Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
For full article and contact information, see Angew. Chem. Int. Ed. 2000, 39 (24), 4599 - 4602
Functional membrane proteins
in a block copolymer matrix
Biological membranes form a fluid matrix, in which proteins "swim". Many of these membrane proteins are of interest for both pharmacological and biotechnological applications - for example, they are under consideration as biosensors for the rapid screening of pharmaceutical agents. This requires the proteins to be anchored in an artificial membrane. In contrast to natural membranes, which are simultaneously highly flexible and enormously stable, the material properties of artificial membranes generally leave a lot to be desired.
A French-Swiss research team has now developed a new type of matrix for membrane proteins. This allows them to produce dense, extensive, planar membranes.
Natural membranes are made of lipids. Every lipid molecule has a water-soluble "head" and a non-water-soluble "tail". Thus, in an aqueous medium, these lipids stick tightly together, tail-to-tail, while their heads protrude into the solution. This is how a lipid bilayer is formed.
However, it isn’t only lipids that can form such membrane-like superstructures. Man-made polymers that are built up in a similar head-tail fashion can also aggregate into "membranes". By varying the molecular composition of these plastics, known as block copolymers, it is possible to generate specific membranes with a whole range of different properties.
Wolfgang Meier, Corinne Nardin and Mathias Winterhalter built proteins that form channels in biological membranes into their artificial polymer membranes. Afterward, the polymer molecules were cross-linked using UV light - to form a giant molecule. Conductivity measurements demonstrated that the proteins kept their biological functionality, even in this unnatural environment.
"It is clear that we can incorporate fully functional membrane proteins in our artificial matrix," Meier is pleased to say. "This allows us to combine the high stability and variability of artificial membranes with the specific functions of biological proteins." Meier predicts that the new protein-polymer hybrid materials will have a wide range of applications in areas such as diagnostics, sensor technology, protein crystallization and controlled release of pharmaceuticals.