In gel electrophoresis, what is a key indicator of sample purity?

In gel electrophoresis, the presence of only one band in the last column of the gel is a strong indicator of sample purity. When analyzing a protein sample, a single band suggests that the sample contains predominantly one type of protein. This is significant because it implies that there are minimal or no contaminants or additional protein species present in the sample. In contrast, multiple bands may represent a mixture of different proteins, indicating that the sample is not pure and contains various components.

For purity assessments, researchers want to see clearly defined bands that correspond to individual proteins. With only one band observed, it further suggests that the sample has been effectively purified, and the protein of interest can be isolated with confidence for further study or application. The other options, while relevant in different contexts, do not directly indicate purity in the same clear manner.