Figure 3.

Imaging membrane order with DNA Zippers. (a) MCF-7 cells were first treated with 10 mM of MβCD for 30 min, and then each pair of P₇ and P* probes was added for 20 min at 25°C before imaging. Cells without adding MβCD was used as the control. Pseudo-color I₆₆₀/I₅₂₀ ratiometric images were shown via excitation through a 488 nm laser. Scale bar, 20 μm. (b) Ratiometric signals on individual MCF-7 cell membranes as measured in the presence or absence of the MβCD pre-treatment. (c) MCF-7 cells were pre-treated with a mixture of 1 mM cholesterol and 10 mM of MβCD for 30 min (cholesterol supplementation) or a mixture of 1.5 mM sphingomyelin and 10 mM of MαCD for 5 min (sphingomyelin supplementation), and then each pair of P₇ and P* probes was added for 20 min at 25°C before imaging. Cells without the pre-treatment was used as the control. Pseudo-color I₆₆₀/I₅₂₀ ratiometric images were shown via excitation through a 488 nm laser. Scale bar, 20 μm. (d) Ratiometric signals on individual MCF-7 cell membranes as measured in the presence or absence of the cholesterol or sphingomyelin supplementation. (e) Ratiometric signals on individual MCF-7 cell membranes either without the pre-treatment (0 mM) or pre-treated with a mixture of 10 mM of MβCD and 0.1-, 0.25-, or 0.75-mM cholesterol for 30 min at 25°C. Shown are the mean and SEM values obtained from at least 20 cell membranes in each case. *p< 0.05, ***p< 0.001 in two-tailed Student’s t-test; ns, not significant. C-P₇, S-P₇, and T-P₇ represent cholesterol-, sphingomyelin-, and tocopherol-modified DNA donor probes. C-P*, S-P*, and T-P* represent the corresponding cholesterol-, sphingomyelin-, and tocopherol-modified acceptor strands.