1. Lipoelectric Modification of Ion Channel Voltage Gating by Polyunsaturated Fatty Acids 
Sara I. Börjesson, Sven Hammarström, Fredrik Elinder 
Biophysical Journal 
Volume 95, Issue 5, Pages (September 2008)
DOI: /biophysj
Copyright © 2008 The Biophysical Society Terms and Conditions

2. Figure 1
Procedure for measuring the shift of the G(V) curve. Data for control (○), 70μM eicosapentaenoic acid (□), and recovery (○) are shown together with Boltzmann raised to the power of n curves (continuous lines; Eq. 1). The area of interest for measurement is enlarged in the inset. The shift was measured at 10% of the maximum conductance.
Biophysical Journal  , DOI: ( /biophysj )
Copyright © 2008 The Biophysical Society Terms and Conditions

3. Figure 2
The importance of the charge for shifting the G(V) curve. (A) 210μM DHA (□) shifted the control G(V) curve (○) in negative direction. The scaled DHA curve (■) overlaps the control curve shifted −6.0mV (●). Mean shift is −8.0±0.7mV (n=7). (B) Addition of a methyl group to the carboxyl end abolished the shift (1.1±0.8mV, n=5). Control (○), DHA-me (□). (C) The positively charged spider toxin GsMTx4 (□) shifted the control G(V) curve (○) in positive direction (+5.7±0.3, n=4). (D) A summary of the effects of DHA, DHA-me, and GsMTx4 on the channel's voltage dependence. Error bars indicate SE.
Biophysical Journal  , DOI: ( /biophysj )
Copyright © 2008 The Biophysical Society Terms and Conditions

4. Figure 3
pH dependence of the DHA effects. (A) 70μM DHA at pH 9.0 increased the current at −40mV 20-fold. (B) The corresponding G(V) curve was shifted −20.2 (mean shift −18.0±1.4mV, n=9). Control (○), DHA (□). (C) DHA-me did not shift G(V) at pH 9.0. Control (○), DHA-me (□). (D) Shift data for DHA at pH 6.5 (●), pH 7.4 (○), pH 9.0 (□), and pH 10.0 (■). Continuous lines show dose-response fits (Eq. 2) for pH 7.4 and 9.0. pH 7.4: ΔVmax=−9.6mV, c0.5=79μM; pH 9.0: ΔVmax=−19.7mV, c0.5=5.5μM. Error bars indicate SE. Small error bars are covered by symbols.
Biophysical Journal  , DOI: ( /biophysj )
Copyright © 2008 The Biophysical Society Terms and Conditions

5. Figure 4
A simple four-state model describing the pH dependence of the FFA effects. (A) At low pH the ion channel conformation prevents FFA interaction (State 1). Increased pH induces conformational changes making FFA interaction possible (State 2). The FFA can interact with the channel in a protonated form (State 3) or a deprotonated form (State 4). The FFA can only change the channel's voltage dependence in State 4. (B) Global least-square fitted solutions for Eq. 3 shown as continuous lines. ΔVMAX=−20.5mV, pKa,FFA=7.4, KD=3.5μM, and pKa,rec=8.8. (C) The mutation line shows the predicted dose-response relationship from Eq. 3 for the triple mutation 419C-ET+/425K/451K at pH 7.4. Experimental data for the triple mutation are plotted as mean (▵)±SE. Small error bars are covered by symbols.
Biophysical Journal  , DOI: ( /biophysj )
Copyright © 2008 The Biophysical Society Terms and Conditions

6. Figure 5
DHA affects the screening effect of a divalent metal ion. (A) Increased extracellular Mg2+ concentration (20mM) shifted G(V) in positive direction by screening the negative surface charges. (B) DHA increased the screening effect (ΔΔVMg is 1.8±0.3mV, n=10). (C) ΔΔVMg plotted versus DHA (□) and DHA-me (○) shifts for wt Shaker and DHA for the triple-positive mutant (■) (data for 210μM). Error bars show SE. pH=7.4. The continuous line shows the solution to the Grahame equation (Eq. 5).
Biophysical Journal  , DOI: ( /biophysj )
Copyright © 2008 The Biophysical Society Terms and Conditions

7. Figure 6
Effect of DHA on the gating currents. (A) On and off-gating currents for control (black trace) and 70μM DHA (gray trace) at pH 9.0. DHA speeds up the on-gating current (extended timescale in inset) and slows down the off-gating current. The holding potential was −80mV, the on-gating step to −20mV, and the off-gating step to −80mV. (B) 70μM DHA (□) at pH 9.0 shifted the control Q(V) curve (○) in negative direction (−6.3±0.5mV, n=7). Dashed line shows control curve shifted −5.0mV. (C) The shift of Q(V) is ∼1/3 of the G(V) shift.
Biophysical Journal  , DOI: ( /biophysj )
Copyright © 2008 The Biophysical Society Terms and Conditions

8. Figure 7
Structure of fatty acids and fatty acid-like compounds used and G(V) shifts for respective compound. All data are for a compound concentration of 70μM at pH 7.4 (except for data denoted with † that are for compound concentrations of 210μM). n denotes the number of experiments, and ††, arachidonic acid with 1μM indomethacin. Error bars indicate SE.
Biophysical Journal  , DOI: ( /biophysj )
Copyright © 2008 The Biophysical Society Terms and Conditions

9. Biophysical Journal 2008 95, 2242-2253DOI: (10. 1529/biophysj. 108
Copyright © 2008 The Biophysical Society Terms and Conditions