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  • Column liquid chromatography  (86)
  • evolution  (41)
  • Springer  (127)
  • American Physical Society
  • Cell Press
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
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  • Springer  (127)
  • American Physical Society
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  • Krefeld : Geologischer Dienst Nordhein-Westfalen
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  • 1
    Digitale Medien
    Digitale Medien
    Presence of a partial urea cycle in the leech,Poecilobdella granulosa (1992)
    Springer
    Cellular and molecular life sciences 48 (1992), S. 729-731 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Urea cycle ; leech ; botryoidal tissue ; hirudineans ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Ornithine carbamoyltransferase (OCT) and arginase, but not arginine synthetase (AS), were detected in the body wall and gut tissues of the leech. The activities of these enzymes were not altered by starvation. The high activity of arginase in body wall is probably due to the association of the latter with botryoidal tissue. Hirudineans, which evolved from oligochaete ancestors, appear to have lost the citrulline-arginine segment of the urea cycle due to their ammonotelic mode of nitrogen excretion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02124288
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  • 2
    Digitale Medien
    Digitale Medien
    Life and teleology (1992)
    Springer
    Journal for general philosophy of science 23 (1992), S. 85-103 
    Details
    ISSN: 1572-8587
    Schlagwort(e): life ; teleology ; evolution ; reality ; representation ; experience
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Philosophie , Wissenschaftskunde und Wissenschaftsorganisation, Hochschul- und Universitätswesen, Museumswissenschaft
    Notizen: Summary A comprehensive definition of the phenomenon called “life” led to the addition of many dimensions to the natural sciences, and especially the conscious mental dimension. Historical attention is paid not only to those employing the natural philosophical paradigms, but also to evolutionary theories and to the Kantian teleological philosophy. The belief that science can solve the riddle of life is a category of purposal thinking. A revised version of critical teleology is essential for comprehension of life.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01801797
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  • 3
    Digitale Medien
    Digitale Medien
    Metabolic pathways inParacoccus denitrificans and closely related bacteria in relation to the phylogeny of prokaryotes (1992)
    Springer
    Antonie van Leeuwenhoek 61 (1992), S. 1-33 
    Details
    ISSN: 1572-9699
    Schlagwort(e): Paracoccus denitrificans ; denitrification ; methylotrophy ; cytochromec ; cytochrome oxidase ; phylogeny ; evolution ; lateral gene transfer ; nitrogen fixation ; Thiosphaera pantotropha
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Denitrification and methylotrophy inParacoccus denitrificans are discussed. The properties of the enzymes of denitrification: the nitrate-nitrite antiporter, nitrate reductase, nitrite reductase, nitric oxide reductase and nitrous oxide reductase are described. The genes for none of these proteins have yet been cloned and sequenced fromP. denitrificans. A number of sequences are available for enzymes fromEscherichia coli, Pseudomonas stutzeri andPseudomonas aeruginosa. It is concluded that pathway specificc-type cytochromes are involved in denitrification. At least 40 genes are involved in denitrification. In methanol oxidation at least 20 genes are involved. In this case too pathway specificc-type cytochromes are involved. The sequence homology between the quinoproteins methanol dehydrogenase, alcoholdehydrogenase and glucose dehydrogenase is discussed. This superfamily of proteins is believed to be derived from a common ancestor. ThemoxFJGI operon determines the structural components of methanol dehydrogenase and the associatedc-type cytochrome. Upstream of this operon 3 regulatory proteins were found. The mox Y protein shows the general features of a sensor protein and the moxX protein those of a regulatory protein. Thus a two component regulatory system is involved in both denitrification and methylotrophy. The phylogeny of prokaryotes based on 16S rRNA sequence is discussed. It is remarkable that the 16S rRNA ofThiosphaera pantotropha is identical to that ofP. denitrificans. Still these bacteria show a number of differences.T. pantotropha is able to denitrify under aerobic circumstances and it shows heterotrophic nitrification. Nitrification and heterotrophic nitrification are found in species belonging to the β-and γ-subdivisions of purple non-sulfur bacteria. Thus the occurrence of heterotrophic nitrification inT. pantotropha which belongs to the α-subdivision of purple non-sulfur bacteria is a remarkable property. FurthermoreT. pantotropha contains two nitrate reductases of which the periplasmic one is supposed to be involved in aerobic denitrification. The nitrite reductase is of the Cu-type and not of the cytochromecd 1 type as inP. denitrificans. Also the cytochromeb of theQbc complex ofT. pantotropha is highly similar to its counterpart inP. denitrificans. It is hypothesized that the differences between these two organisms which both contain large megaplasmids is due to a combination of loss of genetic information and plasmid-coded properties. The distribution of a number of complex metabolic systems in eubacteria and in a number of species belonging to the α-group of purple non sulphur bacteria is reviewed. Two possibilities to explain this haphazard distribution are considered: 1. Lateral gene transfer between distantly related micro organisms occurs frequently. 2. The eubacterial ancestors must have possessed already these properties. The distribution of these properties is due to sporadic loss during evolutionary divergence. With respect to the occurrence and frequency of lateral gene transfer two opposing views exist. According to molecular biologists lateral gene transfer occurs frequently and is very easy. Bacteria are supposed to form one large gene pool. On the other hand population geneticists have provided evidence that strong systems operate that establish reproductive isolation between diverged species and even between closely related cell lines. Data on amino acid sequences of nitrogenase proteins, cytochromesc, cytochrome oxidases, β-subunits of ATP synthase and tryptophan biosynthetic enzymes of various micro organisms were reviewed. In all these cases phylogenetic trees could be constructed based on the amino acid sequence data. In all cases this phylogenetic tree was similar to the one based on 16S rRNA homology. Only in one case evidence for the occurrence of lateral gene transfer was obtained. Therefore it is concluded that lateral gene transfer played a minor role in the distribution of complex metabolic systems among prokaryotes. It must be stressed that this does not exclude the possibility that lateral gene transfer occurred frequently in the initial stage of bacterial evolution. It is hypothesized that the appearance of nitrogen fixation, denitrification and cytochrome oxidase formation were early events in the evolution of micro organisms. Both systems are supposed to have evolved only once. Subsequently the capacity to fix nitrogen or to denitrifymust have been lost many times, just as photosynthetic capacity is supposed to have been lost many times. During evolution many systems have been lost leading to a haphazard distribution of metabolic characters among bacteria. As an example it is suggested that organisms with a respiratory chain similar to that ofEscherichia coli arose by loss of the capacity to form the Qbc complex andc-type cytochromes. The remaining systems could be controlled much better however than in the ancestral organisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00572119
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  • 4
    Digitale Medien
    Digitale Medien
    Development of non-reproductive castes in the neotropical termite generaCornitermes, Embiratermes andRhynchotermes (Isoptera, Nasutitermitinae) (1992)
    Springer
    Insectes sociaux 39 (1992), S. 313-324 
    Details
    ISSN: 1420-9098
    Schlagwort(e): Isoptera ; Termitidae ; Nasutitermitinae ; caste differentiation ; phylogeny ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The developmental pattern of the neuter castes was studied in the mandibulate nasute generaCornitermes, Embiratermes andRhynchotermes. InCornitermes walkeri, all the workers and soldiers are male. There are two larval and a single worker instar. Workers can molt into presoldiers. InEmbiratermes chagresi andRhynchotermes perarmatus, both sexes are present among the neuters. A slight sexual dimorphism (males 〉 females) is discernible among both larval instars and among workers ofE. chagresi; female workers can molt into presoldiers. InR. perarmatus, the sexual dimorphism is conspicuous from the first larval instar on. Male larvae go through two instars, then give rise to workers, which do not molt. InR. perarmatus, there is no worker stage in females, but a third larval instar, preceding the presoldier. Hypotheses are proposed as to the evolution of these caste patterns, attempting to conciliate present knowledge of Nasutitermitinae phylogeny and known evolutionary trends affecting termite caste patterns, according to the species' ecology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01323951
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  • 5
    Digitale Medien
    Digitale Medien
    Social organization in some primitive Australian ants. I.Nothomyrmecia macrops Clark (1992)
    Springer
    Insectes sociaux 39 (1992), S. 425-438 
    Details
    ISSN: 1420-9098
    Schlagwort(e): Formicidae ; Nothomyrmecia ; evolution ; sociogram ; ethogram ; recognition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Results of laboratory-based ethological studies on twoNothomyrmecia macrops colonies with individually marked workers are reported. Interactive behavioural acts constituted less than 1% of all those recorded, revealing a strong tendency by the ants not to engage in social contact. Very few workers performed queen-directed acts. They stayed near the queen, though seldom in direct contact. Division of labour was otherwise barely apparent, except that some individuals showed a propensity to guard the nest entrance. No exchange of food was observed between workers, workers and queen, or adults and larvae (apart from worker placement of prey items with larvae). A queen fed from aDrosophila carcass retrieved from the nest floor, without assistance from workers. Systematic scanned observations confirmed levels of inactivity higher than previously observed in ants (comprising almost 2/3 of recorded behavioural acts). The time budget for activities directed toward the immature stages was the same in both colonies, and fluctuated during the circadian period. Non-nestmate larvae added to worker groups were more frequently licked than nestmate larvae, but this might not involve the particular recognition of nestmateversus non-nestmate brood. These observations support the hypothesis thatNothomyrmecia is primitively eusocial, and of special significance in myrmecology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01240625
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  • 6
    Digitale Medien
    Digitale Medien
    Endogenous synthesis of peptidoglycan in eukaryotic cells; a novel concept involving its essential role in cell division, tumor formation and the biological clock (1992)
    Springer
    Cellular and molecular life sciences 48 (1992), S. 921-931 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Biological clock ; cell division cycle ; diaminopimelate ; evolution ; FSu ; lysine ; muramate ; muramyl dipeptide ; peptidoglycan ; sleep muropeptide ; tumor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Degradation products of peptidoglycan, the universal bacterial cell wall constituent, were previously found in animal tissues and urine. Reassessment and quantitative analysis of available data lead to an original concept, i.e. that eukaryotic cells synthesize peptidoglycan. We present a model in which this endogenously synthesized peptidoglycan is essential for the processes of eukaryotic cell division and sleep induction in animals. Genes for peptidoglycan metabolism, like those for lysine biosynthesis in plants, are probably inherited from endosymbiotic bacteria, the ancestors of mitochondria and chloroplasts. Corollaries of this concept, i.e. roles for peptidoglycan metabolism in tumor formation and in the biological clock, are supported by abundant evidence. We propose that many interactions between bacteria and eukaryotes are conditioned by their common genetic heritage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01919139
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  • 7
    Digitale Medien
    Digitale Medien
    The Light Green Cells ofLymnaea: A neuroendocrine model system for stimulus-induced expression of multiple peptide genes in a single cell type (1992)
    Springer
    Cellular and molecular life sciences 48 (1992), S. 464-473 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Molluscan insulin-related peptides ; schistosomin ; neuropeptide gene family ; generation of neuropeptide diversity ; stimulus-dependent expression ; information-handling capacity ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We review recent experiments showing that the cerebral neuroendocrine Light Green Cells (LGCs) of the freshwater snail,Lymnaea stagnalis, express a family of distinct though related molluscan insulin-related peptide (MIP) genes. The LGCs are involved in the regulation of a wide range of interrelated life processes associated with growth, (energy) metabolism and reproduction. We consider the mechanism of generation of diversity among MIPs, and present evidence that conditions with distinct effects on growth, metabolism and reproduction also can induce distinct patterns of expression of the MIP and schistosomin genes. The stimulus-dependent expression of multiple neuropeptide genes enormously increases the adaptive potential of a peptidergic neuron. We suggest that this contributes significantly to the information-handling capacity of the brain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01928165
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  • 8
    Digitale Medien
    Digitale Medien
    The origin of life — A task in molecular engineering (1992)
    Springer
    Molecular engineering 1 (1992), S. 377-399 
    Details
    ISSN: 1572-8951
    Schlagwort(e): Origin of life ; molecular engineering ; biology ; evolution ; genetic code ; translation machine ; self instruction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In attempting to understand how life originated, we search for a detailed sequence of experimentally testable physico-chemical steps in an appropriately structured system. This goal is approached in two stages. First we search for the organizational structure of processes leading to systems with the basic features of living organisms. This is an engineering problem: finding a certain construct by taking care of logical requirements and restrictions from physics. Then we face this construct with the chemical and geophysical reality, and this leads to the view that systems with the essential features of early living organisms evolve following a distinct pathway. Energy supply and the presence of a particular structure in space and time are necessary to induce and drive the processes triggered by stochastic events; but if these particular conditions are given, the broad line of the evolutionary processes is determined by logical requirements and by chemical and geophysical constrains and invariants. The genetic machinery considered to evolve in this manner agrees, in its organizational structure and in many details, with the actual genetic machinery of biosystems. A surprising simplicity and transparency is observed in the logic of the basic processes involved in the origin of life. In the present view, the processes leading to the origin of life begin in a very particular, highly structured, small region where the relevant chemistry can be quite different from overall prebiotic chemistry. Energy-rich compounds are present in ample amounts and a succession of physico-chemical processes, which are per se thermodynamically allowed, takes place. This is in contrast to popular views that the origin of life is connected with fundamental thermodynamic questions related to the problem of getting order out of chaos.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00176808
