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  • 1
    Electronic Resource
    Electronic Resource
    On the role of magnesium ions in RNA stability (1998)
    New York : Wiley-Blackwell
    Biopolymers 48 (1998), S. 113-135 
    Details
    ISSN: 0006-3525
    Keywords: divalent cations ; magnesium ; RNA ; ion binding ; RNA folding ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Divalent cations, like magnesium, are crucial for the structural integrity and biological activity of RNA. In this article, we present a picture of how magnesium stabilizes a particular folded form of RNA. The overall stabilization of RNA by Mg2+ is given by the free energy of transferring RNA from a reference univalent salt solution to a mixed salt solution. This term has favorable energetic contributions from two distinct modes of binding: diffuse binding and site binding. In diffuse binding, fully hydrated Mg ions interact with the RNA via nonspecific long-range electrostatic interactions. In site binding, dehydrated Mg2+ interacts with anionic ligands specifically arranged by the RNA fold to act as coordinating ligands for the metal ion. Each of these modes has a strong coulombic contribution to binding; however, site binding is also characterized by substantial changes in ion solvation and other nonelectrostatic contributions. We will show how these energetic differences can be exploited to experimentally distinguish between these two classes of ions using analyses of binding polynomials. We survey a number of specific systems in which Mg2+-RNA interactions have been studied. In well-characterized systems such as certain tRNAs and some rRNA fragments these studies show that site-bound ions can play an important role in RNA stability. However, the crucial role of diffusely bound ions is also evident. We emphasize that diffuse binding can only be described rigorously by a model that accounts for long-range electrostatic forces. To fully understand the role of magnesium ions in RNA stability, theoretical models describing electrostatic forces in systems with complicated structures must be developed. © 1999 John Wiley & Sons, Inc. Biopoly 48: 113-135, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Unsymmetric Dinucleating Ligands for Metallobiosite Modelling (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 433-442 
    Details
    ISSN: 0009-2940
    Keywords: Metallobiosites ; Metalloproteins ; Metalloenzymes ; Dinucleating ligands ; Transition metals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Awareness of the asymmetric nature of numerous dinuclear metallobiosites and of the ability of the individual metal ions to have quite distinct roles in the functioning of the metalloenzyme concerned has led to a search for carefully designed unsymmetric dinucleating ligands that will give dinuclear complexes capable of acting as models for the metallobiosites. This review surveys progress made in the design and synthesis of complexes capable of serving as models for donor atom, coordination number and geometric asymmetries found at dinuclear metal centres.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300402
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  • 3
    Electronic Resource
    Electronic Resource
    Amine-quinone polyurethanes. I. Preparation of polyurethane block copolymers containing 2,5-bis(N-2-hydroxyethyl-N-methylamino)-1,4-benzoquinone diol monomer (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2881-2886 
    Details
    ISSN: 0887-624X
    Keywords: polyurethanes ; benzoquinones ; amine-quinones ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The amine-quinone monomer, 2,5-bis(N-2-hydroxyethyl-N-methylamino)-1,4-benzoqui-none (AQM-1), was prepared by the multiple-step condensation of 2-(N-methylam-ino)ethanol with benzoquinone in the presence of oxygen. This crystalline monomer was used to prepare a series of amine-quinone polyurethanes by condensation polymerization, either in the melt or in solution (THF or DMF), with a diisocyanate (MDI, TDI, or IPDI) and an oligomeric diol [poly(caprolactone) or poly(1,2-butylene glycol)]. The amine-quinone functional group was stable under the polymerization conditions, and was incorporated into the main chain, giving red-brown polyurethanes that had molecular weights in the range of 11,000-90,000 and were soluble in THF, MEK, DMF, and DMSO. The thermal properties were consistent with a two-phase morphology with an amorphous soft segment, containing the oligomeric diol, and a microcrystalline hard segment, containing AQM-1. The polymers having a low hard segment content (〈50%) were rubbery (soft segment Tg 〈-25°C); polymers having a high hard segment content (〉50%) were thermoplastic (hard segment Tg〉150°C). © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331704
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  • 4
    Electronic Resource
    Electronic Resource
    Solvent effects on ester alcoholysis at functionalized polyethylene surfaces (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1209-1217 
    Details
    ISSN: 0887-624X
    Keywords: polyethylene ; functionalization ; transesterification ; surface ; fluorescence ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of solvent on the accessibility and reactivity of an ester-bound fluorophore at a functionalized polyethylene-solvent interface have been studied. Fluorophore-labeled polyethylene surfaces were prepared by blending together a small amount of a pyrene esterterminated ethylene oligomer and a host linear low density polyethylene in solution. Films cast from such solutions were then studied by fluorescence spectroscopy to show that a significant number of the entrapped pyrene groups were at the polyethylene-solvent interface and capable of reaction with soluble reagents. Subsequently, transesterification of these ester-bound pyrenes using various sodium alkoxides in alcohol, alcohol-toluene, or alcohol-tetrahydrofuran solvent mixtures was studied by fluorescence and UV-visible spectroscopic analysis of the supernatant. The extent of alcoholysis of such esters was found to be significantly affected by the solvent chosen and by the structure of the alcohol. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330803
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  • 5
    Electronic Resource
    Electronic Resource
    Flexible docking using tabu search and an empirical estimate of binding affinity (1998)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 33 (1998), S. 367-382 
    Details
    ISSN: 0887-3585
