Invitrogen human aβ42 elisa kit

Cortical tissue was harvested at 49 weeks of age, and prepared according to the protocol established for 5XFAD mice by Oakley, et al.^{10 (link)}. Specifically, following extraction, the tissue was flash frozen and re-suspended in 3 to 4 volumes of PBS-0.5% Triton supplemented with protease inhibitors (A32965 ThermoFisher, Waltham, MA). Tissue was homogenized with a Corning Dounce homogenizer (1234F35 Thomas Scientific, Swedesboro, NJ), freeze–thawed 3 times, and cleared at 15,000 rpm for 15 min at 4 °C. Cleared homogenates were supplemented with guanidine hydrochloride to a final concentration of 5 M to solubilize plaques. To detect human Aβ42 levels, cleared homogenates were diluted in Standard Diluent Buffer and measured by the Invitrogen Human Aβ42 ELISA kit (KHB3441, ThermoFisher, Waltham, MA) following manufacturer’s instructions. Final guanidine hydrochloride concentrations were under 0.1 M. All samples were run in duplicate; their readings fell within the range of the standard dose responses curve. Total protein was measured by a protein assay kit (5000002, Bio-Rad, Hercules, CA) and used for normalization.