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  • 9
    Digitale Medien
    Digitale Medien
    Nucleotide sequence ofatpB,rbcL,trnR,dedB andpsaI chloroplast genes from a fernAngiopteris lygodiifolia: a possible emergence of Spermatophyta lineage before the separation of Bryophyta and Pteridophyta (1992)
    Springer
    Plant molecular biology 18 (1992), S. 79-82 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Angiopteris lygodiifolia ; atpB ; chloroplast genome ; evolution ; rbcL ; trnR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract To elucidate the evolutionary relationship between the Spermatophyta, Pteridophyta and Bryophyta, we cloned a fragment of chloroplast DNA from the fernAngiopteris lygodiifolia (Pteridophyta) and determined its nucleotide sequence. The fragment contained theatpB,rbcL,trnR-CCG,dedB andpsaI genes. Comparisons of the deduced amino acid and nucleotide sequences of these genes from the three plant groups indicate thatAngiopteris sequences are more closely related to those of Bryophyta species (85% identity on average) than to those of seed plants (76% identity on average), supporting a hypothesis that the Bryophyta and Pteridophyta diverged more recently from one another than their common progenitor diverged from that of the Spermatophyta.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00018458
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  • 10
    Digitale Medien
    Digitale Medien
    The activation process of Arabidopsis thaliana A1 gene encoding the translation elongation factor EF-1α is conserved among angiosperms (1992)
    Springer
    Plant molecular biology 18 (1992), S. 1083-1089 
    Details
    ISSN: 1573-5028
    Schlagwort(e): translation elongation factor genes ; promoter analysis ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In Arabidopsis thaliana, the activation process of the A1 EF-1α gene depends on several elements. Using the GUS reporter gene, transient expression experiments have shown that mutations of upstream cis-acting elements of the A1 promoter, or the deletion of an intron located within the 5′ non-coding region, similarly affect expression in dicot or monocot protoplasts. The results reported here strongly suggest that this 5′ intron is properly spliced in Zea mays. We show that two trans-acting factors, specifically interacting with an upstream activating sequence (the TEF 1 box), are present in nuclear extracts prepared from A. thaliana, Brassica rapa, Nicotiana tabacum and Z. mays. In addition, a DNA sequence homologous to the TEF 1 box, found at approximately the same location within a Lycopersicon esculentum EF-1α promoter, interacts with the same trans-acting factors. Homologies found between the A. thaliana and L. esculentum TEF 1 box sequences have allowed us to define mutations of this upstream element which affect the interaction with the corresponding trans-acting factors. These results support the notion that the activation processes of A. thaliana EF-1α genes have been conserved among angiosperms and provide interesting data on the functional structure of the TEF 1 box.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00047711
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  • 11
    Digitale Medien
    Digitale Medien
    A 16 kb small single-copy region separates the plastid DNA inverted repeat of the unicellular red alga Cyanidium caldarium: physical mapping of the IR-flanking regions and nucleotide sequences of the psbD-psbC, rps16, 5S rRNA and rpl21 genes (1992)
    Springer
    Plant molecular biology 19 (1992), S. 1001-1010 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Cyanidium caldarium Geitler ; evolution ; Galdieria sulphuraria ; inverted repeat ; plastid DNA ; psbD-psbC operon ; red algae ; 5S rRNA ; rpl21 ; rps16
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The four inverted repeat (IR) flanking regions of the Cyanidium caldarium plastid DNA were cloned. Southern blotting, transcript and sequence analyses of the border regions revealed the psbD-psbC operon and the rps16 gene within the large single-copy region upstream of the 16S rDNA gene and the rpl21 gene downstream of the 5S rDNA within the 16 kb small single-copy region. The size of the IR is ca. 5 kb. The nucleotide sequences of the psbD-psbC, rps16, rpl21 and 5S rRNA genes with the corresponding alignments and physical maps of the regions are presented. Northern analysis revealed a less complex psbD-psbC transcription pattern than has been found in higher plants. Comparisons to other red algal data point to structural diversity within red algal plastid DNA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00040531
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  • 12
    Digitale Medien
    Digitale Medien
    Comparison of regions coding for tRNAHis genes of mitochondrial and chloroplast DNA in sunflower: a proposal concerning the classification of ‘CP-like’ tRNA genes (1992)
    Springer
    Plant molecular biology 20 (1992), S. 1-4 
    Details
    ISSN: 1573-5028
    Schlagwort(e): higher plants ; sunflower ; chloroplast genome ; mitochondrial genome ; tRNAHis genes ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029143
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  • 13
    Digitale Medien
    Digitale Medien
    An equivalent to bacterialompR genes is encoded on the plastid genome of red algae (1992)
    Springer
    Plant molecular biology 18 (1992), S. 777-780 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Cyanidium caldarium ; evolution ; Galdieria sulphuraria ; rRNA operon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00020019
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  • 14
    Digitale Medien
    Digitale Medien
    Domatia as most important adaptations in the evolution of myrmecophytes in the paleotropical tree genusMacaranga (Euphorbiaceae) (1992)
    Springer
    Plant systematics and evolution 180 (1992), S. 53-64 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Angiosperms ; Euphorbiaceae ; Macaranga ; Ant-plant interactions ; domatia ; evolution ; myrmecophytism ; Flora of Malaysia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The paleotropical tree genusMacaranga (Euphorbiaceae) comprises all stages of interaction with ants, from facultative associations to obligate myrmecophytes. In SE.-Asia food availability does not seem to be the limiting factor for the development of a close relationship since all species provide food for ants in form of extrafloral nectar and/or food bodies. Only myrmecophyticMacaranga species offer nesting space for ants (domatia) inside internodes which become hollow due to degeneration of the pith. Non-myrmecophytic species have a solid stem with a compact and wet pith and many resin ducts. The stem interior of some transitional species remains solid, but the soft pith can be excavated. The role of different ant-attracting attributes for the development of obligate ant-plant interactions is discussed. In the genusMacaranga, the provision of nesting space seems to be the most important factor for the evolution of obligate myrmecophytism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00940397
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  • 15
    Digitale Medien
    Digitale Medien
    Phylogenetic evidence for the herbaceous origin of angiosperms (1992)
    Springer
    Plant systematics and evolution 180 (1992), S. 137-156 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Angiosperms ; evolution ; origin ; ancestral angiosperm ; morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The ancestral angiosperm is commonly interpreted as an arborescent to shrubby magnolialean with large, multiparted, complex flowers. We examined this hypothesis using a phylogenetic analysis of new and reevaluated characters polarizabled with outgroup comparison. Our cladistic analysis of basal angiosperms placed the nonmagnolialeanChloranthaceae andPiperaceae at the bottom of the tree. We further inferred the probable ancestral states of characters not polarizable with outgroup comparison by examining their distribution among taxa at the base of our cladogram. The sum of ancestral character states suggests that the protoangiosperm was a diminutive, rhizomatous to scrambling perennial herb, with small, simple flowers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00941148
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  • 16
    Digitale Medien
    Digitale Medien
    Isozyme variation and alleged progenitor-derivative relationships in theMedicago murex complex (Fabaceae) (1992)
    Springer
    Plant systematics and evolution 181 (1992), S. 33-43 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Angiosperms ; Fabaceae ; Medicago murex ; M. lesinsii ; Systematics ; evolution ; isozymes ; chromosomes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Chromosomal studies ofMedicago lesinsii (n = 8) and its close relativeM. murex (n = 7) have led to the competing hypotheses that the latter is derived directly from the former, or that both originated from a common ancestor. In contrast to the relatively variableM. murex, M. lesinsii proved to be almost uniform isozymically, except that most populations of Greece differed by one allele from plants of the remainder of the range. This Greek variant ofM. lesinsii was indistinguishable from one of the isozyme variants ofM. murex. The greater level of allozyme variation inM. murex was consistent with its greater ecological amplitude and competitive ability. Also, this suggests thatM. murex is unlikely to have originated directly from the less variableM. lesinsii. The data suggest that either both species originated from a common ancestor, or that the n = 8 species evolved from the n = 7 species, a mode of chromosome evolution not previously hypothesized for the genus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00937585
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  • 17
    Digitale Medien
    Digitale Medien
    Phenetic, biogeographical, and evolutionary study ofOrnithogalum subg.Heliocharmos (Hyacinthaceae) in the western Mediterranean basin (1992)
    Springer
    Plant systematics and evolution 181 (1992), S. 179-202 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Hyacinthaceae ; Ornithogalum ; Heliocharmos ; O. algeriense ; O. kochii ; O. orthophyllum ; O. umbellatum ; Numerical taxonomy ; phenetics ; systematics ; biogeography ; evolution ; Flora of North Africa ; Mediterranean ; Morocco ; Spain ; France
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A macromorphological study is made on taxa of the genusOrnithogalum subg.Heliocharmos in North Africa, Spain, and France. The results obtained are consistent with data from cytogenetics, reproductive biology and strategies of reproduction. They allow the retention of two species:O. algeriense andO. umbellatum. A biogeographical and phylogenetic interpretation of the subgenus is proposed for the western Mediterranean. Theoretical views on phenetics are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00937443
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  • 18
    Digitale Medien
    Digitale Medien
    The 5S DNA units ofAcacia species (Mimosaceae) (1992)
    Springer
    Plant systematics and evolution 183 (1992), S. 235-247 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Angiosperms ; Mimosaceae ; Acacia ; 5S DNA ; evolution ; phylogeny ; chromosomal lineages
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The DNA sequence structure of 5S DNA units inAcacia species, including representatives from the three subgenera ofAcacia, have been determined. The data was interpreted to suggest that at least three lineages of 5S DNA sequences exist inAcacia and the proposal was made that the lineages be named5S Dna-1, 5S Dna-2, and5S Dna-3. The5S Dna-1 lineage was represented by units fromA. boliviana andA. bidwilli, the5S Dna-2 lineage by units fromA. melanoxylon, A. pycnantha, A. ulicifolia, A. boliviana, A. bidwillii, andA. albida, and the5S Dna-3 lineage by units fromA. bidwillii, A. boliviana, andA. senegal. Based on this interpretation of the sequence data, the Australian species of subg.Phyllodineae grouped together as a cluster, quite separate from the subgeneraAculeiferum andAcacia. As expected from the analyses of morphological characters, the 5S DNA units fromAcacia albida (syn.Faidherbia albida) were quite separate from the otherAcacia spp.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00940806
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  • 19
    Digitale Medien
    Digitale Medien
    Relationships betweenOryza species (Poaceae) based on 5S DNA sequences (1992)
    Springer
    Plant systematics and evolution 183 (1992), S. 249-264 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Poaceae ; Oryza ; 5S DNA ; phylogeny ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Relationships between 9Oryza species, covering 6 different genomes, have been studied using hybridization and nucleotide sequence information from the5S Dna locus. Four to five units of the major size class of 5S DNA in each species, 55 units in all, were cloned and sequenced. Both hybridization and sequence data confirmed the basic differences between the A and B, C, D genome species suggested by morphological and cytological data. The 5S DNA units of the A genome species were very similar, as were the ones from the B, C, and D genome-containing species. The 5S DNA ofO. australiensis (E genome) grouped with the B, C, D cluster, while the units ofO. brachyantha (F genome) were quite different and grouped away from all other species. 5S DNA units fromO. minuta, O. latifolia, O. australiensis, andO. brachyantha hybridized strongly, and preferentially, to the genomic DNA from which the units were isolated and hence could be useful as species/genome specific probes. The 5S DNA units fromO. sativa, O. nivara, andO. rufipogon provided A genome-specific probes as they hybridized preferentially to A genome DNA. The units fromO. punctata andO. officinalis displayed weaker preferential hybridization toO. punctata DNA, possibly reflecting their shared genome (C genome).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00940807
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  • 20
    Digitale Medien
    Digitale Medien
    2-Bromoacetyl-6-methoxynaphthalene: A useful fluorescent labelling reagent for HPLC analysis of carboxylic acids (1992)
    Springer
    Chromatographia 33 (1992), S. 13-18 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fatty acids and bile acids ; Fluorogenic precolumn derivatization ; 2-Bromoacetyl-6-methoxynaphthalene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The use of 2-bromoacetyl-6-methoxynaphthalene as a fluorogenic labelling reagent in pre-column derivatization for the HPLC separation of biologically active carboxylic acids (fatty acids and bile acids) has been investigated. The compound reacts (30 min. at 70°C) with carboxylic acids to give fluorescent esters that can be separated by reversedphase HPLC and detected at λ ex. 300 nm, λ em. 460 nm. The experimental conditions for the derivatization and chromatographic separation are discussed. Applications to the determination of valproic acid and chenodeoxycholic acid in pharmaceutical formulations are described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276844
