  Computation of biological processes creates great promise for everyday life
and great challenges for physical scientists. Simulations of molecular dynamics
appeal to biologists as a natural extension of structural biology. Once
biologists see a structure, they want to see it move. Molecular biology shows
that a few atoms, often messenger ions like Ca$^{2+}$, control biological
function on the scale of cells, sometimes organisms. Enormously concentrated
ions (~20 M) in protein channels and enzymes can control important
characteristics of living systems, just as highly concentrated ions near
electrodes control important characteristics of electrochemical systems. The
scale differences needed to simulate all the atoms of biological cells are
$10^7$ in linear dimension, $10^{21}$ in three dimensions, $10^{9}$ in
resolution, $10^{11}$ in time, and $10^{13}$ in particle number (to deal with
concentrations of Ca$^{2+}$). $\mathbf{These}$ $\mathbf{scales}$
$\mathbf{must}$ $\mathbf{be}$ $\mathbf{dealt}$ $\mathbf{with}$
$\mathbf{simultaneously}$ if the simulation is to deal with most biological
functions. We suggest a computational approach using explicit multiscale
analysis instead of implicit simulation of all scales. Successful computation
of ions concentrated in special places may be a significant step to
understanding the defining characteristics of biological and electrochemical
systems.
