Mechanism of Prevention of Aggregation of Proteins: A Case Study of Aggregation of α-Globulin in Glycerol

The precipitation of proteins due to the changes in pH has been a major limiting factor in
their utility especially when the precipitation is concurrent with irreversible aggregation. In
the present study, an attempt is made to see the effect of glycerol on the pH-induced aggregation
of a- globulin which is the major protein fraction (11S) from Sesame (Sesamum
indicum L.) seeds. A second order polynomial relation existed between the cosolvent concentration
and precipitation which was prevented in presence of the cosolvent. Similarly,
there was a second order polynomial relation between 8-anilino 1-naphthalene sulfonic
acid (ANS) binding of the protein (as indicated by fluorescence emission at 466 nm) and the
cosolvent concentration. The relative precipitation in presence of glycerol is however linearly
proportional to the changes in surface hydrophobicity as seen by behavior of ANS
with the protein in presence of the cosolvent. A possible role of the cosolvents in prevention
of aggregation due to hydrophobicity of the protein is envisaged and the relation between
the different parameters is discussed.