Isoelectric point, floes

Succinylation reduced the isoelectric point of yeast proteins from pH A.5 to 4.0 and markedly improved their solubility in pH range 4.5 to 6. Heat denatured yeast proteins were facilely solubilized following succinylation (74). Succinylated yeast proteins were very stable to heat above pH 5, and remained soluble at temperatures above 80°C. As the degree of succinylation was increased the rate of precipitation of the derivatized protein increased in the neighborhood of the isoelectric point and much larger protein floes were obtained facilitiating their recovery (74). 

That such a relation exists has already been stated by Hardy in 1900 and by Burton in 1906. Hardy studied the properties of egg-albumin, which had been denatured by heat treatment and had lost its solubility. His systems may thus be truly regarded as hydrophobic colloids. Hardy found that, when the denaturing is carried out either in acid or in alkaline solutions, a stable sol results which is positively (acid) or negatively (alkaline) charged but when the denaturing is carried out in or near the isoelectric point, where the egg-albumin is uncharged, a mass of floes results. 

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