IonChannelsFinal

# Aim compute the probability of finding the channel

This preview shows pages 22–28. Sign up to view the full content.

Aim: compute the probability of finding the channel open, p open Boltzmann distr.: the probability of finding a state with energy E is If there is no external driving force, the energy as a function of σ is where ε open ( ε closed ) is the energy of the open (closed) state E = E( σ ) =?

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Ion channels under applied tension For concreteness, we begin by considering the case of mechanosensitive channels. Driving force: the tension in the membrane Mechanosensitive channels have been hypothesized to serve as safety valves to protect cells against membrane rupture due to osmotic imbalance.
Energy of Ion channel under applied tension => energy as a function of the applied tension τ where Δ A is the area change upon gating. In open state, the energy of the loading device is reduced favors the open state

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Energy landscape for an ion channel The entire energy landscape for a channel as a function of the radius for different choices of external gating parameter (membrane tension, ligand concentration, or applied voltage): Presence of the driving force shifts the balance between the energies of the closed and open states.
Open probability of the ion channel Compute the open probability of the channel. The energy is The partition function: => the open probability: Parameters: Δε = –5 k B T, Δ A =10 nm 2 To understand how a channel will behave under a driving force we need to know 2 things: (1) The intrinsic preference for each of its 2 states (2) how the external driving force alters the relative energies of these 2 states => stat. mech. allows us to compute the behavior of the channel under a range of driving forces

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ion channel gating: experimental data Current trace 2-state idealization of the current trace A single channel incorporated into a pure lipid bilayer is subjected to different voltages. The resulting current is measured. Tuning the driving force for gating only changes the relative dwell time and not the existence of the states themselves. Keller et al., J.Gen.Physiol. 1986
Ion gated channels: Acetylcholine
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern