1. You try to study a solution of the protein hen egg white lysozyme (HEWL), whi
ID: 183906 • Letter: 1
Question
1. You try to study a solution of the protein hen egg white lysozyme (HEWL), which carries a positive charge of +8e at pH 7. As a consequence, the proteins experience a significant electrostatic repulsion and rarely get close to each other. The buffer solution in which the proteins are solvated in has an ionic strength of 50 mM (i.e 0.05 mol/l).
The point of your experiment is to study how the proteins behave when they "touch" each other and you want to reduce the electrostatic repulsion between the charged proteins. The easiest way to achieve this (without modifying the proteins) is to change the salt concentration in the buffer solution, i.e. the ionic strength. Do you increase or decrease the concentrations of salts in your buffer?
2. You try to study a solution of the proteins hen egg white lysozyme (HEWL) and bovine serum albumin (BSA). HEWL carries a positive charge of +8e at pH 7, while BSA carries a negative of -18e. As a consquence, the HEWL and BSA proteins attract each other significantly and form aggregates in your solution, which interfere with your experiement. The buffer solution in which the proteins are solvated in has an ionic strength of 50 mM (i.e 0.05 mol/l).
You want to reduce the electrostatic attraction between the HEWL and BSA proteins. The easiest way to achieve this (without modifying the proteins) is to change the salt concentration in the buffer solutions, i.e. the ionic strength. Do you increase or decrease the concentrations of salts in your buffer?
Explanation / Answer
2. Concentrations of salts in the buffer should be increased.
An increase in salt concentration had a dramatic influence on adsorption densities for both proteins. This tendency could be attributed to the well-known electrostatic screening effect that reduces protein-surface electrostatic attraction at high salt concentrations.
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