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  • Life and Medical Sciences  (13)
  • Computational Chemistry and Molecular Modeling  (5)
  • Wiley-Blackwell  (18)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 29 (1986), S. 563-578 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An important class of polymers is comprised, in part, of 1,4-disubstituted phenylene groups. It is widely believed that large amplitude phenylene torsional motions play a critical role in determining such physical properties as the toughness and degree of crystallinity of these polymers. We have studied what is perhaps the simplest polymer in this class, polyphenylene oxide (PPO), using ab initio quantum chemistry methods to determine the conformational properties, torsional potential energy functions, and vibrational frequencies. From our calculations on dimer (diphenyl ether) and trimer (para-diphenoxy benzene) fragments emerges a qualitative description of the mechanism of phenylene rotation in the polymeric material.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 875-886 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The valence-shell vertical ionization potentials of Cl2 were calculated by perturbation corrections to the Koopmans theorem using a traditional effective core potential based on a Phillips-Kleinman derivation and an improved effective core potential obtained by Christiansen, Lee, and Pitzer. Comparison of the results with an all-electron calculation demonstrated the reliability of the Christiansen-Lee-Pitzer effective core potential, which was then used to compute the vertical ionization potentials of ClN3 and ClNCO. The results shed new light in the interpretation of the photoelectron spectra of these molecules.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 279-289 
    ISSN: 1059-910X
    Keywords: Fluorescence microscopy ; Ca channels ; Pyramidal neurons ; CA1 region ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Changes in the intracellular Ca2+ concentration ([Ca2+]i) within CA1 hippocampal pyramidal neurons were imaged using confocal laser scanning microscopy in conjunction with Ca2+ -sensitive fluorescent indicators. The imaging was performed in thick hippocampal brain slices while simultaneously measuring or controlling electrical activity with sharp microelectrodes or whole-cell patch-clamp electrodes. The combination of imaging and electrophysiology was essential for interpreting the changes in [Ca2+]i. We compared the increases in [Ca2+]i produced by either of two methods-direct depolarization of the cell via the somatic electrode or high-frequency stimulations of synaptic inputs. The increases in [Ca2+]i in the soma and proximal dendrites caused by both methods were of comparable magnitude and they always decayed within seconds in healthy cells. However, the spatial patterns of distal Ca2+ increases were different. Separate sets of synaptic inputs to the same cell resulted in different spatial patterns of [Ca2+]i transients. We isolated and observed what appeared to be a voltage-independent component of the synaptically mediated [Ca2+]i transients. This work demonstrates that the combination of neurophysiology and simultaneous confocal microscopy is well suited for visualizing and analyzing [Ca2+]i within neurons throughout the CNS and it raises the possibility of routinely relating subcellular [Ca2+]i changes to structural and functional modifications. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 4
    ISSN: 1040-452X
    Keywords: Fetal gene expression ; hCG-β ; Polymerase chain reaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The glycoprotein hormone human chorionic gonadotropin (hCG) is synthesized in large quantities by the developing placenta, reaching peak concentrations in maternal blood during the late first trimester and early midtrimester of pregnancey. In general it is believed that the β-subunit of this dimeric hormone is expressed in pituitary gonadotropes, thyrotropes, and trophoblasts, while the β-subunit is expressed exclusively by trophoblasts. Studies from our laboratory and other laboratories have shown that some midtrimester human fetal tissues, in addition to the placenta, can synthesize proteins that appear to be very similar to the β-subunit of hCG. To define precisely the nature of this putative hCG-β-subunit in extraplacental fetal tissues, we have examined the mRNA from a variety of human fetal and adult tissues using nucleic acid hybridization and reverse transcription-polymerase chain reaction (PCR) methods. Our results demonstrate that midtrimester fetal kidney and adrenal tissues contain hCG-β mRNA transcripts at concentrations comparable to that of placenta, while fetal lung, brain, muscle, and adult adrenal contain only trace to undetectable levels of hCG-β mRNA. By restriction endonuclease mapping of PCR fragments from fetal tissue cDNAs, we show that the hCG-β transcript expressed in midtrimester human fetal organs is a bone fide copy of hCG-β gene No. 5 of the β-subunit gene family located