Samples or starting materials often contain a mix of many proteins and other molecules. These proteins and molecules may have different sizes, structures, amino acid sequences, binding sites, and charges. The quantity of protein could be only a small fraction of the sample - in some cases as little as 1%. This can skew the findings of your study. Protein purification aims to separate the protein of interest from the unwanted molecules in the mix. Using purified protein in downstream applications provides more accurate results. Protein purification is also important for the specification of the function, structure and interactions of the protein of interest.