Self-assembly of gold nanoparticles in protein crystal

We developed a method to assemble gold nanoparticles three-dimensionally into a lysozyme crystal. The crystals were formed by incubating a crystallization solution containing lysozyme and gold nanoparticles at 20 °C. Observation of the crystals by an optical microscope revealed that the gold nanoparticles were assembled in {1 0 1} sectors of the tetragonal lysozyme crystal. The distribution coefficients of the gold nanoparticle into the crystal were measured as functions of pH and concentrations of NaCl. It was revealed that the gold nanoparticles are assembled into the crystal by an electrostatic interaction between the gold nanoparticles and the lysozyme on the crystal surface.