Elucidation of Binding Mechanism of Photodynamic Therapeutic Agent Toluidine Blue O with Chicken Egg White Lysozyme by Spectroscopic and Molecular Dynamics Studies

Abstract

The nature of binding mechanism of toluidine blue O (TBO) with chicken egg white lysozyme was studied comprehensively by various spectroscopic and computational methods. Both steady state and time-resolved fluorescence studies unambiguously point to the prevalence of static quenching mechanism in lysozyme-TBO system. Thermodynamic parameters revealed that the association of TBO with lysozyme was a spontaneous process in which hydrophobic and hydrogen bond interactions played a pivotal role in the binding process. The secondary and tertiary conformational changes of lysozyme in the presence of TBO were unraveled using absorption, Fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD) techniques. Molecular docking studies of lysozyme-TBO system substantiated the findings of site marker experiment and revealed TBO adjacent to Trp-63 and Trp-108 residues of lysozyme. Molecular dynamics (MD) simulation studies of lysozyme-TBO system indicate a stable and effective complexation of TBO with lysozyme. It is hoped that the results presented here will enable further understanding of TBO toxicity.

Deciphering the Interaction of 5,7‐Dihydroxyflavone with Hen‐Egg‐White Lysozyme through Multispectroscopic and Molecular Dynamics Simulation Approaches

“…Herein, the results from lifetime measurement clearly indicate the formation of HEWL‐chrysin ground‐state complex. Moreover, the above time‐resolved fluorescence results correlate well with the results from steady state emission and UV‐vis ground state complexation experiments ,…”

“…The negative sign of Δ G specify spontaneity of the molecular recognition process and the negative Δ H indicates that HEWL‐chrysin complexation is exothermic in nature. The observed positive Δ S (+31.267±3.151 J K −1 mol −1 ) and negative Δ H (‐17.154±0.872 kJ mol −1 ) values specify the presence of hydrophobic forces along with hydrogen bonding in the interaction of chrysin with HEWL ,,…”

“…Moreover, the above time-resolved fluorescence results correlate well with the results from steady state emission and UV-vis ground state complexation experiments. [32,33] Determination of the binding constants and number of binding sites…”

“…The observed positive DS (+ 31.267 AE 3.151 J K À1 mol À1 ) and negative DH (-17.154 AE 0.872 kJ mol À1 ) values specify the presence of hydrophobic forces along with hydrogen bonding in the interaction of chrysin with HEWL. [32,42,44] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 Binding distance Fö ster's Resonance Energy Transfer (FRET), [45] has been employed for determining the distance of energy transfer between the donor (HEWL) and the acceptor (chrysin). The formation of HEWL-chrysin complex might favour the process of excited energy transfer from donor to the acceptor.…”

Mesocellular Silica Foams (MCFs) with Tunable Pore Size as a Support for Lysozyme Immobilization: Adsorption Equilibrium and Kinetics, Biocomposite Properties

“…This enzyme has high structural stability and inflexibility within pH wide range 1.5 to 12 because the rigidity of the single-chained LYS molecule is imposed by four internal disulphide bonds that help maintain its tertiary structure [47]. This globular protein belongs to the family of hydrolases which, thanks to its biological function (the hydrolysis of the polysaccharide forming the bacterial cell wall), can be applied as an antimicrobial, anti-inflammatory, antiviral, antiseptic, antitumor agents [48].…”