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  • 1
    Electronic Resource
    Electronic Resource
    Alamethicin Pyromellitate: An Ion-Activated Channel-Forming Peptide (1994)
    s.l. : American Chemical Society
    Biochemistry 33 (1994), S. 6850-6858 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00188a014
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  • 2
    Electronic Resource
    Electronic Resource
    Aminoguanidine reduces regional albumin clearance but not urinary albumin excretion in streptozotocin-diabetic rats (1994)
    Springer
    Diabetologia 37 (1994), S. 10-14 
    Details
    ISSN: 1432-0428
    Keywords: Key words Diabetes mellitus, rat, advanced glycation end-products, aminoguanidine, vascular permeability, albuminuria.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Advanced glycation end-product-formation is thought to play a role in the development of diabetic angiopathy. By altering the structure of different extracellular matrix components advanced glycation end-products might affect vascular and glomerular permeability. In this study we investigated the effect of treatment with an inhibitor of advanced glycation end-product-formation, aminoguanidine, on vascular permeability and the development of albuminuria in streptozotocin-induced diabetic rats. Male Wistar Rp rats were randomized into a control group, a diabetic group, and an aminoguanidine-treated diabetic group. After 8 weeks, 24-h urine collections were taken and rats were implanted with an arterial and a venous catheter. Mean arterial blood pressure was determined by intra-arterial measurement. Regional albumin clearances were assessed in the eye, ileum, lung, skeletal muscle and skin using an isotope technique. Mean arterial pressure in the diabetic group was significantly lower in the control and aminoguanidine-treated groups (p 〈0.02). Regional albumin clearances were significantly increased in all tissues of diabetic rats compared to control rats (p 〈0.05). Aminoguanidine treatment of diabetic rats resulted in a significant decrease of regional albumin clearance in all tissues except the lung (p 〈0.05, lung p =0.07). The development of albuminuria in diabetic rats however, was not affected by aminoguanidine. [Diabetologia (1994) 37: 10–14]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250050065
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  • 3
    Electronic Resource
    Electronic Resource
    Aminoguanidine reduces regional albumin clearance but not urinary albumin excretion in streptozotocin-diabetic rats (1994)
    Springer
    Diabetologia 37 (1994), S. 10-14 
    Details
    ISSN: 1432-0428
    Keywords: Diabetes mellitus ; rat ; advanced glycation end-products ; aminoguanidine ; vascular permeability ; albuminuria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Advanced glycation end-product-formation is thought to play a role in the development of diabetic angiopathy. By altering the structure of different extracellular matrix components advanced glycation end-products might affect vascular and glomerular permeability. In this study we investigated the effect of treatment with an inhibitor of advanced glycation end-product-formation, aminoguanidine, on vascular permeability and the development of albuminuria in streptozotocin-induced diabetic rats. Male Wistar Rp rats were randomized into a control group, a diabetic group, and an aminoguanidine-treated diabetic group. After 8 weeks, 24-h urine collections were taken and rats were implanted with an arterial and a venous catheter. Mean arterial blood pressure was determined by intra-arterial measurement. Regional albumin clearances were assessed in the eye, ileum, lung, skeletal muscle and skin using an isotope technique. Mean arterial pressure in the diabetic group was significantly lower in the control and aminoguanidine-treated groups (p〈0.02). Regional albumin clearances were significantly increased in all tissues of diabetic rats compared to control rats (p〈0.05). Aminoguanidine treatment of diabetic rats resulted in a significant decrease of regional albumin clearance in all tissues except the lung (p〈0.05, lung p=0.07). The development of albuminuria in diabetic rats however, was not affected by aminoguanidine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428771
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  • 4
    Electronic Resource
    Electronic Resource
    Compartmentalization of pyridoxal-5′-phosphate during the acute phase of myocardial infarction (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 428-433 
    Details
    ISSN: 1432-1440
