The structural and functional study of the proteins expressed by a genome is
called proteomics. This relatively novel science uses different methodologies in order to
separate and identify specific proteins of interest. Among these techniques, SDS-PAGE
plays an essential role due to its high sensitivity, low sample volume requirement, and
high popularity. Negatively charged proteins migrate towards the positive electrode
according to their size and charge. Smaller proteins migrate further in a given amount of
time. As proteins are separated in this manner, users load molecular weight standards
to estimate the size (in kDa) of the proteins present in their sample. Once the proteins of
a single sample have been isolated and are embedded in the polyacrylamide (PA) gel
matrix, staining procedures are used to visualize them.
Organic dyes, such as Coomassie blue, can be used for this purpose;
nevertheless, their low sensitivity and a detection range that goes from 1 to 50 ng can
be a challenge for detecting low abundance proteins (Jin, Huang, Yoo, & Choi, 2006). A
higher sensitivity can be achieved by fluorescent staining techniques (from 0.1 to 10
ng.); however, UV instruments are necessary in order to read the data (Jin et al., 2006).
The most sensitive method up to date is radiolabeling, but the requirement of hazardous
isotopes and their complex management makes it a complicated procedure (Jin et al.,
2006). Silver staining is a method that offers great sensitivity and an easy to handle
protocol, thus making it one of the most commonly used staining methods.