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. 2000 Aug 29;97(18):9855–9860. doi: 10.1073/pnas.97.18.9855

Figure 3.

Figure 3

An UME tip approaches (1) plastic surface, (2) MDA-MB-231 cell, (3) 11α cell, and (4) MCF-10A cell. Solid lines are the theoretical curves for an insulating substrate (1) and finite heterogeneous kinetics (2, 3, 4). Phosphate buffer (pH 7.4) contained (A) 20 μM menadione, (B) 30 μM 1,2-naphthoquinone, (C) 0.1 mM KI, and (D) 0.1 mM KI + 20 μM I2. (C) Curves for MDA-MB-231 and 11α cells were very similar to curve 4. (D) Curves 1–4 were essentially identical. The tip current is normalized by the iT value measured in the bulk solution. The tip was a 5.5-μm-radius carbon fiber (A and B), and 5-μm-radius Pt (C and D).