Multifunctional S-layer proteins as building blocks for hybrid materials

Nanostructured bio-inorganic hybrid materials are very attractive for technical applications, e.g. nanocatalysts, photocatalytic materials, sensors and filter systems. Self-assembling biomolecules like Surface layer (S-layer) proteins represent a promising tool as hybrid material due to their ability to self-assembly in aqueous solutions and on surfaces. In nature S-layer proteins coat the bacterial and archaeal cells with a highly ordered nanostructure and defined symmetry and fulfill various functions, e.g. protection, binding matrix for exoenzymes and molecular sieves. Isolates, which were taken from a uranium mining waste pile in Saxony, produce S layer proteins to protect themselves from heavy metals and radionuclides. If the S layer proteins are saturated with heavy metals or radio nucleotides, the protein will be rejected and a new one will be produced.

We take advantage of the high affinity to heavy metals to produce hybrid filter materials from micro sieves and S-layers. The so called “S-sieves” will be able to bind heavy and noble metals from aqueous solutions even in low concentration ranges economically.

Another aspect will be the synthesis of Pd, Pt and Au nanoparticles on S-layer proteins. Pd and Au nanoparticles were built in the pores of S-layer proteins. Due to that a surface of nanoparticles of a defined size and regularly arrangement can be constructed. Those surfaces will work as nanocatalysts for many technical applications, e.g. the production of CNTs which has already been demonstrated.

Further work deals with the design of a hybrid materials which will work as photocatalysators for drinking water purification. Especially pharmaceuticals can be disintegrated by radicals. The radicals are formed in sunlight and in presence of the catalytic active ZnO- or TiO2-nanoparticles which are coupled and regularly arranged on S-layer protein interface.

These three examples emphasize the use of S-layer proteins their potential in nanotechnology and will give new prospective in the mentioned techniques.