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  • Polymer and Materials Science  (8)
  • Membrane transport  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Compartmental analysis of amino-acid release from attached and detached pea seed coats (1992)
    Springer
    Planta 187 (1992), S. 75-82 
    Details
    ISSN: 1432-2048
    Keywords: Amino acid efflux ; Membrane transport ; Phloem unloading ; Pisum (seed coats) ; Seed development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using the empty-seed-coat technique, we have studied the release of amino acids from pea (Pisum sativum L. cv. Marzia) seed coats, either attached to or detached from the mother plant, at various stages of development. During an experimental period of 8 h, about 70% of the amino-acid content of the seed coat was released into the solution with which the seed-coat cup was filled. Major components of the released amino-acid mixture were glutamine (25%), alanine (20%) and threonine (15%). At the end of the experimental period (t≥6 h) the amino-acid efflux from attached seed coats was approx. 0.15 μmol · h−1·(seed coat)−1 greater than that from detached seed coats. This difference may be attributed to the import of amino acids into attached seed coats. It is equivalent to approx. 0.3 μmol N · h−1 · (seed coat)−1, whereas the nitrogen demand of the embryo amounted to 0.50 ± 0.04 μmol N · h−1 · embryo−1. The time course of the release from detached seed coats could be described by the sum of two exponentials with t1/2 = 0.4–0.7 h and t1/2 = 3.3–6.9 h, respectively, which probably represent the emptying of the cytoplasmic and vacuolar compartments. During development the vacuolar amino-acid pool decreased considerably (from 6.2 to 1.4 μmol · (seed coat)−1), whereas the cytoplasmic pool was much more constant (2.1–1.2 μmol · (seed coat)−1). For attached seed coats it will be shown that the time course of the amino-acid release could be fully accounted for by the sum of two exponentials and a linear term, where the parameters of the exponentials were, within error, the same as for detached seed coats and the linear term represented the import of amino acids. The results will be discussed with reference to prevailing models of phloem unloading in the seed coat, and in relation to the flux of amino acids from seed coat to the developing embryo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201626
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  • 2
    Electronic Resource
    Electronic Resource
    Changing kinetics of l-valine uptake by immature pea cotyledons during development (1990)
    Springer
    Planta 181 (1990), S. 576-582 
    Details
    ISSN: 1432-2048
    Keywords: Amino acid (l-valine uptake) ; Membrane transport ; Uptake (kinetics) ; Pisum (amino acid, cotyledon) ; Seed development ; l-Valine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influx of L-[14C]valine was measured over a wide concentration range (1 μM to 100 mM) in immature, isolated pea (Pisum sativum L. cv. Marzia) cotyledons at two developmental stages, both in the absence and in the presence of 0.4 M mannitol. At an early developmental stage (water content of the cotyledons ≈80%) the valine influx was strictly proportional to the external amino-acid concentration over the whole concentration range (so-called linear component). This system renders the plasmalemma of the cotyledonary cells approximately 1000-fold more permeable to valine than the presumed basic permeability of the membrane for valine. At a later stage of development (water content of the cotyledons ∼55%) this transport pathway was supplemented by a saturable system (K m = 5mM; V max = 9.5 μmol · gFW−1). The saturable system emerged when the water content of the cotyledons was about 65%, and its activity increased steadily up to the latest developmental stage examined (water content of the cotyledons =50%). As a result, uptake rates of l-valine at low concentrations, expressed on a fresh-weight basis, increased about 15-fold in this phase of development. Low osmolarity of the bathing medium (0 mM mannitol) had no effect on the linear component, and reduced the uptake by the saturable component only slightly by increasing its K m from 3.8 mM to 5.6 mM. The possible role of the saturable system in the acquisition of amino acids by the developing embryo is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193013
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  • 3
    Electronic Resource
    Electronic Resource
    Solid-state photochemical generation of polymeric polyradicals: Poly(4-vinylphenoxy) and copolymers with styrene (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1335-1345 
    Details
    ISSN: 0887-624X
    Keywords: polyradicals ; magnetism ; phenoxyl radicals ; high-spin molecules ; organic ferromagnetism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of poly(4′-vinyl-2,4,6-tri-tert-butyl-diphenyloxalate) and its 65 : 35 and 19 : 81 copolymers with styrene are described. Rigid phase broad-band photolysis of the homopolymer with a quartz filtered xenon arc at 77 K results in production of up to 25% of the theoretical number of spins/mol expected for quantitative production of pendant phenoxyl radicals, and shows no major loss of radical signal in the ESR at temperatures below 100 K. Curie law analysis of the temperature dependence of the ESR radical signal intensity for the neat photolyzed homopolymer 1 shows curvature consistent with antiferromagnetic pairing of radical spins at low temperatures. Since through-bond conjugation of radical spins is not possible in this system, the antiferromagnetic interaction is interpreted in terms of intrachain and/or interchain through-space exchange interactions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300711
