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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of enzymatic DNA sequencing reactions by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 942-947 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The products from base-specific, dideoxy-nucleotide chain-termination DNA sequencing reactions catalyzed by the modified T7 DNA polymerase have been analyzed by using the technique of matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. Preliminary experiments were performed to determine detection limits for a synthetic mixture of mixed-base single-stranded DNA which contained a 14-mer, a 21-mer, and a 41-mer; acceptable spectra, showing peaks for each component, were obtainable for samples that contained as little as 5 fmol per component. Initial sequencing reactions were therefore carried out on 2-pmol amounts of a short synthetic template that was 45 nucleotides in length, employing 2 pmol of 12-mer as the primer strand. This provided readable sequence information out to the 19th base past the primer. Using a 21-mer primer, nearly the entire sequence of the template could be read.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091015
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on the formation of reactive intermediates from the antineoplastic agent N,N′Bis(2-chloroethyl)-N-nitrosourea (BCNU) in vitro and in Vivo. Characterization of novel glutathione adducts by ionspray tandem mass spectrometry (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 57-68 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In a study designed to examine the nature of short-lived, electrophilic intermediates liberated during decomposition of N,N′-bis(2-chloroethyl)-N-nitrosourea (BCNU) in vitro and also on administration of BCNU (140 μmol i.p.) to rats in vivo, both on-line and off-line LC/MS/MS techniques were employed to detect and characterize the corresponding glutathione (GSH) adducts present in incubation media and excreted into bile, respectively. In vitro, four GSH conjugates were formed and these were identified, on the basis of their product ion spectra, as products of S-and N-carbamoylation and alkylation reactions. Although the relative proportions of these in vitro adducts were found to depend on the molar ratios of GSH and BCNU, the major adduct under all conditions studied proved to be S-(2-chloroethylcarbamoyl)glutathione (SCG). Analysis of untreated bile samples by means of on-line LC/MS/MS with constant neutral loss (129 u) and precursor ion (m/z 179) scanning techniques again led to the detection of four GSH conjugates, although only one of these (SCG) was common to the group of adducts identified in vitro. All of the GSH conjugates detected in bile represented products of S-carbamoylation, indicating that the alkylating moiety released from BCNU undergoes reactions in vivo with nucleophiles other than GSH.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300111
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  • 3
    Electronic Resource
    Electronic Resource
    Zeta potential of bone from particle electrophoresis: Solution composition and kinetic effects (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 47-57 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The morphology of bone may be influenced by many factors, including electromechanical ones such as electric potentials, electric fields, or zeta potentials. Stress-generated potential studies in bone and particle electrophoresis studies using calcium-deficient hydroxyapatite have shown that the zeta potential depends on the composition of the steeping fluid and steeping time. To better quantify and understand these in situ potential changes in bovine cortical bone, the effects of alterations in calcium, phosphate, and fluoride concentrations in Neuman's Fluid (NF), which simulates in vivo bone extracellular fluid, were investigated using particle electrophoresis. The zeta potential increased in magnitude with increased calcium concentration in NF in as little as 17 min. Increasing phosphate concentration in NF also increased the zeta potential magnitude. These results provide support for a structural model of the bone matrix surface-bone fluid interface, which incorporates the bone surface proper (composed of collagen, mineral, and boundary regions), stationary layer (in which ions, ionic complexes, and proteins may be adsorbed), and bone extracellular fluid. These results, coupled with those of previous studies, indicate that the protein phase probably has an important role in the determination of the physiologic zeta potential; the role of the mineral phase may also be important. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290108
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  • 4
    Electronic Resource
    Electronic Resource