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  • 21
    Digitale Medien
    Digitale Medien
    HPLC method for the simultaneous analysis of valproic acid and other common anticonvulsant drugs in human plasma or serum (1992)
    Springer
    Chromatographia 33 (1992), S. 37-40 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Valproic acid ; Simultaneous determination of anticonvulsants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The derivatizing procedure of Moody et al. [20] for valproic acid has been simplified and applied to the simultaneous HPLC determination of valproic acid (VPA), barbital (B), primidone (PRM), phenobarbital (PB) and carbamazepine (CBZ) in serum or plasma of epileptic patients. The sample is deproteinized with acetonitrile containing esterification agents and an aliquot of the supernatant is heated to 70°C for 15 min with 4-bromophenacyl bromide. The reaction mixture is analysed on a C18 column at ambient temperature, with gradient elution and with detection at 205 nm. The time required for the chromatographic analysis is 13 min; identification is based on retention time and quantification is by peak area determination with an internal standard. The calibration curves show good linearity in the range 6.25 to 100 mg/L. The detection limits at a signal: noise ratio ≥3, ranged from 1 mg/L for B and CBZ to 2–3 mg/L for PRM, PB and VPA. The method described for the simultaneous determination of the five drugs in the same plasma pool, correlated well with isocratic HPLC methods specific for each drug. The simultaneous procedure described allows a reproducible (CVs≤6.5% within run) and rapid (25 min for sample preparation: 13 min for chromatographic run) therapeutic monitoring of patients treated with VPA and two or more antiepileptic drugs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276848
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  • 22
    Digitale Medien
    Digitale Medien
    Porous polymer packings from vinyl ether derivatives for reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 19-24 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Porous polymer spherical packings ; Vinyl ether ; Alkali resistance ; No abnormal adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Spherical, porous-polymer particles for column packing in high-performance liquid chromatography were prepared by suspension copolymerization of alkylvinyl ether with triethyleneglycol divinyl ether. The hydrophobicity of the packings was easily adjusted by changing the monomer ratio. The packings showed the usual reversed-phase liquid chromatographic properties, but did not sho abnormal retention, tailing and broadening of peaks and irreversible adsorption of ionic and aromatic substances, owing to the lack of ionic or aromatic groups. In addition, the packings were stable in alkaline solutions because of the relative alkali stability of C−O−C bonds as compared with CO−O and Si−O−C bonds in conventional packings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276845
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  • 23
    Digitale Medien
    Digitale Medien
    Comparison study between indirect photometric and direct conductivity detection for anion exchange chromatography using naphthalenesulfonate derivatives as mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 25-31 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Anion exchange ; Indirect photometric and direct conductivity detection ; Naphthalenesulfonate ; Inorganic anions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Indirect photometric and unsuppressed direct conductivity detection modes are examined using naphthalene mono-, di-, and tri-sulfonate as mobile phases for the separation of several anions such as F−, Cl−, NO2 −, Br−, NO3 −, SO4=,I−, and SCN− using a commercial anion exchange column. With all three mobile phases, conductivity detection shows better sensitivities and detection limits than indirect photometry. Conductivity detection is 5 to 16 times more sensitive than indirect photometry for all analytes. Detection limits achieved using these mobile phases are, for example, 0.04 ng and 0.1 ng for chloride ion with conductivity and indirect photometry, respectively. Both detection modes give wide linear ranges extending from at least 100 ppm to the detection limit of each anion which is generally about 0.02 ppm. Sulfur oxide anions such as dithionate and tetrathionate are separated using flow programming with naphthalenetrisulfonate as the mobile phase in less than 20 minutes. With both detection modes, desired chromatographic performance of these three eluents is achieved without pH adjustment of the mobile phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276846
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  • 24
    Digitale Medien
    Digitale Medien
    An enhanced liquid chromatographic method for 5-hydroxymethylfurfural determination in UHT milk (1992)
    Springer
    Chromatographia 33 (1992), S. 45-48 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Heat-treated milk ; Milk quality indicators ; 5-Hydroxymethyl-2-furfuraldehyde
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An enhanced method of HPLC for the determination of 5-Hydroxymethyl-2-furfuraldehyde (HMF) in fluid milk was perfected. Its resolving capacity permitted the specific separation of this compound. The real concentration (μmol/l) of HMF was determined and not the HMF value, as in the colorimetric analysis, where an intermediary coloured compound (HMF-TBA) is utilised. The optimum pH condition (pH=4.0–4.2) for the mobile phase to prevent overlapping between the HMF peak and the peaks of the other compound (α and β) that coeluted with the HMF and also the optimum organic solvent content (3% or 7%) were established. This is a sensitive, quick and safe method for the determination of HMF in fluid milk.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276850
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  • 25
    Digitale Medien
    Digitale Medien
    Ion-pair reversed-phase liquid chromatography of arsenic species on polymeric styrene-divinylbenzene packed columns with an alkaline aqueous mobile phase (1992)
    Springer
    Chromatographia 33 (1992), S. 581-585 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Arsenic compounds ; Polymeric styrene divinylbenzene phase ; Ion-pairing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The resolving power of an ion-pair reversed-phase liquid chromatography method, on a polymeric stationary phase (PRP-1) with an alkaline aqueous mobile phase (pH=9) containing tetrabutylammonium cation as ion-pairing agent, is compared with a traditional ion-pairing system using an octadecyl-modified silica column and a neutral aqueous mobile phase (pH=7.3). This chromatographic system (PRP-1 column) provides a rapid means for the determination of two of the most important arsenic species, arsenobetaine and arsenite. Addition of methanol (5%) to the aqueous mobile phase allows the differentation of arsenobetaine from the system peak when using UV detection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262252
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  • 26
    Digitale Medien
    Digitale Medien
    Comparison of provitamin A determination by normal-phase gravity-flow column chromatography and reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 133-137 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Gravity-flow column chromatography ; Provitamin A determination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The provitamin A content of some food samples was determined by methods involving MgO: Hyflosupercel gravityflow column chromatography (GFCC) and reversed phase high performance liquid chromatography (HPLC), the quantitation being done by external standardization (HPLC-ES) or internal standardization (HPLC-IS) with Sudan. The results obtained with α- and β-carotene in carrots, β-carotene and β-cryptoxanthin in papaya and β-carotene in tomato and kale agreed well, showing that any of the these techniques can be used, provided the analysis is done under optimum conditions. Good separation of the different provitamins using GFCC depends on the analyst's skill and visual acuity. HPLC-ES required a constant supply of provitamin standards, thus the varying purity of commercially available standards and the high instability of these compounds could pose grave problems. Due to the stability of Sudan, HPLC-IS appeared to be the method of choice although passage of the extract through a MgO: Hyflosupercel minicolumn was required prior to injection to separate chlorophylls, dihydroxy- and polyoxycarotenoids which would otherwise elute with Sudan. Nonconformity of the Sudan structure to those of the provitamins did not effect the quantitative results. The chromatographic separation, identity and quantification of the provitamins could be more easily established by using HPLC-IS, complemented with GFCC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275893
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  • 27
    Digitale Medien
    Digitale Medien
    Diastereoselective and enantioselective chromatography of the pyrethroid insecticides allethrin and cypermethrin (1992)
    Springer
    Chromatographia 33 (1992), S. 103-112 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275888
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  • 28
    Digitale Medien
    Digitale Medien
    Estimation of diuretic drugs in biological fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 177-185 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Diuretics ; Screening and determination of diuretics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275902
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  • 29
    Digitale Medien
    Digitale Medien
    Peak recognition technique by a computer program copying the human judgement (1992)
    Springer
    Chromatographia 33 (1992), S. 218-224 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Peak ; Pattern recognition ; Prediction interval
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary It is still difficult to determine peaks and peak boundaries properly, though peak recognition is very important for the precision of quantitative data. A new computer program overcomes these problems using a method which is adapted from human judgements. The algorithm was developed for HPLC but can also be used in other fields of analytical chemistry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276186
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  • 30
    Digitale Medien
    Digitale Medien
    High performance liquid chromatography of raw sugars and polyols using bonded silica gels (1992)
    Springer
    Chromatographia 33 (1992), S. 325-330 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Diol silica gels ; Carbohydrates ; Evaporative light scattering detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Bonded silica columns have been evaluated for their ability to separate carbohydrates and polyols. Mobile phases consisting of dichloromethane/methanol produced the best separations in comparison with the acetonitrile/water mixtures commonly used with amino columns. Of all the bonded phases tested, LiChrospher Diol silica provided the best separations, and selectivities were not very different from those obtained on the most popular system using an amino bonded phase and acetonitrile/water as eluent. In addition, diol columns with a dichloromethane/methanol eluent offer excellent stability with no Schiff’s base formation of reducing sugars. Using an evaporative light scattering detector, low limit detection is obtainable (20 ng of glucose from a column) and gradient elution is quite feasible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275911
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  • 31
    Digitale Medien
    Digitale Medien
    Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters (1992)
    Springer
    Chromatographia 33 (1992), S. 356-360 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Porous graphitized carbon ; Ring-substituted aniline derivatives ; Electronic interactions ; Principal component analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention characteristics of 22 aniline derivatives were determined on a porous, graphitized-carbon column in unbuffered acetonitrile-water and methanol-water mixtures. Each aniline derivative gave symmetrical peaks in each eluent without buffers. Good linear correlations were found between the log k′ and the concentration of the organic component in the eluent. The slope and intercept values differed according to the type of organic modifier and the charcter, number and position of substituents, indicating the different selectivities of methanol and acetonitrile and the good separating power of the column. Multivariate mathematical-statistical calculations proved that the retention of ring-substituted aniline derivatives is mainly governed by electronic parameters and the hydrogen acceptor capacity of substituents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275918
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  • 32
    Digitale Medien
    Digitale Medien
    Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 374-376 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ion-pairing ; Furosine ; Pyridosine ; Milk
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r〉0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275921
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  • 33
    Digitale Medien
    Digitale Medien
    Optimisation of data handling and detection conditions for automated chromatographic assay software (1992)
    Springer
    Chromatographia 33 (1992), S. 361-368 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Automated peak detection ; Discrete Fourier transform ; Frequency acquisition and filtering ; Peak detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The principle of automated chromatographic peak detection and analysis software is summarized, and critical steps are systematically studied. As the only parameter to be entered is the acquisition frequency, evaluation of its effect on software performance is discussed. In the case of relatively noisy chromatograms, it is shown experimentally that numerous points per peak have to be taken, leading to quite fast computer acquisition procedures. The use of discrete Fourier transform filtration techniques can modify peak shapes and a comparative study evaluates the relative errors induced in the shapes and characteristics of the chromatographic profiles. Optimisation of filtering conditions is achieved and it is shown that for a filter position only 2% of the Nyquist frequency no deformation occurs in the chromatographic profile. Detection of the start and finish of chromatographic peaks is optimized according to a simple four step iterative procedure. In the case of simulations, the difference between the values used to simulate peaks and those calculated by the software are less than 1%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275919
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  • 34
    Digitale Medien
    Digitale Medien
