Visualization of unstained protein bands on PVDF

In 1988, two separate investigators reported a novel method of detecting unstained protein bands on polyvinylidene fluoride (PVDF) membranes using white light transillumination. This simple method exploits the intrinsic hydrophobicity of PVDF membrane, which enables the visual observation of transferred protein bands due to differential wetting patterns between protein bands and the membrane itself. This method applies only to hydrophobic PVDF membranes, because hydrophilic membranes such as nitrocellulose wet out completely, rendering the protein bands invisible by transillumination. Transilluminational protein visualization can detect submicrogram quantities of proteins while circumventing the use of protein stains, which can potentially interfere with downstream analysis such as N-terminal sequencing. In this chapter, we demonstrate efficient transilluminational protein visualization on a recently introduced low-fluorescence PVDF membrane, normally used for downstream fluorescent immunodetection.