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  • Inorganic Chemistry  (83,671)
  • Organic Chemistry  (68,964)
  • Cell & Developmental Biology  (25,032)
  • AERODYNAMICS  (12,790)
  • 42.73
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  • 1
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    Frontiers in Chemistry: Rising Stars (2021)
    Frontiers Media SA
    Details
    Publication Date: 2024-04-04
    Description: The Frontiers in Chemistry Editorial Office team are delighted to present the inaugural “Frontiers in Chemistry: Rising Stars” article collection, showcasing the high-quality work of internationally recognized researchers in the early stages of their independent careers. All Rising Star researchers featured within this collection were individually nominated by the Journal’s Chief Editors in recognition of their potential to influence the future directions in their respective fields. The work presented here highlights the diversity of research performed across the entire breadth of the chemical sciences, and presents advances in theory, experiment and methodology with applications to compelling problems. This Editorial features the corresponding author(s) of each paper published within this important collection, ordered by section alphabetically, highlighting them as the great researchers of the future. The Frontiers in Chemistry Editorial Office team would like to thank each researcher who contributed their work to this collection. We would also like to personally thank our Chief Editors for their exemplary leadership of this article collection; their strong support and passion for this important, community-driven collection has ensured its success and global impact.
    Keywords: Green and Sustainable Chemistry ; Analytical Chemistry ; Theoretical and Computational Chemistry ; Polymer Chemistry ; Medicinal and Pharmaceutical Chemistry ; Organic Chemistry ; Nanoscience ; Catalysis and Photocatalysis ; Supramolecular Chemistry ; Electrochemistry ; Inorganic Chemistry ; Chemical Biology ; thema EDItEUR::P Mathematics and Science::PD Science: general issues
    Language: English
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  • 2
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    [Editors' Choice] Lighting the way to fluorine placement (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-03-03
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    [Editors' Choice] Fluorine frolicking with eight friends (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-02-10
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    [This Week in Science] Stitching a belt out of carbon rings (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-04-14
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    [Perspective] Allotropy by design—Carbon nanohoops (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-04-14
    Description: The allotropes formed by carbon reflect differences in its bonding: single bonds in diamond, double bonds in graphite and graphene, and triple bonds in polyynes. Fashioning graphene sheets into bowls, monkey saddles, balls, and tubes has led to a number of molecular allotropes of carbon or carbon-rich quasi-allotropes with novel topologies and shapes. A simple ring of carbon can be reduced to practice in various forms (1): a cyclic array of carbon atoms, a “pearl necklace” of benzene rings, or a cylindrical hoop of flank-fused benzenes, just to name a few. On page 172 of this issue, Povie et al. (2) report on the synthesis of an angular-fused hoop structure, which has been a long-standing target. Author: Jay S. Siegel
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
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  • 6
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    [This Week in Science] Stitching one alkyl group to another (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-04-14
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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    [This Week in Science] A salty route to an all-nitrogen ring (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-01-27
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    [This Week in Science] Boron choreographs a double reaction (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-03-03
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    [This Week in Science] Turning benzene into a C–H bond cleaver (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-04-01
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    [Perspective] Polynitrogen chemistry enters the ring (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-01-27
    Description: Polynitrogens have the potential for ultrahigh-performing explosives or propellants because singly or doubly bonded polynitrogens can decompose to triply bonded dinitrogen (N2) with an extraordinarily large energy release. The large energy content and relatively low activation energy toward decomposition makes the synthesis of a stable polynitrogen allotrope an extraordinary challenge. Many elements exist in different forms (allotropes)—for example, carbon can exist as graphite, diamond, buckyballs, or graphene. However, no stable neutral allotropes are known for nitrogen, and only two stable homonuclear polynitrogen ions had been isolated until now—namely, the N3− anion (1) and the N5+ cation (2). On page 374 of this issue, Zhang et al. (3) report the synthesis and characterization of the first stable salt of the cyclo-N5− anion, only the third stable homonuclear polynitrogen ion ever isolated. Author: Karl O. Christe
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 11
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    [This Week in Science] A cyclic catalyst to pair up sugars (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-01-13
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 12
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    Anatomy, functional morphology, evolutionary ecology and systematics of the invasive gastropod Cipangopaludina japonica (Viviparidae: Bellamyinae) (2016)
    In:  Contributions to Zoology (1383-4517) vol.85 (2016) nr.2 p.235
    Details
    Publication Date: 2016-06-09
    Description: The anatomy, functional morphology and evolutionary ecology of the Viviparidae, and the subfamily Bellamyinae in particular, are incompletely known. Partly as a result, genealogical relationships within the family remain poorly understood. Because of this lack in knowledge, few informed hypotheses exist on ancestral states, how differences in body plans between the subfamilies evolved, and how the peculiar biogeographic distribution patterns of viviparids have arisen. Here we document the anatomy, morphology, life history and systematics of Cipangopaludina japonica, a Japanese species that has been introduced into North America, to resolve taxonomic confusion and to improve our understanding of how form and function are related in bellamyines. Anatomical and histological examinations demonstrate marked differences between C. japonica and other bellamyines in the radula, salivary gland, kidney, nerve ring and reproductive organs. Substantial differences also exist between male and female body organization, but conchological differences between sexes in semi-landmark morphometric analyses are limited. The volume of the brood pouch of females, and hence body and shell size, appear to be good predictors of reproductive success, and the species’ ecological versatility may relate to high fecundity and the ability to alternate between feeding modes. Comparing our observations on C. japonica with other viviparids and basal architaenioglossa, we identify several persistent misinterpretations in the literature on how form and function are related in viviparids, not in the least as to female reproductive anatomy. Our reinterpretations improve understanding of the evolution of Viviparidae and its subfamilies, and hopefully will allow future workers to isolate key traits that shaped the evolution of viviparids at the taxonomic levels of their interest for more detailed studies.
    Keywords: basal Architaenioglossa ; Bellamya ; fecundity ; geometric morphometrics ; histology ; reproductive anatomy ; sexual dimorphism ; 42.73
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
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  • 13
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    [Editors' Choice] Carboxylating stubborn alkyl chlorides (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-07-08
    Description: Author: Phil Szuromi
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 14
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    [This Week in Science] Olefins enlisted to attack ketones (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-07-08
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 15
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    [This Week in Science] A radical route to ophiobolin rings (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-05-27
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 16
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    [This Week in Science] A light approach to C-N bond formation (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-07-15
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 17
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    [Editors' Choice] Iron takes alcohols to carboxylic acids (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-07-22
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 18
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    [This Week in Science] Catalysis gets all tied up in knots (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-06-24
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 19
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    [This Week in Science] Adding two fluorines to just one carbon (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-07-01
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 20
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    [Perspective] Three catalysts for activating carbon-hydrogen bonds (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-06-10
    Description: Transition metal–catalyzed arylation of C–H bonds has been intensively studied for forming C–C bonds in complex-molecule synthesis (1). An acidic C–H bond (for example, one near a double bond or an O atom) is cleaved to form a carbon–metal bond, which then couples to arene. Many of these organometallic species can be generated catalytically. Much less research has dealt with unreactive nonacidic sp3 C–H bond functionalization (3). On page 1304 of this issue, Shaw et al. (3) report an efficient and general method that focuses on arylation of sp3 C–H bonds at carbon atoms adjacent to amines and to cyclic ethers by combining nickel, visible-light photoredox, and hydrogen-atom transfer (HAT) catalysis. Author: Corinne Fruit
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 21
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    [This Week in Science] A tip of the HAT to C-C bond formation (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-06-10
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 22
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    [This Week in Science] A rhodium route from C-H to C-N bonds (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-09-09
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 23
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    [This Week in Science] Copper-catalyzed radical relay (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-09-07
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 24
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    [In Depth] A modular route to new antibiotics (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-05-20
    Description: Antibiotics have been taking it on the chin lately. Not only has resistance to the anti-infective medications been growing, but drug companies have been dropping antibiotic research programs, because the drugs are difficult and expensive to make. Now, new help is on the way. Researchers report this week that they've found a way to churn out new members of one of the most widely used classes of antibiotics. These drugs, called macrolides, were first developed in the 1950s and now represent a major bulwark against infections. A bevy of possible new drugs in this class could lead to new weapons against antibiotic-resistant infections, and possibly save millions of lives. Author: Robert F. Service
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 25
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    [This Week in Science] Copper adds alkyls asymmetrically (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-04-22
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 26
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    [This Week in Science] EZ catalyst control in olefin metathesis (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-04-29
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 27
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    [This Week in Science] Carbon links without helpful neighbors (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-05-13
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 28
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    [Perspective] Rethinking the SN2 reaction (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-04-01
    Description: The SN2 nucleophilic substitution reaction, X− + RY → XR + Y−, is a paradigm reaction in organic chemistry (1). The modern understanding of the SN2 reaction mechanism is based on work of Hughes and Ingold (2), who proposed that the nucleophile (X−) approaches the carbon atom that bears the leaving group (Y−). As a result, the bond between the carbon atom and the leaving group becomes weakened. As this bond breaks and a new bond forms between the nucleophile and the carbon atom, the configuration of the carbon atom is inverted. Analyses of gas-phase reaction rates led to the suggestion of a potential energy surface (PES) with two wells connected by a central barrier transition state (3). Electronic structure calculations have confirmed this picture for some SN2 reactions (4), but recent studies have shown that the actual reaction dynamics may be considerably more complex (see the figure) (5–8). Authors: Jing Xie, William L. Hase
    Keywords: Organic Chemistry
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    [This Week in Science] Beyond textbook SN2 chemistry (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-04-01
    Description: Author: Julia Fahrenkamp-Uppenbrink
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 30
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    [This Week in Science] CO takes the lead to make β-lactam rings (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-11-18
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 31
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    [This Week in Science] Pluses and minuses of BTX behavior (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-11-18
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 32
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    [Editors' Choice] A pair of tablemates for aromatic benzene (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-09-09
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 33
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    [This Week in Science] Catching a break in polyphenol synthesis (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-12-09
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 34
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    [This Week in Science] How to turn olefins into nucleophiles (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
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    Publication Date: 2016-10-21
    Description: Author: Jake Yeston
    Keywords: Organic Chemistry
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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    [This Week in Science] Coordinated scission of N–H or O–H bonds (2016)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2016-11-11
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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    Pectinoidea (Bivalvia: Propeamussiidae and Cyclochlamydidae) from the southwestern Indian Ocean (2015)
    In:  Various articles (2305-2562) vol.56 (2015) nr.3 p.585
    Details
    Publication Date: 2015-12-30
    Description: Twenty-five species of Pectinoidea (24 Propeamussiidae, 1 Cyclochlamydidae) are herein listed from the Mozambique Channel, northwestern and southern Madagascar, and northeastern South Africa. New species: Propeamussium rosadoi, Parvamussium catillus, Parvamussium kilburni, Parvamussium puillandrei, Parvamussium strongae, Cyclopecten cassiculus, Cyclopecten kantori, Cyclochlamys bacachorda. New synonym: Amussium sewelli Knudsen, 1967 = Propeamussium watsoni (E.A. Smith, 1885). New records for the Mozambique Channel and northwestern Madagascar: Propeamussium andamanicum, Propeamussium arabicum, Propeamussium caducum, Propeamussium jeffreysii, Propeamussium sibogai, Propeamussium watsoni, Parvamussium formosum, Parvamussium scitulum, Parvamussium torresi, Parvamussium vesiculatum, Cyclopecten kapalae, Similipecten eous. New records for southern Madagascar: Propeamussium jeffreysii, Propeamussium sibogai, Propeamussium watsoni, Parvamussium formosum, Parvamussium scitulum, Parvamussium thyrideum, Parvamussium vesiculatum, Parvamussium vidalense, Cyclopecten kapalae, Similipecten eous. New record for South Africa: Propeamussium jeffreysii, Parvamussium formosum, Parvamussium scitulum, Cyclopecten horridus, Similipecten eous.
