Comparative studies on interactions ofl-ascorbic acid, α-tocopherol, procyanidin B3, β-carotene, and astaxanthin with lysozyme using fluorescence spectroscopy and molecular modeling methods

Probing the interaction of cephalosporin antibiotic "cefoperazone" with lysozyme using spectroscopic and in silico methods: Effect of paracetamol on binding

The interaction of lysozyme with cefoperazone was studied by means of spectroscopic and computational approaches. The change in the UV-visible spectrum of lysozyme in presence of cefoperazone was an indication of the complex formation between them. Fluorescence spectroscopy suggested that there was a fair interaction between the protein and drug which was taken place via dynamic quenching mechanism and the binding ratio was approximately 1:1. The binding was energetically feasible and principally supported by the hydrophobic forces. CD spectroscopic studies have shown that cefoperazone induced the secondary structure of lysozyme by increasing the α-helical contents of the latter. In silico studies revealed that the large nonpolar cavity was the preferred binding site of cefoperazone within lysozyme and the interaction was taken place mainly through hydrophobic forces with small involvement of hydrogen bonding and electrostatic interactions which is in good agreement with the experimental analyses. Effect of paracetamol was also seen on the binding and it was found that paracetamol had a negative influence on the binding between cefoperazone and lysozyme.

Encapsulation of Folic Acid and α-Tocopherol in Lysozyme Particles and Their Bioaccessibility in the Presence of DNA

Protein particles have been reported as the potential carriers for the co-encapsulation of bioactive components. In this study, lysozyme, a basic protein, was used to simultaneously encapsulate folic acid and α-tocopherol at pH 4.0. The encapsulation efficiency and loading capacity of folic acid or α-tocopherol increased with its respective concentration. Folic acid had no influence on the encapsulation of α-tocopherol. However, the encapsulation of folic acid was improved by α-tocopherol below 40 μg/mL but reduced by α-tocopherol at higher concentrations. The encapsulation by lysozyme shielded folic acid, α-tocopherol, or both partially from the attack of 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical cation. No masking effect of lysozyme encapsulation on α-tocopherol was found in DPPH antioxidant activity assay. Furthermore, the DNA coating was used to improve the dispersion of lysozyme with folic acid and α-tocopherol. The lysozyme/DNA particles with folic acid and α-tocopherol showed a homogenous size distribution of 180-220 nm with ζ-potential values between -33 and -36 mV. The release and bioaccessibility of folic acid in lysozyme/DNA with α-tocopherol were similar to that of folic acid alone, while the release of α-tocopherol was delayed and its bioaccessibility was improved by encapsulation in lysozyme/DNA with folic acid. The data gathered here would provide guidance for the use of lysozyme-based co-encapsulating carriers in the development of functional foods.

A natural strategy for astaxanthin stabilization and color regulation: Interaction with proteins

The pigment astaxanthin, one of the carotenoids, is regarded as a functional factor with various biological activities, widely applied in feed, nutraceutical, and cosmetic industries. However, its low stability and poor water solubility limit its application. Examples in nature suggest that binding to proteins is a simple and effective method to improve the stability and bioavailability of astaxanthin. Proteins from algae, fish, and crustaceans have all been demonstrated to have astaxanthin-binding capacity. Inspired by nature, artificial astaxanthin-protein systems have been established in foods. Binding to proteins could bring aquatic species various colors, and changes in the conformation of astaxanthin after binding to proteins leads to color changes. The review innovatively summarizes multiple examples of proteins as means of protecting astaxanthin, giving a reference for exploring and analyzing pigment-protein interactions and providing a strategy for carotenoids stabilization and color regulation, which is beneficial to the broader and deeper applications of carotenoids.

Spectroscopic and Molecular Docking Investigation on the Noncovalent Interaction of Lysozyme with Saffron Constituent "Safranal"

Owing to the various beneficial properties of the popular spice saffron, the interaction of safranal, a secondary metabolite of the former, with hen egg white lysozyme was investigated. The formation of a complex was evidenced by UV-visible spectroscopy. Fluorescence quenching experiments were also performed to understand the binding mechanism and to evaluate the forces involved in binding. The strong absorption of safranal in the range of excitation and emission wavelengths of lysozyme fluorescence required the correction of the inner filter effect for fluorescence spectra to obtain the apparent extent of binding. There was a considerable difference between the observed spectra and corrected spectra, and a similar observation was found in the case of synchronous fluorescence spectra. From the analysis of quenching data, it was found that the mechanism involved in quenching was static with 1:1 binding between them. The interaction was found to be driven, mainly, by hydrophobic forces and hydrogen bonding. Safranal had negligible impact on the secondary structure of lysozyme. The interaction was also studied by molecular docking, and the results were in good agreement with the results obtained experimentally. The binding site of safranal was in the big hydrophobic cavity of lysozyme. The amino acids involved in the interaction were Asp52, Ile58, Gln57, Asn59, Trp62, Trp63, Trp108, Ile98, Asp101, and Ala107.