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971.
A rapid procedure for creating nested sets of deletions using mini-prep plasmid DNA samples 总被引:3,自引:0,他引:3
A W Steggles 《BioTechniques》1989,7(3):241-242
972.
The biodegradability potentials of three detergent products with the trade names Omo, Teepol and sodium dodecyl sulfate (SDS)
by the native bacteria of the Lagos lagoon was carried out using the lagoon die-away method. Physicochemical parameters of
the water samples showed that the lagoon in Apapa was more polluted than at theUniversity of Lagos. In 12 days, approximately 30, 60 and 97% of Omo, Teepol and SDS respectively were degraded. SDS with an alkyl sulfate moiety
as surfactant supported the highest growth of the detergent-utilizing organisms, indicating that the components of Omo and
Teepol are more resistant to microbial attack. The detergent-utilizing bacteria identified were mainly Gram-negative and of
the following genera:Vibrio, Klebsiella, Flavobacterium, Pseudomonas, Escherichia, Enterobacter, Proteus, Shigella andCitrobacter. Vibrio was the most frequently encountered organism whileProteus was the rarest. Results of this investigation had shown that detergents made in Nigeria may still contain components that
are recalcitrant to biodegradation. 相似文献
973.
Calmodulin-binding proteins also have a calmodulin-like binding site within their structure. The flip-flop model. 总被引:1,自引:0,他引:1
The flip-flop model is a mechanistic model proposed to describe how calmodulin activates enzymes. One prediction based upon this model is that calmodulin-activated enzymes would contain a calmodulin-like binding site which, among other attributes, would bind the peptide melittin. Five purified calmodulin-activated enzymes, namely calcineurin, myosin light chain kinase, phosphorylase b kinase, phosphodiesterase, and NAD kinase, were all found to bind biotinylated melittin and to also bind an antimelittin antibody and biotinylated calmodulins. Using gel blots of crude tissue extracts (rat brain and Arabidopsis), most proteins did not bind any of the probes and thus do not have these characteristics. However, among those which bind any of these probes, a strong correlation was found between those proteins which bind biotinylated calmodulins and those which bind melittin and antimelittin. Gel blots of phosphorylase b kinase demonstrate that the alpha, beta, and gamma subunits all bind calmodulin and melittin. A putative calmodulin-like binding site sequence was identified in eight enzymes or subunits which may play an important role in both melittin binding and calmodulin-dependent regulation of these enzymes. 相似文献
974.
M A Taylor K A Pratt D F Revell K C Baker I G Sumner P W Goodenough 《Protein engineering》1992,5(5):455-459
For the first time the pro-form of a recombinant cysteine proteinase has been expressed at a high level in Escherichia coli. This inactive precursor can subsequently be processed to yield active enzyme. Sufficient protein can be produced using this system for X-ray crystallographic structure studies of engineered proteinases. A cDNA clone encoding propapain, a precursor of the papaya proteinase, papain, was expressed in E. coli using a T7 polymerase expression system. Insoluble recombinant protein was solubilized in 6 M guanidine hydrochloride and 10 mM dithiothreitol, at pH 8.6. A protein-glutathione mixed disulphide was formed by dilution into oxidized glutathione and 6 M GuHCl, also at pH 8.6. Final refolding and disulphide bond formation was induced by dilution into 3 mM cysteine at pH 8.6. Renatured propapain was processed to active papain at pH 4.0 in the presence of excess cysteine. Final processing could be inhibited by the specific cysteine proteinase inhibitors E64 and leupeptin, but not by pepstatin, PMSF or EDTA. This indicates that final processing was due to a cysteine proteinase and suggests that an autocatalytic event is required for papain maturation. 相似文献
975.
976.
Biosorption is becoming an important component in the integrated approach to the treatment of aqueous effluents. The economics of biomass technical applications are improved by using waste biomass instead of purposely-produced biomass. Biomass derived from an alginate extraction industry - Sargassum sp. - was examined for its ability to function as a biosorbent for metals such as cadmium, zinc and copper. For use in column applications, biomass should be immobilized. To the algae reinforcement, the biomass was embedded in polyethleneimine (PEI), followed by glutaraldehyde crosslinking. Equilibrium Zn and Cu isotherms were analysed using the immobilization ratio that showed the best Cd performance. Either Freundlich or Langmuir models can describe the passive biosorption equilibrium of cadmium, zinc and cooper. The preference for this series of metals by the biomass was found to be Cd > Zn > Cu, with maximum uptake values of 157.8, 118.5 and 77.4 mg/g dry weight biomass for Cd, Zn and Cu. respectively. The metal binding capacity by non-living biomass is an important quality for industrial use. 相似文献
977.
