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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 1362-1364 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 38 (1982), S. 535-536 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Total hepatic L-tryptophan 2,3-dioxygenase activity was studied in 2 mouse strains receiving i.p. injections of L-tryptophan. After a single injection, enzyme activity was increased in albino but not pigmented mice. After 3 injections, enzyme activity was reduced in both strains.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 11 (1984), S. 43-50 
    ISSN: 1432-1017
    Keywords: Flux measurement ; photobleaching ; fluorescence microphotolysis ; erythrocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Fluorescence microphotolysis — widely employed for diffusion studies — can be used to measure transfer (flux) of fluorescent solutes through membranes in single cells and organelles. This article analyses the methodological basis of flux measurements, provides experimental tests, and discusses potential applications. The principle of the method is to equilibrate cells, organelles or vesicles with a fluorescent solute, to deplete the interior of individual cells etc. of fluorescene by the pulse of a high-intensity microbeam, and to monitor influx of solute by microfluorometry. Simple equations are given and a computer curve fitting program is described by which rate constants of influx and membrane permeability coefficients can be derived from fluorescence measurements. The permeability of individual “leaky” human erythrocyte ghosts to fluorescein-isothiocyanate-labelled bovine serum albumin has been measured under various conditions. Multiple exposure to the high-intensity microbeam had no effect on permeability within experimental error. Flux measurements have been also performed on individual vesicles of 1–2 μm radius which had been derived from ghosts. The potential application of the method to sub-lightmicroscopic vesicles and to organelles within living cells is discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Properties of electroreceptors (small pits) in the dorsal skin of the head of catfish,Ictalurus nebulosus, were determined by recording the impulse activity from the lumen of individual receptors in intact fish. 2. The sensitivity of a small pit to sinusoidal current was defined as the difference of the maximum and minimum average impulse frequency during the stimulus period, divided by the stimulus current. 3. The statistical distribution of the sensitivity was found to be unimodal, with a modus at 0.5 Hz/nA. The sensitivity of 96% of the small pits is between 0.04 and 1.6 Hz/nA (Fig. 1). 4. The input/output relation of the small pits (impulse frequency versus stimulus current) is sigmoidal, but has a nearly linear segment at small stimulus amplitudes (Fig. 3). 5. The statistical distribution of the mean spontaneous impulse frequency has a modus at 40 Hz. The spontaneous activity of 95% of the small pits is between 15 and 70 Hz (Fig. 2). 6. The frequency of the spontaneous activity of individual small pits fluctuates considerably. The standard deviation (RMS value) of this “frequency noise” is between 6 and 35 Hz, and varies little with sensitivity (Fig. 5). 7. Both the sensitivity and the frequency noise are reduced by an outward current of 0.5 to 6 μA, and by exposition to a calcium free medium. 8. The origin of these phenomena in the receptor structures is discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 70 (1983), S. 294-302 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract Fluorescence microphotolysis is a versatile method for diffusion measurements in single cells and other microscopic systems. A recent development, continuous fluorescence microphotolysis, extends diffusion measurements to ensembles of a few hundred fluorophores. Cell surface membranes are frequently considered as 2-dimensional fluids. Membrane proteins, dispersed in a fluid bimolecular lipid layer, are expected to be highly mobile in the membrane plane. Such expectations are met by artificial bilayers but not always by cell membranes. As first observed for erythrocytes and subsequently for many other cells translational mobility of membrane proteins can be severely restricted. Frequently, integral membrane proteins have mobile and immobile fractions. In order to account for this duality it has been suggested that cell surface membranes are made up of two layers with opposing dynamic properties: a fluid lipidprotein bilayer, the “membrane skin”, and a rather static protein network, the “membrane skeleton”.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of bioenergetics and biomembranes 16 (1984), S. 283-294 
    ISSN: 1573-6881
    Keywords: P515 ; electrochromic bandshift ; thylakoid membrane ; lipid composition ; cytb 563 ; cytf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Flash-induced P515 absorbance changes have been studied in dark-adapted chloroplasts isolated from spinach plants grown under two different light intensities. The slow component (reaction 2), normally present in the P515 response of chloroplasts isolated from plants grown at an intensity of 60 W · m−2, was largely reduced in chloroplasts isolated from plants grown at an intensity of 6 W · m−2. This reduction of the slow component in the P515 response appeared to be coincident with an alteration in the lipid composition of the thylakoid membrane. Mainly the ratio monogalactosyldiacylglycerol to digalactosyldiacylglycerol appeared to be altered. In thylakoids from plants grown at 6 W · m−2, the ratio was approximately 35% lower than that of plants grown at 60 W · m−2. The amount of both cytochromeb 563 and cytochromef was largely reduced in chloroplasts isolated from plants grown at low light intensity. These results may indicate a possible correlation between structural organization of the thylakoid membrane and the kinetics of the flash-induced P515 response.
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  • 7
    ISSN: 1573-6881
    Keywords: P515 ; electrochromic bandshift ; ATPase ; ATP hydrolysis ; spinach chloroplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The P515 absorbance change upon single-turnover light flashes has been studied in intact leaves and isolated chloroplasts from spinach. A comparative study of the effects of preillumination on the kinetics of the P515 response and on the activity of the chloroplast ATPase has been made. The slow component (reaction 2) in the flash-induced P515 response normally present in dark-adapted chloroplasts is reduced or even absent under conditions in which the ATPase is activated by preillumination. This suppression of reaction 2 appeared to be temporary in leaves and chloroplasts; its duration in chloroplasts is shown to be dependent on the amount of ATP present. Tentoxin inhibits the preillumination-dependent suppression of reaction 2.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 4125-4133 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of copolymers based on poly(tetramethylene terephthalate) containing poly(tetramethylene oxide) blocks whose molecular weights ranged from 1000 to 5000 in concentrations from 10 to 30% by weight was prepared. The polymers were melt spun into fibers and the undrawn fibers dyed with a disperse dye at three temperatures. The equibrium adsorption and diffusion coefficient of the dye increased with both the molecular weight and concentration of the polyether. The equilibrium adsorption varied linearly with both the molecular weight and concentration. It has been assumed that the equilibrium dye partition coefficient KM gives a parameter of the accessibility, V, of the fiber for dye. If the diffusion coefficient DM is given by DM = VDo/τ, where Do is the diffusion coefficient of the dye in the amorphous regions and τ is a tortuosity factor, a good correlation can be obtained between KM and DM, suggesting that changes in Do/τ vary in a systematic fashion.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 4087-4094 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The rate of acid hydrolysis of a basic dyeable polyester in water, before and after heat-setting, has been investigated. Intrinsic viscosity measurements and chemical analysis have been used to establish experimental conditions under which the hydrolysis is inhibited. It is suggested that the critical stage of the hydrolysis mechanism is the exchange of sodium ions from the sulphonate groups in the fiber for hydrogen ions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: High-density polyethylene up to about 30% by weight was melt-mixed with polypropylene and short-glass-fiber-reinforced polypropylene. The presence of high-density polyethylene and glass fibers in the polypropylene matrix affects its crystallization characteristics, which were studied with the help of differential scanning calorimetry. The blend and composite samples have a large number of polypropylene domains apparently due to an abundance of surface nuclei; as a result, the tensile strength, tensile modulus, and toughness are enhanced. The temperature dependence of shear modulus and logarithmic decrement indicate that high-density polyethylene can have plasticizing effect below the glass transition temperature of polypropylene. The scanning electron micrographs of fractured ends show the presence of dispersed domains in the composite samples.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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