There are saline electrostatic interactions between cationic
aminos and anionic carboxyls in approximately all proteins,
peptides and even dissolved amino-acids in solutions! By breaking
apart the saline link because the aminos react covalently with the
aldehyde to yield an uncharged methylol derivatives, the pKa of the
carboxyl proton drops from 2 to 5 pH units for all of these
families of peptides, because the saline bond is so long-ranged
coulombic inverse square force that operates at the extended
nano-meter colloidal rehealm of dimensions but the covalent link of
the amino with the aldehyde is very short ranged molecular
dimension. Thus the saline bond being unstable to Debye-Hückel
shielding that can affect the position of the canonical-zwitterion
equilibrium tautomers of all peptides gives the aggregation effects
for the colloidal phenomena of salting in and salting out of
solution of all peptides. Thus the Zwitterion tautomer Canonical
equilibrium can willfully be controlled by ionic strength and
dialectric conditions for all peptides! I discuss this in the
Wilson Memorial LECTURE give at the 107th ALCA Congress in Red-Wing
Minnesota in June 2011.