    Keywords: Pyridoxal-5′-phosphate ; Vitamin B6 ; Compartmentalization ; Adaptive response ; Myocardial infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Vitamin B6 nutritional status is assessed by measuring the plasma concentration of one of its vitamers, pyridoxal-phosphate (PLP). Several conditions, e.g., myocardial infarction (MI), can disturb the dynamic equilibrium between the different vitamers resulting in transiently low plasma PLP levels. An important question is whether these low plasma PLP levels observed during MI represent a transient state of deficiency and what the possible clinical consequences of such a fall in plasma PLP could be. Since the main metabolic function of PLP is to act as an intracellular coenzyme, it was decided to monitor the changes not only of PLP but also of PL (transport form of vitamin B6) in both the plasma and red blood cells (RBCs) in patients with myocardial infarctions (MI): 16 patients with proven MI were investigated measuring the aforementioned parameters at regular intervals. It was found that the approximately 40% fall in plasma PLP levels was accompanied by an equivalent increase in RBC PLP levels. Subsequently plasma PLP concentrations returned to normal but RBC PLP values were maintained at the newly elevated steady state (without any vitamin supplementation). Since membranes are impermeable to PLP, the only way in which PLP could have been redistributed to the intracellular compartment was through hydrolysis to PL and rephosphorylation once inside the RBCs. This compartmentalization could be an important adaptive response since it has been shown that PLP reduces O2 affinity of deoxygenated hemoglobin, thereby facilitating O2 delivery to the tissues. In addition it would also enhance the proposed storage function of RBCs for PLP and PL which is said to be an important source for muscle vitamin B6 which again is essential for energy production by the muscle cells during ischemia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01745511
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  • 5
    Electronic Resource
    Electronic Resource
    Ion channel formation by zervamicin-IIB (1993)
    Springer
    European biophysics journal 21 (1993), S. 369-383 
    Details
    ISSN: 1432-1017
    Keywords: Ion channel ; Peptaibol ; Molecular modelling ; Channel-forming peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Zervamicin-IIB (Zrv-IIB) is a 16 residue peptaibol which forms voltage-activated, multiple conductance level channels in planar lipid bilayers. A molecular model of Zrv-IIB channels is presented. The structure of monomerc Zrv-II3 is based upon the crystal structure of Zervamicin-Leu. The helical backbone is kinked by a hydroxyproline residue at position 10. Zrv-IIB channels are modelled as helix bundles of from 4 to 8 parallel helices surrounding a central pore. The monomers are packed with their C-terminal helical segments in close contact, and the bundles are stabilized by hydrogen bonds between glutamine 11 and hydroxyproline 10 of adjacent helices. Interaction energy profiles for movement of three different probes species (K+, Cl− and water) through the central pore are analyzed. The conformations of: (a) the sidechain of glutamine 3; (b) the hydroxyl group of hydroxyproline 10; and (c) the C-terminal hydroxyl group are “optimized” in order to maximize favourable interactions between the channel and the probes, resulting in favourable interaction energy profiles for all three. This suggests that conformational flexibility of polar sidechains enables the channel lining to mimic an aqueous environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185864
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulations of ion channels formed by bundles of amphipathic α-helical peptides (1996)
    Springer
    European biophysics journal 25 (1996), S. 139-150 
    Details
    ISSN: 1432-1017
    Keywords: Key words Ion channel ; Water ; Molecular dynamics ; Dipole ; α-helix ; Peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Ion channels may be formed by self-assembly of amphipathic α-helical peptides into parallel helix bundles. The transbilayer pores formed by such peptides contain extended columns of water molecules, the properties of which may differ from those of water in its bulk state. The de novo designed peptides of DeGrado et al., which contain only leucine and serine residues, are considered as a simple example of such channels. Molecular dynamics simulations of peptide helix bundles with water molecules within and at the mouths of their pores are used to refine such models and to investigate the properties of intra-pore water. The translational and rotational mobility of water molecules within the pores are reduced relative to bulk water. Furthermore, intra-pore waters orient themselves with their dipoles anti-parallel to the helix dipoles, as do the hydroxyl groups of serine residues. Comparison of approximate predictions of ionic conductances with experimental values provides support for the validity of these models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050025
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  • 7
    Electronic Resource
    Electronic Resource
    Alamethicin and related peptaibols — model ion channels (1993)
    Springer
    European biophysics journal 22 (1993), S. 105-124 
    Details
    ISSN: 1432-1017
