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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4462-4472 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Controlled swelling and shrinking of polyelectrolyte gels is useful for regulating the transport of solutes into, out of, and through these materials. A macroscopic continuum model is presented to predict the kinetics of swelling in polyelectrolyte gel membranes induced by augmentation of electrostatic swelling forces arising from membrane fixed charge groups. The model accounts for ionic transport within the membrane, electrodiffusion phenomena, dissociation of membrane charge groups, intramembrane fluid flow, and mechanical deformation of the membrane matrix. Model predictions are compared with measurements of chemically and electrically induced swelling and shrinking in crosslinked polymethacrylic acid (PMAA) membranes. Large, reversible changes in PMAA membrane hydration were observed after changing the bath pH or by applying an electric field to modify the intramembrane ionic environment and fixed charge density. A relatively slow swelling process and more rapid shrinking for both chemical and electrical modulation of the intramembrane pH are observed. The model indicates that retardation of membrane swelling is dominated by diffusion-limited reaction of H+ ions with membrane charge groups, and that the more rapid shrinking is limited primarily by mechanical processes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 665 (1992), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 720 (1994), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3147-3156 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present association biased Monte Carlo (ABMC), a Monte Carlo method, which is ergodic, microscopically reversible, and specifically designed to simulate associating fluids with long-ranged center-to-center interactions. The canonical ensemble (NVT) algorithm biases sampling to regions of configuration space where particle association is likely to occur, and provides efficient simulation of associating fluids over a broad range of densities. The usual canonical ensemble (NVT) thermodynamic variables (ensemble average internal energy and pressure), as well as the pair distribution functions are presented. The distributions of associated clusters are presented at a selection of state points and are compared with predictions of thermodynamic perturbation theory for the model system. We also present the simulation results for a symmetric, binary associating fluid with a single site on each particle.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 3962-3975 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An association biased Monte Carlo (ABMC) method of simulating associating systems with two bonding sites on each particle is described. The method includes a strategy for frequently forming two simultaneous bonds by a single particle during a Monte Carlo move. This strategy is employed to obtain adequate configuration statistics at each state point and is particularly important when ring formation is possible. A variety of thermodynamic and physicochemical parameters of the associating system were monitored including the compressibility factor, internal potential energy, isothermal compressibility, chain and ring number, and shape were monitored. Our analysis indicated that there is a strong dependence of these monitored quantities upon the angle between vectors representing the bonding sites on each particle. Also presented are results which suggest the existence of a two phase region, which we believe is a gas–liquid coexistence, which is dependent upon density, bonding energy, and the relative angle between the bonding sites. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 745 (1994), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 974-984 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical model for investigating physical phenomena underlying immune complex formation was developed, based on the statistical mechanical theory of associating fluids that identifies each molecule as a hard sphere with a nested point charge and vector dipole. The interaction between binding molecules (epitope-paratope binding) is represented as a cone truncated by two concentric spheres in which the potential energy is a modified square well with respect to particle separation and a square well with respect to mutual molecular orientation. Equilibrium binding results predicted by the model show good agreement with results obtained experimentally for a model system containing a single antigen and a single monoclonal antibody [bovine serum albumin (BSA) - anti-BSA antibody]. Moreover, values obtained for the system isothermal compressibility and the second virial coefficient by both the model and light scattering experiments also show good agreement with one another.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 72-81 
    ISSN: 0006-3592
    Keywords: antisense ; receptor targeted delivery ; acute phase response ; IL-6 ; gp 130 ; HepG2 cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Antisense technology is potentially a powerful means by which to selectively control gene expression. We have used antisense oligonucleotides to modulate the response of the hepatoma cell line, HepG2, to the inflammatory cytokine, IL-6, by inhibiting the expression of its multifunctional signal transducer, gp130. HepG2 cells respond to IL-6 by upregulating acute phase proteins, such as haptoglobin, by five- to tenfold. Gp130 is central to this response, as the upregulation of haptoglobin is almost completely blocked by the addition of high concentrations (∼100 μg/ml) of a monoclonal antibody to gp 130. Antisense oligodeoxynucleotides complementary to the mRNA encoding gp 130 inhibited the upregulation of haptoglobin by IL-6-stimulated HepG2 cells by about 50%. However, a nonsense sequence also inhibited haptoglobin secretion by about 20%. To improve the specificity and efficiency of action, we targeted the antisense oligonucleotides to HepG2 cells using a conjugate of asialoglycoprotein-poly-L-lysine. The targeted antisense reduced the binding of IL-6 to HepG2 cells, virtually eliminating high affinity binding. In addition, it inhibited haptoglobin upregulation by over 70%. Furthermore, the dose of targeted antisense required for biological effect was reduced by about an order of magnitude as compared with unconjugated antisense. These results demonstrate the potential of antisense oligonucleotides as a means to control the acute phase response as well as the need for a greater understanding of the mechanism and dynamics of antisense molecules as they are developed toward therapeutic application. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 72-81, 1997.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 100-111 
    ISSN: 0006-3592
    Keywords: hepatocyte culture ; plasma ; free fatty acids ; bioartificial liver ; oxygen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to examine their potential for use in a bioartificial liver, hepatocytes maintained in a collagen sandwich configuration were cultured for 9 days in heparinized rat plasma. The cells exhibited a progressive accumulation of cytoplasmic lipid droplets which proved to be mainly triglyceride (TG). The rate of TG accumulation correlated with the free fatty acid (FFA) content of the plasma. Removal of FFA and TG from plasma by ether extraction significantly reduced the rate and extent of TG accumulation. A smaller reduction in the rate and extent of TG accumulation was observed when cells were maintained in an oxygen enriched environment. The lipid accumulation suppressed urea synthesis, but clearance of the drug diazepam, although constitutively depressed in plasma, appeared unaffected by the accumulation. The functional and morphological effects of plasma exposure could be fully reversed after at least 6 days of plasma exposure by returning the cells to culture medium.The results indicate that elevated FFA in plasma induces lipid accumulation, which inhibits urea synthesis in cultured hepatocytes. This suggests that estimates of the cell number needed for effective liver support should not be based upon function measurements conducted in culture media. Furthermore, optimization of bioartificial liver support device use may have to be governed by the need to limit the plasma exposure of cultured hepatocytes. However, the highly responsive nature of these cultures and the reversibility of the plasma effects suggest that the collagen sandwich culture system is a promising foundation for the development of an effective bioartificial liver support system. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 10
    Publication Date: 2009-07-17
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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