Investigation on the interaction between an antimicrobial in aquaculture, malachite green and hemocyanin from Mud Crab Scylla paramamosain

•Binding interaction exists between MG and Hc.•MG binds at the binding cavity of Hc.•Multi- noncovalent interactions stabilize MG–Hc complex.•MG induces some conformational changes of Hc.

Interaction between malachite green and hemocyanin of crab plays a crucial role in the metabolism, distribution, and efficacy of toxic dyes in aquaculture. The mechanism of interaction between malachite green and Hc from mud crab was studied by using multi-spectral methods and molecular modeling in this work. The spectroscopic and thermodynamic data show that the interaction is a spontaneous process with the estimated enthalpy and entropy changes of −14.85(±1.86) kJ mol−1 and 30.38(±5.21) J mol−1 K−1, respectively. The binding sites of malachite green in hemocyanin mainly locate in the interface of protein. The hydrophobic and electrostatic forces are the primary contributors to the interaction between hemocyanin and malachite green. The results of ultraviolet–vis absorbance, circular dichroism, and synchronous fluorescence spectroscopy suggest that the binding of malachite green to hemocyanin induces some conformational changes of protein.

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