Experiments using sub-peptides of Aβ42 revealed that the epitope identified by the antibody A8, as described by Ying and coworkers, lies within the 1-6 region of Aβ. The antibody displays high affinity for soluble Aβ42 oligomers in the molecular weight range of 16.5-25 kDa, and detected target antigen in brain sections from senescence-accelerated SAMP 8 mice. Amidated or acetylated and amidated forms of the sequence were used for example for quantitative structure retention relationships (QSRR) experiments. The latter could allow prediction of reversed-phase high-performance liquid chromatography (HPLC) retention of peptides, as reported by Kaliszan and coworkers.