A Light-Modulated Sequence-Specific DNA-Binding Peptide This work was supported by the Spanish M.E.C. (PB97-0524) and the Xunta de Galicia (XUGA 20906B96). A.M.C and E.V. thank the Xunta de Galicia and the University of Santiago for their predoctoral fellowships. We are grateful to Prof. M. Mosquera and Prof. J. Benavente for allowing us to use the spectrofluorimetry and radioactivity facilities, respectively, and to Dr. Chris Abell (Cambridge University, Iberdrola Visiting Professor at the University of Santiago) for critical reading of the manuscript.