    Keywords: ligand-protein docking ; molecular recognition ; tabu search ; empirical scoring function ; binding affinity prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This article describes the implementation of a new docking approach. The method uses a Tabu search methodology to dock flexibly ligand molecules into rigid receptor structures. It uses an empirical objective function with a small number of physically based terms derived from fitting experimental binding affinities for crystallographic complexes. This means that docking energies produced by the searching algorithm provide direct estimates of the binding affinities of the ligands. The method has been tested on 50 ligand-receptor complexes for which the experimental binding affinity and binding geometry are known. All water molecules are removed from the structures and ligand molecules are minimized in vacuo before docking. The lowest energy geometry produced by the docking protocol is within 1.5 Å root-mean square of the experimental binding mode for 86% of the complexes. The lowest energies produced by the docking are in fair agreement with the known free energies of binding for the ligands. Proteins 33:367-382, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Polymer ligands that can regulate reaction temperature in “smart” catalystsSupport of this work by the national science foundation (grant CHE9308414) and the Robert A. Welch Foundation is gratefully acknowledged. (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 69-71 
    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.19950070116
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  • 7
    Electronic Resource
    Electronic Resource
    Local stability of tubular reactors (1972)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 18 (1972), S. 393-401 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Liapunov analysis techniques employing a general quadratic functional are used to derive stability conditions for tubular reactor systems. The adiabatic tubular reactor without axial dispersion is shown to be locally stable, which excludes the possibility of multiple steady states, and the reactor with axial dispersion is proven locally stable if a condition involving only system parameters and steady state values is satisfied. Peclet numbers for heat and mass transfer are not specified equal for the latter proof.Results of simulation studies are used to confirm the validity of the derived stability condition, and it is shown that the parametric region of multiplicity is quite well defined. For the nonlinear equations, single steady state cases appear to possess nonuniform stability.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690180223
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  • 8
    Electronic Resource
    Electronic Resource
    Nonempirical wave functions for very large molecules. II. The PRDDO/M/FCP method (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 61 (1997), S. 67-76 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variation of the frozen-core potential (FCP) method is developed and implemented within the modified version of the method of partial retention of diatomic differential overlap (PRDDO/M). The explicit treatment of core electrons is replaced with a potential based on the actual core-valence integrals rather than upon an arbitrary model potential. The core-valence orthogonality requirement is replaced by an energy shift operator. PRDDO/M/FCP calculations exhibit good agreement with ab initio calculations with the same basis set, while reducing the computational cost significantly. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Ab initio propagator analysis of the valence double-ionization spectra of propyne (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 64 (1997), S. 175-182 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Double-ionization energies, for transitions from the ground state of the neutral propyne molecule to both singlet and triplet states of its dication, are investigated theoretically with the ab initio second-order algebraic diagrammatic construction [ADC(2)] propagator method. The results are compared with a previous study which reported both experimental data obtained from double-charge-transfer (DCT) spectroscopy and their analysis with semiempirical theory. The ADC(2) predictions match almost all the experimental peaks well. In the lower-energy range, for transitions to dication states up to 7 eV above the ground state, ADC(2) predictions indicate that significant energy separations of those dication terms dominated by a common electronic configuration are responsible for previous difficulties in the assignment of peaks in that region. At higher energies, both configuration interaction and satellite ionizations are significant.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64: 175-182, 1997
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of membrane composition on the flow-injection response of an ion-selective electrode: A comparative study based on selectivity coefficients calculated using a data linearization technique (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 274-279 
    Details
    ISSN: 1040-0397
    Keywords: Potentiometry ; Flow-injection analysis ; Membrane ; Selectivity coefficient ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Commercial iodide, sulfide and cadmium-selective electrodes and four electrodes based on laboratory-prepared pressed membranes, the latter composed of either silver iodide or a mixture of silver iodide and sulfide, were assessed for their flow-injection response towards iodide in the absence and presence of bromide, thiocyanate and thiosulfate. With the exception of a pressed membrane based on a 3:1 mixture of AgI and Ag2S, which gave rise to erratic, irreproducible potentials, all the electrodes responded rapidly to iodide. While detection limits were generally similar, slope factors ranged from -44.6 mV/decade for a pressed AgI membrane to -61.2 mV/decade for a 1:3 AgI/Ag2S membrane. Selectivity coefficients were determined for each of the electrodes by intercalating mixed iodide-interferent solutions into a 10-6 M iodide carrier stream, then processing the resultant data by both the accepted IUPAC graphical method and a proposed data linearization technique. Although the two methods returned comparable results for the electrodes and interferents examined, the linearization procedure would be the preferred option in cases where the selectivity coefficients determined are greater than unity. Using electrode membranes composed of either AgI or AgI/Ag2S, a trend in selectivity was observed which suggests a mechanism of response towards the interferents involving the oxidation of the sulfide in the membrane to either sulfate or elemental sulfur.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140080313
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