What does the Binding Buffer (BB) consist of in this purification process?

The Binding Buffer (BB) in the purification of Green Fluorescent Protein (GFP) is designed to establish the right conditions for the protein to adhere to the purification column during chromatography. A very high salt buffer is appropriate for this stage because it can promote the binding of proteins to the column by altering their solubility or charge interactions in a favorable manner.

High salt concentrations often help in the initial stages to reduce non-specific binding and can ensure that the target protein, such as GFP, interacts appropriately with the resin or matrix used in the column. This is essential because the goal is to achieve specific binding of GFP, while also allowing for the unwanted proteins to be washed away during subsequent steps in the purification process.

In contrast, low salt concentrations would generally not provide sufficient ionic strength to facilitate effective binding, and salt-free or medium salt buffers may not create the optimal environment needed for the selective capture of GFP on the chromatography medium.