Many laboratories study the movement of ions through single channel molecules every day using the dazzling techniques of molecular and membrane biology. Atomic details of a channel are changed and the correlations of structure and function are observed routinely, but the correlations have been difficult to understand without a quantitative physical theory that links structure to function. The inputs to such a theory are the structure of the channel, the physical properties of ions, and concentrations and electrical potentials in the bath. The output of the theory is the current observed in a single open channel for a range of transmembrane potentials and compositions and concentrations of the surrounding solutions.
Physical laws are written as mathematical equations, and for good reason. Verbal formulations of physical laws are not specific and do not permit direct comparison with experiments (which usually have numbers as their output). Verbal formulations lead different people...
