Alzheimer's disease (AD) is characterized by the presence of senile plaques in the brain and blood vessel walls. Amyloid Beta A4 (A 4) protein has been found to be the principal constituent of senile plaques of AD's patients (1-2). The amyloid beta-protein precursor (APP) is proteolytically cleaved to generate the 4 kDa A 4 protein. Two variants of A 4 can be detected; A 1-40 "short-tailed" and A 1-42 "long-tailed" (3-4).