Potential toxicity and affinity of triphenylmethane dye malachite green to lysozyme

Malachite green is a triphenylmethane dye that is used extensively in many industrial and aquacultural processes, generating environmental concerns and health problems to human being. In this contribution, the complexation between lysozyme and malachite green was verified by means of computer-aided molecular modeling, steady state and time-resolved fluorescence, and circular dichroism (CD) approaches. The precise binding patch of malachite green in lysozyme has been identified from molecular modeling and ANS displacement, Trp-62, Trp-63, and Trp-108 residues of lysozyme were earmarked to possess high-affinity for this dye, the principal forces in the lysozyme-malachite green adduct are hydrophobic and π–π interactions. Steady state fluorescence proclaimed the complex of malachite green with lysozyme yields quenching through static type, which substantiates time-resolved fluorescence measurements that lysozyme-malachite green conjugation formation has an affinity of 103 M−1. Moreover, via molecular modeling and also CD data, we can safely arrive at a conclusion that the polypeptide chain of lysozyme partially destabilized upon complexation with malachite green. The data emerged here will help to further understand the toxicological action of malachite green in human body.

Based on molecular modeling simulations and ANS displacement, Trp-62, Trp-63, and Trp-108 residues of lysozyme was designated to retain high-affinity for malachite green, hydrophobic, and π–π interactions are operated between them, and the spatial structure of lysozyme was also perturbed upon complexation.Figure optionsDownload as PowerPoint slideHighlights
► Trp-62, Trp-63, and Trp-108 residues on lysozyme are all close to malachite green.
► Static type is dominance for the reduction in the lysozyme fluorescence.
► Hydrophobic and π–π interactions exist between lysozyme and malachite green.
► The spatial structure of lysozyme destabilizes upon complexation.
► Our task provide central clues on the toxicological action of malachite green.