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  • Artikel  (24)
  • Springer  (24)
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  • Artikel  (24)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 40 (1995), S. 545-550 
    ISSN: 1432-1432
    Schlagwort(e): Genetic code ; Aminoacyl-tRNA synthetases ; Ribozyme ; Protein design ; Leucine zippers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The aminoacyl-tRNA synthetases exist as two enzyme families which were apparently generated by divergent evolution from two primordial synthetases. The two classes of enzymes exhibit intriguing familial relationships, in that they are distributed nonrandomly within the codon-amino acid matrix of the genetic code. For example, all XCX codons code for amino acids handled by class II synthetases, and all but one of the XUX codons code for amino acids handled by class I synthetases. One interpretation of these patterns is that the synthetases coevolved with the genetic code. The more likely explanation, however, is that the synthetases evolved in the context of an already-established genetic code—a code which developed earlier in an RNA world. The rules which governed the development of the genetic code, and led to certain patterns in the coding catalog between codons and amino acids, would also have governed the subsequent evolution of the synthetases in the context of a fixed code, leading to patterns in synthetase distribution such as those observed. These rules are (1) conservative evolution of amino acid and adapter binding sites and (2) minimization of the disruptive effects on protein structure caused by codon meaning changes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Chromosoma 26 (1969), S. 201-207 
    ISSN: 1432-0886
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird über Messungen des linearen Dichroismus in den Chromomerenscheiben der Riesenchromosomen von Chironomus thummi mit einem Mikrospektralphotometer für Messungen mit polarisiertem Licht berichtet. Die Meßfläche betrug etwa 2 μm im Durchmesser. Die Ergebnisse zeigen, daß eine einheitliche Orientierung der DNS in den Chromomerenscheiben nicht vorhanden ist. Die Ergebnisse werden im Zusammenhang mit den in der Literatur erhobenen Befunden über die Orientierung der DNS-Moleküle in den Chromomerenscheiben diskutiert.
    Notizen: Abstract Measurements of linear dichroism in the chromomeric bands of giant chromosomes of Chironomus thummi are reported. The measurements were performed by means of a microspectrophotometer specially designed for measuring with polarized light. The diameter of the measuring area was about 2 μm. As was revealed by the results there exists no uniform orientation of the nucleic acid molecules within the chromomeric disks. The results are discussed in connection with the findings stated in literature on the orientation of the nucleic acid molecules in the chromomeric bands.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We report nutrient addition bioassays at 18 stations in Chesapeake Bay (USA) to assess resources limiting phytoplankton growth. Data were pooled from several sampling programs conducted from 1989 to 1994. Spatially, light and P limitation declined from low salinity regions to high salinity regions, as N limitation increased. This spatial pattern was driven primarily by freshwater inflows with high N/P and seawater inflows with low N/P. Seasonally, there was a marked progression of winter light limitation, spring P limitation, and summer N limitation at mesohaline and polyhaline stations. The seasonal pattern appeared to be caused by temperature, mixing, river discharge, and sediment P fluxes. At high salinity stations, we also observed winter N limitation (caused by DIN depletion prior to spring nitrate delivery), and at lower salinity stations there was fall P limitation (caused by reaeration of bottom sediments). At tidal fresh stations, turbidity and nutrient concentrations resulted in continuous light limitation, except at some stations in summer. Interannual decreases in light limitation and increases in N and P limitation appear to represent improvements in water quality.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Microbial ecology 29 (1995), S. 63-70 
    ISSN: 1432-184X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract [3H]leucine incorporation into protein, as a method of measuring bacterial biomass production (BBP), was adapted to epiphytic bacteria. Incorporation of the isotope was saturated at concentrations higher than 400 nM. Disruption of thicker biofilms by sonication resulted in higher values of BBP and ratios of BBP/biomass when compared to those of intact biofilm. Thin biofilms formed early in the decomposition process did not show this phenomenon. These results support to evidence that more internally located cells of the matrices either have greatly reduced access to the leucine from the overlying medium or that fast recycling of leucine occurs in the biofilm.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Naturwissenschaften 47 (1960), S. 521-521 
    ISSN: 1432-1904
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pest science 35 (1962), S. 175-176 
    ISSN: 1612-4766
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 265 (1987), S. 1036-1045 
    ISSN: 1435-1536
