The electrochemical method for detecting 26S proteasome

Detection of 26S proteasome, a multiproteolytic complex that degrades intracellular proteins in eukaryotic cells, by electrochemical methods is of interest for improved understanding of living cells and detection of cancer. This study develops an electrochemical system to detect 26S using a gold electrode modified by a self-assembled monolayer of 1,6-hexanedithiol (HDT) for capture of 26S proteasomes. When 26S is fixed on a HDT-gold electrode, it is found that electrolyte anions can enhance detection but also cause damage to the HDT layer. Cyclic voltammetry and electrochemical impedance spectroscopy demonstrate that HDT stability is better in LiClO4 solution than in sodium sulfate (Na2SO4) solution. Chymotrypsin-like activity of 26S as measured by fluorescence with Suc-LLVY-AMC substrate declines 10% with LiClO4 and 25% with Na2SO4. LiClO4 is a better electrolyte salt in a 26S-HDT-gold electrode application in Tris buffer. Increased electron transfer resistance is observed after binding 26S on the HDT-gold electrode. Stable 26S concentration is from 2 to 100 nM. As 26S concentration increases from 2 to 100 nM, the electron-transfer impedance of Fe(CN)64−/3− redox rises logarithmically. The range of electrochemical detection of 26S proteasome is nanomolar.