Beta-Amyloid (1-42), human

Beta-amyloid 1-42 (Aβ1-42) is a polypeptide composed of 42 amino acids, derived from the enzymatic cleavage of its precursor protein, and is considered one of the core pathogenic factors in Alzheimer's disease (AD). Although its monomeric form may have physiological functions such as antioxidant properties and promoting synapse formation under specific conditions, Aβ1-42 is highly prone to misfolding and aggregation due to its strong hydrophobicity. It progressively aggregates from monomers into soluble oligomers with strong neurotoxicity, and ultimately forms insoluble fibrils that constitute senile plaques. These aggregates, especially the oligomers, can bind to various receptors on the neuronal surface (such as NMDA receptors), disrupt calcium homeostasis, trigger oxidative stress and synaptic dysfunction, and ultimately lead to neuronal damage and death. Therefore, the abnormal aggregation of Aβ1-42 and the plaques it forms in the brain are key pathological hallmarks of AD, and the change in its ratio to Aβ1-40 also serves as an important clinical diagnostic indicator.