    Keywords: Pectinoidea ; Mollusca ; Propeamussiidae ; Cyclochlamydidae ; SW Indian Ocean ; new taxa ; new synonym ; new records ; 42.73
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    Molecular phylogenetics and comparative anatomy of Kimberleytrachia Köhler, 2011 - a genus of land snail endemic to the coastal Kimberley, Western Australia with description of new taxa (Gastropoda, Camaenidae) (2014)
    In:  Contributions to Zoology (1875-9866) vol.83 (2014) nr.4 p.245
    Details
    Publication Date: 2014-11-05
    Description: Kimberleytrachia Köhler, 2011 is a genus of camaenid land snail endemic to the Western Australian Kimberley region. It comprises twelve previously recognised species, all of which occur within the high precipitation zone along the north-western coast between the Admiralty Gulf and King Sound and within less than about 50 km distance from the coast. By evaluating the variation in shell and genital anatomy as well as the differentiation in the mitochondrial markers 16S and COI, we assess the monophyly of Kimberleytrachia with respect to other camaenid genera from north-western Australia. In addition, we newly describe six species (K. jacksonensis n. sp., K. leopardus n. sp., K. nelsonensis n. sp., K. serrata n. sp., K. setosa n. sp. and K. silvaepluvialis n. sp.) based on comparative morphology and mitochondrial DNA differentiation. We found that a rather smooth, weakly elevated shell and, in particular, the complex penial anatomy are key morphological characteristics of Kimberleytrachia. Its constituent species are differentiated by a combination of shell and genital features and their morphological disparity appears to be more pronounced when species occur in sympatry. While island species are usually narrowly endemic to one or a few islands, the mainland species have much larger distributional ranges. One new species from the Maret and Berthier Islands, Bonaparte Archipelago, is phylogenetically and morphologically so distinct from Kimberleytrachia that it is recognized as a new monotypic genus, Succochlea n. gen.
    Keywords: genetic distances ; Helicoidea ; mitochondrial DNA ; new species ; Stylommatophora ; 42.73 ; 42.64
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  • 38
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    Molluscs from the Miocene Pebas Formation of Peruvian and Colombian Amazonia (2006)
    In:  Scripta Geologica (03757587) vol.133 (2006) p.19
    Details
    Publication Date: 2007-01-09
    Description: The mollusc fauna of the Miocene Pebas Formation of Peruvian and Colombian Amazonia contains at least 158 mollusc species, 73 of which are introduced as new; 13 are described in open nomenclature. Four genera are introduced (the cochliopid genera Feliconcha and Glabertryonia, and the corbulid genera Pachyrotunda and Concentricavalva) and a nomen novum is introduced for one genus (Longosoma). A neotype is designated for Liosoma glabra Conrad, 1874a. The Pebas fauna is taxonomically dominated by two families, viz. the Cochliopidae (86 species; 54%) and Corbulidae (23 species; 15%). The fauna can be characterised as aquatic (155 species; 98%), endemic (114 species; 72%) and extinct (only four species are extant). Many of the families represented by a few species in the Pebas fauna include important ecological groups, such as indicators of marine influence (e.g., Nassariidae, one species), terrestrial settings (e.g., Acavidae, one species) and stagnant to marginally agitated freshwaters (e.g., Planorbidae, four species). Only seven species (4%) representing undisputedly elevated salinities were found, whereas 31 species (20%) are undisputed restricted to freshwater biotopes. Only three (2%) terrestrial gastropod species are known. The Pebas system experienced profuse radiations of molluscs that led to an overwhelmingly endemic fauna, typical of a long-lived lake environment. Several extant genera, which nowadays live outside Amazonia, may have originated within the Pebas system. The stratigraphic continuity of species and line ages, at least for the late Early-early Late Miocene interval (c. 18-9 Ma), indicates that lakes continuously occupied the system and never were entirely replaced by rivers or the sea. The rare occurrence of marine taxa indicates that the system was at sealevel and occasionally experienced marine incursions.
    Keywords: Mollusca ; systematics ; Pebas Formation ; Miocene ; western Amazonia ; 42.73 ; 38.22
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    Gulella johannae spec. nov. (Gastropoda, Pulmonata, Streptaxidae), a new land snail from the Drakensberg range in Limpopo Province, South Africa, with notes on G. johannesburgensis (M. & P.) (2006)
    In:  Zoologische Mededelingen (0024-0672) vol.80 (2006) nr.1 p.63
    Details
    Publication Date: 2010-12-12
    Description: Gulella (s.l.) johannae n. sp. is described from a few forest localities in the Tzaneen District, Limpopo Province, South Africa. It is characterized by a cylindrical, costulate shell with an almost entire peristome and a four-fold apertural dentition consisting of a prominent angular lamella (delimiting an only here discontinuous peristome), a mid-labral denticle, a left basal denticle, and a mid-columellar process. The shell is somewhat similar to that of G. johannesburgensis, but is consistently larger and more slender and has more whorls, while at the same time the apertural dentition is better developed; the almost uninterrupted peristome also appears to be a signifi cant character. This new taxon most likely is a restrictedrange endemic on the eastern flanks of the northern Drakensberg escarpment. Numerical data of a lot of material identified and mostly also published as G. johannesburgensis show that probably not all specimens belong to this taxon so that more than one species may be involved here.
    Keywords: Mollusca ; Gastropoda ; Pulmonata ; Streptaxidae ; Gulella, Gulella johannesburgensis ; taxonomy ; Drakensberg range ; South Africa ; 42.73
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  • 40
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    Miocene freshwater Mollusca from western Brazilian Amazonia (2006)
    In:  Scripta Geologica (03757587) vol.133 (2006) p.419
    Details
    Publication Date: 2007-01-09
    Description: Thirteen species of fossil molluscs are reported from the Solimões Formation of western Brazilian Amazonia. Based on mammalian chronology of the Solimões Formation and radiometric ages reported from coeval deposits in adjacent Peru, the age of the fauna is established as Late Miocene. The fauna includes five prosobranch gastropod species, seven pearly freshwater mussel species and one sphaeriid bivalve species. The supposed presence of Pachydon (Corbulidae: Bivalvia) in these deposits is rejected; Pachydon acreanum, whose status has long been uncertain, is transferred to the unionoid genus Callonaia. The Solimões mollusc fauna is entirely composed of obligate freshwater taxa, resembling species-poor modern Amazonian fluvial faunas. The presence of the fauna in outcrops covering large parts of western Amazonia indicates that by that time the preceding Pebas fauna (dominated by corbulid bivalves and cochliopid snails) must have been extinguished.
    Keywords: Mollusca ; western Amazonia ; Miocene ; Solimões Formation. ; 38.22 ; 42.73
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  • 41
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    Evolutionary ecology of the Pachydontinae (Bivalvia, Corbulidae) in the Pebas lake/wetland system (Miocene, western Amazonia) (2006)
    In:  Scripta Geologica (03757587) vol.133 (2006) p.395
    Details
    Publication Date: 2007-01-09
    Description: Miocene deposits in western Amazonia and adjacent areas of South America harbour a diverse suite of endemic corbulid bivalves, commonly referred to as Pachydontinae, that show a wide variety of morphologies. Especially in the Miocene Pebas Formation (Peru, Colombia and Brazil), this group diversified spectacularly. Since these corbulids (a cosmopolitan marine and perimarine bivalve family) occur with freshwater taxa and yield isotope signals strongly indicative of freshwater settings, the success of this group in inland basins of Miocene northwestern South America is surprising. In this paper it is argued that a combination of adaptations to fluid bottom substrates, common dysoxia and high predation intensities explains their abundance, their morphological diversity and the paucity of freshwater bivalve groups, such as Sphaeriidae, Corbiculidae and Unionoidea.
    Keywords: Corbulidae ; Pachydontinae ; Miocene ; Amazonia ; evolution ; adaptation ; 42.73 ; 38.22
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  • 42
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    A Miocene perspective on the evolution of the Amazonian biota (2006)
    In:  Scripta Geologica (03757587) vol.133 (2006) p.439
    Details
    Publication Date: 2007-01-15
    Description: Between c. 23 and 8 Ma, western Amazonia was occupied by the vast Pebas long-lived lake/wetland system. The Pebas system had a variety of influences over the evolution of Miocene and modern Amazonian biota; it formed a barrier for the exchange of terrestrial biota, a pathway for the transition of marine biota into freshwater Amazonian environments, and formed the stage of remarkable radiations of endemic molluscs and ostracods. The lithological variation of the Pebas Formation has furthermore enhanced edaphic heterogeneity in western Amazonia, sustaining present-day high terrestrial diversity in the region.
    Keywords: Miocene ; Amazonia ; biogeography ; biodiversity ; Mollusca ; 42.73 ; 38.22
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    The nature of aquatic landscapes in the Miocene of western Amazonia: an integrated palaeontological and geochemical approach (2006)
    In:  Scripta Geologica (03757587) vol.133 (2006) p.363
    Details
    Publication Date: 2007-01-09
    Description: The Miocene Pebas Formation from the section Santa Rosa de Pichana (Loreto, Peru) was investigated using a combination of analyses of sedimentary facies, molluscan communities and taphonomy, and stable isotopes of both entire shells and growth bands in bivalves. Three sequences, comprising a succession of transgressive, maximum flooding and regressive/prograding intervals, are documented. Molluscs are most common in the transgressive/highstand intervals and are almost absent in regressive/prograding intervals. The fauna is dominated by endemic Pebasian species, such as Pachydon and Dyris spp. The nature of the deposits as well as the availability of oxygen varied in a predictable way within each of the sequences and determined the nature of the assemblages. Highest diversity was reached in the late transgressive phase before the development of dysoxia that was widespread during the late highstand and early regressive/prograding phase. The mollusc and isotope data show no indications of elevated salinities, in contrast to ichnofossils found in the section. This discrepancy is interpreted to result either from temporal separation of the ichnofossils and the mollusc fossils or from evolution beyond usual ecological tolerances of taxa that produced these ichnofossils into freshwater settings.
