Development of a pretreatment method for amyloid β-protein analysis based on the effect of acetic acid on the dissolution of plasma polypeptides

During the evaluation of a pretreatment method for the simultaneous quantification of four amyloid β-protein fragments in transgenic mice plasma by a new gradient system, we have found that acetic acid has potency to completely dissolve plasma polypeptides in the presence of an organic solvent. Based on this observation, we designed a simple pretreatment method using an ultrafiltration membrane. An analysis of the filtrate obtained by this method suggests the possibility that acetic acid inhibits the interaction between amyloid β-protein fragments and plasma polypeptides, which leads to a higher recovery of the amyloid β-protein fragments from mouse plasma. In addition, higher dilution of mouse plasma using a dilution solution produced higher recovery as well. The highest recovery of amyloid β-protein 1–38, 1–40, 1–42 and 1–43 fragments was 101.7, 94.9, 96.2 and 84.8%, respectively. Furthermore, calibration curves with the lower limit of quantification of 0.65 nm were successfully constructed with good accuracy using the developed method. Consequently, a pretreatment method using an ultrafiltration membrane is a powerful tool to determine the amyloid β-protein fragments in transgenic mice plasma containing an abundance of plasma polypeptides such as albumin. Copyright © 2008 John Wiley & Sons, Ltd.