(467c) Correlating Molecular Interactions with Solubility of Alpha-Amylase from Bacillus Licheniformis

There is a strong link between solubility,
and thus crystallisation, and the molecular interactions of proteins in dilute
salt solutions. Such molecular interactions are governed by the weak
interaction forces (electrostatic, hydration and hydrophobic). In this work
molecular interactions were determined and correlated with solubility for the enzyme,
alpha-amylase from Bacillus
licheniformis (BLA) which finds an important application in starch
hydrolysis.

Molecular
interactions were determined using self interaction chromatography (SIC) which
evaluates the second virial coefficient (B₂₂). The second virial coefficient was found to
be highly dependent on the pH, salt type and salt concentration. Strong
molecular interactions were observed at high (>1.2 M) salt concentration in
ammonium sulphate solutions. Correspondingly salting-out behaviour was observed
during solubility experiments, strongly supporting the usefulness of the second
virial coefficient in predicting the crystallisation behaviour of enzymes in
salt solutions.