1. W. R. Perkins, R. B. Dause, R. A. Parente, S. R. Minchey, A. S. Janoff, The Liposome Company, Inc., 1 Research Way, Princeton, NJ 08540, USA.
2. K. C. Neuman and S. M. Gruner, Department of Physics, Princeton University, Princeton, NJ 08544, USA.
3. T. F. Taraschi, Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.