    Keywords: Miocene ; Amazonia ; palaeoecology ; sedimentology ; stable isotopes ; 38.22 ; 42.73
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    The stratigraphy and regional structure of Miocene deposits in western Amazonia (Peru, Colombia and Brazil), with implications for late Neogene landscape evolution (2006)
    In:  Scripta Geologica (03757587) vol.133 (2006) p.291
    Details
    Publication Date: 2007-01-15
    Description: A biozonation based on molluscs is proposed for Miocene deposits of western Amazonia (Peru, Colombia and Brazil), commonly referred to as the Pebas Formation. The new zonation refines existing pollen zonations and provides a key for the quick assessment of the stratigraphic position of Neogene deposits in the field. The regional distribution of twelve mollusc zones reveals a structuring of geological units around the broad Iquitos-Araracuara anteclise. The structure of the subsurface appears to have been a major factor in the determination of present-day second and lower order river courses in the study area. Based on this work a biostratigraphic framework for Miocene deposits of western Amazonia, including fossiliferous deposits from adjacent basins (Putumayo, Llanos and Magdalena basins in Colombia), is proposed.
    Keywords: stratigraphy ; Mollusca ; Miocene ; western Amazonia ; Pebas Formation ; 42.73 ; 38.22
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  • 45
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    Morphology, anatomy and histology of Doto uva Marcus, 1955 (Opisthobranchia: Nudibranchia) from the Chilean coast (2006)
    In:  Contributions to Zoology (13834517) vol.75, 3/4 (2006) p.145
    Details
    Publication Date: 2014-11-07
    Description: Doto uva Marcus, 1955 is a nudibranch species recorded from the Brazilian and Chilean coast. In spite of its wide distribution, D. uva has been described only superficially, mainly as to the pattern of its coloration, external morphology, radular teeth and reproductive system. Here we substantially extend this description, paying special attention to the morphology, anatomy and histology of the digestive and reproductive system. Furthermore, new data on the morphology of the central nervous system and its cell types are given, and finally, the egg mass is described. On the basis of these data, we consider the Doto specimens described from Chile conspecific with those from Brazil.
    Keywords: Opisthobranchia ; Nudibranchia ; Doto ; Histology ; Morphology ; Chilean coast ; 42.73
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  • 46
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    Miocene long-lived lake Pebas as a stage of mollusc radiations, with implications for landscape evolution in western Amazonia (2006)
    In:  Scripta Geologica (03757587) vol.133 (2006) p.1
    Details
    Publication Date: 2007-01-09
    Description: The Miocene Pebas system was a huge (〉 1 million km2) system of long-lived lakes and wetlands that occupied most of western Amazonia between c. 23 and 8 Ma. Remarkable endemic radiations of molluscs and ostracods occurred in the Pebas system. The continuity of many of the endemic lineages between c. 17 and 9 Ma shows that the system was never fully replaced by fluvial or marine settings. Many of the endemic invertebrate groups developed an unusual range of morphologies that reflect adaptation to specific ecological stresses provided by the Pebas system, such as chemical stress, common dysoxia and high predation pressure. Mollusc diversity increased especially during the Middle Miocene. The Pebas system provided pathways for mobile marine organisms to transfer into freshwater biotopes, and at the same time obstructed exchange of terrestrial biota between the tropical Andes and the Guyana region. Short-lived, lowland aquatic corridors over northern shield regions and through the Ecuadorian Andean region almost certainly existed. The Pebas system was terminated just before the establishment of the modern Amazon system (slightly before 8 Ma), possibly coinciding with a single, wide ranging marine incursion into lowland Amazonia. With the termination of the Pebas system, the endemic mollusc fauna became largely extinct. The termination of the Pebas system provided large tracts of land for the establishment and development of terrestrial biota in western Amazonia. Subsequent diversification in lowland Amazonia has been enhanced by the edaphic heterogeneity of the Pebas Formation deposits.
    Keywords: Miocene ; Amazonia ; molluscs ; landscape evolution ; Pebas Formation ; 42.73 ; 38.22
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    Neogene fossil tonnoidean gastropods of Indonesia (2005)
    In:  Scripta Geologica (03757587) vol.130 (2005) p.1
    Details
    Publication Date: 2007-01-12
    Description: Tonnoidean gastropods in K. Martin’s and other collections in the Nationaal Natuurhistorisch Museum, Leiden (and a few other minor collections) are reidentified and classified. The resulting fauna of 99 species is very similar to that of the Indo-West Pacific today, 70% of species still inhabiting the Indonesian region. Species endemic to the Miocene and Pliocene rocks of Indonesia are Bursa sangirana sp. nov., and two new (unnamed) species similar to Bursina ignobilis (Beu); Cassis depressior Martin and C. preangerensis Martin; Cypraecassis denseplicata (Martin) and an unnamed species of Cypraecassis; Sconsia martini van Regteren Altena and S. pulchra Pannekoek; Echinophoria vandervlerki Martin (possibly a synonym of E. wyvillei (Watson)); Phalium menkrawitense Beets and P. rembangense (Martin); Distorsio denseplicata van Regteren Altena and D. djunggranganensis (Martin); Biplex magnifica (Martin), B. pamotanensis (Martin) and B. perliberalis (Beets); Cymatium (Monoplex) gembacanum (Martin) (?=C. exaratum (Reeve)), C. rembangense (Wanner & Hahn), and C. tjaringinense (Martin); Cymatium (Ranularia) pseudopyrum (Martin) and an unnamed species of C. (Ranularia); Cymatium (Septa) dharmai sp. nov.; Sassia (Cymatiella) fennemai (Martin), S. (C.) menkrawitensis (Beets) and an unnamed species of S. (Cymatiella); Eudolium erbi (Haanstra & Spiker), E. errabundum (Beets) and E. pamotanense (Martin); Malea(?) papuana (Beets); and Sconsodolium (gen. nov.) rembangense (Pannekoek). These 30 species (30% of the recorded fauna), and the generic groups Sconsia, Sconsodolium and Sassia (Cymatiella), are all “additional” tropical western Pacific taxa that became extinct before the present day (Sconsia and Sassia (Cymatiella) only locally), as a result of Pleistocene climate change. Species previously included in Bufonaria Schumacher prove to belong in two distinct genera; species closely related to “Bursa” nobilis have a subcentral (rather than mid-left edge) opercular nucleus and are reclassified in Bursina Oyama. “Sconsia” rembangensis Pannekoek is an elongate, axially ridged cassid with a coarsely plicate inner lip; the new genus Sconsodolium is proposed for it. Galeodea bituminata (Martin) and G. carolimartini Beets are both earlier names for the western Pacific species (originally described in the Recent fauna) previously known as G. echinophorella Habe. Eudolium javanum (Martin) is an earlier name for the Indo-West Pacific species (originally described in the Recent fauna) previously known as E. pyriforme (G.B. Sowerby 3rd), whereas E. bituminata Martin is a synonym of the near-cosmopolitan species E. bairdii (Verrill & Smith). Ranella spinosa var. granosa Martin is either an earlier name for the western Pacific species (originally described in the Recent fauna) previously known as Bufonaria perelegans Beu, or a closely similar, but distinct, species. Purpura bantamensis Martin, Cassis tegalensis Martin, Dolium losariense Martin, and Tritonium verbeeki Boettger are all synonyms of Cymatium (Linatella) cingulatum (Lamarck).
    Keywords: Gastropoda ; Tonnoidea ; Neogene ; Indonesia ; taxonomy ; biogeography ; 42.73
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    Changes in the intertidal community structure after a mass mortality event in sandy beaches of Argentina (2005)
    In:  Contributions to Zoology (13834517) vol.74, 1/2 (2005) p.27
    Details
    Publication Date: 2014-11-07
    Description: After a massive mortality of the dominant species (the clam Mesodesma mactroides) occurred in 1995, changes in the intertidal community in sandy beaches of Argentina were monitored. Eight sampling stations were established in a 40 km open stretch and samples were taken every October each year up to 2001. Biomass, density, size frequency distribution and mean growth rates for the most abundant species were analyzed. During the mortality event, only the benthic stages of M. mactroides were affected, their total mean biomass diminishing from 1,399 g to 2 g per running meter beach. Post-mortality recruitment was normal and the growth rates for the youngest cohorts were similar to those previously reported. After a two years’ lag, the wedge clam Donax hanleyanus replaced M. mactroides as the dominant species, increasing from 6.0 g/m up to 24.3 g/m. However, dominance replacement did not restore the productivity of the intertidal macrobenthic assemblage and, despite the increment of D. hanleyanus stocks, the community total biomass remained 〈 1% of the pre-mortality levels. Since 1998 on, M. mactroides and D. hanleyanus showed several peaks in abundance. Disturbance, mainly due to non-regulated fisheries, has been delaying the community recovery. Taking into account the interactions among species and human activities, the present individual resourcebased management should be replaced by an integrated systembased management program including both conservation and tourism requirements.
    Keywords: Surf clams ; Mesodesma mactroides ; Donax hanleyanus ; sandy beaches ; benthos ; Argentina ; species interactions ; 42.73
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    A hitherto unnoticed adaptive radiation: epitoniid species (Gastropoda: Epitoniidae) associated with corals (Scleractinia) (2005)
    In:  Contributions to Zoology (13834517) vol.74, 1/2 (2005) p.125
    Details
    Publication Date: 2015-06-03
    Description: Twenty-two epitoniid species that live associated with various hard coral species are described. Three genera, viz. Epidendrium gen. nov., Epifungium gen. nov., and Surrepifungium gen. nov., and ten species are introduced as new to science, viz. Epidendrium aureum spec. nov., E. sordidum spec. nov., Epifungium adgranulosa spec. nov., E. adgravis spec. nov., E. adscabra spec. nov., E. marki spec. nov., E. nielsi spec. nov., E. pseudolochi spec. nov., E. pseudotwilae spec. nov., Surrepifungium patamakanthini spec. nov., and ‘Epitonium’ crassicostatum spec. nov. and ‘E.’ graviarmatum spec. nov. Although their identities as separate gene pools are convincingly demonstrated by molecular data, some of these species cannot be identified unequivocally on the basis of conchological characters alone. The shell shape and sculpture are only partially diagnostic because of interspecifically overlapping character states. In most of these cases, the operculum, jaw structure, radula, spawn and/or the habitat do reveal the identity. Most of these species are associated with only one or a restricted number of coral host species and have large ranges, similar to those of their hosts.
    Keywords: Indo-Pacific ; parasites ; coral reefs ; coral/mollusc associations ; Epitoniidae ; Epitonium ; Epidendrium ; Epifungium ; Surrepifungium ; new species ; new genera ; Scleractinia ; Fungiidae ; Fungia ; 42.73
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  • 50
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    On the Barremian-Early Albian biogeography (by ammonites) of Colombia (2004)
    In:  Scripta Geologica (03757587) vol.128 (2004) p.515
    Details
    Publication Date: 2007-01-18
    Description: On the basis of new and published palaeontological and stratigraphical data, the qualitative and quantitative variations in the Barremian-early Albian ammonite fauna of Colombia have been documented and analyzed. The position adopted here is that in the early Barremian the Andean Province became replaced by the Caribbean Subprovince in Colombia. The Caribbean Subprovince became separated as an independent unit from the Andean Province on the generic level (Buergliceras, Pedioceras), but especially on the species level. In the middle/upper Aptian many new endemic genera and subgenera appeared; Juandurhamiceras, Neodeshayesites, Laqueoceras, Zambranoites, Riedelites and Pseudoptychoceras. Besides, many endemic middle Aptian species of other, non-endemic genera appeared. Beginning from the middle Aptian the Caribbean area was a separate biogeographic enitity with the rank of Province; the Colombian region is considered to be the core area of the Caribbean Province.
    Keywords: palaeobiogeography ; Early Cretaceous ; ammonites ; Colombia ; 38.22 ; 42.73
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    Barremian-Early Albian Deshayesitidae, Oppeliidae, Desmoceratidae and Silesitidae of Colombia (2004)
    In:  Scripta Geologica (03757587) vol.128 (2004) p.183
    Details
    Publication Date: 2007-01-18
    Description: Forty seven species (among them fourteen new that are listed below) of the following ammonite genera of the families Deshayesitidae Stoyanow, Oppeliidae Douvillé, Desmoceratidae Zittel, and Silesitidae Hyatt are described. Neodeshayesites includes the new species N. buergli, N. striatus, N. biplicatus, N. longicostatus, N. multicostatus, N. euglyphoides and N. tuberculatus. Dufrenoyia includes the new species D. renzi. Pseudohaploceras includes the new species P. gerhardti, P. yucaense, P.? yeseraense and P. simile. Melchiorites includes the new species M. colombianus. Zuercherella includes the new species Z. etayosernai. Other species belong to the genera Juandurhamiceras, Aconeceras, Pseudosaynella, Valdedorsella, Puzosia, Carloscaceresiceras, Kennicottia and Miyakoceras.
    Keywords: ammonites ; Barremian ; Aptian ; Albian ; Colombia ; 38.22 ; 42.73
    Repository Name: National Museum of Natural History, Netherlands
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    Heteromorphic ammonites from the Barremian and Aptian strata of Colombia (2004)
    In:  Scripta Geologica (03757587) vol.128 (2004) p.182
    Details
    Publication Date: 2007-01-18
    Description: Thirty seven species and subspecies of ammonites of the families Ancyloceratidae Gill, 1871, and Heteroceratidae Spath, 1922, are described. The following new taxa are described; Crioceratites (Paracrioceras) leyvaensis, C. (P.) royogomezi, C. (P.) cabreraensis, Pedioceras multicostatum, Pseudocrioceras guanense, Kutatissites creutzbergi, K. densecostatus compactus, K. etayosernai, K. grandis, K.? galanensis, Ammonitoceras galanense, A. giganteum, Hamiticeras ventrotuberculatum, H. longum, Hemihoplites (Matheronites) ridzewskyi sachicaensis, Colchidites riosuarezi, C. pseudovulanensis, C. guanensis and C. striatosulcatus. Moreover, one new genus, Laqueoceras gen. nov., with the type species L. laqueus sp. nov., is proposed.
    Keywords: heteromorphic ammonites ; Barremian ; Aptian ; Colombia ; 38.22 ; 42.73
    Repository Name: National Museum of Natural History, Netherlands
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    Comparative reproductive anatomy in the South African giant land snails (Gastropoda: Pulmonata: Achatinidae) (2004)
    In:  Zoologische Mededelingen (00240672) vol.78, 18-28 (2004) p.417
    Details
    Publication Date: 2007-01-18
    Description: The history and current taxonomic status of 62 nominal taxa are revised that have been associated in the literature with the subgenus Tholachatina Bequaert, 1950, of genus Archachatina Albers, 1850, and the genus Cochlitoma Férussac, 1821, in the land snail family Achatinidae Swainson, 1840. Tangible, reliable characters have been found in the detailed features of the reproductive anatomy in this family. The results of comparative anatomical study convincingly reflect phylogeny in contrast to the comparative study of only the shell characters. This latter more strongly reflects the effects of the intrinsically variable environment over time. In the present study, both sets of characters are needed to refine identification. Change, and therefore speciation, is shown in the reproductive system through anatomical differences that may develop in the functional interrelationships of the two integral reproductive systems of hermaphroditism. Limited adjustment to anatomical change over time has established for each genus a typical, characteristic reproductive anatomical pattern or configuration. Because this pattern has a basically high degree of physical stability within a population, it becomes an identifying character for the genus, and more restrictedly so for the species. Two new genera (Bruggenina and Brownisca) and two new species (Cochlitoma kilburni and C. wigleyi) are described on the basis of distinctive anatomical characters. The genus Cochlitoma sensu Pilsbry (1904) is resurrected and redescribed. It contains most of the southern African achatinid species. Bequaert’s subgenus Tholachatina (1950) of West African genus Archachatina is invalid. The genus Archachatina Albers, 1850, has no endemic species in southern Africa.
    Keywords: Mollusca ; Gastropoda ; Pulmonata ; Achatinidae ; biogeography ; taxonomy ; genital anatomy ; Southern Africa ; East Africa ; 42.73
    Repository Name: National Museum of Natural History, Netherlands
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    Intraspecific and intrageneric variabilities and their implication for the systematics of Cretaceous heteromorph ammonites; a review (2004)
    In:  Scripta Geologica (03757587) vol.128 (2004) p.17
    Details
    Publication Date: 2007-01-18
    Description: The variability in the dimensions of the shell, and some changes in suture line, sculpture, whorl section and mode of coiling in the late ontogenetic stages, have in some cases no taxonomic significance for the recognition of genera and higher taxa of Cretaceous heteromorph ammonites. In many cases, such phenomena are due to intraspecific variation or variation within a genus. The intrageneric variations of some Cretaceous heteromorphs are discussed in detail in the light of new, rich Colombian material. In relation to these problems in systematics, some questions on the systematics of the superfamily Ancyloceratoidea Gill are considered.
    Keywords: ammonites ; heteromorphs ; dimorphism ; systematics ; Cretaceous ; 38.22 ; 42.73
    Repository Name: National Museum of Natural History, Netherlands
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    Aptian and Early Albian Douvilleiceratidae, Acanthohoplitidae and Parahoplitidae of Colombia (2004)
    In:  Scripta Geologica (03757587) vol.128 (2004) p.313
    Details
    Publication Date: 2007-01-18
    Description: Seventy nine species and subspecies of the following ammonite genera and subgenera of the families Douvilleiceratidae Parona & Bonarelli, Acanthohoplitidae Stoyanow, and Parahoplitidae Spath are described from the study area. Fourteen species are new; Cheloniceras rectangulatum, Ch. guanense, Epicheloniceras wiedmanni, E. douvillei, E. bradleyiformis, Vectisites (Zambranoites) nodosus, V. (Z.) etayosernai, V. (Z.) obscurus, V. (Z.) grandis, Gargasiceras subpulcher, Colombiceras formosum, Protacanthoplites originalis, Riedelites latecostatus, R. microtuberculatus.
    Keywords: ammonites ; systematics ; Aptian ; Albian ; Colombia ; 38.22 ; 42.73
    Repository Name: National Museum of Natural History, Netherlands
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    Preface: Early Cretaceous ammonites from Colombia (2004)
    In:  Scripta Geologica (03757587) vol.128 (2004) p.1
    Details
    Publication Date: 2007-01-18
    Keywords: Early Cretaceous ; ammonites ; Colombia ; 38.20 ; 42.73
    Repository Name: National Museum of Natural History, Netherlands
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    The anatomy and phylogeny of the African land snail Limicena Connolly, 1925 (Pulmonata: Cerastidae) (1998)
    In:  Zoologische Mededelingen (00240672) vol.72, 1-10 (1998) p.59
    Details
    Publication Date: 2007-01-23
    Description: An investigation of the anatomy of Limicena confirms its position as a monotypic genus in the Cerastidae. Phylogenetic analysis places Limicena as the most plesiomorphic member of a clade characterised by a pseudosigmurethrous excretory system, the more advanced members of which are Rhachistia, Amimopina and Edouardia. Its position at the base of such a widely dispersed, advanced clade with apparently xerophilic adaptations lends support to a dispersalist hypothesis for the extra-Afrotropical distribution of the Cerastidae.
    Keywords: Pulmonata ; Orthurethra ; Cerastidae ; Limicena ; anatomy ; pseudosigmurethrous condition ; biogeography ; Africa ; parsimony analysis ; 42.73
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    Molecular imprinting technology: challenges and prospects for the future (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 195-209 
    Details
    ISSN: 0899-0042
    Keywords: molecular imprinting ; molecular recognition ; chirality ; chromatography ; catalysis ; biosensor ; immunoassay ; antibody mimic ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular imprinting is a technique for the fabrication of biomimetic polymeric recognition sites or “plastic antibodies/receptors” which is attracting rapidly increasing interest. By this technology, recognition matrices can be prepared which possess high substrate selectivity and specificity. In the development of this technology, several applications have been foreseen in which imprinted materials may be exchanged for natural recognition elements. Thus, molecularly imprinted polymers have been used as antibody/receptor binding mimics in immunoassay-type analyses, as enzyme mimics in catalytic applications and as recognition matrices in biosensors. The best developed application area for imprinted materials, though, has been as stationary phases for chromatography, in general, and chiral chromatography, in particular. This review seeks to highlight some of the more intriguing advantages of the technique as well as pointing out some of the difficulties encountered. The prospects for future development will also be considered. Chirality 10:195-209, 1998. © 1998 Wiley-Liss, Inc.
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    Separation of (R)- and (S)-tert-butyl 2-tert-butyl-4-methoxy-2,5-dihydro-1,3-imidazole-1-carboxylate (building block for amino acid synthesis) by preparative high performance liquid chromatography on a polysaccharide stationary phase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 217-222 
    Details
    ISSN: 0899-0042
    Keywords: amylose ; 3,5-dimethylphenyl-carbamate ; polysaccharide phase ; tert-butyl 2-tert-butyl-4-methoxy-2,5-dihydro-1,3-imidazole-1-carboxylate; amino acid ester synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparative separation of the enantiomers of the title compound, a versatile chiral building block for the synthesis of unnatural amino acid esters, by high performance liquid chromatography on a chiral stationary phase (CSP), is reported for the first time. The CSP consists of amylose-(3,5-dimethylphenyl-carbamate), which has been coated onto the surface of macroporous aminopropyl-functionalized silica gel. The effect of mobile phase composition and the amount of amylose derivative on the silica gel has been thoroughly investigated. Using 2-propanol as organic modifier in hexane as mobile phase, on a semi-preparative column (200 mm × 40 mm ID, containing 192 g of stationary phase) about 200 mg of the racemate was separated per injection. Running the equipment under automatic conditions with repetitive injection mode allowed for the separation of 30 g per day. Both enantiomers were obtained with enantiopurities 〉99.75:0.25. Chirality 10:217-222, 1998. © 1998 Wiley-Liss, Inc.
