Based on the Nernst equation, the equilibrium potential for any ion (Eion) distributed across a membrane is dependent on the internal (Ion_in) and external (Ion_out) concentrations of the ion (in moles or grams/liter), the valence of the ion, z (an integer), the absolute temperature (°K), Faraday’s constant (96,500 coulombs/mole) and the universal gas constant R according to the following relationship:

Eion = (RK/zF)2.303 log ([Ion]out/[Ion]in)

Assuming that the equilibrium potential for sodium ion across a skeletal muscle is +66 mv at a temperature of 37°C when the external concentration is 145 mM and the internal concentration is 12 mM, evaluate both the magnitude and appropriate units for the universal gas constant, R