Covalent modification of Alzheimer's amyloid β-peptide in formic acid solutions

Abstract

β-peptide is a normal component of amyloid deposits in Alzheimer's disease. In aqueous solution, β-peptide is extremely insoluble and rapidly aggregates forming oligomeric β-sheet structures that eventually precipitate from solution. Presumably, this process is related to the production of amyloid deposits in Alzheimer's disease. Formic acid is commonly used to dissolve the β-peptides and prevent aggregation in biological and biophysical studies. However, a side-reaction which covalently modifies β-peptide is encountered with formic acid. In this report, fast atom bombardment mass spectrometry and tandem mass spectrometry demonstrate that both Ser 8 and Ser 26 become O-formylated in 70% aqueous formic acid solutions. The implications of this O-formylation upon the aggregational properties of β-peptide are discussed.