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    Species-dependent enantioselective pharmacokinetics of PNU-103017, a Pyrone HIV protease inhibitor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 210-216 
    Details
    ISSN: 0899-0042
    Keywords: enantiospecific assay ; rat ; dog ; human ; enantiomer disposition ; HIV protease inhibitor ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: PNU-103017, 4-Cyano-N-(3-(cyclopropyl(5,6,7,8,9,10-hexahydro-4-hydroxy-2-oxo-2H-cycloocta(b) pyran-3-yl)methyl)phenyl)-benzenesulfonamide, is a selective HIV aspartyl protease inhibitor under evaluation as a potential oral treatment of Acquired Immunodeficiency Diseases. PNU-103017 is a racemic mixture of two enantiomers, designated PNU-103264 (R-) and PNU-103265 (S-). Stereoselective pharmacokinetics of the two enantiomers of PNU-103017 were observed in the dog, rat, and human after single and multiple dose administration of the racemate and were apparently species-dependent. Mean enantiomeric ratios of plasma concentrations (R-/S-) at each time point were greater than 1 in the dog, ranging from 1.22 to 3.06, but less than 1 in the rat and in the human, ranging from 0.44 to 0.80 and 0.23 to 0.73, respectively. A trend towards increased or decreased (farther from 1:1, R-/S-) enantiomeric ratio of plasma concentrations with time after each administration was also observed. The enantiomeric ratio remained unchanged after multiple dose administration in the rat, dog, and human although enzyme induction and increased plasma clearance were observed for both enantiomers. Chirality 10:210-216, 1998. © 1998 Wiley-Liss, Inc.
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    Chiral interaction and stochastic kinetics in stirred crystallization of amino acids (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 238-245 
    Details
    ISSN: 0899-0042
    Keywords: chiral selectivity ; amino acid crystallization ; molecular recognition ; stochastic kinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of chirally selective interaction in the stirred crystallization of glutamic acid and lysine is presented. The crystallization of S-glutamic acid is influenced by the presence of S-lysine but not R-lysine. Crystal nuclei in stirred systems are produced due to secondary nucleation. Secondary nucleation is an autocatalytic process in which a crystal produces secondary nuclei due to fluid motion, and due to crystal stirrer and crystal-crystal collisions. As a result of this autocatalysis, small fluctuations in the nucleation rates are amplified and the kinetics show a marked stochastic behavior. We investigate the stochastic behavior in detail and propose a kinetic mechanism that explains both the increase and the statistical distribution of the crystallization times of S-glutamic acid due to the presence of S-Lysine. Chirality 10:238-245, 1998. © 1998 Wiley-Liss, Inc.
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    Enantiomers of thalidomide: blood distribution and the influence of serum albumin on chiral inversion and hydrolysis (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 223-228 
    Details
    ISSN: 0899-0042
    Keywords: thalidomide enantiomers ; in vitro kinetics ; blood distribution ; human serum albumin ; chiral inversion ; plasma protein binding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this investigation was to elucidate the distribution and reactions of the enantiomers of thalidomide at their main site of biotransformation in vivo, i.e., in human blood. Plasma protein binding, erythrocyte: plasma distribution, and the kinetics of chiral inversion and degradation in buffer, plasma, and solutions of human serum albumin (HSA) were studied by means of a stereospecific HPLC assay. The enantiomers of thalidomide were not extensively bound to blood or plasma components. The geometric mean plasma protein binding was 55% and 66%, respectively, for (+)-(R)- and (-)-(S)-thalidomide. The corresponding geometric mean blood:plasma concentration ratios were 0.86 and 0.95 (at a haematocrit of 0.37) and erythrocyte:plasma distributions were 0.58 and 0.87. The rates of inversion and hydrolysis of the enantiomers increased with pH over the range 7.0-7.5. HSA, and to a lesser extent human plasma, catalysed the chiral inversion, but not the degradation, of (+)-(R)- and (-)-(S)-thalidomide. The addition of capric acid or preincubation of HSA with acetylsalicylic acid or physostigmine impaired the catalysis to varying extents. Correction for distribution in blood enhances previously observed differences between the pharmacokinetics of the enantiomers in vivo. The findings also support the notion that chiral inversion in vivo takes place mainly in the circulation and in albumin-rich extravascular spaces while hydrolysis occurs more uniformly in the body. In addition, the chiral inversion and hydrolysis of thalidomide apparently occur by several different mechanisms. Chirality 10:223-228, 1998. © 1998 Wiley-Liss, Inc.
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    Mechanistic aspects of the biogenesis of rose oxide in Pelargonium graveolens L'Héritier (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 229-237 
    Details
    ISSN: 0899-0042
    Keywords: deuterium labelling ; menthocitronellol ; citronellol ; enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS) ; dynamic headspace analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanistic aspects of the biogenesis of the chiral monoterpenoid rose oxide in Pelargonium graveolens L'Héritier are investigated using deuterium-labelled precursors. After administration of the precursors using the cut-stem method, the dynamic headspace extracts of the plants are analysed using multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS). It is unequivocally shown that this plant is able to convert citronellol and menthocitronellol into cis-/trans-rose oxide. Menthocitronellol is converted into rose oxide with a clearly detectable enantiodiscrimination. These facts may be explained with the presence of an oxidase, which is able to oxidize citronellol and menthocitronellol in allylic position. A photooxygenation mechanism including singlet oxygen as the oxidizing agent is rather unlikely. Chirality 10:229-237, 1998. © 1998 Wiley-Liss, Inc.
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    Chloroperoxidase-induced asymmetric sulfoxidation of some conformationally restricted sulfides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 246-252 
    Details
    ISSN: 0899-0042
    Keywords: sulfoxides ; chloroperoxidase ; asymmetric oxidation ; enantioselective ; episulfide ; gas chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Asymmetric sulfoxidation by means of a chloroperoxidase from Caldariomyces fumago and hydrogen peroxide as the oxygen source was studied for a series of sterically well-defined substrates. The stereochemistry of the sulfoxidation was the same for all substrates studied. While 2,3-dihydrobenzo[b]thiophene (1) is an excellent substrate (giving 99.5% yield and 99% e.e. of the (R)-sulfoxide), replacement of a methylene group by either a more sterically demanding group or a heteroatom caused a substantial decrease in reactivity or in reactivity as well as enantioselectivity. A further investigation of the lowered catalytic efficiency of chloroperoxidase with these substrates has been carried out in a series of competitive reactions. Thus, benzo[1,3]oxathiole (5) acted as a competitive inhibitor of the enzyme, whereas 1-thiochroman (2) and 1-thiochroman-4-one (3) were shown to be too sterically demanding to significantly compete for the active site. For the oxidation of 2, 3, and 5, it was found that in the low CPO concentration range the chemical yield after 60 min reaction time increased almost linearly with the amount of CPO used. The products from 2 and 3 could be obtained in over 80% yield with an e.e. exceeding 96%. Chloroperoxidase was also found to be an effective catalyst in the oxidation of labile episulfides, yielding the corresponding anti-sulfoxides quantitatively and giving 12% e.e. of (1R, 2R)-sulfoxide in the oxidation of propylene sulfide. Chirality 10:246-252, 1998. © 1998 Wiley-Liss, Inc.
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    1997 Chirality Medal (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 281-281 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Circular dichroism of axially chiral methaqualone, 3-Aryl-2-mercapto- and 3-aryl-2-alkylthio-4(3H)-quinazolinones: conformational dependence of CD and assignment of absolute configuration (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 253-261 
    Details
    ISSN: 0899-0042
    Keywords: chiroptical properties ; Cotton effect ; atropisomerism ; quantum-mechanical calculation ; AM1 ; CNDO/S ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rotational strengths calculated on the basis of quantum-mechanically obtained minimum energy geometries were used to determine the absolute configurations of axially chiral 3-aryl-4(3H)-quinazolinones from the sign of the observed Cotton effects (CEs). For the spectral data, CNDO/S calculations were used; for the geometries, ab initio (RHF/6-31G) and semiempirical (AM1) theories were used. Oscillator and rotational strengths of all excited states down to 200 nm were compared to experimental absorption and circular dichroism (CD) data. It was found that the sign of the 1Lb Cotton effects obtained for the enantiomers of methaqualone and derivatives of 3-aryl-2-alkylthio-4(3H)-quinazolinones can be correlated unambiguously with the absolute configuration. Furthermore, the sign of the Cotton effect of the π-π* transition of the thiocarbonyl chromophore of 3-aryl-2-mercapto-4(3H)-quinazolinones is suitable for a successful stereochemical correlation. Chirality 10:253-261, 1998. © 1998 Wiley-Liss, Inc.
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    Sympathomimetic enantiomers and asthma (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 262-272 
    Details
    ISSN: 0899-0042
    Keywords: airway ; beta2-agonist ; racemic ; eutomer ; distomer ; hyperreactivity ; bronchospasm ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Airways of asthma patients can become hyperresponsive to airway spasmogens following regular use of isoprenaline or β2-selective sympathomimetics. Hyperreactivity that results from acute exposure of animals to these drugs is pre-empted by vagal section (a procedure which does not influence spasmolytic efficacy of sympathomimetics), is not diminished by antagonism of β2-adrenoceptors and is not associated with loss of responsivity of β2-adrenoceptors in the airways. Since activation, modulation, or blockade of β2-adrenoceptors does not determine this form of hyperreactivity, the possibility that distomers may induce hyperreactivity must be considered. Ocular and vascular responses to distomers of sympathomimetics have long been recognised and, more recently, comparable observations have been made for the airways. Thus, reactivity of guinea-pig airways to spasmogens was increased following exposure to S-isoprenaline, S-salbutamol, or S-terbutaline and exposure to S-isoprenaline or S-salbutamol can intensify symptoms in asthmatics. Regular exposure to the racemate, especially during or following an allergic reaction, predisposes to expression of hyperreactivity, which is nullified, acutely, by the eutomer. These observations imply that biological effects of sympathomimetic distomers may contribute to morbidity and mortality in asthma patients. Chirality 10:262-272, 1998. © 1998 Wiley-Liss, Inc.
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    Immobilized vancomycin as chiral stationary phase in packed capillary liquid chromatography (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 273-280 
    Details
    ISSN: 0899-0042
    Keywords: direct chiral separation ; mobile phase composition ; NSAIDs ; retention model ; vancomycin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fused silica-packed capillary columns containing vancomycin immobilized by reductive amination on an aldehyde-silica were used to separate enantiomers of some non-steroidal anti-inflammatory drugs. Attempts have been made to qualitatively explain the influence of various mobile phase compositions on the enantioselective retention. The effects of mobile phase pH, buffer, and organic modifier concentrations were investigated as well as the influence of salts of hydrophobic ions added to the mobile phase to induce ion pair retention. Chirality 10:273-280, 1998. © 1998 Wiley-Liss, Inc.
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    Carbamates of cellulose bonded on silica gel: Chiral discrimination ability as HPLC chiral stationary phases (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 283-288 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; cellulose carbamates ; enantiomeric resolution ; warfarin ; flurbiprofen ; lorazepam ; oxazepam ; pindolol ; tertatolol ; nicardipine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four cellulose mixed 10-undecenoate/carbamate derivatives, simultaneously bearing 10-undecenoyl and variously substituted phenylaminocarbonyl groups, were chemically bonded on allylsilica gel. The study of the effect of these substitutions on the performance of the resulting chiral supports, and a comparison with the recently described 10-undecenoate/3,5-dimethylphenylcarbamate derivative, are presented. In this study heptane/2-propanol or heptane/chloroform mixtures were used as mobile phases. Chirality 10:283-288, 1998. © 1998 Wiley-Liss, Inc.
