γ-Oxo-1-pyrenebutyric acid used for fluorescent detection of serum albumins and trypsin

Fluorescence spectroscopy, one of the most informative analytical techniques, has played and continues to play a key role in modern research due to its high sensitivity, rapid response rate, and relatively low cost. Herein we report its application to the detection of the proteins bovine serum albumin (BSA) and human serum albumin (HSA) as well as a protease (trypsin). The detection is based on a fluorescent molecule: γ-oxo-1-pyrenebutyric acid (OPBA), which exhibits a quenched fluorescent change at 455 nm toward serum albumins (SAs). OPBA interacted with SAs with a 1:1 stoichiometry and a strong affinity due to π-stacking, hydrophobic interactions, and hydrogen bonding interactions. The microenvironment created by HSA and BSA played an important role in their respective interactions with OPBA. In addition, OPBA can be used for monitoring trypsin by the cleavage of HSA or BSA in the presence of copper ions, and the successful cleavage of SAs was demonstrated by the SDS polyacrylamide gel electrophoresis (PAGE) results. This indirect detection of trypsin might be developed as a strategy for sensors without substrate selection. All of these tests do not require sophisticated instrumentation and should be applicable to standard fluorescence assays. © The Royal Society of Chemistry 2012.