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis, characterization, and photolysis of poly[3,5-di-tert-butyl-4-[(2,4,6-tri-tert-butylphenyl)oxalato]phenylacetylene], a photochemical polyradical precursor (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2167-2176 
    Details
    ISSN: 0887-624X
    Keywords: polyradicals ; magnetism ; polyacetylene ; polyphenylacetylene ; molecular magnetism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A photochemical precursor to a pendant conjugated polyradical has been synthesized, poly[3,5-di-tert-butyl-4-[(2,4,6-tri-tert-butylphenyl)oxalato]phenylacetylene], 3. Irradiation of 3 at 77 K in the solid state at 〈 300 nm yielded poly(3-5-di-tert-butyl-2-oxyphenyl acetylene), 2, with 30-40% of the expected number of radical spins. Spin yields on the surface of solid samples appears to be considerably higher. Electron spin resonance experiments showed no evidence of cooperative exchange interaction between the pendant spins. Computational modeling indicated that a major reason for the failure of this and other polyphenylacetylenes to show ferromagnetic exchange between spins is the substantial twisting of the polyacetylene backbone required by steric interactions, leading to deconjugation and a loss of exchange interaction between pendant radicals along the chain. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2167-2176, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular recognition by self-assembled monolayers detected with surface plasmon resonanceWe thank A. T. M. Lenferink (UT) for assistance with the SPR measurements. (1996)
    Weinheim : Wiley-Blackwell
    Advanced Materials 8 (1996), S. 561-564 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19960080704
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  • 6
    Electronic Resource
    Electronic Resource
    Polymer chain organization and orientation in ultrathin films: A spectroscopic investigation (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2335-2349 
    Details
    ISSN: 0887-6266
    Keywords: morphology ; polysilanes ; thin film ; chain orientation ; spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of confinement on the crystallinity and chain orientation of ultrathin poly(di-n-hexylsilane) films has been investigated using UV absorption, fluorescence and IR spectroscopies. UV absorption measurements in a series of poly(di-n-hexylsilane) films having thicknesses between 50 and 3500 Å have shown that, for thicknesses less than 500 Å, the polymer backbone disorders and extensive crystallization of the films is hindered irrespective of molecular weight or surface hydrophobicity. Fluorescence studies showed that rapid energy transfer occurs from the disordered chain segments to the crystalline ones. The orientation of both the polymer backbone and side chains was probed with IR absorption and grazing incidence reflection measurements. The side chains are extended, although not completely in the all-trans conformation, with their carbon plane mostly perpendicular to the substrate. The backbone lies extended, with the polymer axis parallel to the plane of the film. The hexyl side-chains disorder in films less than 2000 Å thick and this disordering occurs through the introduction of gauche bonds. Our findings suggest the possibility of using thickness to control the chain organization and morphology of a polymer thin film. © 1996 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Quantum chemistry - methods and applications, R. DAUDEL, R. LEFEBVRE, and C. MOSER, Interscience, New York-London 1959, xiii + 572 pp. $14.50 (1960)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 45 (1960), S. 551-552 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1960.1204514635
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  • 8
    Electronic Resource
    Electronic Resource
    Fluorescence studies of polymer blends: Effect of host matrix on copolymers of 1-naphthyl alkyl methacrylates and 9-anthryl methyl methacrylate (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1749-1753 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.180200923
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  • 9
    Electronic Resource
    Electronic Resource
    Copolymers of vinyl chloride with the vinyl esters and acrylates of low molecular weight polyesters of hydroxyacids (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 8 (1970), S. 1247-1259 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinyl esters and acrylates of polyesters derived from C10-C18 hydroxyacids have been synthesized and copolymerized with vinyl chloride with the hope of achieving an internally plasticized poly(vinyl chloride). Copolymers containing 10-30% polyester are film-forming materials, and the films cast from THF solutions are generally flexible. A number of these vinyl chloride copolymers with polyesters at approximately 15 and 25% level have been tested for various properties. The internal plasticization is not extensive.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.150080517
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  • 10
    Electronic Resource
    Electronic Resource
    Solid phase forming of plastics by high frequency impact (1981)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 1 (1981), S. 50-55 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1981.060010208
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