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  • Springer  (305)
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  • 1
    Electronic Resource
    Electronic Resource
    The oscillator strength of theC 2 Swan bands (1985)
    Springer
    The European physical journal 321 (1985), S. 75-77 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Litetimes of six individual rotational levels in theν=0 vibrational level of the3 π g state of C2 were measured by monitoring the fluorescent decay after pulsed laser excitation. A value of 92±5 ns was obtained, 25% lower than previous measurements. The corresponding oscillator strength for the Swan (0-0) band isf 00=0.032±0.002, in agreement with recent theoretical work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411947
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  • 2
    Electronic Resource
    Electronic Resource
    Nachweis von Corticosteroiden in menschlicher Placenta und Isolierung von 16α-Hydroxytestosteron (1961)
    Springer
    Cellular and molecular life sciences 17 (1961), S. 510-512 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The occurrence of cortisol, cortisone, 20-dihydrometabolites of cortisone and several other steroidlike compounds in fresh placental tissue is described. Neither aldosterone, corticosterone nor 11-dehydrocorticosterone has been found. One of the most abundant compounds present has been identified as 16α-hydroxy-testosterone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02158627
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  • 3
    Electronic Resource
    Electronic Resource
    Zur Histo- und Cytotopik der unspezifischen alkalischen Phosphatase (1960)
    Springer
    Histochemistry and cell biology 2 (1960), S. 87-104 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00744574
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  • 4
    Electronic Resource
    Electronic Resource
    Untersuchungen an synthetischem Hydroxylapatit im Hinblick auf den Knochenstoffwechsel von Calcium, Strontium, Barium und Radium (1968)
    Springer
    Radiation and environmental biophysics 5 (1968), S. 55-65 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Description / Table of Contents: Zusammenfassung Das zeitliche Verhalten inkorporierter radioaktiver Erdalkalien im Knochen wird in einer Kette von Mechanismen durch das langsamste Glied bestimmt. Dieses ist durch den Austausch der anorganischen Knochenkristallite mit der umgebenden Lösung gegeben. An Hand einer Suspension von Hydroxylapatitkristalliten wird versucht, der Potenzfunktion als Retentionsfunktion der Erdalkalien im Knochen ein physikalisches Bild zugrunde zu legen. Sie ergibt sich aus einer Überlagerung von Reaktionen erster Ordnung infolge einer Verteilung von Bindungsenergien der Ionen an die Oberfläche der Kristallite.
    Notes: Summary Influenced by a chain of mechanisms the time course of incorporated radioactive alkaline earths in bone is determined by the slowest link. This is given by the exchange of the anorganic crystals of bone with the surrounding solution. Using a suspension of hydroxyapatite crystals there is tried to explain the power function as a mathematical description of retention of alkaline earths in bone in physical terms. It results from superimposing first order reactions caused by a distribution of binding energies of the ions to the crystal surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01388132
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  • 5
    Electronic Resource
    Electronic Resource
    Untersuchungen an synthetischem Hydroxylapatit im Hinblick auf den Knochenstoffwechsel von Calcium, Strontium, Barium und Radium (1968)
    Springer
    Radiation and environmental biophysics 5 (1968), S. 42-54 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Description / Table of Contents: Zusammenfassung Das System Hydroxylapatitkristallite in einer geeigneten Lösung stellt in gewisser Hinsicht einin vitro-Analogon für den Knochenstoffwechsel der Erdalkalien dar. Es wird über Versuche berichtet, Unterschiede im Verhalten von Ca, Sr, Ba und Ra in synthetischem Hydroxylapatit festzustellen. Dazu wurden die Diskriminierungsfaktoren von Ca gegen Sr, Ba und Ra bei der Herstellung der Kristallite gemessen. Weiterhin wurde der Austausch der Erdalkalien zwischen vorgefertigten Kristalliten und einer geeigneten Lösung über eine Zeitdauer von 1000 h verfolgt. Die Diskriminierungsfaktoren nehmen mit zunehmender Ionengröße in der Reihenfolge Sr, Ba, Ra zu. Während Sr, Ca-Ionen auch im Inneren der Kristallite ersetzen kann, sind Ba und Ra fast ausschließlich auf die Oberfläche beschränkt. Für die Diskriminierung des Gesamtknochens muß angenommen werden, daß zusätzliche Prozesse eine Rolle spielen.
