Role of electrostatic repulsion on colloidal stability of Bacillus halmapalus alpha-amylase
| Autor: | Peter Westh, Søren Nymand Olsen, Kim Bruno Andersen, John F. Carpenter, Theodore W. Randolph |
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| Rok vydání: | 2008 |
| Předmět: |
Valence (chemistry)
Spectrophotometry Infrared Chemistry Static Electricity Biophysics Bacillus Protein aggregation Electrostatics Biochemistry Analytical Chemistry Ion Particle aggregation Colloid Crystallography Chemical physics DLVO theory Colloids alpha-Amylases Molecular Biology Protein secondary structure |
| Zdroj: | Biochimica et biophysica acta. 1794(7) |
| ISSN: | 0006-3002 |
| Popis: | The colloidal stability of charged particles in suspension is often controlled by electrostatic repulsion, which can be rationalized in a semi-quantitative way by the DLVO theory. In the current study, we investigate this approach towards understanding irreversible protein aggregation, using Bacillus halmapalus α-amylase (BHA) as a model protein. Repulsive forces between partly unfolded monomers were shown to strongly affect aggregation. Adding salt, increasing valence of counter ions or decreasing pH in the direction of p I resulted in a shift in the rate-limiting step from association to unfolding as evidenced by a change in aggregation kinetics from second to first-order in protein concentration. Charge screening effects by salts resulted in increased average size of protein aggregates but only moderately affected the secondary structure of protein within the aggregates. Salt and pH effects could be explained within the DLVO framework, indicating that partially unfolded BHA monomers can be modelled realistically as colloids with a random charge distribution. |
| Databáze: | OpenAIRE |
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