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Unformatted text preview: the total surface area. 2. Nature of current flow through a single channel b (e.g.) 10,000 ions/msec @ emf (V m – E Na ) of -100mV b unitary current 3. Voltage-dependent gating b sliding helix model 4. Basis for channel selectivity b size, dehydration energy vs. site-interacting energy Voltage-dependent gating: (e.g.) Na channel Open Open S4 – positively charged (e.g. arginine) + + + + + + + + + + + + + + + + Channel selectivity: selectivity filter 1. Charges @ the opening of the ion channel 2. Size 3. Site-interacting > Dehydration b ion channels act as molecular sieves Na+ ion < K+ ion Hydrated Na+ > Hydrated K+ s Cation vs. Anion ? (Na + , K + ) (Cl-) s K + vs. Na + ? s Na + vs. K + ?...
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- Spring '09
- Electric charge, Ion channel, Voltage-gated ion channel, Potassium channel