Photoreaction Unit Sheet of Rhodopseudomonas viridis

A sheet structure was prepared with the photoreaction unit (PRU), a complex of the reaction center and the light-harvesting chlorophyll proteins from Rhodopseudomonas viridis, by the dialysis method. The sheet had properties characteristic of a three-dimensional thin crystal. The absorption spectrum and the protein subunit composition of PRU were maintained during the sheet formation. Electron microscopy observation found that PRU molecules are regularly arrayed and stacked in the sheet. The sheet showed linear dichroism in the absorption spectrum, indicating also that chromophores in the sheet were arranged with orientation.