Ionic specificity of the gramicidin channel and the thallous ion

The thallous ion was found to interact very specifically with gramicidin channels in black lipid membranes. Although the ion itself carries current through the channel better than Na⁺ or K⁺, it blocks Na⁺ currents at concentrations which are two orders of magnitude lower than the Na⁺ concentrations.     

High affinity binding of thrombin to platelets. Inhibition by tetranitromethane and heparin

[¹²⁵I] iodo-α-thrombin has been modified at the macromolecular substrate binding site in order to study the importance of this region in the platelet-thrombin interaction. Modification was effected by the nitration of tyrosine residues with tetranitromethane. This chemical modification abolished the ability of the enzyme to bind with a high affinity to the platelet surface but did not significantly alter low affinity binding. The presence of heparin was also found to inhibit high affinity binding. These results indicate that the high affinity binding site interacts with the fibrinogen binding region of the thrombin molecule and suggests that there are two distinct classes of binding sites for thrombin on the platelet membrane.     

Eine ornithologische Studienfahrt in den Parco Nazionale d'Abruzzo

Ohne Zusammenfassung(Mit den Tafeln I und II)     

Spiza?tus alboniger (Blyth) undSpiza?tus nanus Wallace, zwei f?lschlich vereinigte Arten

Ohne Zusammenfassung