Volume dependence of rate constant in passive transport.
(a) Histogram of rate constants for passive transport obtained from single-exponential fits to the traces in Fig. 3b. Each bin is 0.00007 s−1 in 3-fL chambers (black, top), 0.00025 s−1 in 800-aL chambers (cyan, middle) and 0.001 s−1 in 200-aL chambers (magenta, bottom). The dark-coloured lines show double Gaussian fits to each histogram excluding the left-most, which corresponds to empty chambers. The inset shows a magnified region between 0–100 counts on the y-axis. The rate constants of passive transport by single α-haemolysin molecules obtained from the Gaussian fits are 0.26 × 10−3, 1.1 × 10−3 and 4.0 × 10−3 s−1 for chambers with 471 nm, 116 nm and 30 nm heights, respectively. (b) The proportion of active chambers reflecting α-haemolysin incorporation. The data and errors are obtained from Fig. 4a. The grey dashed line represents the average of all probabilities, 41.3%. (c) Volume dependence of the rate constant for fluorescent decay by single α-haemolysin. The data and errors are obtained from Fig. 4a. The grey dashed line represents a linear fit with a correlation coefficient of 1.0.