1. University of Pennsylvania, Institute for Medicine and Engineering, 1010 Vagelos Research Laboratories, 3340 Smith Walk, Philadelphia, Pennsylvania 19104, Department of Physiology, Medical Academy of Bialystok, 15-230 Bialystok, Poland, Peptide Synthesis Laboratory, Organiskas Sintezes Instituts, Aizkraukles Iela 21, Riga LV-1006, Republic of Latvia, and Laboratoire des Biomembranes et Messagers Cellulaires, CNRS UMR 8619, Université Paris XI, 91405 Orsay Cedex, France