Interaction between tangeretin and ovalbumin to reduce the allergic effects of ovalbumin

Multispectroscopic and Computational Investigations on the Binding Mechanism of Dicaffeoylquinic Acids with Ovalbumin

Recently, studies on the interactions between ovalbumin (OVA) and polyphenols have received a great deal of interest. This study explored the conformational changes and the interaction mechanism of the binding between OVA and chlorogenic acid (CGA) isomers such as 3,4-dicaffeoylquinic acids (3,4-diCQA), 4,5-dicaffeoylquinic acids (4,5-diCQA), and 3,5-dicaffeoylquinic acids (3,5-diCQA) using multispectroscopic and in silico analyses. The emission spectra show that the diCQAs caused strong quenching of OVA fluorescence under different temperatures through a static quenching mechanism with hydrogen bond (H-bond) and van der Waals (vdW) interactions. The values of binding constants (OVA-3,4-diCQA = 6.123 × 10⁵, OVA-3,5-diCQA = 2.485 × 10⁵, OVA-4,5-diCQA = 4.698 × 10⁵ dm³ mol^-1 at 298 K) suggested that diCQAs had a strong binding affinity toward OVA, among which OVA-3,4-diCQA exhibits higher binding constant. The results of UV-vis absorption and synchronous fluorescence indicated that the binding of all three diCQAs to OVA induced conformational and micro-environmental changes in the protein. The findings of molecular modeling further validate the significant role of vdW force and H-bond interactions in ensuring the stable binding of OVA-diCQA complexes. Temperature-dependent molecular dynamics simulation studies allow estimation of the individual components that contribute to the total bound free energy value, which allows evaluation of the nature of the interactions involved. This research can provide information for future investigations on food proteins' physicochemical stability and CGA bioavailability in vitro or in vivo.

Investigation into the site-specific binding interactions between chlorogenic acid and ovalbumin using multi-spectroscopic and in silico simulation studies

The binding interactions of bioactive compounds with proteins are of great importance in the food, biochemistry and pharmaceutical fields. Herein, the binding mechanisms between 5-O-caffeoylquinic acid (5-CQA) and ovalbumin (OVA) were investigated by multi-spectroscopic studies combined with docking and molecular dynamics (MD) simulations. The emission intensity of OVA was quenched by 5-CQA and Stern-Volmer analysis indicated the existence of a static suppression by OVA-5-CQA complex formation. Thermodynamic parameters revealed that the formation of complex was spontaneously driven by electrostatic and hydrogen-bonding interactions. Circle dichroism analyses showed that 5-CQA decreased the α-helix content of OVA structure from 58.05% to 54.32% upon increased OVA:5-CQA ratio to 1:3. Molecular docking results suggested 5-CQA forms hydrogen bond interactions with N88, T91, K92, N94, S98, F99, S100 and L101 residues of OVA. The experimental values were in good agreement with the calculated binding free energy values obtained by MD simulation (R² = 0.89).Communicated by Ramaswamy H. Sarma.

Investigation of the Interaction between N-Acetyl-l-Cysteine and Ovalbumin by Spectroscopic Studies, Molecular Docking Simulation, and Real-Time Quartz Crystal Microbalance with Dissipation

This study investigated the interaction between N-acetyl-l-cysteine (NAC) and ovalbumin (OVA) using multispectroscopic technology, molecular docking, and quartz crystal microbalance with dissipation (QCM-D). Fluorescence intensity and UV absorption of OVA were decreased substantially upon the addition of NAC. The calculated K_q values were obtained at 298, 304, and 310 K for 13.48, 15.59, and 17.50 (× 10¹² L mol^-1), respectively, suggesting that the static quenching was dominated. Thermodynamic parameters such as ΔH (-150.58 kJ mol^-1), ΔS (-433.51 J mol^-1 K^-1), and ΔG values (-21.39 kJ mol^-1), combined with molecular docking and QCM-D data, showed that the interaction was spontaneous and van der Waals and hydrogen bonding were identified as the main driving forces. FTIR and CD results showed that the α-helix content of OVA increased from 2.8 to 22.9%, and the β-sheet decreased from 0.2 to 21.9% in the presence of 5 and 10 μM NAC, respectively, compared to the pure OVA, respectively.