on chromosome 19. © 1992 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 133 (1987), S. 25-36 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Bovine erythrocytes, which normally lack phosphatidyl choline in their membranes, when treated with either H2O2 or diamide (1-3 mM), showed a partial appearance of phosphatidyl ethanolamine (PE 40%) and phosphatidyl serine (PS, 30-33%) in the external leaflet of the bilayer and a concomitant increased (four- to five-fold) propensity to adhere to cultured bovine aortic endothelial cells. Similar treatment of normal human erythrocytes caused an alteration in the organization of the phospholipid bilayer and also resulted in their increased adherence to endothelial cells derived either from human umbilical vein or bovine aorta. Treatment of RBCs with H2O2 at low concentration (0.5 mM) resulted in cross-linking of spectrin without significant changes in the orientation of aminophospholipids but the RBCs exhibited 15-20% increase in adherence to endothelial cells. Pretreatment of either human or bovine erythrocytes with antioxidants such as vitamin E (2 mM) prevented both oxidant-induced reorganization of phospholipids in the bilayer and enhancement of adherence to endothelial cells. Introduction of either phosphatidyl serine or phosphatidyl ethanolamine but not phosphatidyl choline into erythrocyte membranes increased their adherence to endothelial cells threefold. Oxidant-treated RBCs exhibited enhanced binding and fluorescence of Merocyanine 540 dye (MC-540), which is sensitive to the packing of lipids in the lipid bilayer. On flow cytometric analysis, 78% of H2O2 (0.5 mM)-treated erythrocytes compared to 30% of untreated RBCs exhibited MC-540 binding and fluorescence, indicating differences in the lipid packing in the outer leaflet of the bilayer. Oxidant-treated erythrocytes adhere preferentially to endothelial cells rather than to bovine aortic smooth muscle cells and skin fibroblasts. It is suggested that the alterations in the erythrocyte membrane surface due to spectrin cross-linking and the organization of the phospholipids concomitant with less ordered packing in the external leaflet of the bilayer, either induced by oxidative manipulation in normal RBC or in pathological erythrocytes, play a role in erythrocyte-endothelial cell interaction.
    Additional Material: 9 Ill.
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To characterize the endothelial cell surface membrane glycoproteins that mediate thrombin stimulation of PGI2 synthesis by human umbilical vein endothelial cells (HUVEC), HUVEC were stimulated with thrombin in the presence or absence of different lectins. Of the lectins tested, only wheat germ agglutinin (WGA) inhibited thrombin-induced rises in cytosolic free calcium ([Ca2+]i), measured using Quin 2-loaded HUVEC and PGI2 production measured by radioimmunoassay. However, WGA by itself had no influence on baseline [Ca2+]i or PGI2 production and did not inhibit histamine-induced rises in [Ca2+]i. The inhibition of thrombin-induced rises in [Ca2+]i and PGI2 production by WGA was dose dependent, with half-maximal inhibition occurring at 2 μg/ml WGA also inhibited thrombin-induced release of 3H-arachidonic acid. These effects of WGA were reversed by N-acetyl-glucosamine (GlcNAc) and N-acetyl-neuraminic acid, which bind specifically to WGA, but not by unrelated sugars. Succinylated WGA (succ-WGA), a chemically modified derivative of WGA that binds to GlcNAc but, unlike native WGA, not to sialoglycoproteins, did not inhibit thrombin-induced rises in [Ca2+]i and PGI2 production. These results suggest that thrombin induces rises in [Ca2+]i and PGI2 production by interacting with an endothelial surface membrane sialoglycoprotein.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 4 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 5 (1986), S. 292-294 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 84-88 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The use of symmetry coordinates (SC) in geometry optimization is discussed. A computer program incorporating the use of sc, together with analytical calculation of the gradient and quadratic acceleration, is described. Also reported are careful test results on a series of small molecules and typical results with a long series of molecules up to quite large size (40-60 atoms).
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 604-607 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: This article describes the numerical application of projection operators to restore the symmetry of molecular orbitals in self-consistent field (SCF) calculations when the symmetry is lost because of degeneracy or near degeneracy. The application of projection operators is particularly useful in cases of near degeneracies of three or more molecular orbitals, where it is difficult to find an effective algorithm for restoring the symmetry of molecular orbitals by orthonormal transformations.
    Additional Material: 3 Tab.
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