SPECIFIC BINDING OF PHOTOSYNTHETIC REACTION CENTERS TO HERBICIDE-MODIFIED GRATING COUPLERS

The photosynthetic reaction centre (RC) of Rhodobacter sphaeroides binds not only ubiquinones, but also most of the photosystem II herbicides. This binding has been observed by several means, usually using free herbicides capable of moving into the quinone binding site. It is shown that the binding process can be observed directly, i.e., in real time, if a herbicide derivative is immobilized on a grating coupler surface and the RC is solubilized with the aid of a stabilizing detergent; it also binds if incorporated in an artificial membrane forming liposomes. The specificity of the binding is demonstrated by binding inhibition by an overdose of free quinones and photosystem II herbicides. First quantitative analyses are reported, showing the direction for a new kind of sensing device.