The molecular construction of a reaction center with quinonyllipid at the air-water interface was examined. Quinonylphospholipid, N-(12-(3-(2-chloro-1,4-naphthoquinonyl))aminododecanoyl) dipalmitoyl-L-alpha-phosphatidylethanolamine (Q-DPPE) was synthesized. A monolayer of a mixture of Q-DPPE and DPPE (1:9) was formed on the water surface under which quinone-depleted bacterial photosynthetic reaction centers (RC(-Q)s) from Rhodopseudomonas viridis were injected into the subphase. RC(-Q) binding to the Q-DPPE monolayer was observed with the increment of surface area. The deposited film contained a high density of RCs : 4.9 x 10(11) molecules cm-2. RCs in the film showed photobleaching indicating that the quinone moiety of Q-DPPE was incorporated into the quinone binding site of the RC.