Analysis of N-Terminal Fragment of β-Amyloid Peptides Using an Aerolysin Nanopore

Alzheimer's disease(AD) is one of the most common diseases caused by multiple neurodegenerative protein misfolding and aggregation disorders. Abnormal deposition of amyloid protein caused by beta-amyloid ( A beta ) peptides has been suggested as a possible predisposing factor for Alzheimer's disease. Unlike human A beta peptide, rodent A beta peptide rarely has these characteristic lesions. The difference between rodent A beta peptide and human A beta peptide is that the 5th, 10th and 13th amino acids(Arg, Tyr, His) are replaced by Gly, Phe and Arg, respectively. In this study, molecular dynamics simulation and nanopore-based single molecule detection technology were used to study the structural differences between human AJ3 1 -15 and rodent AJ31-15. The experimental results show that rodent AJ3 1 -15 has lower blocking frequency and energy barrier when passing through nanopore than human AJ3 1 -15 , which proves that aerolysin nanopore can distinguish AJ3 1 -15 with small structural differences. Furthermore, the interaction between AJ3 1 -15 and sulfate ion was studied by using sulfate K2SO4 as a simplified model of glycosaminoglycan ( glycosaminoglycans , GAGs). Statistical analysis showed that both peptides could bind to sulfate ions and reduce their capture frequency by aerolysin nanopore, reducing the capture frequency of human AJ31-15by 25% and rodent AJ3 1 -15 by 59%. However, after the addition of sulfate ion, there was a significant difference in the dwell time of the two peptides. Compared with the results in the absence of sulfate, the dwell time of human AJ3 1 -15 increased by 14% and that of rodent AJ3 1 -15 decreased by 7%. It is inferred from the experimental results that the different sequences and conformations of the two peptides lead to different binding ways and binding intensity to sulfate ions, which have different effects on the translocation behavior. This study is helpful to better screen small molecular inhibitors and further promote the diagnosis and treatment of Alzheimer's disease.