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Biomedical subjects

E Bamberg

Publications and source records attributed to E Bamberg.

At least 145 records · Page 8Linked to original sources
PubMed1975

[Frequently recurring cyclic megakaryocytopenic-thrombopenic purpura].

An unusual case of acquired frequently remitting megakaryocytopenic-thrombocytopenic purpura in a 54 years old man is reported. The patient could be followed up anamnestically for 11 years. Regularly megakaryocytopenic-thrombocytopenic periods were followed by complete remissions. Platelet survival was normal in thrombocytopenic and in remission phases. No immune mechanism could be detected. The exceptional position of this disorder within the inhomogenous group of intermittent thrombocytopenic purpuras is discussed, and the common criteria with three other published cases are pointed out.

Adult↗
PubMed1975

Correlation analysis of electrical noise in lipid bilayer membranes: kinetics of gramicidin A channels.

If a membrane contains ion-conducting channels which form and disappear in a random fashion, an electric current which is passed through the membrane under constant voltage shows statistical fluctuations. Information on the kinetics of channel formation and on the conductance of the single channel may be obtained by analyzing the electrical noise generated in a membrane containing a great number of channels. For this purpose the autocorrelation function of the current noise is measured at different concentrations of the channel-forming substance. As a test system for the application of this technique we have used lipid bilayer membranes doped with gramicidin A. From the correlation time of the current noise generated by the membrane, the rate constants of formation (k-R) and dissociation (k-D) of the channels could be determined. In addition, the mean square of the current fluctuations yielded the single-channel conductance lambda. The values of k-R, k-D, and lambda obtained from the noise analysis agreed closely with the values determined by relaxation measurments and single-channel experiments.

Binding Sites↗
PubMed1975

On the determination of free L-tryptophan.

The determination of free L-tryptophan depends on several analytical well checked points e.g. absorbing effects, pH of the serum, dependence of the throughput, concentration dependence of retention, volume ultrafiltrated, cut-off, temperature dependence of the binding rate, purification on ion-exchange column, interfering substances of the fluorometric method. Ultrafiltration was compared to an ultracentrifugation technique. In normal human serum the concentration of free L-tryptophan is 3,1 +/- 0,6 microgram/ml and of the bound plus free form 12,2 +/- 1,12 microgram/ml. Both values are dependent on the albumin concentration.

Collodion↗
PubMed1969

Nonlinear electrical effects in lipid bilayer membranes. I. Ion injection.

In this and the following papers a theoretical analysis of the current-voltage characteristic of lipid bilayer membranes is presented. In order to explain the observed nonlinearity, three different mechanisms have to be considered: the injection of ions into the membrane, the distortion of the potential energy profile, and the dissociation field (or Wien) effect. In this first part of the paper, the ion injection effect is analyzed. As both the ion concentration and the thickness of the membrane are extremely small, the constant field approximation can be introduced into the Nernst-Planck equations. In this way the general treatment of Bruner can be greatly simplified, so that the solution is obtained in closed form. The result shows that the ion injection effect gives a contribution to the current-voltage characteristic only at low ionic strength (< 10 (3)M) of the aqueous solution.

Electric Conductivity↗
PubMedDate not supplied

Bacteriorhodopsin mutants D85N, D85T and D85,96N as proton pumps.

Proton translocation in the BR mutants D85N, D85T and D85,96N was studied by attachment of purple membranes to planar lipid bilayers. Pump currents in these mutants were measured via capacitive coupling and by use of the appropriate ionophores. All mutants have a reduced pK of their Schiff bases around 8-8.5 in common. At physiological pH, a mixture of chromophores absorbing at 410 nm (deprotonated form) and around 600 nm (protonated form) coexists. Excitation with continuous blue light induces in all three mutants an outwardly directed stationary pump current. These currents are enhanced upon addition of azide in D85N and D85,96N by a factor of 50, but no azide enhancement is observed in D85T. Yellow light alone induces transient inwardly directed currents in the mutants but additional blue light leads to a stationary current with the same direction. All the observed currents are carried by protons, so that the consecutive absorption of a yellow and a blue photon leads to inverted stationary photocurrents by the mutants, as observed with halorhodopsin (HR). A mechanistic model describing the inversion of proton pumping is discussed by the cis-trans, trans-cis isomerization of the retinal and the different proton accessibility of the Schiff base from the extracellular or the cytoplasmic side of the membrane.

Journal Article↗