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    Correlation between time reversal symmetry and chirality in certain molecular processes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 289-293 
    Details
    ISSN: 0899-0042
    Keywords: chirality ; time reversal symmetry ; asymmetric synthesis ; enantiomerism ; isomerism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If a molecule is identified not only by its static spatial constructions, but also by the motions at the sub-molecular level, application of time reversal symmetry operation to a certain molecule could lead to another distinguishable from the original in the sense of sub-molecular motions, a phenomenon now defined as time reversal isomerism. Assessment of the consideration of certain enantiomers as distinguishable time reversal isomers is suggested in order to evoke a comprehensive interpretation of a likely correlation between the two types of isomerisms. The conceptual basis of a connection between absolute asymmetric synthesis under the influence of external fields and the intrinsic time reversal symmetry violation at the molecular level is also established to encourage new experimental investigations on this theme. Chirality 10:289-293, 1998. © 1998 Wiley-Liss, Inc.
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    Synthesis of regioselectively substituted cellulose derivatives and applications in chiral chromatography (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 294-306 
    Details
    ISSN: 0899-0042
    Keywords: cellulose ; regioselective derivatization ; chiral stationary phases ; liquid chromatography ; enantioseparation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various cellulose-2,3-bis-arylcarbamate-6-O-arylesters and cellulose-2,3-bis-arylester-6-O-arylcarbamates, designed to test the possible combined effects of the known tris-arylcarbamate and tris-arylester classes, were synthesized with high regioselectivity at O-C(6), and their use as CSPs in liquid chromatography for enantiomeric separations was investigated. The separations obtained with the synthesized CSPs were compared to the separations achieved on a self-packed reference column, consisting of cellulose-tris-(3,5-dimethylphenyl-carbamate) as CSP standard. Among the synthesized, regioselectively substituted cellulose derivatives, 2,3-bis-O-(3,5-dimethylphenylcarbamate)-6-O-benzoate-cellulose and 2,3-bis-O-(benzoate)-6-O-(3,5-dichlorophenylcarbamate)-cellulose gave the best CSPs for the separation of the test racemates. CSPs from regioselectively substituted cellulose derivatives seem to exhibit higher selectivities than cellulose-tris-(3,5-dimethylphenylcarbamate) for certain classes of racemic compounds. Chirality 10:294-306, 1998. © 1998 Wiley-Liss, Inc.
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    Enantiomeric separation of rac-indoprofen by a biocatalytic procedure (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 321-324 
    Details
    ISSN: 0899-0042
    Keywords: NSAID ; esterification ; resolution ; Candida antarctica lipase ; rac-Indoprofen ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipase from Candida antarctica, commercially available immobilised on acrylic resin as Novozym® 435, allows for enantioselective esterification of rac-indoprofen (±)-1, with methanol in a dioxane-toluene solvent system. A double esterification process affords methyl ester (-)-(R)-2 in 85% e.e. and enantiopure (+)-(S)-1, both in good chemical yield. Chirality 10:321-324, 1998. © 1998 Wiley-Liss, Inc.
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    Kinetics of racemization of (+)- and (-)-diethylpropion: Studies in aqueous solution, with and without the addition of cyclodextrins, in organic solvents and in human plasma (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 307-315 
    Details
    ISSN: 0899-0042
    Keywords: configurational stability ; pH ; temperature ; ionic strength ; phosphate buffer concentration ; plasma protein affinity ; native cyclodextrins ; cyclodextrin derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configurational stability of (+)- and (-)-diethylpropion [(+)- and (-)-2-(diethyl)-1-phenyl-1-propanone or (+)- and (-)-DEP] was investigated systematically from chemical, pharmaceutical, and pharmacological aspects. The enantiomeric ratio was monitored directly with a recently developed stability-indicating enantioselective HPLC method.In aqueous solutions, the rate of racemization increased non-linearly with increasing pH and with increasing phosphate buffer concentration. The racemization rate showed a positive slope with increasing temperature and decreasing ionic strength.The racemization rates of (+)- and (-)-DEP in the presence of cyclodextrins (CDs) did not differ significantly. CDs that were added to (+)- and (-)-DEP in a molar ratio 5:1 showed the following effects after dissolution in 10 mM phosphate buffer (final pH 6.7): sulfobutyl ether-β-CD (SBE-β-CD) and methylated-β-CD (Me-β-CD) retarded racemization; whereas hydroxypropyl-β-CD (HP-β-CD), acetyl-γ-CD (Ac-γ-CD), acetyl-β-CD (Ac-β-CD), γ-CD, and β-CD showed a weak destabilising effect. In contrast to the described CDs, α-CD distinctly accelerated the rate of racemization.The configurational stability of (+)- and (-)-DEP was also studied under physiological conditions. The half-life of racemization in heparinised human plasma was for both enantiomers determined to be approximately 23-25 min.In phosphate buffer (10 mM, pH 7.4), rac-DEP showed a high, but unselective affinity towards human α1-acid glycoprotein (orosomucoid) immobilised on silica (Chiral AGP).The rate of racemization of the free base of (-)-DEP dissolved in organic solutions generally increases with the polarity of the solvating agent. Chirality 10:307-315, 1998. © 1998 Wiley-Liss, Inc.
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    Determination of the rotational barriers of atropisomeric polychlorinated biphenyls (PCBs) by a novel stopped-flow multidimensional gas chromatographic technique (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 316-320 
    Details
    ISSN: 0899-0042
    Keywords: atropisomeric polychlorinated biphenyls (PCBs) ; Chirasil-Dex ; rotational barrier ; stopped-flow multidimensional gas chromatographic technique ; on-line enantiomerization kinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers ΔG
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    Discrimination in resolving systems. III: Pseudoephedrine-mandelic acid (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 325-337 
    Details
    ISSN: 0899-0042
    Keywords: diastereomeric salts ; molecular recognition ; hydrogen bonding ; thermal analysis ; crystallography ; solubility ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (+)-(1S;2S)-Pseudoephedrine and racemic mandelic acid form three distinct diastereomeric salts from solutions in 95% ethanol. The least-soluble phase, a hemihydrate, contains the (2R)-mandelate. A salt phase of intermediate solubility is the unsolvated double salt, containing both the (2R)- and the (2S)-mandelate. The most-soluble salt phase contains the (2S)-mandelate. Mandelate configuration and order of solubility (based on the heats of fusion) is inverted from that found in the same system synthesized from chiral base and acid, and then crystallized from benzene solution. The (2R)-mandelate hemihydrate (-H2O at 349.5K, mp 391K), monoclinic, P21, a = 6.788(5), b = 29.415(35), c = 9.488(10)Å, β = 108.91(8)°, Z = 4 (2 ion-pairs/asymmetric unit). Intermediate double salt (2S)- and (2R)-mandelate, mp 377.6K, anorthic, P1, a = 7.758(4), b = 9.966(5), c = 13.366(6)Å, α = 72.99(4), β = 79.98(4), γ = 70.51(4)°, Z = 1 (2 ion-pairs/asymmetric unit). The (2S)-mandelate (mp 386.2K), orthorhombic, P212121, a = 7.079(6), b = 13.443(10), c = 18.820(14)Å, Z = 4 is identical to a salt made from a combination of enantiomeric moieties from benzene solution. While differing from ephedrine mandelates in configuration at one center, solubilities of pseudoephedrine mandelates in 95% ethanol are much larger. A comparison of molecular structure (non-polar and H-bonding) regions of pseudoephedrine and ephedrine mandelates shows similarities and differences that are tentatively linked to crystal properties. This study reemphasizes the necessity for consistency in solvent use in resolution and in phase identification and comparison because the phases produced are frequently dependent upon the solvent. Chirality 10:325-337, 1998. © 1998 Wiley-Liss, Inc.
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    Manipulation of chiral resolution for isoxazoline-based IIb/IIIa receptor antagonists using various mobile phase additives in subcritical fluid chromatography (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 338-342 
    Details
    ISSN: 0899-0042
    Keywords: additive ; selectivity ; efficiency ; modifier ; subcritical fluid chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Subcritical fluid chromatography (SubFC) using a carbon dioxide-methanol mobile phase is used for the chiral resolution of IIb/IIIa receptor antagonist enantiomers. The chiral resolution of three analogs, each containing two chiral centers, is optimized using various mobile phase additives. The effects that acidic, basic, and neutral additives have on retention, efficiency, and resolution are examined. The additive that gives the best resolution was found to be dependent upon the functionality and charge of the chiral analyte. For charged analytes, additives that act as competing ions of the same charge as the chiral analyte dramatically improve efficiency and resolution. Resolution of neutral chiral analyte enantiomers is also greatly affected by the choice of mobile phase additive. Chirality 10:338-342, 1998. © 1998 Wiley-Liss, Inc.
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    Mechanism of chiral asymmetry generation by chiral autocatalysis in the preparation of chiral octahedral cobalt complex (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 343-348 
    Details
    ISSN: 0899-0042
    Keywords: chiral asymmetry generation ; chiral autocatalysis ; primary nucleation ; secondary nucleation ; chiral cobalt complex ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral asymmetry generation, the predominant production of one enantiomer in a non-chiral environment, could occur in the production of the chiral complex cis-[CoBr(NH3)(en)2]Br2 by the reaction of [Co(H2O)2{(OH)2Co(en)2}2](SO4)2 with ammonium bromide in an aqueous medium. The main kinetic steps in the reaction system have been determined. During the reaction, the product crystallizes at an early stage. When a very small amount of crystalline enantiomer was added to the reaction system at an early stage, the same enantiomer was produced preferentially; in addition, the enantiomeric excess of the product increased with increasing the stirring rate. Thus, it seems that each enantiomer generates chiral crystals that could self-replicate through secondary nucleation when the solution is stirred; these crystals in turn enhance the production of the same enantiomer. With a computer code that simulates such a kinetic mechanism, it is shown that enantiomeric excess observed in the experiments could be reproduced. Chirality 10:343-348, 1998. © 1998 Wiley-Liss, Inc.
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    Stereoselective renal secretion of carbenicillin in rabbits: Role of the organic anion transporter at the renal brush border membrane (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 349-357 
    Details
    ISSN: 0899-0042
    Keywords: carbenicillin ; stereoselective ; secretion ; transport ; rabbit ; membrane vesicles ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselectivity in the renal secretion of carbenicillin (CBPC) was studied in rabbits. Significant renal secretion of CBPC was observed in vivo, with the secretion of the S-epimer being greater than that of the R-epimer. Stereoselective transport of CBPC was further studied in vitro using basolateral and brush border membrane vesicles prepared from rabbit kidneys. The transport of CBPC by the organic anion transporter into the basolateral membrane vesicles (BLMV) was not stereoselective. In contrast, a distinct stereoselectivity was observed in the transport of CBPC by the organic anion transporter into the brush border membrane vesicles (BBMV), with the transport of the S-epimer being more favorable. Significant epimer-epimer interactions were also observed in the transport into BBMV. The stereoselectivity of the transport of CBPC was calculated from the kinetic parameters with consideration of epimer-epimer interactions and was similar to that observed in vivo. It was concluded that the observed stereoselectivity in the renal secretion of CBPC in vivo reflected that of transport via the organic anion transporter located at the brush border membrane. Chirality 10:349-357, 1998. © 1998 Wiley-Liss, Inc.
