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  • 1
    Electronic Resource
    Electronic Resource
    Efficiency, Na+/K+ selectivity and temperature dependence of ion transport through lipid membranes by (221)C10-Cryptand, an ionizable mobile carrier (1987)
    Springer
    The journal of membrane biology 97 (1987), S. 79-95 
    Details
    ISSN: 1432-1424
    Keywords: cryptand ; Na+ selectivity ; temperature ; ionizable mobile carrier ; nonactin ; cation transport kinetics ; lipid membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The kinetics of Na+ and K+ transport across the membrane of large unilamellar vesicles (LUV) were determined at two pH's when transport was induced by (221)C10-cryptand (diaza-1,10-decyl-5-pentaoxa-4,7,13,16,21-bicyclo [8.8.5.] tricosane) at various temperatures, and by nonactin at 25°C and (222)C10-cryptand at 20 and 25°C. The rate of Na+ and K+ transport by (221)C10 saturated with the cation and carrier concentrations. Transport was noncooperative and exhibited selectivity for Na+ with respect to K+. The apparent affinity of (221)C10 for Na+ was higher and less pH-dependent than that for K+, and seven times higher than that of (222)C10 for K+ ions (20.5vs. 1.7 kcal·mole−). The efficiency of (221)C10 transport of Na+ was pH-and carrier concentration-dependent, and was similar to that of nonactin; its activation energy was similar to that for (222)C10 transport of K+ (35.5 and 29.7 kcal · mole−1, respectively). The reaction orders in cationn(S) and in carrierm(M), respectively, increased and decreased as the temperature rose, and were both independent of carrier or cation concentrations; in most cases they varied slightly with the pH.n(S) varied with the cation at pH 8.7 and with the carrier for Na+ transport only, whilem(M) always depended on the type of cation and carrier. Results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869415
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  • 2
    Electronic Resource
    Electronic Resource
    Transport of alkali cations through thin lipid membranes by (222)C10-Cryptand, an ionizable mobile carrier (1986)
    Springer
    The journal of membrane biology 89 (1986), S. 251-267 
    Details
    ISSN: 1432-1424
    Keywords: cryptand ; ionizable mobile carrier ; transport kinetics ; lipid membrane ; alkali cations ; valinomycin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The kinetics of K+ and Na+ transport across the membrane of large unilamellar vesicles (L.U.V.) were compared at two pH's, with two carriers: (222)C 10-cryptand (diaza-1, 10-decyl-5-hexaoxa-4,7,13,16,21,24-bicyclo[8.8.8.]hexacosane) and valinomcyin, i.e. an ionizable macrobicyclic amino polyether and a neutral macrocyclic antibiotic. The rate of cation transport by (222)C10 saturated as cation and carrier concentrations rose. The apparent affinity of (222)C10 for K+ was higher and less pH dependent than that for Na+ but resembled the affinity of valinomycin for K+. The efficiency of (222)C10 transport of K+ decreased as the pH fell and the carrier concentration rose, and was about ten times lower than that of valinomycin. Noncompetitive K+/Na+ transport selectivity of (222)C10 decreased as pH, and cation and carrier concentrations rose, and was lower than that of valinomycin. Transport of alkali cations by (222)C10 and valinomycin was noncooperative. Reaction orders in cationn(S) and carrierm(M) varied with the type of cation and carrier and were almost independent of pH;n(S) andm(M) were not respectively dependent on carrier or cation concentrations. The apparent estimated constants for cation translocation by (222)C10 were higher in the presence of Na+ than of K+ due to higher carrier saturation by K+, and decreased as pH and carrier concentration increased. Equilibrium potential was independent of the nature of carrier and transported cation. Results are discussed in terms of the structural, physicochemical and electrical characteristics of carriers and complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870668
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  • 3
    Electronic Resource
    Electronic Resource
    Interconversion of single and double helices formed from synthetic molecular strands (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 407 (2000), S. 720-723 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Synthetic single-helical conformations are quite common, but the formation of double helices based on recognition between the two constituent strands is relatively rare. Known examples include duplex formation through base-pair-specific hydrogen bonding and stacking, as found in nucleic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35037545
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  • 4
    Electronic Resource
    Electronic Resource
    An approach to channel type molecular structures. 1. Synthesis ofBouquet-shaped molecules based on an [18]-O6 polyether macrocycle (1992)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 12 (1992), S. 55-74 
    Details
    ISSN: 1573-1111
