[1] BOSTON BIOMED RES INST, DEPT MUSCLE RES, BOSTON, MA 02114 USA
[2] HARVARD UNIV, SCH MED, DEPT NEUROL, BOSTON, MA 02115 USA
[3] HARVARD UNIV, SCH MED, DEPT BIOCHEM, BOSTON, MA 02115 USA
[4] MASSACHUSETTS GEN HOSP, DEPT NEUROL, BOSTON, MA 02114 USA
[5] PENN STATE UNIV, DEPT CHEM, UNIVERSITY PK, PA 16802 USA