    Simultaneous determination of 5′-deoxy-5-fluorouridine, 5-fluorouracil and its main metabolites in body fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 413-417 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fluoropyrimidine drugs ; Pharmacokinetics of doxifluridine ; Chemotherapy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A reversed phase high performance liquid chromatographic method has been developed for the simultaneous determination of the pro-drug 5′-deoxy-5-fluorouridine (5′-dFUR), its metabolite 5-fluorouracil (5-FU) and some fluorinated pyrimidines involved in the metabolic activation process of 5-FU. The method has been used to monitor the bioavailability of 5′-dFUR and 5-FU in patients undergoing anticancer chemotherapy. Serum sample treatment involves addition of internal standard (5-bromouracil), protein precipitation with saturated ammonium sulphate solution and liquid-liquid extraction with ethyl acetate-isopropanol (90 ∶ 10 v/v). Urine is simply diluted with mobile phase and injected. The average recovery from serum (at 0.5 μg/mL level) was 95.0%±1.4 for 5′-dFUR and 86.3%±3.5 for 5-FU. A linear response extending over four decades of concentration was observed. Detection limits in the low ng/ mL range were obtained using a 250 μL sample size and a 20 μL injection volume. Within-day and between-day coefficients of variation were below 4 and 10%, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262320
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  • 35
    Digitale Medien
    Digitale Medien
    Total and individual determination of carbamate pesticides by use of an integrated flow-injection/HPLC system (1992)
    Springer
    Chromatographia 33 (1992), S. 449-453 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Flow injection analysis ; Combined flow injection/HPLC ; Carbamate pesticides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An integrated flow injection (FI)/HPLC system for the total and individual determination of carbamate pesticides (propoxur, carbofuran and carbaryl) is proposed. The determination is based on the alkaline hydrolysis of the analytes and subsequent coupling with diazotized sulphanilic acid to yield the monitored dyes with or without a prior separation step by HPLC in a C18 column. The calibration curves obtained are linear in the μg/ml range and r.s.d. values are between 0.5 and 3.7% in all instances. Injection of the sample into the FI manifold allows the total pesticide content in the sample to be screened. The manifold thus acts as a post-column reactor/detector of the chromatograph for samples with high overall carbamate content, which are also injected into the HPLC instrument. The performance was checked with contaminated water samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262326
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  • 36
    Digitale Medien
    Digitale Medien
    Evaluation of the enantioselectivity towards β-blocking agents of the α1 glycoprotein type chiral stationary phase: Chiral AGP®glycoprotein type chiral stationary phase: Chiral AGP® (1992)
    Springer
    Chromatographia 33 (1992), S. 454-462 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The enantioselectivity of the α1 glycoprotein chiral stationary phase, Chiral AGP® has been evaluated for a number of β-blocking agents. A correlation has been found between the retention behaviour on this stationary phase and the hydrophobicity of the compounds. The separation factor α is higher for compounds that are well retained. Retention, and thus α, are also controlled by pH and the percentage of organic modifier in the mobile phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262327
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  • 37
    Digitale Medien
    Digitale Medien
    Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings (1992)
    Springer
    Chromatographia 33 (1992), S. 473-477 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Perfluoroalkylated polymer-gel packings ; Aromatic and fluorine-containing compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Porous, perfluoroalkylated polymer-gels for column packings in high-performance liquid chromatography (HPLC) were prepared by suspension polymerization of heptadecafluorodecyl arcylate and ethylene glycol dimethacrylate. The packings showed no abnormal retention for ionic or aromatic compounds, due to the lack of ionic or aromatic groups. In addition, the packings showed no excessive retention for strongly hydrophobic compounds which is often the case with long-chain, alkylated silica gels and polymer gels. This is due to the extremely low surface energy of perfluoroalkyl groups. Therefore, perfluoroalkylated polymer gels enable isocratic HPLC separation of solutes with significantly different hydrophobicity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262330
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  • 38
    Digitale Medien
    Digitale Medien
    Comments on the paper “correlation between retention in liquid chromatography and the adsorption energy” by J. Kloubek (1992)
    Springer
    Chromatographia 33 (1992), S. 485-486 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262332
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  • 39
    Digitale Medien
    Digitale Medien
    Correlation between retention in liquid chromatography and the adsorption energy (1992)
    Springer
    Chromatographia 33 (1992), S. 478-484 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Porous glass adsorbents ; Surface free energy ; Oriented adsorption of hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The relationship between the specific capacity factor (k/S, where k is the capacity and S is the surface area of the sorbent, in m2) in the liquid chromatography of aromatic hydrocarbons and the adsorption energy (-°GA) has been investigated. The previously published results, based on the calculation of the work of adhesion (WSA) from contact angles, were re-examined and a new hypothesis on interactions at interfaces was employed. Direct proportionality has been found between k/S and-°GA, which allows prediction of the chromatographic behavior of adsorbates on sorbents. The surface free energy components were calculated in order to determine-°GA in terms of the work of adhesion. The dispersion component of the surface free energy of glass was obtained from the adsorption isotherm of n-octane and it was found that the hydrocarbon molecules are adsorbed in an oriented position. The contact angles of liquids on the outer surface of porous solids do not yield reliable values of WSA and of the surface free energy components. A higher intermolecular attraction increases WSA and decreases the contact angle in pores.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262331
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  • 40
    Digitale Medien
    Digitale Medien
    A high-performance liquid chromatographic method for the analysis of adenosine and some metabolites in the brain tissue of rats (1992)
    Springer
    Chromatographia 34 (1992), S. 563-567 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Adenosine and some metabolites ; Extraction from brain tissue ; Quantitative determination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An analytical procedure has been developed for the assay of adenosine and some metabolites in brain tissue extracts of rats. This paper reports the extraction method, the technique adopted to avoid enzymatic transformations and the chromatographic conditions for the identification and quantitation of these nucleosides and bases. Peaks in the chromatograms of brain tissue extracts were identified by retention times, absorbance ratios of reference compounds and by enzymatic peak-shift.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269864
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  • 41
    Digitale Medien
    Digitale Medien
    Influence of silica gel surface purity on the coverage density of chemically bonded phases (1992)
    Springer
    Chromatographia 34 (1992), S. 573-580 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chemically bonded phases (CBP) ; Surface heterogenity ; Surface purification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The surface chemistry of eight silica-gels with different siliceous matrix structures have been described. The influence of surface impurities on the chemical modification process (coverage density) with monooctadecylsilane has been studied. The surfaces of the adsorbents, before chemical modification, were cleaned by extraction with 20% HCl. Bare and modified materials were characterized using different physico-chemical methods e.g.: SIMS, CP/MAS NMR, porosimetry, pH measurement, elemental analysis and chromatography (GC & HPLC). The presence of trace amounts of different metallic elements creating new adsorption centers on the surfaces of the packings, have been demonstrated. Moreover, it has been shown that washing of silica gel adsorbents increases the coverage density of alkylsilyl ligands and improves the chromatographic properties of prepared packings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269866
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  • 42
    Digitale Medien
    Digitale Medien
    Zone electrophoretic sample treatment coupled on-line with column liquid chromatography for the determination of basic and acidic compounds in biological samples (1992)
    Springer
    Chromatographia 34 (1992), S. 581-588 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A modified valve arrangement for zone-electrophoretic sample treatment (ZEST)-which is coupled on-line with column liquid chromatography — is used to pretreat biological (plasma) samples. Carry-over of plasma proteins depends on the pH of the electrophoresis buffer. The determination of propranolol, metoprolol, cromolyn and salicylic acid demonstrates that both basic and acidic analytes can be isolated from the plasma matrix with high selectivity. Analogous piperazines, with different protein binding properties, were used to study the influence of protein binding on the recovery. It is shown that high protein can cause a decreased recovery.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269867
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  • 43
    Digitale Medien
    Digitale Medien
    HPLC analysis of the main oxindole alkaloids fromUncaria tomentosa (1992)
    Springer
    Chromatographia 34 (1992), S. 597-600 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Oxindole alkaloids ; Uncaria tomentosa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The main oxindole alkaloids from the root bark ofUncaria tomentosa were separated by reversed phase HPLC with an acetonitrile/methanol/phosphate buffer solvent gradient. UV detection was carried out at 245 nm. The chromatographic parameters for the separation of the alkaloids were optimized by studying the impact of the pH value of the mobile phase and the column temperature on the separation efficiency of the analytical system. The best separation was achieved with a mobile phase pH of 6.6 and a column temperature of 15°C. The method developed is suitable for the qualitative characterisation and quantitative determination of oxindole alkaloids in crudeUncaria tomentosa extracts and phytopharmaceuticals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269869
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  • 44
    Digitale Medien
    Digitale Medien
    Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 618-620 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Enantiomers of furprofen ; Human plasma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A sensitive and stereoselective liquid chromatographic (HPLC) assay for the S and R enantiomers of furprofen in human plasma has been developed. The assay is based on derivatization with S(−)-1-phenylethylamine with formation of two diastereoisomeric derivatives and on their separation and quantitation using HPLC with uv detection. The method is linear from 25 to 600 ng ml−1 of both enantiomers, with a variation coefficient below 10.8%, and a detection limit of 20 ng ml−1. This procedure is suitable for pharmacokinetic studies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269873
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  • 45
    Digitale Medien
    Digitale Medien
    Solute-micelle association constants and correlation of octanol-water coefficients with hydrophobicity for polycyclic aromatic hydrocarbons by micellar chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 627-635 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Micelle-solute association constants ; Polynuclear aromatic hydrocarbons ; Octanol/water partition coefficients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Sodium dodecyl sulphate, hexadecyltrimethylammonium bromide and polyoxyethylene(23) lauryl ether were investigated as mobile phases in the micellar liquid chromatography of polycyclic aromatic hydrocarbons of environmental concern. A wide range of surfactant concentrations were used and the retention parameters and distribution coefficients calculated. The trends in the retention data for the PAHs are discussed and several conclusions are presented concerning the partition coefficients when these surfactants are present in the mobile phase. Comparisons are made between the structural features of the compounds and their capacity factors, and the octanol/water partition coefficients are correlated with hydrophobicity for the PAHs studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269875
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  • 46
    Digitale Medien
    Digitale Medien
    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs (1992)
    Springer
    Chromatographia 34 (1992), S. 115-120 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276122
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  • 47
    Digitale Medien
    Digitale Medien
    A column switching technique for the determination of lidocaine and its metabolites in horse urine (1992)
    Springer
    Chromatographia 34 (1992), S. 143-145 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A rapid method is described for the determination of lidocaine and its metabolites in horse urine using a column switching technique and HPLC analysis. This procedure offers a sensitive assay without the need for time consuming extractions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276127
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  • 48
    Digitale Medien
    Digitale Medien
    Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates (1992)
    Springer
    Chromatographia 34 (1992), S. 132-136 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Cysteine, cystine ; Phenylthiocarbamyl derivatives ; Protein hydrolyzates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new approach is described, and a novel explanation presented, for the high performance liquid chromatographic analysis of cystine and cysteine as their phenylthiocarbamyl derivatives. PTC cystine and cysteine have been eluted with the same retention times and molar responses, most probably due to electrophilic attack of phenylisothiocyanate on cystine resulting in the scission of the disulfide bond yielding two moles of cysteine. Further, total PTC cystine and cysteine have been measured both in model solutions and in standard protein hydrolyzates (lysozyme, bovine albumin, ribonuclease) with the same linearity as the other ineteen amino acids. The reproducibility of the measurements, at the 250–750 pmole level, proved to be 4.1% (Relative Standard Deviation %) or less.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276125
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  • 49
    Digitale Medien
    Digitale Medien
    Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 155-158 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na+] and not on [K+] at concentrations of K+ from 5×10−7 to 10−1 mol l−1. Hence, actinomycin D may be classified as an ionophore-antibiotic.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276129
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  • 50
    Digitale Medien
    Digitale Medien
    Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns (1992)
    Springer
