Fig. 1

AFM topographical observation of the recognition of native or oxidized LDL by receptors (LDLR or CD36) pre-immobilized on micas. A LDLR only. B Native LDL particles only. C–F Binding of native LDL particles to LDLRs at pH 7.4, pH 6.4, pH 5.4, and pH 4.4, respectively. A–F Top panels: AFM topographical images; bottom panels: Schematic diagrams presenting the binding of LDL particles (brown) onto LDLR molecules (purple) pre-immobilized on mica (gray). AFM imaging was performed in PBS buffer at different pH values. G Quantitative analysis of the LDL–LDLR binding ratio at different pH values. H Quantitative analysis of the oxLDL–CD36 binding ratio at different pH values (the representative AFM topographical images are not shown). The control group (Ctrl) means the group incubating of LDL/oxLDL on a mica surface coated without receptors to exclude the possibility of nonspecific interaction. ^*p < 0.05, ^**p < 0.01, and ^***p < 0.001 compared with pH 7.4; ^#p < 0.05 compared with pH 6.4 (n ≥ 3 images in each group)