Kooperativer Bibliotheksverbund

Berlin Brandenburg


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  • 1
    Language: English
    In: Russian Journal of Physical Chemistry A, 2014, Vol.88(12), pp.2225-2235
    Description: Aqueous electrolyte solutions play an important role in many electrophysical and chemical processes in aerospace technology and industrial applications. As noncovalent interactions, the interactions between ions are crucially important for biomolecular structures as well (protein structure folding, molecular level processes followed by ionic pair correlations, the formation of flexible hydrate shells, and so on). Specifically, ions (cations and anions with the same valence charges) can form stable pairs if their sizes match. The formation of ionic pairs can substantially affect the thermodynamic stabilities of proteins in the alkali salts physiologically present in the human body. Research aims and problems impose severe demands on readjustments of the ionic force fields and potential parameters developed to describe aqueous solutions and electrolytic systems. Ionic solutions and their interaction with biomolecules have been observed for over 100 years [1], but the behavior of such solutions remains poorly studied today. New data obtained in this work deals with parameterization strategies and adjustments for the ionic force fields of the alkali cations and halide anions that should be helpful in biomolecular research. Using molecular dynamics (MD) models, four electrolytic systems (HCl-H 2 O, LiCl-H 2 O, NaCl-H 2 O, and KCl-H 2 O) are investigated as binary mixtures of water and cations and anions, respectively. The intermolecular interaction parameters are varied for two of the four model electrolytes (HCl-H 2 O and NaCl-H 2 O) to simulate the possibility of different ionic shells forming during interaction with water. It is found that varying the potential parameters strongly affects the dynamic and structural characteristics of electrolyte systems. MD simulations are performed in the temperature range of 300 to 600 K with a step of 50 K. MD simulations for all electrolyte models (HCl-H 2 O, LiCl-H 2 O, NaCl-H 2 O, KCl-H 2 O) are also conducted for different molar fractions of electrolyte concentration: 16, 8, and 1 mol/kg. Energies of diffusion activation are calculated using the Arrhenius equation, thereby constructing temperature dependence graphs of diffusion coefficients for all four electrolyte systems. The observed diffusion properties of the electrolyte systems are found to correlate well with the energy and structural radial distribution data.
    Keywords: molecular dynamics simulations ; electrolyte solutions ; microstructure analysis ; diffusion coefficient ; radial distribution function
    ISSN: 0036-0244
    E-ISSN: 1531-863X
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  • 2
    Language: English
    In: International Journal of Cancer, 01 May 2004, Vol.109(5), pp.759-767
    Description: Glioblastomas belong to the most aggressive human cancers with short survival times. Due to the blood‐brain barrier, they are mostly inaccessible to traditional chemotherapy. We have recently shown that doxorubicin bound to polysorbate‐coated nanoparticles crossed the intact blood‐brain barrier, thus reaching therapeutic concentrations in the brain. Here, we investigated the therapeutic potential of this formulation of doxorubicin using an animal model created by implantation of 101/8 glioblastoma tumor in rat brains. Groups of 5–8 glioblastoma‐bearing rats (total = 151) were subjected to 3 cycles of 1.5–2.5 mg/kg body weight of doxorubicin in different formulations, including doxorubicin bound to polysorbate‐coated nanoparticles. The animals were analyzed for survival (% median increase of survival time, Kaplan‐Meier). Preliminary histology including immunocytochemistry (glial fibrillary acidic protein, ezrin, proliferation and apoptosis) was also performed. Rats treated with doxorubicin bound to polysorbate‐coated nanoparticles had significantly higher survival times compared with all other groups. Over 20% of the animals in this group showed a long‐term remission. Preliminary histology confirmed lower tumor sizes and lower values for proliferation and apoptosis in this group. All groups of animals treated with polysorbate‐containing formulations also had a slight inflammatory reaction to the tumor. There was no indication of neurotoxicity. Additionally, binding to nanoparticles may reduce the systemic toxicity of doxorubicin. This study showed that therapy with doxorubicin bound to nanoparticles offers a therapeutic potential for the treatment of human glioblastoma. © 2004 Wiley‐Liss, Inc.
    Keywords: Nanoparticles ; Doxorubicin ; Glioblastoma ; Chemotherapy ; Histology
    ISSN: 0020-7136
    E-ISSN: 1097-0215
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