    Chromatographia 34 (1992), S. 146-154 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Isocratic column liquid chromatographic systems with UV absorbance detection at 280 nm have been developed for the separation of 29 phenolics and related compounds. The selectivity was investigated on silica-, carbon- and polymer-based separation columns for the separation of phenolic type of components. The effects of various acetonitrile/buffer mixtures, and pH of the mobile phase, and their impact on the retention of the phenols was assessed. Tables of retention times on the four columns for the 29 phenols with two different acetonitrile/buffer mixtures, together with the retention times at three pHs from 6.5 to 2.3 with varying levels of organic modifier on the LiChrospher RP 18 column are presented. As an application, the analysis of real river water samples from the Ebro river is described using a solid phase extraction step prior to injection into the chromatographic system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276128
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  • 51
    Digitale Medien
    Digitale Medien
    Microcolumn liquid chromatography on carbon sorbents (1992)
    Springer
    Chromatographia 34 (1992), S. 173-176 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention volume dependences on the molar volume were found for aromatic compounds using liquid microcolumn chromatography. The contributions of the functional groups in molecules of these compounds to the total retention value were calculated from the capacity factor values. The comparison of capacity factor values for carbon sorbents and octadecyl-silicagel has shown that for several microcolumn separations the carbon sorbent column has a better selectivity and resolution than the octadecyl-silicagel column.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276133
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  • 52
    Digitale Medien
    Digitale Medien
    Synthesis of acceptor bonded phases for donor-acceptor liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 177-181 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The synthesis of several electron-acceptor stationary phases has been reviewed the materials evaluated for their capacity to separate polyaromatic hydrocarbons (PAHs). Chemically bonded phases were obtained by the same procedure; the organosilane moiety is monofunctional and the HPLC behaviour is compared under identical conditions. Examples of PAHs separations are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276134
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  • 53
    Digitale Medien
    Digitale Medien
    Silanol group effect in C18 bonded phases in HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 182-184 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary If any residual (free) silanol groups remain at the surface of silica gel after bonding treatment, they may affect the retention of solutes since the dissociated groups (≡SiO−) will attract cations. The silanol group effect on the retention of cationic solutes will increase with increasing pH of the mobile phase but the effect will decrease with increasing hydrophobic-ion concentration at the C18 surface because such ions can mask the residual silanol groups. A method for the separation of metal complexes with 2-(5-bromo-2-pyridylazo)-diethylaminephenol (5-Br-PADAP) has been developed. The hydrophobic ion in the MeOH/H2O mobile phase was tetrabutylammonium (TBA).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276135
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  • 54
    Digitale Medien
    Digitale Medien
    Michael Tswett's columns: Facts and speculations (1992)
    Springer
    Chromatographia 34 (1992), S. 342-346 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Although Michael Tswett is the originator of chromatography, little is known about the performance of his chromatographic systems. His descriptions of the separation of plant pigments are detailed but nevertheless difficult to interprete by today's chromatographic theory. By our own experiments with the system calcium carbonate/benzene it was found that the separation factor of chlorophyll a and b is approx. 1.6 which means that less than 100 theoretical plates are necessary for separation. Tswett's columns with 50 μm particles and 2–3 cm of bed height presumably exceeded this plate number. His separations could have been impaired by mass overload and by a volume flow rate which was two orders of magnitude faster than the optimum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268366
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  • 55
    Digitale Medien
    Digitale Medien
    Factors influencing retention and resolution of substituted alkylbenzenes in reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 347-356 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention data of isomeric xylenes, ethyltoluenes and diethylbenzenes, and of mesitylene, benzene, toluene and ethylbenzene were obtained on a reversedphase column using methanol-water and ethanol-water mobile phases at four different temperatures. This database was used to relate the dependence of solute retention and resolution on the polarity of the mobile phase, solute dipole moment, and column temperature. The additivity of the free energy of the transfer of solute molecules or solute segments from the stationary phase to the mobile phase, was examined for the isomeric compounds. For this, the logarithm of the net retention volume was substituted for the free energy. Deviations from the additivity of free energies indicate that the separation of isomeric substituted alkylbenzenes is governed by their differential interactions with both the polar mobile phase and nonpolar stationary phase. Among the disubstituted alkylbenzenes,ortho-isomers favor the mobile phase more andpara-isomers tend to prefer the stationary phase more. Themeta-isomers are found to follow the additivity rule closely. These trends are amplified as the polarity of the mobile phase is increased indicating that these isomers are resolved better in water-rich mobile phases. These findings are substantiated by analogous results from gas-liquid chromatographic retention data, estimation of dipole moment effects, and examination of the entropic and enthalpic contributions to the net retention volume.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268367
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  • 56
    Digitale Medien
    Digitale Medien
    Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching (1992)
    Springer
    Chromatographia 34 (1992), S. 376-380 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268371
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  • 57
    Digitale Medien
    Digitale Medien
    Gradient high performance liquid chromatography of block copolymers of styrene andt-butyl methacrylate II. Association phenomena in mixtures of block copolymer with polystyrene (1992)
    Springer
    Chromatographia 34 (1992), S. 363-368 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Block copolymers of styrene andt-butyl methacrylate can be analysed by methanol/tetrahydrofuran gradients on C18 or phenyl bonded phase columns. On both of these columns, retention increases with styrene content of the samples. At 50°C, the retention of PS or a block copolymer containing 45% styrene was longer on the phenyl than the C18 columns. This indicates the contribution of adsorption to retention on phenyl bonded phase columns. Lowering the temperature from 50 to 30°C caused earlier elution of part of the sample from the phenyl phase. On a C18 phase the same drop in temperature improved the shape of the peak, which also started later than at 50°C. This effect of temperature is generally observed in polymer retention due to an adsorption mechanism, whereas increasing retention with decrease in temperature is characteristic of a precipitation mechanism. The block copolymer investigated contained 15% free polystyrene precursor which could not be separated from the block copolymer under the conditions employed. The addition of 20% PS homopolymer with a molecular weight similar to that of the styrene block in the copolymer showed that the polystyrene eluted together with the block copolymer, whereas the addition of PS homopolymer with a much higher molecular weight caused an extra peak at the expected elution time.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268369
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  • 58
    Digitale Medien
    Digitale Medien
    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary New multidentate phenyl-bonded phases (MPBPs) were synthesized and evaluated the chromatographic retention behaviour with polycyclic aromatic hydrocarbons as sample probes in high-performance liquid chromatography. The new MPBPs show different retention characteristics from the previously synthesized MPBP, designated TP. Nevertheless, the results indicate that the retention mechanism is still the same as the TP phase: the size and shape of the solute molecule can be recognized by a cavity-like space formed by the methyl groups and phenyl rings of MPBPs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268372
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  • 59
    Digitale Medien
    Digitale Medien
    Comparison and evaluation of HIC columns of different hydrophobicity (1992)
    Springer
    Chromatographia 34 (1992), S. 391-397 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log kw values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (kg) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268374
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  • 60
    Digitale Medien
    Digitale Medien
    Chromatographic characteristics of porphyrine ether glycerides (1992)
    Springer
    Chromatographia 34 (1992), S. 431-432 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Efficient TLC and HPLC conditions for the separation of a newly synthesized class of compounds, porphyrine ether glycerides, have been established. Supplementary physico-chemical characteristics are given for this group of solutes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268379
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  • 61
    Digitale Medien
    Digitale Medien
    Integrated FIA/HPLC method for preconcentration and determination of transition metal ions (1992)
    Springer
    Chromatographia 34 (1992), S. 445-449 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An automatic method based on the combination of a flow injection (FI) manifold with a liquid chromatograph has been developed for the enrichment and determination of transition metal ions in water samples. Alternatively, the FI configuration can be used as a screening system for the determination of the total concentration of heavy metals. Two-parameter expressions for calibration graphs involving preconcentration time and concentration of the analytes were established for both the FIA and the integrated FIA/HPLC methods. The preconcentration time depends on the concentration level of the analytes in the samples. The method is linear in the range 2–200 ng/ml, with r.s.d. values between 1.5 and 5.0. It has been applied to the determination of copper, lead, zinc, nickel, cobalt, cadmium and manganese in synthetic water samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290233
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  • 62
    Digitale Medien
    Digitale Medien
    Comparison of HPLC and solid phase clean-up methods for identification of PCBs in cod-liver oil by HRGC/MS-SIM technique (1992)
    Springer
    Chromatographia 34 (1992), S. 421-430 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A group of non-planar PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) was identified in a cod-liver oil product by using high resolution gas chromatography-mass spectrometry (HRGC/MS) in electron impact (EI) and negative chemical ionization (NCI) modes. The cod-liver oil samples were prepared either in a cyano column by high performance liquid chromatography (HPLC) or by a solid phase extraction (SPE) clean-up procedure that included e.g. purified charcoal treatment. The two methods of sample preparation were evaluated on the basis of the detectabilities of the congeners. The GC/MS-SIM method allowed quantitative monitoring of congeners nos. 52, 101, 118, 138, 153, and 180 at low concentration levels. Detection limits were 1.2 pg and 130 fg (m/z 292.00) in EI and NCI modes, respectively. The determination levels in EI and NCI were 1.8 pg and 290 fg in HPLC followed by HRGC/MS and 170 pg and 27 pg in SPE followed by HRGC/MS. The linear range was from 5.0 pg/μl to 1.0 ng/μl and from 1.0 pg/μl to 1.0 ng/μl in EI and NCI modes, respectively. In addition, the co-planar PCBs, PCDDs, and PCDFs were also screened and two of the chlorinated furanes were identified by HRGC/MS-NCI after separation from non-planar PCBs by SPE. In this case the only congeners that could be quantified were 2,3,4,7,8-PCDF and 1,2,3,4,6,7,8-HCDF, the detection limit for them being 740 fg (m/z 351.90) with NCI. SPE allows the separation of the planar and non-planar compounds, but LC separation is more effective for separation of the compounds of interest from the matrix. LC clean-up is easier and faster to perform than SPE clean-up.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268378
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  • 63
    Digitale Medien
    Digitale Medien
    Separation of stereoisomers of tetramethylcalix[4]arenoctol and derivatives by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 453-456 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A high performance liquid chromatographic procedure on 5 μm RP-18 was developed for the separation of the four possible cis-trans isomers of tetramethyl-calix[4]arenoctol, and of their octaacetates, and their octamethyl ethers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290235
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  • 64
    Digitale Medien
    Digitale Medien
    HPLC separation of molecular species of intact sphingomyelin, utilizing multivariate design and optimization (1992)
    Springer
    Chromatographia 34 (1992), S. 529-533 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An improved method has been developed for the separation of molecular species of intact sphingomyelins from natural sources (chicken egg yolk, bovine brain, and bovine milk) by high performance liquid chromatography with light-scattering detection. The method was developed and optimized using a novel multivariate optimization strategy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290247
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  • 65
    Digitale Medien
    Digitale Medien
    High-performance liquid chromatography of carbohydrates in enzymic hydrolysate of waste paper (1992)
    Springer
    Chromatographia 34 (1992), S. 534-536 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Waste paper was pretreated with 5M sulfuric acid at 28°C to give a gel-like solution which was then hydrolyzed with cellulase, purified fromTrichoderma viride, to form carbohydrates. The determination of the carbohydrates was accomplished using an aminopropylbonded silica HPLC column and an RI detector. The detection limits were 20 ppm; xylose, glucose, and cellobiose were the major components. Salts from the buffer solution may affect the activity of cellulase. The analysis of carbohydrates can be performed under acid conditions. HPLC analysis of carbohydrates from enzymatic hydrolysis is reliable and successful.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290248
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  • 66
    Digitale Medien
    Digitale Medien
    Mental content and evolutionary explanation (1992)
    Springer
    Biology and philosophy 7 (1992), S. 1-12 
    Details
    ISSN: 1572-8404