    Notes: Summary The system hydroxyapatite crystals in a proper solution, in a way, represents anin vitro analogue to metabolism of alkaline earths in bone. Experiments are described to find differencies in the behaviour of Ca, Sr, Ba and Ra to synthetic hydroxyapatite crystals. Synthesizing the crystals the discrimination ratios of Ca to Sr, Ba and Ra were measured. Furthermore the exchange of alkaline earths between preformed crystals and a proper solution was studied over a period of 1000 h. The discrimination ratios grow larger with increasing ionic radius in the order Sr, Ba, Ra. While Sr can replace Ca ions also in the interior of the crystals, Ba and Ra are limited to crystal surface. With respect to the discrimination of bone it must be concluded that further processes participate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01388131
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  • 6
    Electronic Resource
    Electronic Resource
    A laser-T-jump study of the adsorption of dipolar molecules to planar lipid membranes (1988)
    Springer
    European biophysics journal 15 (1988), S. 299-310 
    Details
    ISSN: 1432-1017
    Keywords: Adsorption ; lipid membranes ; laser-T-jump ; Langmuir isotherm ; 2,4-D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The adsorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as well as of other dipolar molecules to the interface of artificial lipid membranes gives rise to a change of the dipole potential between the membrane interior and water. As a consequence of the adsorption of the neutral species, the conductance of planar membranes, observed in the presence of the macrocyclic ion carriers nonactin or valinomycin, may change by many orders of magnitude. Using this effect in combination with a laser-T-jump technique, the kinetics of the adsorption process were measured and were interpreted on the basis of a Langmuir-isotherm. A partition coefficient (at small concentrations) of β HA =4.7·10−4 cm, a rate constant of desorption k HA≧100 s-1 and a maximum surface density N D=7.7·1013/cm2 were found. The concentration at half saturation is K HA=2.7·10-4 M. Using these values the membrane conductance induced by the ion carrier nonactin and the shape of the current-voltage relationship as a function of the ligand concentration in water was analyzed. A maxiumum dipole potential of V D max =-239 m V and a contribution of b=3.1·10-15V cm2 per single adsorbed 2,4-D molecule was found. 74% of the dipole potential acts on the inner membrane barrier separating the two interfacial adsorption planes of nonactin. The remainder (26%) favours interfacial complex formation between nonactin and K+ from the aqueous phase. The data hold for membranes formed from dioleoyllecithin in n-decane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00256481
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of ion transport in lipid membranes induced by lysine-valinomycin and derivatives (1979)
    Springer
    European biophysics journal 6 (1979), S. 39-56 
    Details
    ISSN: 1432-1017
    Keywords: Lipid membranes ; Valinomycin ; Ion transport ; Fast kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Lysine-valinomycin and two N∈-acyl derivatives are compared with respect to their potency to transport Rb+ ions across thin lipid membranes. Lysine-valinomycin acts as a neutral ion carrier only above a pH of about 7 of the aqueous solutions, while at lower pH the molecules seem to be positively charged due to a protonation of the ε-NH2 group of the lysine residue. A kinetic analysis based on voltage jump relaxation experiments and on the nonlinearity of the current-voltage characteristics showed that the conductance increment λ per carrier molecule for uncharged lysine-valinomycin is similar to that of natural valinomycin. The attachment of a rather bulky side group such as the dansyl or para-nitrobenzyloxycarbonyl group reduced λ by approximately one order of magnitude. Some of the relaxation data of the valinomycin analogues were influenced by an unspedfic relaxation of the pure lipid membrane. This structural relaxation represents a limitation to the possibility of analyzing specific transport systems in thin lipid membranes by the voltage jump or charge pulse techniques. It is shown that the time dependence of this structural relaxation — which was first published by Sargent (1975) — is at variance with a three capacitor equivalent circuit of the membrane, which was suggested by Coster and Smith (1974) on the basis of a.c. measurements. A modified equivalent circuit has been found to represent a satisfactory analogue for the current relaxation in the presence of valinomycin. It turned out, however, that such an equivalent circuit provides little insight into the molecular mechanism of transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00537594
