This is a short fragment of the b-Amyloid peptide containing Histidine 13 and 14. Alzheimer’s beta amyloid peptides form A? ion channels in lipid bilayers. It is postulated that ion channel activity of A? is related to cytotoxic activity of A?. Small peptides that contain the amino acid sequence of the predicted mouth region of the A? channel pore can inhibit A? ion channel activity. And, Histidines 13 and 14 have been shown to be essential for the peptide to inhibit Alzheimer’s disease A? ion channel and cytotoxicity.