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Lecture13-2009W - the total surface area 2 Nature of...

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Structure & Function of Ion Channels: e.g. Na+ Channels ion channel Top view Channel pore Membrane topology Quaternary structure of Na + channel barb2right α -subunits + β -subunit(s) In general, the structure of ion channels is well conserved. But they are different in detail (think about the ion selectivity). K + channel Ca 2+ channel Primitive K + channel
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Patch clamping technique barb2right late 70’s, Drs. E. Neher & B Sakmann Unitary currents Summated Types of configuration (1) Cell-attached (2) Whole-cell patch (3) Outside-out patch (4) Inside-out patch Features of Voltage-gated ion channels, with related to AP generation barb2right Na+ & K+ channels 1. Distribution of ion channels in neuronal membrane barb2right nonmyelinated axon, node of Ranvier, cell body etc. barb2right (e.g.) 100 -500 Na channels / μ m 2 , very small fraction of
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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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Lecture13-2009W - the total surface area 2 Nature of...

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