The binding energies between luciferin and luciferase adsorbed on a Si surface were estimated by docking simulations. These binding energies were more stable on a hydrophilic Si surface than on a hydrophobic Si surface, but their difference was small. Luciferase adsorbed more strongly on the hydrophobic Si surface than on the hydrophilic Si surface. The luciferase active site was not covered by the Si surface in this adsorption state. The hydrophobic surface would be suitable for the immobilization of luciferase both from the viewpoints of the binding of luciferin to luciferase and the adsorption of luciferase to the Si surface. (C) 2007 Elsevier B.V. All rights reserved.