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  • Polymer and Materials Science  (45)
  • Analytical Chemistry and Spectroscopy  (33)
  • General Chemistry  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Deformational dynamics and nmr relaxation of supercoiled DNAs (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1023-1056 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation and internal dynamics of supercoiled pUC 8 DNA (2717 bp) are examined by dynamic light scattering, and the magnitude and uniformity of its torsional rigidity are determined using time-resolved fluorescence polarization anisotropy of intercalated ethidium dye. Neither measurement gives any indication of an appreciably reduced bending or twisting rigidity, or anomalously rapid internal motions. For 31P, in supercoiled pUC 8, we measure T2 = (2.0 ± 0.5) × 10-3 s. This lies within the range of present theoretical estimates obtained using normal rigidities. The proton linewidths observed for pUC 8 and pBR322 (4363 bp) DNAs are within a factor of 2-3 of those similarly estimated assuming ordinary rigidities.According to Bendel, Laub and James [(1982) J. Am. Chem. Soc. 104, 6748-6754], supercoiled pIns36 DNA (7200 bp) exhibits an astonishingly long T2 = 1.17 s for 31P, a slowest rotational relaxation time, τ = 5 × 10-9 s, and an enormously reduced bending rigidity. Serious questions raised by these findings are examined here. The 5 × 10-9 s slowest rotational relaxation time is shown to be physically inadmissible.The nmr relaxation theory developed previously by Allison, Shibata, Wilcoxon, and Schurr [(1982) Biopolymers 21, 729-762], is modified to incorporate new results for deformable filaments, which directly introduce the highly nonexponential tumbling correlation function for reorientation of the local helix axis. Essential requirements for a complete calculation of R2, including estimation of the tumbling correlation function and evaluation of the still unknown DIP/CSA cross-term, are described in detail. Slow coil-deformation modes analogous to the Rouse-Zimm modes of linear DNAs are shown to make an important, if not dominant, contribution to the R2 relaxation rate. Geometrical parameters in the theory are chosen to provide good agreement with literature data for 600-bp linear DNA. Using this theory and an informed guess for the tumbling correlation function, we find that the 31P-nmr relaxation data of Bendel et al., if correct, necessarily impose on their DNA one or more extreme properties, such as enormously reduced bending or twisting rigidities. In contrast, the same theory yields reasonable agreement with the T2 reported here for 31P in supercoiled pUC 8 DNA when its rigidities are assumed to be quite ordinary.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240609
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of the urinary polymer-related material from rats given poly[biguanide-1,5-diylhexamethylene hydrochloride] (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 2591-2605 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die gastrointestinale Absorption von Poly(biguanid-1,5-diylhexamethylen-hydrochlorid) (1) in Ratten beträgt nur 5,6% einer einzigen oralen Dosis, und auch nach Langzeitbehandlung liegen die Konzentrationen im Gewebe höchstens bei 0,3 μg g-1. Durch cinfache chromatographische und spektroskopische Methoden konnte gezeigt werden, daß die im Harn ausgeschiedenen Substanzen in kleinen Mengen aus 1-Oligomeren mit zwer Cyanguanidino-Endgruppen bestehen, sowie aus Spuren von 3,3′-Dicyano-1,1′-hexamethylendiguanidin (8a) und einer Verbindung, die für 1-(6-Aminohexyl)-3-cyanoguanidin (2) gehalten wird, und die bei der Synthese von 1 entsteht. Die Bestandteile von 1 werden demnach in Ratten nicht metabolisiert.
    Notes: Gastro-intestinal absorption in rats of poly[biguanide-1,5-diylhexamethylene hydrochloride] (1) amounts to only 5,6% of a single oral dose, and after chronic administration, tissue concentrations do not exceed 0,3 μg g-1. It has been shown by simple chromatographic and spectroscopic methods that urinary polymer-related material consists of small amounts of 1-oligomers, with two cyanoguanidino end groups, as well as the trace constituents, 3,3′-dicyano-1,1′-hexamethylenediguanidine (8a) and a compound which is considered to be 1-(6-aminohexyl)-3-cyanoguanidine (2) that is formed during the synthesis of 1. Hence, the constituents of 1 are unmetabolized in rats.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770902
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  • 4
    Electronic Resource
    Electronic Resource
    Packed column supercritical fluid chromatography/mass spectrometry using a thermospray source in the filament-on mode (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 105-109 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Combined packed column supercritical fluid chromatography/mass spectrometry has been effected using a thermospray ion source in the filament-on mode. If organic modifiers are used with carbon dioxide as the supercritical mobile phase, chemical ionization mass spectra are obtained. With carbon dioxide electron impact type mass spectra are obtained. The potential of the system is illustrated with studies of mixtures of carbamate and organochlorine pesticides and a crude ergot fermentation extract.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150208
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  • 5
    Electronic Resource
    Electronic Resource
    Continuous flow fast atom bombardment liquid chromatography/mass spectrometry: Studies involving conventional bore liquid chromatography with simultaneous ultraviolet detection (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 179-182 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A conventional bore liquid chromatograph has been interfaced to quadrupole and magnetic sector mass spectrometers configured for fast atom bombardment ionization via a continuous flow FAB probe. It is shown that post-column addition of FAB matrix and in-line ultraviolet detection facilities do not significantly compromise chromatographic integrity and that high quality mass spectra are obtainable from such FAB LC/MS studies.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150310
