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11.
Sperm protamines have been isolated from representatives of three major plant groups: algae (Chara corallina ), bryophytes ( Marchantia polymorpha), and ferns ( Marsilea vestitia ). We previously reported the complete displacement of histones by protamines in Marchantia (Reynolds W F & Wolfe, S L, Exp cell res 116 (1978) 269 [8] ). Marchantia protamines appear as four components on acid-urea gels, whereas Chara and Marsilea protamines comigrate as a single band with a mobility comparable to salmon protamine. The amino acid compositions of the plant protamines show these to be arginine-rich, highly basic (35-42%) proteins which display overall similarity in amino acid composition (84-91%). The molecular weights of Chara and Marsilea protamines are approx. 4700-5300 D. 相似文献
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Formation of reduced nicotinamide adenine dinucleotide peroxide 总被引:1,自引:0,他引:1
Incubation of NADH at neutral and slightly alkaline pH leads to the gradual absorption of 1 mol of H+. This uptake of acid requires oxygen and mainly yields anomerized NAD+ (NAD+), with only minimal formation od acid-modified NADH. The overall stoichiometry of the reaction is: NADH + H+ + 1/2O2 leads to H2O + NAD+, with NADH peroxide (HO2-NADH+) serving as the intermediate that anomerizes and breaks down to give NAD+ and H2O2. The final reaction reaction mixture contains less than 0.1% of the generated H2O2, which is nonenzymically reduced by NADH. The latter reaction is inhibited by catalase, leading to a decrease in the overall rate of acid absorption, and stimulated by peroxidase, leading to an increase in the overall rate of acid absorption. Although oxygen can attack NADH at either N-1 or C-5 of the dihydropyridine ring, the attack appears to occur primarily at N-1. This assignment is based on the inability of the C-5 peroxide to anomerize, whereas the N-1 peroxide, being a quaternary pyridinium compound, can anomerize via reversible dissociation of H2O2. The peroxidase-catalyzed oxidation of NADH by H2O2 does not lead to anomerization, indicating that anomerization occurs prior to the release of H2O2. Chromatography of reaction mixtures on Dowex 1 formate shows the presence of two major and several minor neutral and cationic degradation products. One of the major products is nicotinamide, which possibly arises from breakdown of nicotinamide-1-peroxide. The other products have not been identified, but may be derived from other isomeric nicotinamide peroxides. 相似文献
14.
Growth of Oscillatoria agardhil was studied in ammonium-limited chemostat cultures, at various dilution rates (=growth rates, μ). The uptake kinetics for
ammonium of nitrogen (ammonium or nitrate)-limited chemostat cultures also was investigated.
The kinetics of ammonium-limited growth could be adequately described by both the Monod and Droop equations, and were closely
similar to the nitrate-limited growth kinetics of this species. The uptake kinetics for ammonium showed similarities as well
as differences with the uptake kinetics for nitrate. The similarities were apparent in the uptake capacity values for ammonium
and nitrate
, which were identical, high and independent of μ. The differences were to be found in the half-saturation constants for ammonium
uptake
and nitrate uptake
, the former being hardly influenced by μ. A consitutive, high affinity, system is likely to operate in the uptake and assimilation
of ammonium by nitrogen-limited O. agardhii.
The use of ammonium uptake parameters in studies of growth-limiting factors in nature can provide information as to whether
a nitrogen-limitation prevails in natural habitats of this species. 相似文献
15.
Analysis, Production, and Isolation of an Extracellular Laccase from Polyporus anceps 总被引:4,自引:3,他引:1 下载免费PDF全文
Richard J. Petroski Wanda Peczynska-Czoch John P. Rosazza 《Applied microbiology》1980,40(6):1003-1006
Methods are described for the analysis, production, and isolation of laccase produced by a strain of Polyporus anceps. A simple quantitative colorimetric assay based on the oxidation of syringaldazine to syringaldazine quinone is described. Using a defined medium supplemented with the amino acids cysteine and histidine and with elevated phosphate, consistently high titers of laccase were obtained. The enzyme was isolated directly from fermentation medium by binding to diethylaminoethyl cellulose, and, once bound to the ion exchanger, it could be stored for 6 months at -70°C with minimal loss of activity. The enzyme was quantitatively recovered from the resin by elution with 0.2 M phosphate buffer (pH 5.0). 相似文献
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Wanda S. Smith Barbara Nawrot Andrzej Malkiewicz Paul F. Agris 《Nucleosides, nucleotides & nucleic acids》2013,32(10):1683-1694
Abstract The conformation of chemically synthesized acp3U is 60& 3′-endo, gauche+, whereas that of m1acp3Ψ is 60& 2′-endo, gauche+. We conclude that the difference in conformation probably imparts important local structures to their respective tRNA and rRNA. 相似文献
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Wanda G. H. Han Inonge van Twillert Martien C. M. Poelen Kina Helm Jan van de Kassteele Theo J. M. Verheij Florens G. A. Versteegh Claire J. P. Boog Cécile A. C. M. van Els 《PloS one》2013,8(12)
Pertussis is still occurring in highly vaccinated populations, affecting individuals of all ages. Long-lived Th1 CD4+ T cells are essential for protective immunity against pertussis. For better understanding of the limited immunological memory to Bordetella pertussis, we used a panel of Pertactin and Pertussis toxin specific peptides to interrogate CD4+ T cell responses at the epitope level in a unique cohort of symptomatic pertussis patients of different ages, at various time intervals after infection. Our study showed that pertussis epitope-specific T cell responses contained Th1 and Th2 components irrespective of the epitope studied, time after infection, or age. In contrast, the breadth of the pertussis-directed CD4+ T cell response seemed dependent on age and closeness to infection. Multi-epitope specificity long-term after infection was lost in older age groups. Detailed knowledge on pertussis specific immune mechanisms and their insufficiencies is important for understanding resurgence of pertussis in highly vaccinated populations. 相似文献
20.
Joe Kgaladi Nicolette Wright Jessica Coertse Wanda Markotter Denise Marston Anthony R. Fooks Conrad M. Freuling Thomas F. Müller Claude T. Sabeta Louis H. Nel 《PLoS neglected tropical diseases》2013,7(10)
Mokola virus (MOKV) appears to be exclusive to Africa. Although the first isolates were from Nigeria and other Congo basin countries, all reports over the past 20 years have been from southern Africa. Previous phylogenetic studies analyzed few isolates or used partial gene sequence for analysis since limited sequence information is available for MOKV and the isolates were distributed among various laboratories. The complete nucleoprotein, phosphoprotein, matrix and glycoprotein genes of 18 MOKV isolates in various laboratories were sequenced either using partial or full genome sequencing using pyrosequencing and a phylogenetic analysis was undertaken. The results indicated that MOKV isolates from the Republic of South Africa, Zimbabwe, Central African Republic and Nigeria clustered according to geographic origin irrespective of the genes used for phylogenetic analysis, similar to that observed with Lagos bat virus. A Bayesian Markov-Chain-Monte-Carlo- (MCMC) analysis revealed the age of the most recent common ancestor (MRCA) of MOKV to be between 279 and 2034 years depending on the genes used. Generally, all MOKV isolates showed a similar pattern at the amino acid sites considered influential for viral properties. 相似文献