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Updated: Nov 9, 2025

Quantifying the Binding Interactions Between CuII and Peptide Residues in the Presence and Absence of Chromophores
Published on: April 5, 2022
Colorimetric detection of homocysteine by a pyridylazo dye-based Cu2+ complex via indicator displacement mechanism
Yasumasa Fukushima1, Shunichi Aikawa2
1Faculty of Science and Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama, 350-8585, Japan.
Abstract:
A BrPAPS based Cu2+ complex has been developed as a colorimetric probe for the selective recognition of homocysteine (Hcy) over cysteine (Cys) and glutathione (GSH) in an aqueous solution via the indicator displacement assay. BrPAPS formed a complex with Cu2+ in a 1:1 ratio (BrPAPS-Cu2+) accompanied by the color change from yellow to red. Detecting Hcy is based on high affinity of Hcy for Cu2+. The addition of Hcy to BrPAPS-Cu2+ caused the complex formation of Hcy with Cu2+ in a 2:1 stoichiometry, resulting a hypsochromic shift with change back of color from red to yellow by the release of BrPAPS from BrPAPS-Cu2+. The absorption response is linear with the Hcy concentration in the range of 0-20 μM with a detection limit of 1.46 μM. Moreover, the detection of Hcy was not significantly affected by other amino acids from the competition experiments. Thus, BrPAPS-Cu2+ can be used as a simple probe for Hcy in aqueous solution.
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