A quantitative assessment of models for voltage-dependent gating of ion channels.

Voltage-gated ion channels open and close, or "gate," in response to changes in membrane potential. The electric field across the membrane-protein complex exerts forces on charged residues driving the channel into different functional conformations as the membrane potential changes. To act with the greatest sensitivity, charged residues must be positioned at key locations within or near the transmembrane region, which requires desolvating charged groups, a process that can be energetically prohibitive.

Electrostatic model of S4 motion in voltage-gated ion channels.

The S4 transmembrane domain of the family of voltage-gated ion channels is generally thought to be the voltage sensor, whose translocation by an applied electric field produces the gating current. Experiments on hSkMI Na(+) channels and both Shaker and EAG K(+) channels indicate which S4 residues cross the membrane-solution interface during activation gating. Using this structural information, we derive the steady-state properties of gating-charge transfer for wild-type and mutant Shaker K(+) channels.

Mutual information in a dilute, asymmetric neural network model.

Neural networks with asymmetric synaptic connections (w(ij) not equal to w(ji)) display a broad range of dynamical behavior including fixed point, periodic, and "chaotic" trajectories. Previous work has shown that such networks undergo an order-chaos phase transition as various network parameters, such as the connectivity or the degree of asymmetry, are changed. Here, using an information theoretic approach, we present results which suggest that neurons are able to communicate information to each other most effectively in networks that are near the order-chaos transition.

Noise analysis of ion channels in non-space-clamped cables: estimates of channel parameters in olfactory cilia.

Ion channels in the cilia of olfactory neurons are part of the transduction machinery of olfaction. Odorant stimuli have been shown to induce a biphasic current response, consisting of a cAMP-activated current and a Ca(2+)-activated Cl- current. We have developed a noise analysis method to study ion channels in leaky cables, such as the olfactory cilium, under non-space-clamp conditions.

Noise analysis of the glutamate-activated current in photoreceptors.

The glutamate-activated current in photoreceptors has been attributed both to a sodium/glutamate transporter and to a glutamate-activated chloride channel. We have further studied the glutamate-activated current in single, isolated photoreceptors from the tiger salamander using noise analysis on whole-cell patch-clamp recordings. In cones, the current is generated by chloride channels with a single-channel conductance of 0.