Deborah Shaw Ian R. Poxton John R.W. Govan 《FEMS immunology and medical microbiology》1995,11(2):99-106
Abstract Burkholderia cepacia has emerged as an important multiresistant pathogen in cystic fibrosis (CF), associated in 20% of colonised patients with a rapid and fatal decline in lung function. Although knowledge of B. cepacia epidemiology has improved, the mechanisms involved in pathogenesis remain obscure. In this study, B. cepacia lipopolysaccharide (LPS) was assessed for endotoxic potential and the capacity to induce tumour necrosis factor (TNF). LPS preparations from clinical and environmental isolates of B. cepacia and from the closely related species Burkholderia gladioli exhibited a higher endotoxic activity and more pronounced cytokine response in vitro compared to preparations from the major CF pathogen Pseudomonas aeruginosa . This study may help to explain the vicious host immune response observed during pulmonary exacerbations in CF patients colonised by B. cepacia and lead to therapeutic advances in clinical management. 相似文献
978.
M J Blommers H J Slot G A van der Marel J H van Boom C W Hilbers 《Journal of biomolecular structure & dynamics》1990,8(2):233-251
The conformational properties of the cyclic dinucleotide d less than pApA greater than were studied by means of molecular mechanics calculations in which a multiconformation analysis was combined with minimum energy calculations. In this approach models of possible conformers are built by varying the torsion angles of the molecule systematically. These models are then subjected to energy minimization; in the present investigation use was made of the AMBER Force field. It followed that the lowest energy conformer has a pseudo-two-fold axis of symmetry. In this conformer the deoxyribose sugars adopt a N-type conformation. The conformation of the sugar-phosphate backbone is determined by the following torsion angles: alpha +, beta t, gamma +, epsilon t and zeta +. The conformation of this ringsystem corresponds to the structure derived earlier by means of NMR spectroscopy and X-ray diffraction. The observation of a preference for N-type sugar conformations in this molecule can be explained by the steric hindrance induced between opposite H3' atoms when one sugar is switched from N- to S-type puckers. The sugars can in principle switch from N- to S-type conformations, but this requires at least the transition of gamma + to gamma -. In this process the molecule obtains an extended shape in which the bases switch from a pseudo-axial to a pseudo-equatorial position. The calculations demonstrate that, apart from the results obtained for the lowest energy conformation, the 180 degrees change in the propagation direction of the phosphate backbone can be achieved by several different combinations of the backbone torsion angles. It appeared that in the low energy conformers five higher order correlations are found. The combination of torsion angles which are involved in changes in the propagation direction of the sugar-phosphate backbone in DNA-hairpin loops and in tRNA, are found in the dataset obtained for cyclic d less than pApA greater than. It turns out, that in the available examples, 180 degrees changes in the backbone direction are localized between two adjacent nucleotides. 相似文献
979.
W J Firth 《BMJ (Clinical research ed.)》1991,303(6817):1565-1568
980.
Trichome-borne and artificially applied acylsugars of wild tomato deter feeding and oviposition of the leafminer Liriomyza trifolii 总被引:1,自引:0,他引:1
D. J. Hawthorne J. A. Shapiro W. M. Tingey M. A. Mutschler 《Entomologia Experimentalis et Applicata》1992,65(1):65-73
Oviposition and adult feeding of the leafminer Liriomyza trifollii (Burgess) (Diptera, Agromyzidae) on Lycopersicon pennellii (Corr.) D'Arcy and its F1 hybrid with Lycopersicon esculentum (Mill.) was significantly less than that on the cultivated tomato, L. esculentum. The resistance of L. pennellii and the F1 was reduced following rinsing of foliage with ethanol. Resistant attributes of L. pennellii were transferred to L. esculentum through appression of L. pennellii foliage to L. esculentum leaflets. Application of purified 2,3,4-tri-O-acylglucoses (the principal component of type IV glandular trichome exudate of L. pennellii) to L. esculentum significantly decreased feeding and oviposition on L. esculentum leaflets by 61–99%. Therefore the principal mechanism of resistance to this leafminer by L. pennellii is the secretion of these acylglucoses. Dose response analysis of acylglucoses applied to L. esculentum shows that dosages as low as 10% those found on L. pennellii provide large reductions (91%) in leaf punctures and mines. 相似文献