Page 37 - Cardiac Electrophysiology | A Modeling and Imaging Approach

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Figure 2.21. Effect of V and KCNQ1 channel current. A. The transmembrane potential field is
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perturbed by water penetration (arrow to ripples in equi-potential lines). B. Membrane
potential (V =100mV) stabilizes the open state, introducing a difference of ≈10 kJ/mol between
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closed and open configurations. C. Energy landscape at V = -80mV (left) and V =+60mV (right).
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Triangles are mean S4 position (red) and standard deviation (blue). Note stabilization of closed con-
figurations at negative potential and of open configuration at positive potential.
D. Markov model of KCNQ1. When all 4 subunits reside in the permissive state (left of dotted white
line on the energy landscapes) the channel can transition to the open states (O -O ). Inactivation
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occurs from O and a flicker blocked state is accessible from any conformation. E. Single channel
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current traces during a depolarizing pulse, computed by the model in panel D. F. Macroscopic
KCNQ1 current (sum of 1000 single channel currents). The hook (arrow) is characteristic of KCNQ1
current and is caused by channel recovery from inactivation. From Silva et al. [101], with permission.