1. Basic Research Program, SAIC-Frederick, Inc., Center for Cancer Research Nanobiology Program, NCI-FCRDC, Frederick, Maryland 21702, Departament d'Enginyeria Química, E. T. S. d'Enginyeria Industrial de Barcelona, Universitat Politécnica de Catalunya, Diagonal 647, Barcelona E-08028, Spain, and Sackler Institute of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel