Voltage gating

The dependence of the activity of ohmic synthetic ion channels and pores on the membrane potential, i.e. the voltage V applied to BLMs or the polarization of LUVs, follows Ohm s law 

The slope of the IV profile of ohmic ion channels and pores gives their conductance g (Fig. 11.4, 8c, dotted). Non-ohmic ion channels are ion channels that violate Eq. (11.4) (Fig. 11.8c, solid). Because of importance in biology and materials science, the creation of non-ohmic ion channels and pore has attracted considerable interest in supramolecular chemistry [2, 9]. The key parameter characterizing non-ohmic behavior is the gating charge Zg [5, 9]. 

Supramolecular chemists without BLM-workstation can determine gating charges in polarized vesicles (Fig. 11.8), using the HPTS assay for synthetic ion channels and the ANTS/DPX assay for synthetic pores (Fig. 11.5) [7]. To polarize vesicles, an inside-negative Nernst potential is applied with a potassium gradient (Eq. 11.6), osmotically balanced with sodium, coupled with the potassium carrier valinomycin at intermediate concentrations sufficient for rapid potential buildup without immediate collapse, and monitored by an emission increase of the externally added probe safranin O (Fig. 11.8a and b). 

V = Nernst potential R = gas constant T = absolute temperature z = +1 (charge of K ) F = Faraday constant. 

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Autoantibodies are directed against nicotinic acetylcholine receptors in myasthenia gravis, resulting in receptor loss, skeletal muscle paralysis, and dysfunction (100). In addition, antibodies directed against voltage-gated Ca " channels produce similar neuromuscular dysfunction of Lambert-Eaton... 

Capsaicin receptor" agonists capsaicin, resmiferatoxin II, Via voltage-gated channels maitotoxm ( ) OH ... 

Ionotropic Glutamate Receptors Voltage-dependent Ca2+ Channels Voltage-gated K+ Channels... 

Voltage-gated Ca2+ channels are Ca2+-selective pores in the plasma membrane of electrically excitable cells, such as neurons, muscle cells, (neuro) endocrine cells, and sensory cells. They open in response to membrane depolarization (e.g., an action potential) and permit the influx of Ca2+ along its electrochemical gradient into the cytoplasm. 

Like other voltage-gated cation channels, Ca2+ channels exist in at least three states A resting state stabilized at negative potentials (such as the resting potentials of most electrically excitable cells) that is a closed state from which the channel can open. The open state is induced by depolarization. Channels do not stay open indefinitely because they are turned off during prolonged depolarization by transition into an inactivated state. Inactivation is driven both by depolarization... 

Ca2+ Channel Blockers. Figure 1 Most voltage-gated Ca2+ channels exist as a hetero-oligomeric complex of several subunits, a 1 subunits form the Ca2+-selective ion pore and contain the voltage-sensors of the channel. 

Catterall WA, Perez-Reyes E, Snutch TP et al (2005) International Union of Pharmacology. XLVIII. Nomenclature and structure-function relationships of voltage-gated calcium channels. Pharmacol Rev 57 411-425... 

Furthermore, PKCe is required for nerve growth factor-induced activation of mitogen-activated protein kinases and neurite outgrowth by ethanol. It is also required for ethanol-induced increases in N-type voltage-gated calcium channels in PC 12 neural cells. 

Inward Rectifier K+ Channels. Figure 1 The role of inward rectifier (Kir) channels in cardiac action potentials. Depolarization is generated and maintained by Na and Ca currents (/Na, /Ca). Voltage-gated K currents (Kv) and Kir channels contribute to repolarization and maintenance of a negative resting potential. 

Kv 3 -subunits are auxiliary subunits of Shaker-related Kv-channels, which belong to the Kvl subfamily of voltage-gated potassium channels. Kv(3 -subunits may function as chaperones in Kva -subunit assembly and may modulate the gating properties of Kv-channels. In particular, some Kv(3 -subunits may confer a rapid inactivation to otherwise non-inactivating Kv-channels. 

Kv-channel is an abbreviation of voltage-gated potassium channels. K stands for potassium and v for voltage. 

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