Pierce fitc labeling kit

Each protein was reacted with fluorescein isothiocyanate following the user’s guide (Pierce FITC Labeling Kit; Thermo Scientific, Waltham, MA, USA). The excess fluorescent dye was removed by Slide-A-Lyzed MINI Dialysis Units (3, 500 MWCO; Thermo Scientific). The degree of labeling and the concentration of the FITC-labeled proteins were quantified by spectrophotometry at 280 nm and 495 nm.

Aβ1–42 (i.e., Aβ1–42 trifluoroacetate salt) and its FITC-labeled derivative (FITC-εAhx-Aβ1–42) trifluoroacetate salt was purchased from BACHEM (Bubendorf, Switzerland) (cat. no. H-8146 and H-7666) while recombinant ApoEs were purchased from Peprotech Germany, Hamburg, Deutschland. Aβ1–42 peptides (either unlabeled or fluorescently labeled) were kept lyophilized, while fresh Aβ1–42 solutions were prepared by dissolving the lyophilized Aβ1–42 in DMSO immediately prior to the experiments. Fluorescent labeling of ApoE isoforms was performed with the Pierce™ FITC Labeling Kit according to the manufacturer’s instructions (Thermo Fisher Scientific, Waltham, MA, USA, cat. no. 53027). The calculated yield of the labeling was 4.5 mol dye/ApoE. The even fluorescent labeling of the ApoE isoform was confirmed with spectrophotometry (Metertech UV/VIS) and gel electrophoresis (Supplementary Figure S8).