A natural fluorescent protein for ciprofloxacin sensing and mechanism study using molecular docking and circular dichroism

Ciprofloxacin (CIP) is one of the common drug pollutants whose residues are often detected in the environment. In the current work, CIP was studied in aqueous environment based on a natural fluorescing compound called phycocyanin (PC). Using, a Spectro fluorophotometer, fluorescence detection of CIP was performed, and absorbance properties were studied using a UV-Visible spectrophotometer. In addition, a circular dichroism (CD) spectrophotometer and molecular docking analysis were implemented for further investigation. As the fluorometric measurement results showed, the fluorescence intensity of PC dropped linearly upon the addition of increasing amounts of CIP ranging from 0 to 120 mu mol/L of final concentrations, with the limit of detection reaching down to 95 nM. In addition, the fluorescent sensor was found to be more selective towards CIP when tested against other six antibiotics and six pesticides. In the case of analysis of the PC-CIP interaction using a CD spectrophotometer the alpha-helix content of PC decreased in the presence of CIP, which is an indication of conformational changes in the secondary structure of PC. Moreover, the molecular docking analysis of the PC-CIP