Binding interaction of isoxsuprine hydrochloride and levothyroxine to milk β-lactoglobulin; from the perspective of comparison

Change in thermal stability and molecular structure characteristics of whey protein beta-lactoglobulin upon the interaction with levamisole hydrochloride

The interaction between beta-lactoglobulin (BLG) and anthelmintic compounds including levamisole (LEV) is a matter of great concern as it not only poses potential health and environmental risks but also has significant implications for food processing and production. The mechanisms of LEV-BLG interaction were investigated through spectral and molecular modeling approaches. Fluorescence and UV-Visible investigations indicated the formation of a spontaneous and stable LEV-BLG complex. Structural changes of BLG were revealed by circular dichroism and Fourier transform infrared studies. The thermal stability of BLG increased in the presence of LEV. Molecular docking studies indicated the best mode of LEV-BLG interaction and molecular dynamics simulation confirmed the stability of the LEV-BLG complex. In conclusion, our study sheds light on the potential of BLG to interact with deleterious substances such as anthelmintic agents, thus highlighting the necessity of further research in this field to assure food safety and prevent any health hazards.

The impact of ascorbic acid (E 300) on digestion of different nutrients using In Vitro digestion model.. [DOI: 10.21203/rs.3.rs-3108018/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Ascorbic acid is a very common antioxidant food additive and vitamin supplement which is used by human on daily basis. Especially during corona virus pandemic because it is included in COVID-19 treatment guidelines. During this study the physicochemical properties as well as cytotoxicity, antioxidant activity and anti-diabetic activity were determined. Moreover, the effect of ascorbic acid on the digestibility of different nutrients including proteins, and fats were evaluated using INFOGEST in vitro digestion model. The structural analysis of ascorbic acid reveals that it has a monoclinic crystal structure with particle size in the nanoscale (41.496 ± 12.96 nm ). Cytotoxicity and antioxidant activity measurements proved that ascorbic acid is a powerful antioxidant with high safety profile. Moreover, it stimulates cell growth and proliferation at a dose dependent manner (12.5, 25, 50,100, and 200 mM). Ascorbic acid showed to have a low inhibition effect on alpha glucosidase enzyme, even at high concentrations (22.1% at 1800 ppm ). Digestibility measurements demonstrates that it has a positive effect on proteins and fats digestibility with a concentration dependent manner.

Interaction of vitamin B12 with β-lactoglobulin: a computational study

The β-Lactoglobulin (βLG) is a major whey protein that has the potential to bind various ligands; hence it is used as a model protein in protein-ligand interaction studies. Vitamin B12 is an essential nutrient for the human body, which helps in the synthesis of DNA, proteins, and the production of red blood cells. Binding interaction of vitamin B12 with βLG will help to understand the potency of βLG as a transporter for vitamin B12. Our experimental findings already showed that βLG binds with vitamin B12 successfully (Swain et al., 2020). Nevertheless, to further support our experimental results firmly, here, we have employed computational tools such as molecular docking and molecular dynamics (MD) simulation. The molecular docking technique was used to elucidate the probable binding sites and binding affinity of vitamin B12 on βLG. The docked complex of vitamin B12 with βLG was subjected to MD simulation to investigate its stability and other interaction properties over a time frame. The study revealed that the compound is stable, and vitamin B12 imposes no change to the secondary structure of the βLG. The computational results agree reasonably well with our experimental study.

Structure-based design approach to rational site-directed mutagenesis of β-lactoglobulin

Recombinant proteins play an important role in medicine and have diverse applications in industrial biotechnology. Lactoglobulin has shown great potential for use in targeted drug delivery and body fluid detoxification because of its ability to bind a variety of molecules. In order to modify the biophysical properties of β-lactoglobulin, a series of single-site mutations were designed using a structure-based approach. A 3-dimensional structure alignment of homologous molecules led to the design of nine β-lactoglobulin variants with mutations introduced in the binding pocket region. Seven stable and correctly folded variants (L39Y, I56F, L58F, V92F, V92Y, F105L, M107L) were thoroughly characterized by fluorescence, circular dichroism, isothermal titration calorimetry, size-exclusion chromatography, and X-ray structural investigations. The effects of the amino acid substitutions were observed as slight rearrangements of the binding pocket geometry, but they also significantly influenced the global properties of the protein. Most of the mutations increased the thermal/chemical stability without altering the dimerization constant or pH-dependent conformational behavior. The crystal structures reveal that the I56F and F105L mutations reduced the depth of the binding pocket, which is advantageous since it can reduce the affinity to endogenous fatty acids. The F105L mutant created a unique binding mode for a fatty acid, supporting the idea that lactoglobulin can be altered to bind unique molecules. Selected variants possessing a unique combination of their individual properties can be used for further, more advanced mutagenesis, and the presented results support further research using β-lactoglobulin as a therapeutic delivery agent or a blood detoxifying molecule.

Preparation, characterization and comparison of biological potency in two new Zn(II) and Pd(II) complexes of butanedione monoxime derivatives

A novel Schiff base ligand (2-iminothiophenol-2,3-butanedione monoxime, ITBM) and its complexes with Pd(II) and Zn(II) metal ions ([M(ITBM)₂]Cl₂) were synthesized and characterized in the present study. The formulated complexes were evaluated for in vitro antioxidant activity as radical scavengers against 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH^•). According to the results, antioxidant activity of Pd complex (IC₅₀=36 mg L^-1) was more effective than that of Zn(II) complex (IC₅₀=72 mg L^-1). Biophysical techniques along with computational modeling were employed to examine the binding of these complexes with human serum albumin (HSA) as the model protein. The trial findings revealed an interaction between Schiff base complexes and HSA with a modest binding affinity [K_b=6.31(±0.11)×10⁴ M^-1 for Zn(II) complex and 0.71(±0.05)×10⁴ M^-1 for Pd(II) complex at 310 K]. An intense fluorescence quenching of protein through a static quenching mechanism was occurred due to the binding of both complexes to HSA. Hydrogen bonds and van der Waals forces in both examined systems were the main stabilizing forces in the development of drug-protein complex. Based on far-UV-CD observations, the content of α-helical structure in the protein was reduced through induction by both complexes. Analysis of protein-ligand docking demonstrated binding of the two Schiff base complexes to residues placed in the IIA subdomain of HSA. In addition, Zn complex with HSA showed a stronger binding ability than that of Pd complex.Communicated by Ramaswamy H. Sarma.

β-Lactoglobulin as a potential carrier for bioactive molecules

In this study, the interaction and binding behavior of anesthetic tetracaine (TET) with bovine β-lactoglobulin (LGB) isoform A and a mixture of isoforms A and B were investigated under varying environmental conditions (pH, ionic strength, concentration, LGB-TET complex molar ratio). A wide range of analytical techniques (dynamic light scattering (DLS), electrophoretic mobility, UV-Vis spectroscopy, circular dichroism (CD), quartz crystal microbalance (QCM-D) were used to analyze the physicochemical properties of the complexes in bulk solution and on the surface of gold. The experiments revealed that TET, which is amphiphilic, could bind with LGB not only in the β-barrel but also onto the surface. The zeta potential of the LGB becomes more positively charged upon interaction with TET due to electrostatic interaction of the amino group present in the TET structure. Changes in the zeta potential values are mostly visible above pH 6 for all tested systems. CD spectra show that interaction with the ligand does not change the secondary structure of the protein. The physicochemical properties of LGB-TET complex were examined in an adsorbed state on a gold surface using the QCM-D method. Additionally, molecular docking was used to evaluate the most likely binding site for TET with LGB.