PLATINIZATION - A NOVEL TECHNIQUE TO ANCHOR PHOTOSYSTEM-I REACTION CENTERS ONTO A METAL-SURFACE AT BIOLOGICAL TEMPERATURE AND PH

Photosystem I (PSI) reaction centre core antenna complexes containing about 40 chlorophylls per P700 (PSI-40) are 6 nm biological photovolta ic devices. PSI particles carry positively-charged domain(s) and can t herefore interact electrostatically with a negatively-charged surface. PSI particles were platinized by reduction of [PtCl6](-2) at neutral pH and 20 degrees C. The presence of metallic platinum on PSI particle s was observed directly by scanning tunnelling microscopy (STM). The p latinized PSI particles were larger than control PSIs (without platini zation), due to the presence of metallic platinum. The electric proper ties of PSI and metallic platinum were characterized by STM tunnelling conductance (I-V) measurements. Diodic response was obtained in plati nized PSI. Metallic platinum formed during the reduction of [PtCl6](2- ) caused bonding between PSI particles and a gold metal surface. Using the technique of chemical platinization, PSI particles can be ''welde d'' onto gold plates under biologically compatible conditions, resulti ng in a 2-dimensional spatial array of PSI particles anchored on the m etal surface. Metallic platinum is not only a good conductor but also an active catalyst. This platinization ''welding'' technique is potent ially important for both bioelectronics and biometallocatalysis.