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    Emanuel Gil-Av honorary issue of Chirality (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 371-372 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Determination of the enantiomeric purity of commercial Jacobsen's catalyst samples (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 362-363 
    Details
    ISSN: 0899-0042
    Keywords: Jacobsen's catalyst ; enantiomeric purity determination ; chiral HPLC ; cyclodextrin chiral stationary phases ; enantioseparation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A HPLC method is described for the chiral analysis of the commercially available Jacobsen's catalyst. A hydroxypropyl β-cyclodextrin stationary phase was used in conjunction with a nonaqueous, polar-organic mobile phase. The method can be applied to control the enantiomeric purity of the catalyst, which is of great importance for quality control of that product. High accuracy in the determination of trace levels of the unwanted enantiomer in the presence of large amounts of the desired enantiomer is demonstrated. Chirality 10:362-363, 1998. © 1998 Wiley-Liss, Inc.
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    Enantiomeric separation of several cyclic imides on a macrocyclic antibiotic (vancomycin) chiral stationary phase under normal and reversed phase conditions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 358-361 
    Details
    ISSN: 0899-0042
    Keywords: cyclic imides ; barbiturates ; piperidine-2,6-diones ; mephenytoin ; chiral recognition ; enantioselectivity ; vancomycin chiral stationary phase ; normal-phase mode ; reversed-phase mode ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several cyclic imidic compounds (barbiturates, piperidine-2,6-diones, and mephenytoin) are enantiomerically resolved via high-performance liquid chromatography (HPLC) on a macrocyclic antibiotic covalently bonded to a silica gel support. The Chirobiotic V chiral stationary phase (CSP) column contains the antibiotic vancomycin as the chiral selector. The results of the analysis show that the substituents at the chiral carbon position of the racemic drugs affect chiral resolution. In addition, ring size may also play a role when considering the formation of analyte-CSP inclusion complexes. Contrary to the piperidine-2,6-diones, the chromatographic parameters for the barbiturates are much the same under normal- or reversed-phase conditions. The details of these results are discussed. Chirality 10:358-361, 1998. © 1998 Wiley-Liss, Inc.
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    Emanuel Gil-Av (1916-1996): A man with a legacy (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 373-374 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
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    Separation of nicotine and nornicotine enantiomers via normal phase HPLC on derivatized cellulose chiral stationary phases (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 364-369 
    Details
    ISSN: 0899-0042
    Keywords: (±)nicotine ; (±)nornicotine ; chiral separation ; enantiomers ; normal phase HPLC ; mobile phase additive ; cellulose-based chiral stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes the enantiorecognition of (±)nicotine and (±)nornicotine by high-performance liquid chromatography using two derivatized cellulose chiral stationary phases (CSPs) operated in the normal phase mode. It was found that different substituents linked to the cellulose backbone significantly influence the chiral selectivity of the derivatized CSP. The results showed that, in general, the tris(4-methylbenzoyl) cellulose CSP (Chiralcel OJ) surpasses tris(3,5-dimethylphenyl carbamoyl) cellulose CSP (Chiralcel OD). On the former column, the resolution (±)nicotine and (±)nornicotine enantiomers depended largely on mobile phase compositions. For the separation of the nicotine enantiomers, the addition of trifluoroacetic acid to a 95:5 hexane/alcohol mobile phase greatly improved the enantioresolution, probably due to enhanced hydrogen bonding interactions between the protonated analytes and the CSP. For (±)nornicotine separation, a reduction in the concentration of alcohol in the mobile phase was more effective than the addition of trifluoroacetic acid. Possible solute-mobile phase-stationary phase interactions are discussed to explain how different additives in the mobile phase and different substituents on the cellulose glucose units of the CSPs affect the separation of both pairs of enantiomers. Chirality 10:364-369, 1998. Published 1998 Wiley-Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
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    Chiral separation of enantiomers via selector/selectand hydrogen bondings (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 382-395 
    Details
    ISSN: 0899-0042
    Keywords: selector/selectand associates ; hydrogen bonding ; chiral separation ; chiral phases ; enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The progress made in the development of chiral stationary phases based on hydrogen-bonding selector/selectand associates is reviewed here. The structure of the different selectand/selector systems was established through X-ray diffraction and other spectroscopic techniques. The structure of the energetically more stable diastereomeric-associate was then correlated to the chromatographic results, namely to the elution order and the enantioselectivity of each of the systems. Chirality 10:382-395, 1998. © 1998 Wiley-Liss, Inc.
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    A closer study of chiral retention mechanisms (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 375-381 
    Details
    ISSN: 0899-0042
    Keywords: retention mechanisms ; separation of enantiomers ; chiral stationary phases ; equilibrium isotherms ; bonding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The retention mechanisms and the separation of enantiomers on the classes of chiral stationary phases which are made by bonding isolated groups on the surface of an adsorbent are discussed. It is shown that retention on these phases originates from mixed mechanisms and how the individual contributions of these two mechanisms can be separated, by determining and modeling the equilibrium isotherms. A contribution originating from interactions of the isomers with the nonselective sites (type-I) and another one due to interactions with the enantioselective sites (type-II) can be determined and their importance studied as a function of several parameters, e.g., temperature or pH. This approach is illustrated with results obtained with different pairs of enantiomers on bovine serum albumin, 4-methylcellulose tribenzoate, or cellobiohydrolase immobilized on silica. Chirality 10:375-381, 1998. © 1998 Wiley-Liss, Inc.
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    Tripodal trispeptide selector as a model for establishing the importance of hydrogen-bonding in enantiomer-separation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 396-404 
    Details
    ISSN: 0899-0042
    Keywords: chirality ; helicity ; GC-stationary phase ; conformations ; 1H-NMR-studies ; molecular mechanics calculations ; enantiomer separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The manner of hydrogen-bonding to peptide selectors in enantiomer separation is examined with the help of a structural model. This model relies on a C3-symmetric trispeptide selector, which is stabilized by a network of distinct intramolecular hydrogen bonds. A combination of experimental and theoretical tools enables us to identify the lowest-energy conformation of the trispeptide selector and the sites of selector-substrate interactions. Experimental tools include temperature dependent 1H-NMR studies, 1D-NOE-measurements, and titration experiments, with the theoretical tools being EFF and CFF91 molecular mechanics calculations. The structural information deduced from these investigations is shown to bear on the enantioseparation of the corresponding chiral stationary phase towards derivatized amino acids. These observations, taken together, help to rationalize the mode of enantiomer-separation by amide phases as involving predominantly C7-hydrogen bonding sites. Chirality 10:396-404, 1998. © 1998 Wiley-Liss, Inc.
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    The chiral code: From DNA primary structures to quaternary assemblies (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 405-414 
    Details
    ISSN: 0899-0042
    Keywords: chiral-discrimination ; homochirality ; stereospecificity ; self-assembly ; supercoiling ; cholesteric mesophase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleic acids are characterized by a predominant right-handed helical configuration that derives from the chirality of the sugar moiety. Hitherto, only “local” effects of this helical asymmetry, exemplified by DNA interactions with small compounds, have been documented. The results described in this study indicate that an enhanced asymmetry is required for the manifestation of chiral effects in DNA self-assembly processes or for chiral discrimination upon interactions with peptides. Two cases in which the intrinsic DNA asymmetry is enhanced are reported: rod-like superhelical species derived from linear DNA molecules, and topologically constrained supercoiled DNA. In the first case, the superhelical grooves within the DNA rods allow for a stereospecific complexation with peptides, resulting in chiral discrimination. In the second case, it is shown that the properties of cholesteric assemblies derived from supercoiled DNA are strictly determined by the enhanced asymmetry associated with molecular supercoiling. The results allow for new reflections on the concept of molecular complementarity, and indicate that spontaneously obtained chiral DNA mesophases might have played a key role in determining terrestrial homochirality. Chirality 10:405-414, 1998. © 1998 Wiley-Liss, Inc.
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    Aspects of spontaneous separation of enantiomers in two- and three-dimensional crystals (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 415-424 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; two- and three-dimensional crystals ; grazing incidence X-ray diffraction ; atomic force microscopy ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spontaneous separation of enantiomers in two- and three-dimensional crystals is driven by the same thermodynamic and kinetic factors. However, amphiphilic crystalline monolayers at an interface cannot possess a center of inversion, the most common symmetry element in bulk crystals. This fact should, in principle, lead to better chances for spontaneous separation in the Langmuir or Langmuir-Blodgett monomolecular films. On the other hand, the monolayers of most amphiphiles studied to date incorporate long aliphatic chains that have an intrinsic tendency to pack in a herring-bone motif requiring glide plane symmetry, thus creating a bias towards racemate formation. Moreover, 2-D crystals supposedly have a much higher degree of molecular and therefore enantiomeric disorder compared to bulk crystals. All these factors necessitate a careful choice of molecules to guarantee enantiomeric separation in two dimensions. Unambiguous detection of spontaneous resolution in 2-D appears to require atomic resolution of molecular packing arrangement, which can in principle be obtained by grazing incidence X-ray diffraction or atomic force microscopy, whereas in bulk solids spontaneous resolution can be easily detected by various macroscopic methods. This short review provides analogies between spontaneous separation in 3-D and recent examples in 2-D, showing that spontaneous separation generally depends upon subtle differences in molecular structure. Chirality 10:415-424, 1998. © 1998 Wiley-Liss, Inc.
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    Determination of the rotational barriers of atropisomeric polychlorinated biphenyls (PCBs) by a novel stopped-flow multidimensional gas chromatographic techniqueThis article was orginally published in Chirality, Volume 10, Number 4, pages 316-320. As it is suited to the theme of this issue, this article appears again here. All citations to this article should use the original volume, issue, and page range. (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 425-429 
    Details
    ISSN: 0899-0042
    Keywords: atropisomeric polychlorinated biphenyls (PCBs) ; Chirasil-Dex ; rotational barrier ; stopped-flow multidimensional gas chromatographic technique ; on-line enantiomerization kinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers ΔG† (T) of the four atropisomeric polychlorinated biphenyls (PCBs) 2,2′,3,5′,6-pentachlorobiphenyl (PCB 95), 2,2′3,3′,4,6′-hexachlorobiphenyl (PCB 132), 2,2′,3,3′,6,6′-hexachlorobiphenyl (PCB 136), and 2,2′,3,4′,5′,6-hexachlorobiphenyl (PCB 149) were determined via on-line enantiomerization kinetics by a new stopped-flow multidimensional gas chromatographic technique (stopped-flow MDGC) employing Chirasil-Dex as chiral stationary phase for enantiomer separation. The calculated rotational barriers ΔG† (T) of the trichloro-ortho-substituted atropisomers are 184 ± 2 kJ/mol for PCB 95, 189 ± 4 kJ/mol for PCB 132, and 184 ± 1 kJ/mol for PCB 149 at 300°C. The rotational barrier ΔG† (T) of tetrachloro-ortho-substituted PCB 136 is at least (or higher than) 210 kJ/mol at 320°C. Chirality 10:425-429, 1998. © 1998 Wiley-Liss, Inc.