    Schlagwort(e): Cognitive ethology ; mental content ; mental representations ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract Cognitive ethology is the comparative study of animal cognition from an evolutionary perspective. As a sub-discipline of biology it shares interest in questions concerning the immediate causes and development of behavior. As a part of ethology it is also concerned with questions about the function and evolution of behavior. I examine some recent work in cognitive ethology, and I argue that the notions of mental content and representation are important to enable researchers to answer questions and state generalizations about the function and volution of behavior.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00130160
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  • 67
    Digitale Medien
    Digitale Medien
    What is hierarchical selection? (1992)
    Springer
    Biology and philosophy 7 (1992), S. 27-33 
    Details
    ISSN: 1572-8404
    Schlagwort(e): Additivity ; ANOVA ; evolution ; hierarchical selection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract It has been proposed that natural selection occurs on a hierarchy of levels, of which the organismic level is neither the top nor the bottom. This hypothesis leads to the following practical problem: in general, how does one tell if a given phenomenon is a result of selection on level X or level Y. How does one tell what the units of selection actually are? It is convenient to assume that a unit of selection may be defined as a type of entity for which there exists, among all entities on the same “level” as that entity, an additive component of variance for some specific component F of fitness which does not appear as an additive component of variance in any decomposition of this F among entities at any lower level. But such a definition implicitly assumes that if f(x, y) depends nonadditively on its arguments, there must be interaction between the quantities which x and y represent. This assumption is incorrect. And one cannot avoid this error by speaking of “transformability to additivity” instead of merely “additivity”. A general mathematical formulation of the concepts of interaction and non-interaction is proposed, followed by a correspondingly modified approach to the definition of a unit of selection. The practical difficulty of verifying the presence of hierarchical selection is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00130162
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  • 68
    Digitale Medien
    Digitale Medien
    An ecological approach to biosystem thermodynamics (1992)
    Springer
    Biology and philosophy 7 (1992), S. 35-60 
    Details
    ISSN: 1572-8404
    Schlagwort(e): Action principles ; ecosystem structure ; evolution ; information ; natural selection ; non-equilibrium thermodynamics ; teleology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract The general attributes of ecosystems are examined and a naturally occurring “reference ecosystem” is established, comparable with the “isolated” system of classical thermodynamics. Such an autonomous system with a stable, periodic input of energy is shown to assume certain structural characteristics that have an identifiable thermodynamic basis. Individual species tend to assume a state of “least dissipation”; this is most clearly evident in the dominant species (the species with the best integration of energy acquisition and conservation). It is concluded that ecosystem structure results from the antagonistic interaction of two nearly equal forces. These forces have their origin in the Principle of Most Action (“least dissipation” or “least entropy production”) and the universal Principle of Least Action. “Most action” is contingent on the equipartitioning of the energy available, through uniform interaction of similar individuals. The trend to “Least action” is contingent on increased dissipation attained through increasing diversity and increasing complexity. These principles exhibit a basic asymmetry. Given the operation of these opposing principles over evolutionary time, it is argued that ecosystems originated in the vicinity of thermodynamic equilibrium through the resonant amplification of reversible fluctuations. On account of the basic asymmetry the system was able to evolve away from thermodynamic equilibrium provided that it remained within the vicinity of “ergodynamic equilibrium” (equilibrium maintained by internal work, where the opposing forces are equal and opposite). At the highest level of generalization there appear to be three principles operating: i) maximum association of free-energy and materials; ii) energy conservation (deceleration of the energy flow) through symmetric interaction and increased homogeneity; and iii) the principle of least action which induces acceleration of the energy flow through asymmetrical interaction. The opposition and asymmetry of the two forces give rise to natural selection and evolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00130163
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  • 69
    Digitale Medien
    Digitale Medien
    On the relationship between evolutionary and psychological definitions of altruism and selfishness (1992)
    Springer
    Biology and philosophy 7 (1992), S. 61-68 
    Details
    ISSN: 1572-8404
    Schlagwort(e): Altruism ; evolution ; group selection ; selfishness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract I examine the relationship between evolutionary definitions of altruism that are based on fitness effects and psychological definitions that are based on the motives of the actor. I show that evolutionary altruism can be motivated by proximate mechanisms that are psychologically either altruistic or selfish. I also show that evolutionary definitions do rely upon motives as a metaphor in which the outcome of natural selection is compared to the decisions of a psychologically selfish (or altruistic) individual. Ignoring the precise nature of both psychological and evolutionary definitions has obscured many important issues, including the biological roots of psychological altruism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00130164
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  • 70
    Digitale Medien
    Digitale Medien
    Evolution, altruism, and the prisoner's dilemma (1992)
    Springer
    Biology and philosophy 7 (1992), S. 161-175 
    Details
    ISSN: 1572-8404
    Schlagwort(e): Altruism ; evolution ; Prisoner's Dilemma ; sociobiology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract I first argue against Peter Singer's exciting thesis that the Prisoner's Dilemma explains why there could be an evolutionary advantage in making reciprocal exchanges that are ultimately motivated by genuine altruism over making such exchanges on the basis of enlightened long-term self-interest. I then show that an alternative to Singer's thesis — one that is also meant to corroborate the view that natural selection favors genuine altruism, recently defended by Gregory Kavka, fails as well. Finally, I show that even granting Singer's and Kavka's claim about the selective advantage of altruism proper, it is doubtful whether that type of claim can be used in a particular sort of sociobiological argument against psychological egoism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00129881
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  • 71
    Digitale Medien
    Digitale Medien
    The evolution of altruism: Correlation, cost, and benefit (1992)
    Springer
    Biology and philosophy 7 (1992), S. 177-187 
    Details
    ISSN: 1572-8404
    Schlagwort(e): Altruism ; evolution ; game theory ; group selection ; kin selection ; prisoner's dilemma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract A simple and general criterion is derived for the evolution of altruism when individuals interact in pairs. It is argued that the treatment of this problem in kin selection theory and in game theory are special cases of this general criterion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00129882
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  • 72
    Digitale Medien
    Digitale Medien
    Phylogenetic definitions and taxonomic philosophy (1992)
    Springer
    Biology and philosophy 7 (1992), S. 295-313 
    Details
    ISSN: 1572-8404
    Schlagwort(e): Clade ; class ; composite whole ; definition ; defining property ; essentialism ; evolution ; individual ; intension ; name ; ostensive definition ; phylogeny ; population ; set ; species ; taxon ; taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract An examination of the post-Darwinian history of biological taxonomy reveals an implicit assumption that the definitions of taxon names consist of lists of organismal traits. That assumption represents a failure to grant the concept of evolution a central role in taxonomy, and it causes conflicts between traditional methods of defining taxon names and evolutionary concepts of taxa. Phylogenetic definitions of taxon names (de Queiroz and Gauthier 1990) grant the concept of common ancestry a central role in the definitions of taxon names and thus constitute an important step in the development of phylogenetic taxonomy. By treating phylogenetic relationships rather than organismal traits as necessary and sufficient properties, phylogenetic definitions remove conflicts between the definitions of taxon names and evolutionary concepts of taxa. The general method of definition represented by phylogenetic definitions of clade names can be applied to the names of other kinds of composite wholes, including populations and biological species. That the names of individuals (composite wholes) can be defined in terms of necessary and sufficient properties provides the foundation for a synthesis of seemingly incompatible positions held by contemporary individualists and essentialists concerning the nature of taxa and the definitions of taxon names.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00129972
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  • 73
    Digitale Medien
    Digitale Medien
    Parental care and the allocation of resources across generations (1992)
    Springer
    Evolutionary ecology 6 (1992), S. 187-197 
    Details
    ISSN: 1573-8477
    Schlagwort(e): parental care ; resource allocation ; ESS ; inclusive fitness ; menopause ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary To understand the evolution of parental care behaviour, the cost of care must be evaluated in terms of lost reproductive potential. Using population genetics theory, a quantitative model of parental care is presented here to evaluate the allocation of resources between production and care of offspring, and care of grandoffspring. The results show that the evolutionarily stable investment ratio of resources to offspring versus grandoffspring is equal to 2∶1. The expected investment in grandoffspring will decrease when there is a lower probability of survival of the parents to a late stage of the life cycle. These results are discussed in the context of general life history theory, inclusive fitness models, animal behaviour field studies, and the evolution of human menopause.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02214161
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  • 74
    Digitale Medien
    Digitale Medien
    Phylogenetic analysis of pines using ribosomal DNA restriction fragment length polymorphisms (1992)
    Springer
    Plant systematics and evolution 179 (1992), S. 141-153 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Gymnosperms ; Conifers ; Pinaceae ; Pinus ; rDNA ; restriction fragments ; molecular systematics ; evolution ; phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phylogenetic relationships among 30 species of the genusPinus were studied using restriction site polymorphism in the large subunit of nuclear rDNA. Of the 58 restriction sites scored, 48 were phylogenetically informative, and the 30 species reduced to ten taxa when species with identical restriction site patterns were combined. These ten taxa corresponded to the currently recognized subsections of the genus, with the sole exception ofP. leiophylla, which was identical in its pattern of restriction sites to all three species included from subsect.Oocarpae despite its being in a different section of subg.Pinus (Pinea instead ofPinus). A measure of the proportion of phylogenetic information contained within the data set (Homoplasy Excess Ratio, or HER) revealed that the character states were significantly non-randomly distributed among the ten taxa (HER = 0.71, p 〈 0.01). Branchand-bound searches using either Wagner or Dollo parsimony as the optimization criterion were carried out using PAUP in order to estimate phylogenetic relationships among the ten taxa. Three taxa (Picea pungens, Tsuga canadensis, andLarix decidua) were used independently as outgroups for purposes of rooting the trees. Despite the extreme differences in the assumptions underlying the Wagner and Dollo parsimony, the two gave surprisingly similar estimates of phylogeny, with both analyses supporting the monophyly of the two major subgeneraPinus andStrobus and differing in topology only in the placement of subsect.Ponderosae within subg.Pinus. The likelihood for the Wagner tree was only slightly higher than that computed for the Dollo tree.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00937592
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  • 75
    Digitale Medien
    Digitale Medien
    The importance of Endosperm Balance Number in potato breeding and the evolution of tuber-bearing Solanum species (1992)
    Springer
    Euphytica 60 (1992), S. 105-113 
    Details
    ISSN: 1573-5060
    Schlagwort(e): bridging crosses ; chromosome addition lines ; Endosperm Balance Number ; evolution ; 2n gametes ; imprinting ; interspecific crosses ; ploidy manipulations ; tuber-bearing Solanum species
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Endosperm failure is considered the primary reason for the lack of success in intra-and interspecific crosses. The Endosperm Balance Number (EBN) hypothesis is a unifying concept for predicting endosperm function in intraspecific, interploidy, and interspecific crosses. In the EBN system, every species has an ‘effective ploidy’ (EBN), which must be in a 2:1 maternal to paternal ratio in the endosperm for crosses to succeed. The knowledge of EBN is very useful in the transfer of genes from exotic germplasm, and in the development of new breeding schemes in potato. The paper describes the strategies for introducing 2x(1EBN), 2x(2EBN), 4x(2EBN) and 6x(4EBN) germplasm into the cultivated 4x(4EBN) potato gene pool. A new methodology for producing 4x(4EBN) and 2x(2EBN) chromosome addition lines is also discussed. EBN has evolutionary importance in the origin of tuber-bearing Solanums. The role of the EBN in the origin of diploid and polyploid potato species, and as a barrier for hybridization and speciation of sympatric species within the same ploidy level is demonstrated. The origin of 3x and 5x cultivated tuber-bearing Solanums may also be explained using the EBN concept. EBN has been reported to exist in other plant species: alfalfa, beans, blueberries, rice, soybeans, squashes, tomato, forage legumes, grasses, ornamentals and Datura stramonium. This indicates that EBN may have broad application and could be useful for germplasm transfer and breeding in other crop species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029665
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  • 76
    Digitale Medien
    Digitale Medien
    Light, iron, Sam Granick and the origin of life (1992)
    Springer
    Photosynthesis research 33 (1992), S. 163-170 
    Details
    ISSN: 1573-5079