    Keywords: Polyether macrocycle ; molecular channel ; molecular bundle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An approach to a transmembrane cation channel is described. It is based on the grafting of oxygen bearing side-chains on a macrocyclic polyether unit that constitutes the organizing core. The resulting species has a structure of overall bouquet shape. The synthesis of such a molecule .ℬ M 0 ,14a is described, together with that of its analogue bearing polymethylene side-chains ℬ M C ,14b. The physicochemical properties of these molecules indicate that they possess the features expected on the basis of their structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053855
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular Recognition of Anionic Substrates. Crystal Structures of the Supramolecular Inclusion Complexes of Terephthalate and Isophthalate Dianions with a Bis-intercaland Receptor Molecule (1999)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 33 (1999), S. 191-202 
    Details
    ISSN: 1573-1111
    Keywords: anionic substrates ; molecular recognition ; cryptates ; crystal structures ; H-bonds ; intercalation ; inclusion complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular recognition of flat substrates requires the design of receptor molecules containing complementary flat units. If two such units are incorporated into a macrocyclic framework, a face to face inclusion of a planar substrate may take place, leading to an intercalative supramolecular structure. The water-soluble macrocyclic bis-intercaland receptor 1.4H+, containing two naphthalene subunits, linked by two positively charged oxy-bis- ethylamine binding sites, is able to bind strongly flat organic anions. The crystal structures of the terephthalate 2 and isophthalate 3 inclusion complexes are reported here. Complex 2, triclinic, P-1(N°), a = 7.717(3), b = 10.625(6), c = 16.238(9) Å, α = 99.00(7), β = 99.70(6), γ = 109.46(4)°, Z = 1. Complex 3, triclinic, P1 (N°1), a = 7.513(10), b = 10.640(9), c = 16.164(10) Å, α = 98.81(5), β = 99.77(10), γ = 109.36(12)°, Z = 1. Comparison of the environment (water molecules, anions and macrocycle) in the two X-ray structures highlights the formation of a similar organized assembly with the two different substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008093826105
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  • 6
    Electronic Resource
    Electronic Resource
    Supramolecular chemistry — Scope and perspectives: Molecules — Supermolecules — Molecular devices (1988)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 6 (1988), S. 351-396 
    Details
    ISSN: 1573-1111
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Supramolecular chemistry is the chemistry of the intermolecular bond, covering the structures and functions of the entities formed by association of two or more chemical species. Molecular recognition in the supermolecules formed by receptor-substrate binding rests on the principles of molecular complementarity, as found in spherical and tetrahedral recognition, linear recognition by co-receptors, metallo-receptors, amphilic receptors and anion coordination. Supramolecular catalysis by receptors bearing reactive groups effects bond cleavage reactions as well as synthetic bond formation via co-catalysis. Lipophilic receptor molecules act as selective carriers for various substrates and allow the setting up of coupled transport processes linked to electron and proton gradients or to light. Whereas endo-receptors bind substrates in molecular cavities by convergent interactions, exo-receptors rely on interactions between the surfaces of the receptor and the substrate; thus new types of receptors such as the metallonucleates may be designed. In combination with polymolecular assemblies, receptors, carriers and catalysts may lead to molecular and supramolecular devices, defined as structurally organized and functionally integrated chemical systems built on supramolecular architectures. Their recognition, transfer and transformation features are analyzed specifically from the point of view of molecular devices that would operate via photons, electrons or ions, thus defining the fields of molecular photonics, electronics and ionics. Introduction of photosensitive groups yields photoactive receptors for the design of light conversion and charge separation centres. Redox active polyolefinic chains represent molecular wires for electron transfer through membranes. Tubular mesophases formed by stacking of suitable macrocyclic receptors may lead to ion channels. Molecular self-assembling occurs with acyclic ligands that form complexes with a double helical structure. Such developments in molecular and supramolecular design and engineering open perspectives towards the realization of molecular photonic, electronic and ionic devices, that would perform highly selective recognition, reaction and transfer operations for signal and information processing at the molecular level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658981
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  • 7
    Electronic Resource
    Electronic Resource
    Book reviews (1986)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 4 (1986), S. 209-214 
    Details
    ISSN: 1573-1111
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655936
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  • 8
    Electronic Resource
    Electronic Resource
    Supramolecular Architectures through Self-organization (1999)
    Springer
    Journal of nanoparticle research 1 (1999), S. 7-7 
    Details
    ISSN: 1572-896X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010098213777
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