Investigating the Structural Bases of Voltage-Gating Model Channels by Using Aligned Multilayer Samples.

摘要

The conventional biochemical methods have not been very successful in providing the structural information for membrane proteins, including membrane-active peptides. Our methods, including oriented circular dichroism and x-ray scattering with the momentum transfer in the plane of the membrane, exploit the structural orders provided by the smectic liquid crystals composed of membranes. With these new methods, we have resolved some long-standing controversial questions about alamethicin and gramicidin, two extensively researched peptides. More importantly we discovered a new phase transition phenomenon of amphiphilic helical pepitdes: at low concentrations, the peptides are found to bind parallel to the membrane surface; above a lipid-specific critical concentration, the peptides transform into a different state, e.g., perpendicularly inserted in the membrane. These transitions appear to be related to the membrane selective cytolytic activity of these peptides. The latter have now been recognized as a new class of antibiotics.... Uniformly aligned multilayers of membranes, X-ray diffraction, Oriented circular dichroism, Alamethicin, Gramicidin.