    Schlagwort(e): biosynthetic pathway ; evolution ; free energy ; photochemistry ; photosynthesis ; porphyrin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Living matter is an organized system which requires a continual flux of energy for its survival. As a working assumption, the flux of energy required for the origin of a self-duplicating cell is taken as the power required for the maintenance of a modern cell: 10 mW per g of carbon or some 105 times the output per gram of the sun. Solar photochemistry supplies the energy for the continuing evolution of life and, by continuity, for its origin. The iron oxide-sulfide photosynthetic unit proposed by S. Granick 35 years ago was meant to supply this energy. The evolution of complex organic photosensitizers is rationalized by the Granick hypothesis that biosynthetic pathways recapitulate their evolution. These concepts are discussed in the context of the evolution of photosynthetic systems and the known properties of these pigments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039178
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  • 77
    Digitale Medien
    Digitale Medien
    Protein sequences and redox titrations indicate that the electron acceptors in reaction centers from heliobacteria are similar to Photosystem I (1992)
    Springer
    Photosynthesis research 32 (1992), S. 11-22 
    Details
    ISSN: 1573-5079
    Schlagwort(e): iron-sulfur centers ; evolution ; green sulfur bacteria ; bacteriochlorophyll g
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic reaction centers isolated from Heliobacillus mobilis exhibit a single major protein on SDS-PAGE of 47 000 Mr. Attempts to sequence the reaction center polypeptide indicated that the N-terminus is blocked. After enzymatic and chemical cleavage, four peptide fragments were sequenced from the Heliobacillus mobilis apoprotein. Only one of these sequences showed significant specific similarity to any of the protein and deduced protein sequences in the GenBank data base. This fragment is identical with 56% of the residues, including both cysteines, found in the highly conserved region that is proposed to bind iron-sulfur center FX in the Photosystem I reaction center peptide that is the psaB gene product. The similarity to the psaA gene product in this region is 48%. Redox titrations of laser-flash-induced photobleaching with millisecond decay kinetics on isolated reaction centers from Heliobacterium gestii indicate a midpoint potential of −414 mV with n=2 titration behavior. In membranes, the behavior is intermediate between n=1 and n=2, and the apparent midpoint potential is −444 mV. This is compared to the behavior in Photosystem I, where the intermediate electron acceptor A1, thought to be a phylloquinone molecule, has been proposed to undergo a double reduction at low redox potentials in the presence of viologen redox mediators. These results strongly suggest that the acceptor side electron transfer system in reaction centers from heliobacteria is indeed analogous to that found in Photosystem I. The sequence similarities indicate that the divergence of the heliobacteria from the Photosystem I line occurred before the gene duplication and subsequent divergence that lead to the heterodimeric protein core of the Photosystem I reaction center.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00028794
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  • 78
    Digitale Medien
    Digitale Medien
    Quantitative nuclear DNA differences associated with genome evolution in Guizotia (Compositae) (1992)
    Springer
    Genetica 85 (1992), S. 241-247 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Compositae ; DNA amount ; evolution ; Guizotia ; karyotype
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The present communication deals with 2C nuclear genome size variation in a fairly small genus Guizotia. Twenty-four accessions belonging to six species, out of seven known, were analysed in order to elucidate the extent of DNA variation both at an intra—as well as interspecific level. At the intraspecific level none of the species exhibited significant differences in their genome size. Between the species, the 2C DNA amounts ranged from 3.61 pg in G. reptans to 11.37 pg in G. zavattarii; over three-fold DNA variation is evident. Apparently these interspecific DNA differences have been achieved independent of the numerical chromosomal change(s), as all the Guizotias share a common chromosome number 2n=2x=30. The cultivated oilseed crop, G. abyssinica (7.57 pg), has accommodated nearly 78% extra DNA in its chromosome complement during the evolutionary time scale of its origin and domestication from the wild progenitor G. schimperi (4.25 pg). The extent of genomic DNA difference(s) between the species has been discussed in the light of their interrelationships and diversity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00132276
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  • 79
    Digitale Medien
    Digitale Medien
    Ty1-copia group retrotransposons and the evolution of retroelements in the eukaryotes (1992)
    Springer
    Genetica 86 (1992), S. 203-214 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Copia ; Ty element ; evolution ; retrotransposon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Ty1-copia group retrotransposons are among the best studied transposable elements in the eukaryotes. This review discusses the extent of these transposons in the eukaryote kingdoms and compares models for the evolution of these genetic elements in the light of recent phylogenetic data. These data show that the Ty1-copia group is widespread among invertebrate eukaryotes, especially in the higher plant kingdom, where these genetic elements are unusually common and heterogeneous in their sequence. The phylogenetic data also suggest that the present day spectrum of Ty1-copia group retrotransposons has been influenced both by divergence during vertical transmission down evolving lineages and by horizontal transmission between distantly related species. Lastly, the factors affecting Ty1-copia group retrotransposon copy number and sequence heterogeneity in eukaryotic genomes and the effects of transpositional quiescence and defective retrotransposons upon evolution of Ty1-copia group retrotransposons are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00133721
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  • 80
    Digitale Medien
    Digitale Medien
    Evolution of structure and function of V-ATPases (1992)
    Springer
    Journal of bioenergetics and biomembranes 24 (1992), S. 415-424 
    Details
    ISSN: 1573-6881
    Schlagwort(e): ATPases ; evolution ; eukaryotes ; endomembranes ; archaebacteria ; progenote ; bioenergetics ; flagella assembly ; endosymbiont theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Proton pumping ATPases/ATPsynthases are found in all groups of present-day organisms. The structure of V- and F-type ATPases/ATP synthases is very conserved throughout evolution. Sequence analysis shows that the V- and F-type ATPases evolved from the same enzyme already present in the last common ancestor of all known extant life forms. The catalytic and noncatalytic subunits found in the dissociable head groups of the V/F-type ATPases are paralogous subunits, i.e., these two types of subunits evolved from a common ancestral gene. The gene duplication giving rise to these two genes (i.e., encoding the catalytic and noncatalytic subunits) predates the time of the last common ancestor. Mapping of gene duplication events that occurred in the evolution of the proteolipid, the noncatalytic and the catalytic subunits, onto the tree of life leads to a prediction for the likely subunit structure of the encoded ATPases. A correlation between structure and function of V/F-ATPases has been established for present-day organisms. Implications resulting from this correlation for the bioenergetics operative in proto-eukaryotes and in the last common ancestor are presented. The similarities of the V/F-ATPase subunits to an ATPase-like protein that was implicated to play a role in flagellar assembly are evaluated. Different V-ATPase isoforms have been detected in some higher eukaryotes. These data are analyzed with respect to the possible function of the different isoforms (tissue specific, organelle specific) and with respect to the point in their evolution when these gene duplications giving rise to the isoforms had occurred, i.e., how far these isoforms are distributed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00762534
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  • 81
    Digitale Medien
    Digitale Medien
    The Cuban homegarden ‘conuco’: a perspective environment for evolution and in situ conservation of plant genetic resources (1992)
    Springer
    Genetic resources and crop evolution 39 (1992), S. 9-22 
    Details
    ISSN: 1573-5109
    Schlagwort(e): Cuba ; evolution ; genetic resources ; homegarden ; in situ conservation ; landraces
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Cuban homegardens are called ‘conucos’. On the basis of new case studies additional information is provided about these ‘conucos’, their history, composition and importance. They and other gardens of similar type are characterized as suitable environment for in situ conservation and for the continuation of evolutionary processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00052650
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  • 82
    Digitale Medien
    Digitale Medien
    Insect resistance in potatoes: sources, evolutionary relationships, morphological and chemical defenses, and ecogeographical associations (1992)
    Springer
    Euphytica 61 (1992), S. 83-111 
    Details
    ISSN: 1573-5060
    Schlagwort(e): chemical defense ; Colorado potato beetle ; Empoasca fabae ; Epitrix cucumeris ; evolution ; germplasm ; green peach aphid ; insect resistance ; Leptinotarsa decemlineata ; Macrosiphum euphorbiae ; morphology ; Myzus persicae ; potato aphid ; potato flea beetle ; potato leafhopper ; relationship ; Solanum ; taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The past 25 years, 1686 potato accessions, representing 100 species in the genus Solanum L., subgenus Potatoe, section Petota, were evaluated for field resistance to one or more of the following insect pests: green peach aphid, Myzus persicae (Sulzer); potato aphid, Macrosiphum euphorbiae (Thomas); Colorado potato beetle, Leptinotarsa decemlineata (Say); potato flea beetle, Epitrix cucumeris (Harris); and potato leafhopper, Empoasca fabae (Harris). Accessions highly resistant to green peach aphid were identified within 36 species, to potato aphid within 24 species, to Colorado potato beetle within 10 species, to potato flea beetle within 25 species, and to potato leafhopper within 39 species. Resistance levels were characteristic within Solanum species. Insect resistance appears to be a primitive trait in wild potatoes. Susceptibility was most common in the primitive and cultivated Tuberosa. Insect resistance was also characteristic of the most advanced species. The glycoalkaloid tomatine was associated with field resistance to Colorado potato beetle and potato leafhopper. Other glycoalkaloids were not associated with field resistance at the species level. Dense hairs were associated with resistance to green peach aphid, potato flea beetle, and potato leafhopper. Glandular trichomes were associated with field resistance to Colorado potato beetle, potato flea beetle, and potato leafhopper. Significant correlations between insect score and altitude of original collection were observed in six of thirteen species. Species from hot and arid areas were associated with resistance to Colorado potato beetle, potato flea beetle, and potato leafhopper. Species from cool or moist areas tended to be resistant to potato aphid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00026800
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  • 83
    Digitale Medien
    Digitale Medien
    Digestive enzyme activities and their distribution in the alimentary canal of larvae of the three extant lamprey families (1992)
    Springer
    Fish physiology and biochemistry 10 (1992), S. 1-10 
    Details
    ISSN: 1573-5168
    Schlagwort(e): larval lampreys ; exocrine pancreas ; lipase ; amylase ; chymotrypsin ; trypsin ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The activities of trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), lipase (EC 3.1.1.3) and amylase (EC 3.2.1.1) were measured in different regions of the alimentary tract of ammocoetes from each of the three extant lamprey families. In the southern hemisphere speciesGeotria australis (Geotriidae), and even more particularlyMordacia mordax (Mordaciidae), enzymatic activity was almost entirely confined to prominent diverticular extensions which arise at the oesophageal-intestinal junction. However, in the holarcticLampetra richardsoni (Petromyzontidae), which does not possess a diverticulum, the enzymatic activity was highest in the upper anterior intestine. It is not clear whether the presence of significantly higher amylolytic and lower lipolytic activities in the diverticulum ofG. australis than in the exocrine tissue of the other two species reflects interspecific differences in the composition of their diets. The capacity of exocrine tissue extracts for chymotryptic and tryptic digestion was assayed before and afterin vitro exposure to trypsin and enteropeptidase, their respective catalytic activators. Prior to exposure to these exogenous activators, both proteolytic enzymes were fully active inL. richardsoni, partially active inG. australis and totally inactive inM. mordax. Maximal chymotryptic activity was greater inM. mordax than inL. richardsoni andG. australis. In contrast, maximal tryptic activity was greater inL. richardsoni than inG. australis and was very low inM. mordax. Since trypsin is the only known activator of chymotrypsinogen, the negligible activity of trypsin inM. mordax would appear anomalous unless a trypsin inhibitor is present in the protopancreas of this species. Differences in the distribution of enzymatic activity within the alimentary tract of the three species is discussed in relation to proposed phylogenetic relationships amongst the extant lamprey families.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00004649
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  • 84
    Digitale Medien
    Digitale Medien
    On the concepts of the taxonomic distinction, nature and essence of man (1992)
    Springer
    Human evolution 7 (1992), S. 41-47 
    Details
    ISSN: 1824-310X
    Schlagwort(e): evolution ; origin of man ; nature and essence of humanity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract It is proposed that the peculiarity of the specific nature of man consists in his polarisation into an ape-like «Australopithecoid» and specifically human sides. Its possible origin, as well as, differences between the concepts of the taxonomic distinction, species specific nature and essence of man are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02436259
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  • 85
    Digitale Medien
    Digitale Medien
    Human evolution and epigenesis (1992)
    Springer
    Human evolution 7 (1992), S. 25-31 
    Details
    ISSN: 1824-310X
    Schlagwort(e): Epigenesis ; evolution ; history
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02436410
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  • 86
    Digitale Medien
    Digitale Medien
    Japan and human evolutionary research (1992)
    Springer
    Human evolution 7 (1992), S. 85-91 
    Details
    ISSN: 1824-310X
    Schlagwort(e): Japan ; Japanese ; evolution ; microevolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The trends in evolutionary research in Japan have largely changed through the introduction of new methodologies such as molecular genetics and multivariate statistics since the 1960’s. The development of ecology and primatology brought another new wave into fields of physical anthropology. This paper reviews briefly general trends in anthropological research now on-going in Japan. Microevolutionary studies of the Japanese and neighboring populations which have a long history in Japan will be reviewed in more detail.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02437456
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  • 87
