Recent Advances in Nuclear Electrophysiology - Fig. 6 - Smallest

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Fig. 6. Theoretical and experimental amplitude histograms for patch-clamp recordings from the nuclear envelope. (a) Binomial distribution histograms (gray bars) for a population of N identical and independent ion conducting channels having two states: open and closed. N was set to 4, 8, 16 and 24 to predict the effect of the putative peripheral channels (thought to be 8 per NPC). The histograms on the left and right columns were generated for single channel open probability, p_open, of 50% and 70%, respectively. On the horizontal axis, the relative NE conductance amplitude is given. The number n represents the relative level of conductance (as ion channel opens and closes, their populations will display quantum jumps in the value of NE conductance). Therefore, n corresponds to the number of channels simultaneously open. On the vertical axis, the relative probability of finding the particular value of NE conductance is given. As the measured current is a continuous variable and is contaminated by noise, for each particular level, there is a normal distribution of values described by a Gaussian curve (black bell-shaped curves). The simulations were carried out with the binomial java applet given by Stark (2002). (b) Experimental histograms from 12 experiments. The histograms were generated with pClamp (Axon Instruments). As for our discussion, neither the height nor the width is relevant, to facilitate comparison, the peaks of each histogram was set to the same height. Although the width of the histograms are the same, they do not necessarily correspond to the same conductance interval because not all channels have the same conductance (e.g. one may be 350, the other may be 450 pS). Finally, note that the NE conductance starts at zero conductance (leftmost point in the axis).