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Figure 5 Biophysical assay. (A) Whole-cell current recordings of wild-type (WT) and mutant sodium (Na) channels. Sodium channels were expressed with transient transfection in HEK293 cells in the presence of hß1. Currents were recorded at various membrane potentials from –90 to +90 mV in 10-mV increments from a holding potential of –120 mV. No currents were detected in cells expressing each mutant. (B) Voltage dependence of steady-state inactivation and activation of mutant Na channels cotransfected with WT (mutant-hH1 [or pRcCMV as a control to adjust the total amount of DNA]: WT-hH1: hß1 = 1:1:1). The curve was fit with the Boltzmann equation: I/Imax = [1+exp((V-V1/2)/k)–1]. (C) Current densities of mutant Na channels. Na currents were elicited at –30 mV from a holding potential of –120 mV. hH1 = human cardiac Na channel -subunit.
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