    Platelet and monoclonal antibody binding to fibrinogen adsorbed on glow-discharge-deposited polymers (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 729-739 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The state of fibrinogen adsorbed on untreated and glow-discharge-treated surfaces was examined by measuring platelet adhesion, monoclonal antibody (mAb) binding, the amount of fibrinogen adsorbed, and the amount of adsorbed fibrinogen which could be eluted with sodium dodecyl sulfate (SDS). Tetrafluoroethylene (TFE) glow-discharge-treated polymers have a lower surface free energy (in air) and retain a larger fraction of adsorbed fibrinogen than untreated surfaces after SDS elution. Platelet adhesion was lowest on the TFE-treated surfaces which retain the highest amounts of fibrinogen after SDS elution. Fibrinogen may undergo unfolding or spreading on the TFE-treated surfaces to minimize interfacial free energy (in water) and maximize protein-;surface interactions. When it is adsorbed on the TFE-treated surfaces, fibrinogen evidently assumes a state which somehow prevents its recognition and binding by platelet receptors. Monoclonal antibodies that bind to the three regions in fibrinogen thought to be involved in platelet adhesion were therefore used to detect changes in adsorbed fibrinogen. These regions and the antibodies which bind to them are: the COOH-terminal of the γ-chain, mAb M1; the RGD peptide sequence at Aα 95-98, mAb R1; the RDG sequence at Aα 572-575, mAb R2. For fibrinogen adsorbed on the untreated or TFE-treated surfaces, M1 and R2 binding was relatively high compared to background, while R1 binding was low. However, the amount of binding of each mAb to fibrinogen adsorbed on the TFE-treated surfaces was equal to or greater than fibrinogen adsorbed to the untreated surfaces. Therefore, antibody-detectable changes in the platelet binding regions of adsorbed fibrinogen that might have been caused by conformational or orientational rearrangements were not observed for the TFE-treated surfaces. The data suggest that the tight binding of fibrinogen on a surface may directly affect the ability of the fibrinogen to interact with the platelet receptors - i.e., that fibrinogen must be loosely held to facilitate maximal interaction with platelet receptors. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290609
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  • 5
    Electronic Resource
    Electronic Resource
    Biodegradable positively charged ion exchange beads: A novel biomaterial for enhancing soft tissue repair (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 376-386 
    Details
    ISSN: 0021-9304
    Keywords: charged beads ; soft tissue repair ; degradable ; wound healing ; crosslinked diethylaminoethanol dextran ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previous work in the area of vulnerary agents is extensive. One material of focus has been positively charged ion exchange beads, which have been shown to promote a variety of wound-healing responses in several models. The goal of this work was to improve upon the clinical utility of positively charged dextran beads by creating a biodegradable version that maintains the material's inherent efficacy. A chemical method consisting of a sodium periodate oxidation was used to create a degradable diethylaminoethanol crosslinked dextran bead. The ability of this process to create a degradable bead was verified in vitro and in vivo. Furthermore, efficacy was shown in a rat linear incision model for a variety of beads exhibiting different degradation rates. The results show that efficacy is maintained by a degradable bead, but there is a diminution of the magnitude of the response as the mass loss rate is increased. Efficacy also was investigated for a moderate but completely degrading bead material over time and dose. Wound breaking strength was evaluated at days 7, 10, 14, 21, and 28 for degradable beads at doses of 10 mg/mL and 50 mg/mL. Although little difference in efficacy was noted for the increased dose, statistically significant increases over control were seen at days 7, 10, and 14 for the 10 mg/mL dose and at days 10 and 14 for the 50 mg/mL dose. At days 21 and 28 there were no differences between treated and control wounds. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 376-386, 1998.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Thin-layer composite enzyme electrodes for glucose determinations (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 1035-1040 
    Details
    ISSN: 1040-0397
    Keywords: Glucose ; Biosensor ; Nafion ; Oxygen dependence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have prepared amperometric glucose sensitive electrodes with a composite active layer consisting of Nafion, glucose oxidase, and carbon-supported platinum particles. A particularly advantageous configuration results from the use of such a film on a gas diffusion electrode. We demonstrate that the gas diffusion electrode configuration enables us to supply oxygen from the back of the electrode, thus providing the capability of operating the sensor independent of dissolved oxygen. The insensitivity to solution oxygen concentration has been demonstrated by monitoring the glucose response of the electrode after extensive deoxygenation of solution. Cast composite layers yield mechanically robust coatings with high enzyme loadings, and thus high sensitivity to glucose. The electrode responds rapidly and is stable over a long period (90% activity after more than half a year) when stored in solution. We have optimized the composition of the sensitive layer with respect to Nafion to C/Pt ratio and enzyme loading.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140071108
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  • 7
    Electronic Resource
    Electronic Resource
    Crosslinked polymer chains with excluded volume: A new class of branched polymers? (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 7 (1998), S. 59-63 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this note microgels with and without excluded volume interactions are considered. Based on earlier exact computations on Gaussian mircogels, which are formed by self-crosslinking (with M crosslinks) of polymer chains with chainlength N, Flory type approximations are used to get first insight to their behavior in solution. It is shown that two different types of microgels exist: A special type of branched polymer whose size scales as R ∝ N2/5/M-1/5, instead of R ∝ N1/2. The second type are c*-microgels whose average mesh sizes r are swollen and form self avoiding walks with a scaling law of the form r = a(N/M)3/5.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Scattered intensity by a cross-linked polymer blend (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 67-76 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cross-linked mixtures of polystyrene and poly(vinyl methyl ether) exhibit a non-vanishing zero-angle intensity in small-angle neutron scattering experiments. A possible explanation is that fluctuations in composition in the mixture may be frozen by the presence of cross-links. Assuming this, we introduce a screening length κ by the condition that the scattered intensity should not be changed by cross-linking. We find κ2 ∼ C/(χ - χi), where C is an elastic constant, χ and χi, respectively, the inverse temperature and that where cross-linking is performed. When the temperature is varied, we find three regimes. In the first one, the scattered intensity is monotonously decreasing. In the second one, it has a finite maximum. In the last one, the maximum eventually diverges.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1995.040040104
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  • 9
    Electronic Resource
    Electronic Resource
    Adsorption of polymer chains onto charged spheres: Experiment and theory (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 7 (1998), S. 241-247 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A self-consistent field (SCF) theory for the adsorption of polyelectrolyte chains onto oppositely charged spheres is considered. It is demonstrated that the criterion for critical adsorption shows a different behavior for small and large curvature of the surface. Experiments give indeed evidence for the power-law behavior as theoretically predicted for large curvature.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    The structure and phase transitions in polymer blends, diblock copolymers and liquid crystalline polymers: The Landau-Ginzburg approach (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 573-643 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymer systems are discussed in the framework of the Landau-Ginzburg model. The model is derived from the mesoscopic Edwards Hamiltonian via the conditional partition function. We discuss flexible, semiflexible and rigid polymers. The following systems are studied: polymer blends, flexible diblock and multi-block copolymer melts, random copolymer melts, ring polymers, rigid-flexible diblock copolymer melts, mixtures of copolymers and homopolymers and mixtures of liquid crystalline polymers. Three methods are used to study the systems: mean-field model, self consistent one-loop approximation and self consistent field theory. The following problems are studied and discussed: the phase diagrams, scattering intensities and correlation functions, single chain statistics and behavior of single chains close to critical points, fluctuations induced shift of phase boundaries. In particular we shall discuss shrinking of the polymer chains close to the critical point in polymer blends, size of the Ginzburg region in polymer blends and shift of the critical temperature. In the rigid-flexible diblock copolymers we shall discuss the density nematic order parameter correlation function. The correlation functions in this system are found to oscillate with the characteristic period equal to the length of the rigid part of the diblock copolymer. The density and nematic order parameter measured along the given direction are anticorrelated. In the flexible diblock copolymer system we shall discuss various phases including the double diamond and gyroid structures. The single chain statistics in the disordered phase of a flexible diblock copolymer system is shown to deviate from the Gaussian statistics due to fluctuations. In the one loop approximation one shows that the diblock copolymer chain is stretched in the point where two incompatible blocks meet but also that each block shrinks close to the microphase separation transition. The stretching outweights shrinking and the net result is the increase of the radius of gyration above the Gaussian value. Certain properties of homopolymer/copolymer systems are discussed. Diblock copolymers solubilize two incompatible homopolymers by forming a monolayer interface between them. The interface has a positive saddle splay modulus which means that the interfaces in the disordered phase should be characterized by a negative Gaussian curvature. We also show that in such a mixture the Lifshitz tricritical point is encountered. The properties of this unusual point are presented. The Lifshitz, equimaxima and disorder lines are shown to provide a useful tool for studying local ordering in polymer mixtures. In the liquid crystalline mixtures the isotropic nematic phase transition is discussed. We concentrate on static, equilibrium properties of the polymer systems.
    Additional Material: 28 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1996.040050401
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