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.