Figure 1.
Schematic representation of the experimental setup to measure the Φs of a fixed PC12 cell.
During the KPFM scan, the tip was lifted a height of 30 nm and applied with an alternative-current voltage (VAC sin (ωt)) and a direct-current voltage (VDC), and the substrate was connected to the ground.
Figure 2.
Various Φs distribution histograms of PC12 cell plasma membrane.
A fixed PC12 cell was air-dried and then a 66 µm2 region of the plasma membrane was scanned at a resolution of 256
128 pixels. Figures A and B show the simultaneously recorded AFM and KPFM images, respectively. C. The Φs from B was binned with 40 steps and the histogram was fitted with a two-peak Gaussian model (red line). The two Gaussian peaks were plotted in green and blue. D–E. Two other representative cells having Φs distribution histograms with differing skewness values.
Figure 3.
PS-micelles altered the Φs distribution histogram.
Figures A and B show the AFM and KPFM images, respectively, of a PC12 cell treated with PS-micelles. C. The Φs from B was binned with 40 steps and the histogram was fitted with a two-peak Gaussian model (red line). The two Gaussian distributions were plotted in green and blue. D. Averaged skewness in PC12 cells without treatment (control) or treated with PC- and PS-micelles (PC & PS, respectively). Data are expressed as mean ± SEM, and N = 11 for each group. * indicates p<0.05 (by Student's t-test) compared with the control group.
Figure 4.
Chemical treatments increased the surface PS content.
Figures A–D. The distribution plots of PC12 cells at various PI and annexin V fluorescence intensities, after treatment with different chemicals. Q1–Q4 represent four quadrants with various levels of PI and annexin V fluorescence intensities. E. The averaged P2 fraction across all cells. The P2 fraction (red) was the cells distributed in Q4 quadrant with FITC intensity over . The data represent mean
SEM from three batches of cells. ** indicates p<0.01 (by Student's t-test) compared with the control group.
Figure 5.
Oxidative stresses shifted the skewness to a positive value.
Figures A–D. are the AFM (left column) and KPFM (middle column) images from representative PC12 cells treated with plain buffer (Control), H2O2, dopamine, or Zn2+, respectively. The Φs values were binned with 40 steps, and the skewness value of each cell was analyzed (right column). The distribution was fitted with a two-peak Gaussian model (red line) and the two Gaussian curves were plotted in blue and green. E. Plots of the average skewness values of cells with various treatments. The sample numbers for groups A to D were 42, 14, 29, and 28, respectively. * and ** indicate p<0.05 and p<0.01, respectively, compared with the control group (by Student's t-test).