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  • 1
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 22 (1985), S. 272-277 
    ISSN: 1432-1432
    Keywords: Principal components analysis ; Pattern recognition ; Multivariate analysis of physical properties of amino acids ; Genetic code
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 20 naturally occurring amino acids are characterized by 20 variables: pKNH 2, pKCOOH, pI, molecular weight, substituent van der Waals volume, seven1H and13C nuclear magnetic resonance shift variables, and eight hydrophobicity-hydrophilicity scales. The 20-dimensional data set is reduced to a few new dimensions by principal components analysis. The three first principal components reveal relationships between the properties of the amino acids and the genetic code. Thus the amino acids coded for by adenosine (A), uracil (U), or cytosine (C) in their second codon position (corresponding to U, A, or G in the second anticodon position) are grouped in these components. No grouping was detected for the amino acids coded for by guanine (G) in the second codon position (corresponding to C in the second anticodon position). The results show that a relationship exists between the physical-chemical properties of the amino acids and which of the A (U), U (A), or C (G) nucleotide is used in the second codon (anticodon) position. The amino acids coded for by G (C) in the second codon (anticodon) position do not participate in this relationship.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of medicinal chemistry 30 (1987), S. 1126-1135 
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Yersinia species utilize a type III secretion system to inject toxins, called Yops (Yersinia outer proteins), into eukaryotic cells. The N-termini of the Yops serve as type III secretion signals, but they do not share a consensus sequence. To simplify the analysis of type III secretion signals, we replaced amino acids 2–8 of the secreted protein YopE with all permutations (27 or 128) of synthetic serine/isoleucine sequences. The results demonstrate that amphipathic N-terminal sequences, containing four or five serine residues, have a much greater probability than hydrophobic or hydrophilic sequences to target YopE for secretion. Multiple linear regression analysis of the synthetic sequences was used to obtain a model for N-terminal secretion signals. The model accurately classifies the N-terminal sequences of native type III substrates as efficient secretion signals.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 399 (1983), S. 177-189 
    ISSN: 1432-2307
    Keywords: Achilles tendon ; Tendon injuries ; Muscles ; Myofibrils ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unilateral tenotomy of the Achilles tendon was carried out in 60 rabbits. The limb was then either mobilized directly or immobilized for 10 to 35 days using a plaster usually after tendon suture. In certain cases the plaster was removed early (on the 7th or 16th day) and the animals were than allowed to use this leg. Separation between tendon ends was apparent from steel markers, placed close to each cut end of the tendon and examined by X-ray. The separation curve was biphasic and both the first and the inactive phase reflected the degree of tension over the tendon suture. However, during the second separation phase, which began between the 17th and 21st day, the separation gradually reached the same level in all groups. Enzyme histochemistry and electron microscopy revealed severe degenerative changes in immobilized and in shortened muscles. Furthermore, a gradual shift in fibre type characteristics from type 1 slow-twitch fibres towards type 2 fast-twitch fibres occurred. Rapid recovery followed removal of the plaster. The findings indicated that both degenerative and regenerative processes and adaptive processes had been initiated in all experimental muscles when the tendon continuity was broken. The adaptive processes progressed gradually during the five-week post-operative period and might have been responsible for the second phase of the tendon end separation. The fibre adaptation, i.e. the transformation, may be accounted for by changes in structure of the myofibrils and composition of the myosin molecules.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Planta 181 (1990), S. 560-567 
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Photoinhibition of photosynthesis ; Photosynthesis (photoinhibition) ; Salix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The occurrence of photoinhibition of photosynthesis in leaves of a willow canopy was examined by measuring the chlorophyll-a fluorescence ratio of F V/F M (FM is the maximum fluorescence level of the induction curve, and FV is the variable fluorescence, F V=F M−F 0, where F0 is the minimal fluorescence). The majority of the leaves situated on the upper parts of peripheral shoots showed an afternoon inhibition of this ratio on clear days. This was the consequence of both a decrease in F M and a rise in F O. In the same leaves the diurnal variation in intercepted photosynthetic photon flux density (PPFD) was monitored using leaf-mounted sensors. Using the multivariate method, partial least squares in latent variables, it is shown that the dose of PPFD, integrated and linearly weighted over the last 6-h period, best predicts