rhizogenesis were regenerated on the same media and grafted onto normal plants of different species. 57 hybrid cell lines differing in their genetic constitution were produced. Analysis of hybrid lines involved the determination of the lysopine dehydrogenase (LpDH) activity and the molecular forms of esterase and amylase, a restriction analysis of chloroplast DNA and a cytogenetic study.Abbreviations LS-H
Linsmaier and Skoog (1965) hormone-free medium
- LpDH
lysopine dehydrogenase 相似文献
225.
In somatic hybrids between tumourous Nicotiana tabacum (B6S3) and normal mesophyll Atropa belladonna cells, the following traits, directly or indirectly connected with T-DNA gene expression and tumourous growth, were analysed: lysopine dehydrogenase activity (LpDH), shoot suppression, root suppression, ability to grow on media with D-lactose as a sole carbon source and resistance to 2-aminoethylcysteine, 5-bromodeoxyuridine and 5-methyltryptophan. Dominant (semidominant) expression was observed for all but one trait studied, e.g. shoot suppression which behaved as a recessive character.Abbreviations LS-H
Linsmaier and Skoog (1965) hormone-free medium
- NAA
Naphtaleneacetic acid
- BAP
6-Benzylaminopurine
- 2,4-D
2,4-Dichlorophenoxyacetic acid
- 5-BUdR
5-Bromodeoxyuridine
- 2-AEC
2-Aminoethylcysteine
- 5-MT
5-Methyltryptophan 相似文献
226.
A general method for the synthesis of azido-ubiquinone derivatives has been developed directly by substituting one hydrogen atom on the benzoquinone ring with an azido group under weakly acidic conditions. The reaction takes several hours and the yield is generally low. The azido-ubiquinone was purified by preparative thin layer chromatography, and identified by NMR, IR and mass spectra. All the synthesized azido-ubiquinone derivatives show partial activity in mediating biological electron transfer in the dark, and show partial or complete inhibition upon photolysis. 相似文献
227.
The 13C-n.m.r. spectra of asialo-GM1 and GM1-oligosaccharide are completely assigned and compared to those previously found for intact GM1 and for the series GM4, GM3, GM2, GM1, GD1a, GD1b, and GT1b. Removal of the ceramide residue from GM1 liberated a free, reducing aldehyde group, which was reflected in a doubling of the 13C-n.m.r. signals assignable to the d-glucose residue because of α,β equilibrium. The spectrum of asialo-GM1 lacks the resonances from the sialic acid residue, as expected; in addition, several resonances from the neutral gangliotetraglycosyl residue shifted to different field positions after removal of sialic acid from GM1. These resonances include that of C-4 of the inner β-d-galactosyl residue, and C-1 of the 2-acetamido-2-deoxy-d-galactosyl residue that is near the site of attachment of the sialosyl residue. The differences between the chemical shifts of the carbon resonances of oligomeric and monomeric saccharides, termed linkage shifts, provide a quantitative assignment aid. They are ~ of those for residues linked to sialic acid than those for residues linked to the neutral hexose chain. Correlations among linkage shifts for pairs of glycosidically-linked carbon atoms for asialo-GM1 and GM1-oligosaccharide were compared with those for the series of gangliosides GM4 to GT1b, and differences are noted for resonances for carbon atoms near the sialic acid residue. The spectrum of ganglioside GM1b, a positional isomer of GM1 whose 13C-n.m.r. spectrum has not yet been observed, is predicted. 相似文献
228.
Abstract: The activity of the pyruvate carboxylase was determined in brains of newborn and adult mice as well as primary cultures of astrocytes, of cerebral cortex neurons, and of cerebellar granule cells. The activity was found to be 0.25 ± 0.14, 1.24 ± 0.07, and 1.75 ± 0.13 nmol · min−1 · mg−1 protein in, respectively, neonatal brain, adult brain, and astrocytes. Neither of the two types of neurons showed any detectable enzyme activity (i.e., < 0.05 nmol · min−1 · mg−1 ). It is therefore concluded that pyruvate carboxylase is an astrocytic enzyme. 相似文献
229.
The UDS induced in cultured FL cells by exposure to chemicals was measured as hydroxyurea-resistant incorporation of 3H-TdR in the acid-insoluble fraction of the 14C-TdR-prelabelled cells synchronized by the combination of arginine starvation and pretreatment with hydroxyurea. The level of UDS is represented by the ratios of 3H/14C radioactivities which are measures of specific activities of 3H. Two direct-acting alkylating agents, MMS and MNNG, a cross-linking agent, mitomycin C, and 3 procarcinogens, B(a)P, AFB1 and cyclophosphamide elicited UDS in the absence or presence of the liver-metabolizing system. Three chemicals of unknown carcinogenicity were also able to induce UDS in this assay system, i.e., bis-(O,O-diethylphosphinothioyl)-disulphide, 4-chlorophenoxy acetic acid (sodium salt) and caramelized malt sugar. With the exception of 4-chlorophenoxy acetic acid, they were also active in the Ames test. 相似文献
230.
Two types of electroreceptive neurons — tonic and phasic — were found in acute experiments with extracellular recording of unit activity from the lateral lobes of the medulla in the Turkestan catfishGlyptosternum reticulatum. Tonic neurons were more sensitive to the potential gradient in water (the threshold for most neurons was 1–6 µV/cm) than phasic neurons, they possessed spontaneous activity (mean frequency 4–10 spikes/sec), and their response characteristics depended significantly on the intensity and duration of stimulation. Phasic neurons had no spontaneous activity; their sensitivity was about one order of magnitude lower than that of the tonic neurons, and the response was independent of the parameters of the stimuli. The probable mechanisms of differentiation of neurons into two types, with a possible link with the characteristics of the receptor formations or with the functional organization of the corresponding brain centers, are discussed. 相似文献