Paramyxoviruses are the leading cause of respiratory disease in children. Several paramyxoviruses possess a surface glycoprotein, the hemagglutinin-neuraminidase (HN), that is involved in attachment to sialic acid receptors, promotion of fusion, and removal of sialic acid from infected cells and progeny virions. Previously we showed that Newcastle disease virus (NDV) HN contained a pliable sialic acid recognition site that could take two states, a binding state and a catalytic state. Here we present evidence for a second sialic acid binding site at the dimer interface of HN and present a model for its involvement in cell fusion. Three different crystal forms of NDV HN now reveal identical tetrameric arrangements of HN monomers, perhaps indicative of the tetramer association found on the viral surface. 相似文献
Plasmodium chabaudi chabaudi can be considered as a rodent model of human malaria parasites in the genetic analysis of important characters such as drug resistance and immunity. Despite the availability of some genome sequence data, an extensive genetic linkage map is needed for mapping the genes involved in certain traits.
Methods
The inheritance of 672 Amplified Fragment Length Polymorphism (AFLP) markers from two parental clones (AS and AJ) of P. c. chabaudi was determined in 28 independent recombinant progeny clones. These, AFLP markers and 42 previously mapped Restriction Fragment Length Polymorphism (RFLP) markers (used as chromosomal anchors) were organized into linkage groups using Map Manager software.
Results
614 AFLP markers formed linkage groups assigned to 10 of 14 chromosomes, and 12 other linkage groups not assigned to known chromosomes. The genetic length of the genome was estimated to be about 1676 centiMorgans (cM). The mean map unit size was estimated to be 13.7 kb/cM. This was slightly less then previous estimates for the human malaria parasite, Plasmodium falciparum
Conclusion
The P. c. chabaudi genetic linkage map presented here is the most extensive and highly resolved so far available for this species. It can be used in conjunction with the genome databases of P. c chabaudi, P. falciparum and Plasmodium yoelii to identify genes underlying important phenotypes such as drug resistance and strain-specific immunity. 相似文献
The synthesis of enantiomerically pure (-)-(S)- and (+)-(R)-2-acyl-3,6-dihydroxycyclohex-2-enone starting from diastereomerically pure N-tosyl-(S)-proline esters 3-methoxy-6-hydroxycyclohex-2-enone 1 is presented. An enantioconvergent synthesis of either (-)-(S)- and (+)-(R)-2-acyl-3,6-dihydroxycyclohex-2-enone starting with the racemic alpha-ketol 1 through a conversion of ( approximately 1:1) mixture of diastereomeric esters into one diastereomer by a repeated crystallization, followed by dimethylaminopyridine-catalyzed equilibration as key steps is described. 相似文献
The growth ofRhodococcus opacus GM-14 on mixtures of 2-chloro- and 2-bromophenol, of 4-chloro, 4-bromo-, and 4-iodophenol, and of chloro-, bromo-, and iodobenzenes
was accompanied by the consumption of the substrates and the excretion of halogen ions into the medium. During the growth
on monochlorophenols, the substrates were consumed sequentially in the following order: 4-chloro-, 3-chloro-, and then 2-chlorophenol.
Chlorine ions were excreted in a two-phase manner in amounts comprising 79% of the theoretical yield. The diauxic growth ofR. opacus GM-14 can be explained by the existence in this bacterium of two modified metabolic pathways for theortho- cleavage of halogenated pyrocatechols. The first pathway included 4-halogeno- or dihalogenopyrocatechols as intermediates,
whereas the second pathway included 3-halogenopyrocatechols. 相似文献
A total of 645 subjects between the ages of 5 and 24 years were examined by the original computer methods. Test subjects had
to differentiate the visual stimuli by shape, color, size, and orientation. The latent periods of visual object differentiation
had dissimilar significant characteristics and age dynamics. The obtained results are treated in the context of the concept
of multichannel visual information processing. 相似文献
A simple method for determining the enzymic hydrolysis parameters of lipid-like substrates and trilaurin assembled in monolayers
at the water-air interface was suggested. At a surface pressure of 10 mN/m, the initial rates of lipolysis were found to be
proportional to the decrease in area of the substrate monolayer caused by the enzymic hydrolysis in a single-compartment Langmuir
balance. The kinetic parameters for the hydrolysis of trilaurin and three 1,3-dilaurylpseudoglycerides acetylated in position
2 with an amino acid (phenylalanine, leucine, or valine) catalyzed with lipase fromPseudomonas fluorescens were determined. Unlike models of enzymic hydrolysis that neglect the thickness of the substrate monolayer, our method allows
the determination of kinetic parameters in standard dimensions. The values ofkcat for the synthetic pseudoglycerides were found to be significantly higher than that for trilaurin, while the values ofKm(app) were close. This may be due to the presence of positively charged primary amino groups in the molecules of pseudoglycerides. 相似文献
Biophysics - The formation of steady-state visual evoked potentials on the basis of visual evoked potentials was analyzed. Using the regression model, it was shown that the accumulation of... 相似文献
Antibiotics are widely used in medicine, veterinary medicine, and the food industry. However, the active use of antibacterial drugs leads to environmental pollution. In this regard, there is a great need for monitoring and determining antibiotics in various environments such as drinking water, food, drinks, waste water from pharmaceutical factories, etc. A number of methods, including those based on biosensors, have been developed to determine antibiotics. Biosensor methods of analysis are widely used and are an integral part of environmental monitoring. Electrochemical, optical, acoustic, microbial biosensors, immuno- and aptasensors, as well as sensors based on molecularly imprinted polymers are in the most demand for the analysis of antibiotics. This article provides a brief overview of biosensor methods and approaches for the determination of antibiotics. The most promising biosensor systems for determining antibacterial drugs were analyzed.
Journal of Applied Phycology - Pharmaceuticals (mostly antibiotics and non-steroid anti-inflammatory drugs) are hazardous micropollutants (HMP). Incomplete degradation of the HMP leads to their... 相似文献
A study is made of the Z-pinch plasma expansion after the current is switched off. Measurements were carried out in experiments on the implosion of tungsten wire arrays in the Angara-5-1 facility. It is found experimentally that, at a distance of 2 m from the pinch, the ion velocity in the expanding Z-pinch plasma is about (2.5–4.0) × 107 cm/s, which substantially exceeds the thermal velocity of tungsten ions. A model describing the plasma expansion process is proposed that is based on the ambipolar acceleration mechanism. The results of numerical simulations are compared with the experimental data. 相似文献