photoinhibition. Photoinhibition occurred even among leaves that did not intercept PPFDs above 1000 μmol·m−2·s−1. Exposure of leaves to a standard photoinhibitory treatment demonstrated that the depression in the F V/F M ratio was paralleled by an equal depression in the maximal quantum yield of CO2 uptake and a nearly equal depression in the rate of bending (convexity) of the light-response curve of CO2 uptake. As a result, the rate of net photosynthesis is depressed over the whole natural range of PPFD. By simulating the daily course in the rate of net photosynthesis, it is estimated that in the order of one-tenth of the potential carbon gain of peripheral willow shoots is lost on clear days as a result of photoinhibition. This applies to conditions of optimal temperatures. Photoinhibition is even more pronounced at air temperatures below 23° C, as judged from measurements of the FV/FM ratio on clear days: the afternoon inhibition of this ratio increased in a curvilinear manner from 15% to 25% with a temperature decrease from 23° to 14° C.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2048
    Keywords: Alnus ; Ammonium ; Carbon translocation ; Endophyte damage ; Nitrogen fixation ; Root nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cloned plants of Alnus incana (L.) Moench were inoculated and grown without combined nitrogen for seven weeks. The effects of ammonium on the function and structure of the root nodules were studied by adding 20 mM NH4Cl (20 mM KCl=control) for four days. Nitrogenase activity decreased to ca. 50% after one day and to less than 10% after two days in ammonium treated plants, but was unaffected in control plants. The results were similar at photon flux densities of 200 and 50 μmol m-2 s-1. At the higher light level the effect was concentration dependent between 2 and 20 mM NH4Cl. The recovery was slow, and more than 11 d were needed for plants treated with 20 mM ammonium to reach initial activity. The distribution of 14C to the root nodules after assimilation of 14CO2 by the plants was not changed by the ammonium treatment. Microscopical studies of root nodules showed high frequencies of endophyte vesicles being visually damaged in nodules from ammonium-treated plants, but not in nodules from control plants. When nitrogenase activity was restored, visually damaged vesicles were again few, whereas young developing vesicles were numerous. The slow recovery, the 14C-translocation pattern, and the structural changes of the endophyte indicate a more complex mechanism of ammonium influence than simply a short-term reduction in supply of carbon compounds to the nodules.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The effects of combined toxicity were studied, using marine periphyton communities exposed to mixtures of tri-n-butyl tin (TBT) and diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea, DCMU) in indoor aquaria during four weeks. The experimental design of the study followed a central composite design (CCD) and utilized dose-response surface methodology for evaluation of the results. The detection of pollution-induced community tolerance (PICT) was accomplished by short-term (1 h) tests on inhibition of photosynthesis. Both single-toxicant and two-toxicant short-term tests were used. Two tentative measures of tolerance are proposed to achieve convenient comparisons of the tolerances from the two-toxicant tests. With the detection of PICT, effects of the long-term exposure were recorded on diatom species richness, chlorophyll a accumulation and copepod abundance. The decrease of diatom species richness was accompanied by an increased tolerance (PICT), which was detectable by all tolerance measures used. Primary effects on microalgae were recorded as a decrease in chlorophyll a at higher toxicant concentrations. At lower concentrations, primary effects on copepods were found, which resulted in reduced grazing and increased chlorophyll a content.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1572-882X
    Keywords: dissolving pulp ; alkali resistance ; filterability ; NIR spectroscopy ; solid state NMR spectroscopy ; multivariate data analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two processability variables, filter clogging and alkali resistance, were measured in a series of laboratory‐cooked viscose pulps. The pulps were also characterised by 13C‐CP/MAS solid state nuclear magnetic resonance (NMR) and near infrared (NIR) spectroscopy. Partial least squares (PLS) regression was used to investigate the information provided by the spectroscopic methods with respect to the processability measurements. The study showed that the alkali resistance, R18, of the pulp and the filter clogging value, Kw, of the laboratory‐prepared viscose can be modelled by NIR and multivariate data analysis (MVA). The alkali resistance, R18, of the pulp can also be calculated by NMR and partial least squares (PLS) regression. Analysis of the loading values in the PLS model showed that pulps with high alkali resistance have higher crystallinity than pulps with low alkali resistance. Analysis of variables of the cooking conditions showed that the chemical charge (Na2O) and pH should be kept low to give high alkali resistance, whereas high Na2O gives low filter clogging values.
    Type of Medium: Electronic Resource
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