A novel fluorescent peptide probe for the specific detection of Cu<sup>2+</sup> and Cys in cells

Abstract

<p indent=0mm>As the third most abundant essential trace elements in the organism, Cu²⁺ plays an important role in normal physiological activities and metabolism, while excessive Cu²⁺ has been found to be closely related to serious diseases such as Down’s syndrome and Alzheimer’s disease. As an indispensable amino acid in the organism, Cys participates in the regulation of protein synthesis, post-translational modification and other biological functions. However, its pronounced accumulation may cause neurotoxicity, liver damage, kidney stones and other diseases. Therefore, the development of efficient assays for Cu²⁺ and Cys is critical for the diagnosis and treatment of these diseases. We have synthesized a hairpin type fluorescent peptide probe P ((Dansyl-Glu-Asp)₂-Lys) by using two amino groups in the side chain of lysine to react with aspartic acid in the peptide sequence. We found that the peptide probe P can highly specifically detect Cu²⁺ by fluorescence quenching without the interferences of other metal ions. The formation of P-Cu biosensor at 1:1 stoichiometry can highly selectively detect Cys and recover its fluorescence. We have demonstrated that the fluorescent peptide probe P provides an “On-Off-On” sensing mode for Cu²⁺ and Cys with detection limits of 52 and 43 nM, respectively. The fluorescent peptide probe P has been successfully used for the imaging of Cu²⁺ and Cys in HeLa cells. The newly developed fluorescent peptide probe P has extraordinary features such as good biocompatibility, low biotoxicity, and high specificity of Cu²⁺ and Cys, which shows new detection method in the studies of various Cu²⁺/Cys-involved diseases.