What effect does the ionic strength of the buffer have on the electrophoretic movement of proteins?

The ionic strength of the buffer plays a significant role in the electrophoretic movement of proteins. A decrease in the ionic strength generally leads to a decrease in the migration of proteins during electrophoresis.

This occurs because lower ionic strength means fewer ions are present in the solution, which leads to a reduced screening effect. The screening effect is essential for reducing electrostatic interactions between proteins and the buffer’s ions. When the ionic strength is low, these interactions can become more significant, effectively slowing down the movement of proteins through the gel or medium, as they encounter greater resistance.

Additionally, with a decrease in ionic strength, the overall conductivity of the buffer can also decrease, thereby resulting in a less efficient electric field within the electrophoretic system. This further contributes to the slower migration of proteins.

In essence, a decrease in ionic strength increases the viscosity of the medium and enhances interactions between proteins and the buffer components, which results in a reduction of migration speeds during electrophoresis.