A novel constrained peptide epitope derived from ?ß wherein the eptitope comprises the amino acid sequence SNK related antibody compositions and methods of use. An isolated antibody that specifically binds to a cyclic peptide comprising the conformational epitope which comprises the amino acid sequence SNK and corresponding to a solvent exposed antibody accessible knuckle region of oligomeric ?ß is described. An antigenic peptide comprising an epitope having a constrained cyclic configuration which comprises the amino acid seqeuence SNK and corresponding to a solvent exposed antibody accessible knuckle region of oligomeric ?ß is also described. Methods of treating preventing and diagnosing Alzheimer s disease are also described.