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  • 8
    Electronic Resource
    Electronic Resource
    A laser-T-jump study of the adsorption of dipolar molecules to planar lipid membranes (1988)
    Springer
    European biophysics journal 15 (1988), S. 321-328 
    Details
    ISSN: 1432-1017
    Keywords: Adsorption ; lipid membranes ; laser-T-jump ; Langmuir isotherm ; phloretin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Phloretin and structurally related neutral molecules adsorb to the interface of lipid membranes and modify the electric dipole potential of the membrane/water interface. The adsorption process has been studied using a laser-T-jump relaxation technique in combination with an analysis of nonactin mediated potassium transport (see part I, Awiszus and Stark 1988). Deviations from the Langmuir isotherm were observed for most of the substance. The discrepancies were most pronounced at large surface densities, whereas good agreement was found at low concentrations in many cases. The partition coefficient in the limit of low concentrations was compared with that of octanol/water bulk phases. No correlation was found. The individual values of the two partition coefficients differed by more than three orders of magnitude. The contribution, b, of a single adsorbed molecule to the dipole potential could not be predicted from the dipole moment, μ L , of the molecule measured in the bulk phase. Different values of b were found at identical values of μ L . The study shows the limitations of the use of bulk phase data to predict molecular properties in lipid membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254719
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  • 9
    Electronic Resource
    Electronic Resource
    Optical and electrical studies on dansyllysine-valinomycin in thin lipid membranes (1976)
    Springer
    European biophysics journal 2 (1976), S. 119-137 
    Details
    ISSN: 1432-1017
    Keywords: Valinomycin ; Lipid membranes ; Fluorescence ; Relaxation methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary Dansyllysine-valinomycin, a fluorescent analogue of the ionophore valinomycin was synthesized and incorporated into black lipid membranes. Its concentration inside the membrane was measured fluorometrically and was also determined from electrical relaxation experiments, which were analyzed on the basis of a previously proposed carrier model. The results of both methods agreed within less than one order of magnitude. This appears satisfactory in view of the sources of error inherent in both procedures. A conductance increment per carrier molecule of about 3 · 10−17 Ω−1 was obtained for dansyllysine-valinomycin in diphytanoyllecithin membranes at 25
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863705
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  • 10
    Electronic Resource
    Electronic Resource
    Exercise increases plasma concentrations of (R)- and (S)-propranolol (1996)
    Springer
    European journal of clinical pharmacology 50 (1996), S. 339-342 
    Details
    ISSN: 1432-1041
    Keywords: Key words Propranolol; stereoselectivity ; chirality ; enantiomers ; isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: We recently reported a highly stereoselective increase in plasma concentrations of (S)-atenolol during exercise which is most likely due to a release of the drug from adrenergic cells. The objective of the present study was to investigate the influence of physical exercise on plasma concentrations of the (R)- and (S)-enantiomers of propranolol. Methods: Blood samples were taken immediately before and at the end of exercise in 12 patients receiving chronic treatment with racemic (R, S)-propranolol. Plasma concentrations of (R)- and (S)-propranolol were determined by HPLC. Results: In contrast to atenolol, mean plasma concentrations of (S)-propranolol were significantly higher (+20%) than those of (R)-propranolol at rest. During exercise there was an increase in plasma concentrations of both (R)-propranolol (+129%) and (S)-propranolol (+109%). Conclusion: Based on information from in vitro studies we conclude that the increase in plasma concentrations of (S)-propranolol during exercise is caused by a release of the drug from adrenergic nerves, whereas the reason for the increase in (R)-propranolol remains to be determined. This release of the β-adrenoceptor blocking (S)-enantiomer directly at the synaptic gaps might be one reason for the poor correlation between plasma concentration and effect of β-adrenoceptor antagonists repeatedly described in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050119
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