Stereoselective Determination of Amino Acids in β-Amyloid Peptides and Senile Plaques

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Abstract
A novel method for the determination of the enantiomeric composition of peptides is presented. In this paper, the focus has been on β-amyloid peptides from deceased Alzheimer's disease patients. The peptides are hydrolyzed using mineral acid. The free amino acids are derivatized with the chiral reagent (+)- or (−)-1-(9-anthryl)-2-propyl chloroformate and subsequently separated using micellar electrokinetic chromatography (MEKC) and detected using laser-induced fluorescence (LIF) detection. The high separation efficiency of the MEKC-LIF system, yielding ∼1 million theoretical plates/m for most amino acids, facilitates the simultaneous chiral determination of nine amino acids. The samples that have been analyzed were standard 1−40 β-amyloid peptides, in vitro precipitated β-amyloid fibrils, and human senile plaque samples.