    Keywords: Ion channel ; Peptaibol ; Channel-forming peptide ; Molecular modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Peptaibols are considered as models of those ion channels which consist of a bundle of transbilayer helices surrounding a central pore. X-Ray diffraction and NMR studies have yielded high resolution structures for several peptaibols. In conjunction with other spectroscopic investigations and molecular dynamics simulations, these studies suggest that peptaibols form proline-kinked α-helices, and that there may be “hinge-bending” movement of the helix in the region of the central proline residue. The amphipathicity of peptaibol helices is analyzed in relation to their channel-forming properties. Studies of the interactions of peptaibols with lipid bilayers suggest that they are helical when in a membrane-like environment, and that the helix orientation relative to the bilayer is sensitive to the peptaibol: lipid ratio, and to the degree of hydration of the bilayer. Electrical studies reveal that many peptaibols form multiple-conductance level channels in a voltage-dependent fashion. Analysis of conductance levels provides support for the “barrel stave” model of channel formation, whereby different conductance levels correspond to different numbers of monomers in a helix bundle. Alternative models for voltage-activation are discussed, and the roles of molecular dipoles and of hinge-bending in this process are considered. Two molecular models for an N = 6 bundle of alamethicin helices are presented and their electrostatic properties analyzed. The relevance of studies of peptaibols to channel and transport proteins in general is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196915
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  • 8
    Electronic Resource
    Electronic Resource
    Production of Superconducting Niobium Films by Vacuum-Arc Deposition (1962)
    [s.l.] : Nature Publishing Group
    Nature 193 (1962), S. 766-767 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] One of our major interests has been to produce superconducting niobium films with the transition characteristics of the pure bulk metal. It is a well-known fact that superconducting niobium films are difficult to prepare. The main obstacles to be overcome are: high melting temperature, low vapour ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/193766b0
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  • 9
    Electronic Resource
    Electronic Resource
    Multi-Walled Carbon Nanotube Coatings Using Electrophoretic Deposition (EPD) (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A method based on electrophoretic deposition (EPD) has been developed to produce uniform deposits of multi-walled carbon nanotubes on stainless-steel substrates. Aqueous suspensions were used under constant voltage conditions in the range of 5–50 V, with deposition times ranging from 0.5 to 10 min. The thickness of the coatings was controlled by variation of voltage and deposition time during EPD. Coatings of up to 10 μm thickness were achieved, with a homogeneous microstructure. The EPD technique is fast, effective, and can be applied to complex shapes. Possible applications are in heat extraction devices or porous coatings for tissue engineering scaffolds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00155.x
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  • 10
    Electronic Resource
    Electronic Resource
    Zinc hyperaccumulation and cellular distribution in Arabidopsis halleri (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Although Arabidopsis halleri (=Cardaminopsis halleri) is known as a Zn hyperaccumulator, there have been no detailed studies on Zn accumulation, tolerance and cellular distribution in this species. In a hydroponic experiment, A. halleri grew healthily with Zn concentrations varying from 1 to 1000 μM, without showing phytotoxicity or reduction in root or shoot dry weights. The concentration of Zn in the shoots increased from 300 μg g−1 dry weight in the 1 μM Zn treatment to 32 000 μg g−1 in the 1000 μM Zn treatment. Approximately 60% of the total Zn in the shoots were water-soluble, and there was no evidence of Zn and P co-precipitation. Both citric and malic acid concentrations in the shoots were not significantly affected by the Zn treatments, whereas in the roots there was a positive response in both organic acids to increasing Zn in solution. Cellular distribution of Zn, Ca and K in frozen hydrated leaf tissues was examined using energy-dispersive X-ray microanalysis. Zinc was sequestered in the base of trichomes, whereas the middle and upper parts of trichomes were highly enriched with Ca. Mesophyll cells appeared to have more Zn than the epidermis, probably because the latter were very small in size. Similarities and differences between A. halleri and the other well-known Zn hyperaccumulator, Thlaspi caerulescens, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00569.x
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