Stereoselective determination of amino acids in beta-amyloid peptides and senile plaques

A novel method for the determination of the enantiomeric composition of pep tides is presented. In this paper, the focus has been on beta -amyloid pept ides from deceased Alzheimer's disease patients. The peptides are hydrolyze d using mineral acid. The free amino acids are derivatized with the chiral reagent (+)- or (-)-1-(9-anthryl)-2-propyl chloroformate and subsequently s eparated using micellar electrokinetic chromatography (MEKC) and detected u sing laser-induced fluorescence (LIF) detection. The high separation effici ency of the MEKC-LIF system, yielding similar to1 million theoretical plate s/m for most amino acids, facilitates the simultaneous chiral determination of nine amino acids. The samples that have been analyzed were standard 1-4 0 beta -amyloid peptides, in vitro precipitated beta -amyloid fibrils, and human senile plaque samples.