The interaction of allyl isothiocyanate (AIT) with the mustard 12S protein was studied as a function of pH, temperature, ratio of AIT to protein, and duration of interaction, etc. The interaction was found to increase with pH, temperature, and duration of interaction, in the range studied, and it was complete at an AIT to protein ratio of 100 to 1. The electrophoretic mobility of the protein increased with interaction. There was an alteration in the UV absorption spectrum and quenching of the fluorescence intensity. AIT interacted with «-amino groups of lysine and phenolic groups of tyrosine residues. Interaction of the protein with AIT did not affect its hydrolysis by -chymotrypsin or papain. But, hydrolysis by trypsin is decreased.

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The effect of low pH on the molecular properties of mustard 12S protein has been studied by the techniques of ultracentrifugation, viscometry, electrophoresis, turbidimetry, u.v. difference spectroscopy, fluorescence spectroscopy and circular dichroism. Ultracentrifugation and electrophoresis experiments indicated dissociation of the protein in the pH range 5.0 to 3.0 and below this pH reaggregation was indicated. Viscosity, turbidimetry, u.v. difference spectroscopy, fluorescence spectroscopy and circular dichroism studies showed that denaturation of the protein occurred between pH 5.0 and 3.0 and refolding at pH values below 3.0.

Vanillin is a plant secondary metabolite and has numerous beneficial health applications. Divanillin is the homodimer of vanillin and used as a taste enhancer compound and also a promissory anticancer drug. Here, divanillin was synthesized and studied in the context of its interaction with bovine serum albumin (BSA). We found that divanillin acquires axial chi-rality when complexed with BSA. This chiroptical property was demonstrated by a strong induced circular dichroism (ICD) signal. In agreement with this finding, the association constant between BSA and divanillin (3.3 x 10 5 mol-1 L) was higher compared to its precursor vanillin (7.3 x 10 4 mol-1 L). The ICD signal was used for evaluation of the association constant , demonstration of the reversibility of the interaction and determination of the binding site, revealing that divanillin has preference for Sudlow's site I in BSA. This property was confirmed by displacement of the fluorescent markers warfarin (site I) and dansyl-L-proline (site II). Molecular docking simulation confirmed the higher affinity of divanillin to site I. The highest scored conformation obtained by docking (dihedral angle 242˚) was used for calculation of the circular dichroism spectrum of divanillin using Time-Dependent Density Functional Theory (TDDFT). The theoretical spectrum showed good similarity with the experimental ICD. In summary, we have demonstrated that by interacting with the chiral cavities in BSA, divanillin became a atropos biphenyl, i.e., the free rotation around the single bound that links the aromatic rings was impeded. This phenomenon can be explained considering the interactions of divanillin with amino acid residues in the binding site of the protein. This chiroptical property can be very useful for studying the effects of divanillin in biological systems. Considering the potential pharmacological application of divanillin, these findings will be helpful for researchers interested in the pharmacological properties of this compound.

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