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  • 6
    Electronic Resource
    Electronic Resource
    Detection of residues of chloramphenicol in crude extracts of fish and milk by tandem mass spectrometry (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 5-11 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collision-induced dissociation mass spectrum, observed with a hybrid tandem instrument, of the ammonia chemical ionization protonated molecular ion of chloramphenicol was used for the detection of residues of the drug in biological samples. The extracted oil from fish was subjected to a rapid clean-up on a pre-packed silica gel cartridge prior to non-chromatographic tandem mass spectral analysis. Fat extracted from milk was analysed directly by on-line combined high-performance liquid chromatography/tandem mass spectrometry with rapid elution of chloramphenicol. Identification was on the basis of agreement of the daughter ion spectra obtained from sample extracts with that of the chloramphenicol standard. Detection was unambiguous at 0.5 mg kg-1. The sensitivity advantage normally expected with multiple reaction monitoring was not achieved owing to the effect of neutral noise phenomena.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180103
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  • 7
    Electronic Resource
    Electronic Resource
    Anionic syntheses of terminally functionalized ethylene oligomers (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 4205-4226 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic procedures for preparation of terminally functionalized linear ethylene oligomers are described. The preferred synthetic method is anionic oligomerization of ethylene with n-butyllithium-tetramethylethylenediamine and electrophilic substitution of the living oligomer so-formed. Conditions and procedures for subsequent chemistry to elaborate the end groups of these oligomers are described. These procedures afford strictly linear ethylene oligomers which contain a wide variety of end groups and which range in molecular weight from 1000 to 4500 (Mn). The product oligomers were characterized spectroscopically as toluene-d8 solutions at 110°C using multinuclear NMR, FT-IR, fluorescence, and UV-visible spectroscopies as appropriate. Alternative stepwise approaches to such oligomers are also discussed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080271226
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  • 8
    Electronic Resource
    Electronic Resource
    Modification of polyolefin surfaces with iron cluster oxidants (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 389-396 
    Details
    ISSN: 0887-624X
    Keywords: polyethylene ; polypropylene ; oxidation ; biodegradation ; C—H bond activation ; functionalization ; XPS ; ATR-IR ; surface ; Gif ; oxidase ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modification of polyethylene and polypropylene film and powder surfaces with oxygen and hydrogen peroxide is promoted by nonporphyrinic, nonfree radical based iron reagents such as Fe3O(OCOCH3)6(C6H5N)3.5 and FeCl3 • 6H2O/picolinic acid. These oxidation systems introduced small amounts of carbonyl groups onto the surface of these hydrocarbon polymers. The most visible manifestation of this reaction was increased polyolefin wettability toward water. IR spectroscopy, XPS spectroscopy, and chemical derivatization all were used to verify that the reaction had occurred and that a chemically derivatizable surface had been prepared. The overall process produced a fraction of the density of functional groups introduced by conventional etching chemistry.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300306
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Water-Soluble imide-amide copolymers. I. Preparation and characterization of poly [acrylamide-co-sodium N-(4-sulfophenyl) maleimide]Presented at the 72nd Canadian Chemical Conference, Victoria, British Columbia, June 4-8, 1989.Dedicated to the memory of Dr. W. M. Leung (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 2949-2968 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sodium N-(4-sulfophenyl) maleimide (SPMI) and its saturated succinimide counterpart were first prepared according to established methods. Hydrolysis experiments on these monomers monitored by 1H-NMR showed that although SPMI monomer was about 15% hydrolyzed in D2O at 23°C in 24 h. Sodium N-(4-sulfophenyl) succinimide, which is similar in structure to the imide units in the copolymers, was only 1% hydrolyzed after 18 days at 23°C and 29% hydrolyzed after 18 days at 60°C. This indicated that the saturated imide rings in the copolymer might be sufficiently stable to hydrolysis for the copolymers to be useful. However, hydrolysis at high pH demonstrated that the imide rings would be rapidly saponified under alkaline conditions, destroying the structural rigidity that the intact rings might have provided in the copolymer chains. Sodium N-(4-sulfophenyl) maleimide (SPMI) was copolymerized with acrylamide in water at 30°C without cleavage of the imide ring. Water-soluble poly [acrylamide-co-sodium-N-(4-sulfophenyl) maleimide] (PAMSM) samples containing from 7.4 to 64 mol % imide were prepared. Photoacoustic FTIR and 13C-NMR spectra were used to confirm the structure of the copolymers obtained. Elemental analysis was used to determine the imide content of the copolymers, and from this composition data reactivity ratios were calculated for the two component monomers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281106
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