What is a common method to assess the purity of GFP post-purification?

Western blot analysis is commonly used to assess the purity of purified proteins, including green fluorescent protein (GFP). This technique allows for the specific detection and quantification of proteins in a sample. After proteins are separated by gel electrophoresis, they are transferred to a membrane, typically made of nitrocellulose or PVDF. The membrane is then probed with antibodies specific to GFP, which bind only to the GFP molecules.

The presence of a band corresponding to the expected size of GFP indicates that the protein is present, while the intensity of the band can provide insights into the relative abundance, thus indicating the purity of the sample. Any additional bands present could suggest contamination by other proteins, making Western blotting an effective method to determine the purity of the GFP after purification.

While mass spectrometry and ELISA can also provide valuable information about protein identity and concentration, respectively, they may not offer the same level of specificity for assessing purity in a straightforward manner as Western blot analysis. Additionally, DNA sequencing is not relevant for protein purity assessment, as it pertains to the analysis of nucleotide sequences rather than proteins.