    Schlagwort(e): Gelatin structure ; thermaldenaturation ; hydration ; gelatin films ; circulardichroism ; trans-cis conversion ; chain reversals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The structural behaviour of gelatins from different raw materials and manufacturing processes at thermal denaturation and isothermal dehydration and rehydration is investigated by CD. At both thermal denaturation and isothermal dehydration with all gelatins examined, the triple helix content decreases. Simultaneously, the appearance of cis peptide bonds is observed. At rehydration, a structural hysteresis occurs, the reconstitution of the triple helix structure being correlated with a decrease in the content of cis peptide bonds. The possibility of the formation of chain reversals upon destruction of the triple helix is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1435-1536
    Schlagwort(e): Circular dichroism ; gelatin ; sodium alkyl sulphates ; aqueousgelatinsolutions ; secondary structure ; pH ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The modification of the triple helical structure in aqueous gelatin solutions by changing pH and adding alkyl sulphates at 298 K and after rechilling the solution to 283 K was investigated by CD-measurement. At 298 K the triple helical content at the IEP of the gelatin has its maximum value. It is only weakly affected by adding sodium dodecyl sulphate (SDDS) at concentrations 〈10−4 M/dm3. The unfolding of the triple helix affected by pH and SDDS is reversible by rechilling the solution. The triple helical content of gelatin solutions decreases at SDDS concentrations higher than 10−4 M/dm3. In all cases the decrease of the amount of triple helical structure is connected with an increase of the cis-configuration in single chains and leads to chain reversals. At sufficiently high SDDS concentrationsβ-sheets are formed. These changes are thermally irreversible. Sodium decyl sulphate (SDS) has a more minor influence than SDDS except in the range of the c.m.c. of SDS. At sufficiently high SDS concentrations,β-turns appear.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 1435-1536
    Schlagwort(e): Gelatin ; hexadecyl- and dodecyl-ammonium bromide ; circular dichroism ; gelatin triple helical structure ; influence of temperature ; pH
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The interaction between cationic surfactants (hexadecyl and dodecyl trimethyl ammonium bromide) and gelatin was characterized by measuring the circular dichroism. The interaction between the cationic surfactants and gelatin is weak in comparison to that of anionic surfactants. When the concentration of cationic surfactants is sufficiently low, refolding of the gelatin-strands to the triple helical structure by rechilling the solution from 298 K to 283 K is complete. The triple helical content of the solution is affected more strongly by the cationic surfactants in acidic solution than at pHs 7 or 10. The interaction depends on the apolar group of the surfactant and is found to be stronger for DTAB than for CTAB at 298 K. Coagulation of the hydrophobic gelatin-cationic surfactant complexes does not comprise that pan of gelatin which is able to refold the triple helical structure. Therefore, the gelatin-strands of lower molecular weights are thought to react favorably with the surfactant ions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Limnology 1 (2000), S. 3-9 
    ISSN: 1439-863X
    Schlagwort(e): Key words Limnology ; Freshwater ecology ; Fresh water ; Microbial ecology ; Lakes ; Streams ; Biomanipulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The past development and evolution of limnology as a discipline has demonstrated that experimentally controlled disturbances of parts of aquatic ecosystems are essential for quantitative evaluation of causal mechanisms governing their operation. Correlative analyses and modeling only establish hypotheses, not causality, and allow only therapeutic management applications. Rather than constantly searching for differences, commonality must be sought. Among the large diversity of species, communities, and biogeochemical processes controlling growth and reproduction, commonality emerges at the levels of regulation of metabolism. Five areas of current and future limnological research are discussed in relation to greatest needs and promise to yield insights into material and energy flows in freshwater ecosystems and their effective management: (1) coupled metabolic mutualism in the physiological ecology of microbes (viruses, bacteria, fungi, and protists) and their biogeochemical, especially organic, couplings with the environment; (2) biochemical regulation of collective metabolism, recycling, and bioavailability of nutrients and growth regulators; (3) application of genetic and molecular techniques to addressing biogeochemical, evolutionary, and pollution remediation problems; (4) recognition that the metabolism within lakes and streams is dependent upon and regulated to a major extent by organic matter of the drainage basin and especially by the land-water interface biogeochemistry; and (5) recognition that food-web alterations ("biomanipulation") are short-term, expensive therapeutic tools that may minimize effects of eutrophication but will not solve or control eutrophication.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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