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    Chiral recognition of phthalides and lactams (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 430-433 
    Details
    ISSN: 0899-0042
    Keywords: Whelk-O 1 ; chromatography ; HPLC ; enantiodifferentiation ; heterocycles ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In concert with a larger study of the processes by which chiral stationary phase CSP 1 differentiates between enantiomers, we have investigated the chromatographic separation of the enantiomers of a series of aryl-substituted heterocycles of systematically varied structure. A mechanistic picture of how these and similar resolutions occur is emerging. The mechanistic hypothesis described herein is of predictive value. Chirality 10:430-433, 1998. © 1998 Wiley-Liss, Inc.
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    Highly enantioselective HPLC separations using the covalently bonded macrocyclic antibiotic, ristocetin A, chiral stationary phase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 434-483 
    Details
    ISSN: 0899-0042
    Keywords: ristocetin A ; macrocyclic antibiotic ; enantiomeric separations ; underivatized amino acids ; chiral stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The macrocyclic glycopeptide, ristocetin A, was covalently bonded to a silica gel support and evaluated as a liquid chromatographic (LC) chiral stationary phase (CSP). Over 230 racemates were resolved in either the reversed-phase mode, the normal-phase mode, or the polar-organic mode. The retention behavior and selectivity of this CSP were examined in each mode. Optimization of separations on this column is discussed. The ristocetin A CSP appeared to be complimentary to other glycopeptide CSPs (i.e., vancomycin and teicoplanin). Column stability was excellent. The CSP was not irreversibly altered when going from one mobile phase mode to another. Chirality 10:434-483, 1998. © 1998 Wiley-Liss, Inc.
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    Determination of the enantiomers of albuterol in human and canine plasma by enantioselective high-performance liquid chromatography on a teicoplanin-based chiral stationary phase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 484-491 
    Details
    ISSN: 0899-0042
    Keywords: salbutamol ; chiral separation ; validated assay ; fluorescence detection ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sensitive enantioselective high-performance chromatographic (HPLC) method was developed and validated to determine low levels of (-)-R and (+)-S-albuterol in plasma. Baseline resolution was achieved by using a teicoplanin-based chiral stationary phase with a polar organic mobile phase consisting of methanol/acetonitrile/glacial acetic acid/diethylamine, 40:60:0.3:0.2, (v/v/v/v) and a flow-rate of 1.0 ml/min. Enantioselectivity (α) equaled 1.18 and resolution (Rs) equaled 1.8. By using fluorescence detection maximized at 230 and 310 nm for excitation and emission, respectively, concentrations of each enantiomer could be measured down to 125 pg/ml from a 1-ml plasma sample. Initially, the method was applied to plasma samples from a small single-dose inhalation study of racemic albuterol in a human volunteer and, later, to in vivo samples from a canine inhalation study of the single enantiomer, (-)-R-albuterol. Results from the canine study showed that no chiral inversion of (-)-R-albuterol occurs in the dog. Chirality 10:484-491, 1998. © 1998 Wiley-Liss, Inc.
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    Achiral derivatization as a means of improving the chromatographic resolution of racemic alcohols on benzoylcellulose CSPs (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 492-498 
    Details
    ISSN: 0899-0042
    Keywords: racemate ; enantiomer ; HPLC ; chiral stationary phase ; benzoylcellulose ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The advantages that can be gained from derivatization of various racemic aliphatic and aromatic alcohols prior to enantiomeric chromatographic separation have been systematically investigated for a series of benzoate derivatives. Three cellulose-based CSPs available in the pure polymeric form - tribenzoyl cellulose (TBC), meta-methylbenzoyl cellulose (MMBC), and para-methylbenzoyl cellulose (PMBC) - were selected and several benzoate derivatives varying in the nature and the position of the substituent on the benzoyl group were prepared and analysed. TBC clearly gives the broadest application range, and among the different benzoate esters the best selectivity was generally obtained with either the 4-methoxybenzoate or the 4-methylbenzoate derivatives. Based on these results, some empirical rules could be formulated for optimizing the enantiomeric separation of racemic alcohols, which make up one of the most important classes of chemical substances used as drugs and biocides, or as building blocks for their synthesis. An application of this approach to the preparative separation of the enantiomers of a drug intermediate is also shown. Chirality 10:492-498, 1998. © 1998 Wiley-Liss, Inc.
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    Enantioselective capillary gas chromatography in the investigation of stereochemical correlations of terpenoids (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 499-504 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective capillary gas chromatography ; cyclodextrin derivatives ; stereochemistry of terpenes ; monoterpenes ; essential oils ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary gas chromatography employing the unique selectivities of specifically substituted cyclodextrins is highly suited for stereochemical investigations of terpenoid compounds. The analysis of many essential oils have shown that monoterpene derivatives regularly occur as enantiomeric mixtures. In the case of sesquiterpene hydrocarbons, liverworts (Hepaticae) and other lower organisms usually biosynthesize compounds of opposite stereochemistry as compared to higher plants and enantiomeric mixtures occur only occasionally. The investigation of diterpene hydrocarbons has so far shown no indication of the presence of both enantiomers in the same plant. Chirality 10:499-504, 1998. © 1998 Wiley-Liss, Inc.
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    Determination of drug levels in human serum by circular dichroism (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 507-512 
    Details
    ISSN: 0899-0042
    Keywords: chiroptical method ; drug analysis ; β-lactam antibiotics ; CD spectroscopy ; human fluids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the applicability of circular dichroism (CD) for the determination of drug levels in human serum is described and a new method for the quantitative determination of optically active absorbing drugs having Cotton effects at wavelengths above 250 nm in human serum and/or plasma is proposed. The principal advantages of this method are speed, economy, and simplicity, no derivatization or chromatographic separation steps being needed. The validity of the CD determination was confirmed by analysis of variance, β-lactam antibiotics being chosen as model drugs. In addition, the validation studies performed confirm the accuracy and precision of the proposed method. For β-lactam antibiotics lacking Cotton effects above 250 nm, an alternative method based on the extraction of the drug from serum is considered. Chirality 10:507-512, 1998. © 1998 Wiley-Liss, Inc.
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    Unexpected difference in enantioselective retention on cellulase (CBH I) silica stationary phase caused by exchange of potassium for sodium ion in the mobile phase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 513-518 
    Details
    ISSN: 0899-0042
    Keywords: CBH I ; cellulase ; cation ; sodium ; potassium ; enantioselectivity and temperature ; ionic strength ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An increase in both retention and enantioselectivity for some β-blocking agents was observed when exchanging potassium to sodium ion in the buffer used as mobile phase. A large effect of ionic strength on retention was observed, while the enantioselectivity was constant. Chirality 10:513-518, 1998. © 1998 Wiley-Liss, Inc.
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    Weak interactions and the tunneling racemization (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 519-521 
    Details
    ISSN: 0899-0042
    Keywords: optical activity of enantiomers ; weak interactions ; stability of optical activity ; racemization ; tunneling effect ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Assuming the active molecule as a two-level system, we calculate the racemization, due to the tunneling effect, taking into account the effects of the weak interactions and of an external potential. We show that the weak interactions would block the tunneling racemization of enantiomers in compressed gases and liquids. Chirality 10:519-521, 1998. © 1998 Wiley-Liss, Inc.
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    Structure and substituent effect on chiral separation of some 4a-methyl-2,3,4,4a-tetrahydro-1H-fluorene derivatives and 4a-methyl-1,2,3,4,4a,9a-hexahydro-fluoren-9-one derivatives on CTA-I and chiralcel OJ chiral stationary phases (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 522-527 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; quantitative substituent effect ; recognition mechanism ; fluorene derivative-chiral separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chromatographic parameters for 12 structurally related compounds in the 4a-methyl-2,3,4,4a-tetrahydro-1H-fluorene and 4a-methyl-1,2,3,4,4a,9a-hexahydro-fluoren-9-one series are reported on CTA-I and Chiralcel OJ chiral stationary phases. Arrangement of the k' values according to configurationally related enantiomer series (Class I and Class II) and not according to the actual order of elution, allows the treatment of the data by linear correlation with structure and substituent effect. A detailed analysis of the capacity factor variation with respect to the structural changes shows clearly that the framework and substitution effects do not result in the same response on the two cellulose ester chiral stationary phases. More interestingly, it emerges that chiral discimination may be attributed to certain areas of the molecule, these areas being different in the interaction within CTA-I and Chiralcel OJ. Furthermore, our analysis points out the relevance of attempting to develop quantitative relationships for configurationally related series of enantiomers (in our case Class I and Class II), the main effort being devoted to the understanding of the capacity factor variation in each class rather than of the α values, which are derived entities. Chirality 10:522-527, 1998. © 1998 Wiley-Liss, Inc.
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    Drugs for chiral discrimination: Non-coded amino acids and dipeptides by asymmetric hydrogenation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 535-539 
    Details
    ISSN: 0899-0042
    Keywords: asymmetric hydrogenation ; non-coded amino acids ; enantioselectivity ; dipeptides ; diastereoselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of Propranolol, Pindolol, and Carazolol, well-known β-blockers, have been used to prepare cationic aminophosphine phosphinite rhodium complexes. Propraphos-Rh and Pindophos-Rh are very efficient catalysts in the asymmetric hydrogenation of N-Boc-protected unusual dehydroamino acid derivatives. Carazolol-Rh is less suitable in both activity and enantioselectivity. Under the same conditions, N-Boc-protected dehydrodipeptides are hydrogenated with diastereoselectivities between 70 and 90% de. Chirality 10:535-539, 1998. © 1998 Wiley-Liss, Inc.
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    Extent of chiral inversion of the 2-arylpropionic acids by Cordyceps militaris (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 528-534 
    Details
    ISSN: 0899-0042
    Keywords: chiral inversion ; ibuprofen ; ketoprofen ; flurbiprofen ; indoprofen ; suprofen ; fenoprofen ; metabolism of 2-arylpropionic acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fungus Cordyceps militaris has been previously shown to be capable of inverting the chirality of 2-phenylpropionic acid from its (R)-enantiomer to its (S)-antipode. The structure of this compound is similar to the 2-arylpropionic acid non-steroidal anti-inflammatory drugs, which have also been reported to undergo a similar chiral inversion process in mammals and man. We report here an investigation into the substrate specificity of the enzyme system present in C. militaris using pure enantiomers and racemates of ibuprofen and ketoprofen and racemates of indoprofen, suprofen, flurbiprofen, and fenoprofen and the structurally related compounds 2-phenylbutyric acid and 2-phenoxypropionic acid as substrates, using optimised incubation conditions developed for the inversion of 2-phenylpropionic acid. The results demonstrated that C. militaris is capable of inverting the chirality of all the compounds investigated, which suggests that the active sites of the enzymes are very flexible with regard to the molecular dimensions of the substrate molecule and the spatial occupation of the groups surrounding the chiral centre. Metabolism of all the substrates was observed but the rate of metabolism varied extensively depending on the substrate. Achiral HPLC analysis was used to detect any potential metabolites and the results suggested that the site of the metabolism appeared to be at the aliphatic side groups only, with the aromatic ring being left intact in all cases. These results suggest that C. militaris could be a valuable tool in the investigation of the prospective metabolic fates of new 2-arylpropionic acids during their development. Chirality 10:528-534, 1998. © 1998 Wiley-Liss, Inc.
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