[Effects of neutral salts on the conformational state of glycogen, interacting with iodine]

The effects of salts on helix formation of linear (outer) chains of branched alpha-glucane, muscle glycogen, was judged upon by the state of polyiodine chromophore of the iodine reaction surrounded by a polysaccharide asymmetric helix and recorded by the circular dichroism method. It was demonstrated that apart from the known changes in the absorption of the iodine-glycogen complex the salts induce changes in the ellipticity by affecting the helix formation of the linear chains of the polysaccharide. The nature of these effects depends on the type and concentration of the salt used. Monovalent metal salts produce a more favourable effect on helix formation than the divalent metal salts. Among divalent metal salts transient metal salts produce a weaker effect. The action of neutral salts on helix formation is of dual nature: helix formation and helix destruction. The helix formation is largely impaired by high concentrations of LiCl (greater than 6 M) or CaCl2 (greater than 2M). It was shown that a certain role in the mechanism of neutral salt action on helix formation belongs both to electrostatic and lyotropic effects. The latter determine the effects of salts on helix formation at concentrations above the monomolar one, when the specific effect of a salt is especially well-pronounced. The salts which enhance the orderliness of H2O structure produce a favourable effect on helix formation of the linear polysaccharide chains and, consequently, on the iodine reaction. In terms of molar efficiency of their action on the iodine reaction the salts correspond to the Hofmeister lyotropic sequence.