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A novel fluorescence-based method for protein staining on SDS polyacrylamide gel is described. In this method, proteins are stained using counterion (palmatine and SDS) staining solution, which is inexpensive, easy to perform, and does not involve a destaining step. Fixing and staining of proteins using the counterion protocol take less than an hour. As little as 2 ng of protein can be detected. Another interesting feature of the staining protocol described here is the compatibility with MALDI-TOF MS which shows a similar number of identification score and sequence coverage compared with those of SYPRO Ruby.

A simple and sensitive fluorescent staining method for the detection of proteins in SDS-PAGE, namely IB (improved 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid) stain, is described. Non-covalent hydrophobic probe 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid was applied as a fluorescent dye, which can bind to hydrophobic sites in proteins non-specifically. As low as 1 ng of protein band can be detected briefly by 30 min washing followed by 15 min staining without the aiding of stop or destaining step. The sensitivity of the new presented protocol is similar to that of SYPRO Ruby, which has been widely accepted in proteomic research. Comparative analysis of the MS compatibility of IB stain and SYPRO Ruby stain allowed us to address that IB stain is compatible with the downstream of protein identification by PMF.

A fast and sensitive protein fluorescent detection method in SDS-PAGE using the natural product palmatine is described. Palmatine is an alkaloid found in various plants exhibiting a broad spectrum of antibiotic activity in humans. The sensitivity of palmatine staining is similar to those of the SYPRO Red, SYPRO Tangerine, and SYPRO Orange protein gel stains - about 4 ng per protein band. This detection sensitivity is comparable to colloidal CBB staining. Since proteins stained with palmatine do not need destaining, the staining procedure can be easily shortened and completed in about 30 min. Stained proteins can be photographed using a UV transilluminator. The results of the present study suggest that the palmatine staining is sensitive, rapid, low cost, and safe for a broad application to the research of protein.

An improved periodate/Schiff's base based fluorescent stain with dansylhydrazine (DH) for glycoproteins in 1D and 2D SDS-PAGE was described. Down to 4-8 ng of glycoproteins can be selectively detected within 2 h, which is approximately 16-fold higher than that of original protocol, but similar to that of Pro-Q Emerald 488 stain (Invitrogen, Carlsbad, USA). Furthermore, subsequent study of deglycosylation, glycoprotein affinity isolation, and LC-MS/MS analysis were performed to confirm the specificity of the improved method. As a result, improved DH stain may provide a new choice for selective, economic, MS compatible, and convenient visualization of gel-separated glycoproteins.

As a non-covalent fluorescence probe, in this study, salicylaldehyde azine (SA) was introduced as a sensitive fluorescence-based dye for detecting proteins both in 1-D and 2-D polyacrylamide electrophoresis gels. Down to 0.2 ng of single protein band could be detected within 1 h, which similars to that of glutaraldehyde (GA)-silver stain, but approximately four times higher than that of SYPRO Ruby fluorescent stain. Furthermore, comparative analysis of the MS compatibility of SA stain with SYPRO Ruby stain indicated that SA stain is compatible with the downstream of protein identification by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Additionally, the probable mechanism of the SA stain was investigated by molecular docking. The results demonstrated that the interaction between SA and protein was mainly contributed by hydrogen bonding and hydrophobic forces.

An improved Stains-All (ISA) staining method for phosphoproteins in SDS-PAGE was described. Down to 0.5-1 ng phosphoproteins (α-casein, β-casein, or phosvitin) can be successfully selectively detected by ISA stain, which is approximately 120-fold higher than that of original Stains-All stain, but is similar to that of commonly used Pro-Q Diamond stain. Furthermore, unlike the original Stains-All protocol that was time consuming and light unstable, ISA stain could be completed within 60 min without resorting to protect the gels from light during the whole staining procedure. According to the results, it is concluded that ISA stain is a rapid, sensitive, specific, and economic staining method for a broad application to the research of phosphoproteins.