What method is primarily used for separating proteins in complex mixtures, such as in GFP purification?

Chromatography is the primary method used for separating proteins in complex mixtures, including during the purification of Green Fluorescent Protein (GFP). This technique takes advantage of the different physical and chemical properties of proteins, allowing for their separation based on size, charge, hydrophobicity, or affinity for specific ligands.

In the context of GFP purification, various types of chromatography can be utilized, such as affinity chromatography, which exploits the specific binding affinity of GFP to a ligand that is attached to a stationary phase. This allows for efficient separation from other proteins and impurities present in the mixture.

While electrophoresis is also a technique used for protein separation, it is primarily used for analyzing protein samples rather than large-scale purification. Centrifugation is useful for separating components based on density but does not provide the same level of resolution in separating specific proteins from a mixture. Filtration is generally employed for removing particulates or concentrating solutions but lacks the selectivity needed for protein purification. Thus, chromatography stands out as the most effective and widely used method for this purpose.