Proteins and nucleic acids, like cells, can only survive in ionic solutions. Every biochemist knows that proteins must be
put into "buffers"  of (typically) 150 mM KCl if they are to survive. Every molecular biologist knows that the properties
of DNA depends on the salt and salt concentration. Every cell biologist knows that ions are important for cell function.
Every physiologist and physician that life does not survive in distailled water.

Ion in water are indeed the solutions of life.  Sfimulations and theory in biology are more useful
if they deal with the central experimental realities. Thus, they should deal with the real properites
of the ionic solutions needed to maintain life. Sadly, this is not always easy and thus not always the case.

Ionic solutions are almost never ideal in the theermodynamic sense. The fundamental thermodynamic variable 
of ionic solutions is the free energy per mole, which has a role equivalent to that of height in gravity, or electrical
potential in electricity, or concentration in biochemical reactions. In an ideal solution the free energy per mole
(also called 'the activity': note the activity is an experimental parameter that can be measured in many different
ways giving quantitatively the same result to several significant figures) follows a simple law proportional to 
the logarithm of the concentration. In ionic solutions, this law is (essentially) never followed because of shielding:
ions can move easily in solutions and rearrange in an ionic atmosphere around a charge (i.e., around any ion 
in the solution) to balance the central charge. After a few nsec, the ionic atmosphere balances the central charge
'perfectly' and the complex of ion and its atmosphere is uncharged. Shielding phenomena produce a square root 
dependence in properties of ionic solutions that make them nonideal, as has been understood for a very long time.
Thus, any treatment of ionic solutions in biological systems must get shielding right.

Ionic solutions in biological concentrations are not well characterized, however, by simple theories of shielding.
Debye Huckel for example fails at low concentrations (mM) of many salts and does poorly even with NaCl, clearly
missing the main properties of a graph of activity vs. concentration. Such graphs describe the fundamental properties
of ionic solutions as importantly as a graph of gravitational potential energy vs. height, or electrical potential energy 
vs. charge. In my view, a theory or simulation must get the plot of free energy per mole vs concentration roughly right
if it is to have any hope of dealing with proteins and nucleic acids quantiatively, just as any theory must get
the osmolarity