Ponceau S is widely used as a biological stain in various laboratory applications. It is particularly effective for staining proteins after electrophoresis, such as in SDS-PAGE gels, allowing for the visualization of protein bands. The stain provides a quick and simple method to assess the quality and quantity of protein samples. Additionally, Ponceau S is used in membrane staining to verify protein transfer efficiency during Western blotting. Its reversible nature makes it a preferred choice, as it can be easily washed off without interfering with subsequent immunodetection steps.