    Digitale Medien
    Digitale Medien
    HPLC separation of catecholamines after derivatization with 9-fluorenylmethyl chloroformate (1992)
    Springer
    Chromatographia 33 (1992), S. 83-86 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Pre-derivatization ; Catecholamines ; 9-fluorenylmethyl chloroformate (FMOC-Cl)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Optimum conditions for the separation of 9-fluorenylmethyl chloroformate derivatized catecholamines by HPLC are described; three catecholamines (noradrenaline, adrenaline and dopamine) and an internal standard (epinine) were separated in less than 20 minutes under isocratic conditions. This method is 17 to 350 times more sensitive than electrochemical detection, depending on the test compounds. It has been applied to the analysis of catecholamines in urine. The sample was extracted by a metal-loaded silica prior to separation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276857
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  • 88
    Digitale Medien
    Digitale Medien
    Preparation and determination of manganese(III) chlorophylls by reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 567-570 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chlorophylls ; Manganese(III) chlorophylls
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Manganese chlorophylls have been synthesized by refluxing a mixture of pheophytins dissolved in acetone and manganese(II) acetate anhydride dissolved in glacial acetic acid. A good separation of manganese(III) chlorophylls has been attained by RP-HPLC using chemically bonded C18 silica as a stationary phase and methanol with 3% acetic acid as a mobile phase. An accurate and rapid HPLC method is described for the simultaneous determination of manganese(III) chlorophyll-a [Mn(III)-chl-a] and manganese(III) chlorophyll-b [Mn(III)-chl-b]. Tailing arising from dissociation of acetate ions is improved by addition of sodium acetate (5×10−3 M) to the mobile phase (acetone: methanol=90∶10, vol/vol). The analytical values obtained by the HPLC method are very close to the calculated contents in all samples, but those obtained by spectrophotometry are high because of the interferences from overlapping of absorption bands. In the proposed HPLC method the calibration graphs of Mn(III)-chl-a and Mn(III)-chl-b are linear in the concentration range 0–20 μg cm−3 with relative standard deviations (n=10) of 3.46% and 4.54%, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262249
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  • 89
    Digitale Medien
    Digitale Medien
    Liquid chromatographic separation of the anomers and isomers of 2′-deoxyuridine (1992)
    Springer
    Chromatographia 33 (1992), S. 571-574 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; 2′-Deoxyuridine ; Anomer separation ; Isomer separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A liquid chromatographic assay method was developed to separate 2′-deoxyuridine from its anomer and pentopyranosyl isomers. The influence of the pH of the mobile phase, the type of organic modifier and the column temperature on the chromatographic parameters was systematically investigated. Using a Hypersil C18 (5 μm) column at 10°C, the following mobile phase was found suitable: tetrahydrofuran −0.2 M potassium phosphate buffer pH 4.0-water (0.1∶5∶94.9, v/v).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262250
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  • 90
    Digitale Medien
    Digitale Medien
    Controlled-porosity glasses as alternative adsorbents to silica gel for HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 122-126 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Controlled-porosity glasses ; Correlation between silica and porous glass ; Hydrocarbons separations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The paper deals with the use of controlled-porosity glasses (CPGs) as adsorbents for HPLC. The physicochemical and chromatographic properties of small-pore CPGs are compared to the analogous properties of silica gels. The results show good correlation between them and suggest the possibility of application of CPGs as adsorbents for liquid chromatography.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275891
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  • 91
    Digitale Medien
    Digitale Medien
    Retention, enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column (1992)
    Springer
    Chromatographia 33 (1992), S. 127-132 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chiral separation ; Alpha 1-acid glycoprotein-bonded column ; Propranolol ; Propranolol ester derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an α1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275892
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  • 92
    Digitale Medien
    Digitale Medien
    The development and validation of a solid phase extraction/HPLC method for the determination of aflatoxins in groundnut meal (1992)
    Springer
    Chromatographia 33 (1992), S. 208-212 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Solid phase extraction ; Validation ; Aflatoxins in groundnut meal ; CB method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The efficiency of an analytical method for the determination of aflatoxins in groundnut meal has been statistically examined. The procedure consists of a phenyl bonded phase (PH) clean-up of an acetone: water (85∶15) extract followed by HPLC quantification. Average recoveries from spiked groundnut meal extracts were calculated to be 101.3% and 101.8%, with limits of detection of 7.4 and 2.62 μg/kg for aflatoxins-B1 and-B2 respectively. Higher recoveries of aflatoxin-B1 from naturally contaminated samples were recorded using the proposed procedure than those recorded using the official AOAC (CB) method although the precisions of the two methods were not found to differ at the 5% significance level. Similar recoveries of aflatoxin-B2 were recorded for both methods but the proposed procedure was found to be more precise. The proposed PH-HPLC method was far less time consuming and more economical on solvents than the CB procedure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276184
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  • 93
    Digitale Medien
    Digitale Medien
    Preparation of octadecyl modified column gels using heat-treated silicas and their retention behaviour in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 203-207 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Octadecyl modified silica ; Hexamethyldisilazane treated silica ; Calcination ; Heat-treated silica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The effect of silanol groups on three types of octadecylmodified column gels using heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at 180°C, 500°C and 950°C, the silicas treated with octadecyldimethylchlorosilane were used for the measurement of physical and chemical analysis. From elemental carbon analysis data, the reactive silanol group concentrations, αOH(s), were determined to be 2.0 in the 180°C treated silica, 2.1 in the 500°C treated silica and 1.6 in the 950°C treated silica, respectively (original silica: mean pore diameter 116 Å, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0 μm). The separation factors, α, of pyridine versus phenol were measured to be 0.79 on 180°C treated silica, 0.91 on 500°C treated silica and 1.98 on 950°C treated silica, using acetonitrile-water mixtures as the eluent. And then, on the basis of the physico-chemical and chromatographic data, the three types of octadecyl modified column gels using heat-treated silicas by calcination have been compared.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276183
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  • 94
    Digitale Medien
    Digitale Medien
    Determination of chloride in biological fluids as pentafluorobenzylchloride by reversed-phase high-performance liquid chromatography and UV detection (1992)
    Springer
    Chromatographia 33 (1992), S. 317-320 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; UV detection ; Pentafluorobenzyl chloride by UV detection ; Chloride in biological fluids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A reversed-phase high-performance liquid chromatographic method for the determination of chloride in plasma, urine, saliva, sweat and aqueous solution is described. Chloride, in solution in aqueous acetone, is converted by means of pentafluorobenzyl bromide into pentafluorobenzyl chloride. This derivative is separated on a ODS-5 μm reversed-phase column using isocratic elution with acctonitrile/water, 50/50, v/v, at a flow rate of 2.0 ml/min, and detected by a UV detector at 264 nm. The method is rapid, accurate and sufficiently sensitive for the determination of chloride in less than 10 μl sample volume of a biological fluid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275909
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  • 95
    Digitale Medien
    Digitale Medien
    Liquid chromatography of carbon clusters (1992)
    Springer
    Chromatographia 33 (1992), S. 344-346 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Charge-transfer chromatography ; Carbon clusters ; Fullerenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A comparison of three binary mobile phases in LC separation of C60 and C70 fullerences on chemically bonded 2,4-dinitroanilinopropyl (DNAP) stationary phase was carried out, n-Hexane-benzene has been found to be the best mobile phase for efficient separation of the all-carbon molecules permitting high loads in preparative LC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275915
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  • 96
    Digitale Medien
    Digitale Medien
    Determination of trichlormethiazide in human plasma and urine by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 339-343 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Trichlormethiazide ; Electrochemical detection ; Diuretics in plasma and urine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This paper describes a high-performance liquid chromatographic (HPLC) assay method for the determination of trichlormethiazide (TCM) in human plasma and urine. After extraction and separation on an ODS column TCM from plasma was detected by oxidation in an electrochemical detector (ECD) by a porous graphite electrode. The sensitivity was better than HPLC with UV detection, enabling the determination of 2 ng ml−1 TCM in human plasma. This method also allows determination of TCM at higher concentrations by exchanging the UV for the electrochemical detector. To study the pharmacokinetics, TCM in plasma and urine was assayed with coefficients of variation in the range 2–3%. The method has the advantages of high sensitivity for plasma assay and high precision with a simple procedure for both plasma and urine samples. Small samples of 0.5 ml plasma per assay also reduced the total volume of plasma needed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275914
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  • 97
    Digitale Medien
    Digitale Medien
    Partial separation of lactic acid enantiomers by HPLC using (S)-(+)mandelic acid as chiral mobile-phase additive (1992)
    Springer
    Chromatographia 34 (1992), S. 31-34 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chiral mobile-phase additive ; Inductive adsorption ; Enantiomer resolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Separation of lactic acid enantiomers by inductive adsorption has been studied on silica columns using (S)-(+)mandelic acid as the chiral mobile-phase additive. The lactic acid peak is not very strongly retained, broad, strongly tailing and splits in two at loadings lower than 60 μmol cm−2 column cross-section and at mandelic acid concentrations higher than 10−4M. The splitting indicates partial separation of enantiomers: enantiomerically enriched fractions are obtained but not enantiomerically pure. Lactic acid retention strongly decreases with increasing concentration of both hydroxy-acids; mandelic acid acts by displacement and lactic acid acts by an overloading effect.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290455
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  • 98
    Digitale Medien
    Digitale Medien
    Chromatographic resolution of racemic amines, carboxylic acids, and alcohols by a new homochiral reagent derived fromendo-borneol (1992)
    Springer
    Chromatographia 34 (1992), S. 48-50 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Diastereomer separation ; Chiral derivatizing agent ; Chiral oxazolidin-2-one
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Chromatographic separation of racemic amines, carboxylic acids and alcohols can be achieved with excellent resolution as measured in terms of the chromatographic separation factor α by derivatization with a homochiral oxazolidin-2-one easily prepared in three steps fromendo-borneol. The resolved materials can be isolated in excellent yields by cleavage of the resultant diastereomers using conventional methods, which also allow recovery of the chiral resolving agent for re-use.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290458
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  • 99
    Digitale Medien
    Digitale Medien
    Combined Kalman filtering and steepest descent minimization for quantitative analysis of unresolved misaligned chromatographic peaks. The resolution of alternariol and altenuisol mycotoxins in mixtures by HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 56-62 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Kalman filter ; Deconvolution ; Mycotoxins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The potential of a computational approach for the quantitative resolution of seriously overlapping chromatographic peaks when there is loss of collinearity between the pure component peaks and the mixture peak has been explored. The program makes iterative use of the Kalman filter algorithm for resolving the mixture peak with the component peaks aligned according to some values of the position parameters, and of a steepest descent minimization procedure to find the optimal alignment. This combined procedure has been applied to the quantitive resolution of the HPLC chromatograms of alternariol and altenuisol mycotoxins in synthetic mixtures and in real samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290460
    Standort Signatur Erwartet Verfügbarkeit
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    Digitale Medien
    Digitale Medien
    Direct injection analysis of hexamethylene bisacetamide in biological fluids by an HPLC column switching technique with a micellar mobile phase (1992)
    Springer
    Chromatographia 34 (1992), S. 63-66 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Micellar mobile phase ; Direct injection of biological fluids ; Hexamethylene bisacetamide (HMBA)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This paper describes the direct injection analysis of the anti-cancer drug hexamethylene bisacetamide (HMBA) in biological fluids by an HPLC column switching technique. The first chromatographic column, which provides for sample extraction and cleanup, employs a micellar mobile phase with SDS as the modifier. The second column, coupled on-line to the first, utilizes reversed-phase conditions for analysis. UV detection is employed at 210 nm. 282 samples from 12 cancer patients were analysed and good pharmacokinetics curves obtained. The drug gives recoveries of 94.0–100.9% with a relative standard deviation of 1.88%. A sample analysis is completed within 15 minutes. This method should be satisfactory not only for the analysis of HMBA but also, probably for other drugs in biological fluids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290461
    Standort Signatur Erwartet Verfügbarkeit
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