Spectroscopic and thermodynamic studies on ferulic acid – Alpha-2-macroglobulin interaction

Binding characteristics and conformational changes in alpha-2-macroglobulin by the dietary flavanone naringenin: biophysical and computational approach

In the present study, we investigated the interaction of alpha-2-macroglobulin (α2M) with naringenin using multi-spectroscopic, molecular docking, and molecular simulation approaches to identify the functional changes and structural variations in the α2M structure. Our study suggests that naringenin compromised α2M anti-proteinase activity. The results of absorption spectroscopy and fluorescence measurement showed that naringenin-α2M formed a complex with a binding constant of (kb)∼104, indicative of moderate binding. The value of ΔG° in the binding indicates the process to be spontaneous and the major force responsible to be hydrophobic interaction. The findings of FRET reveal the binding distance between naringenin and the amino acids of α2M was 2.82 nm. The secondary structural analysis of α2M with naringenin using multi-spectroscopic methods like synchronous fluorescence, red-edge excitation shift (REES), FTIR, and CD spectra further confirmed the significant conformational alterations in the protein. Molecular docking approach reveals the interactions between naringenin and α2M to be hydrogen bonds, van der Waals forces, and pi interactions, which considerably favour and stabilise the binding. Molecular dynamics modelling simulations also supported the steady binding with the least RMSD deviations. Our study suggests that naringenin interacts with α2M to alter its confirmation and compromise its activity.Communicated by Ramaswamy H. Sarma.

Probing the binding of morin with alpha-2-macroglobulin using multi-spectroscopic and molecular docking approach : Interaction of morin with α2M

Alpha-2-macroglobulin (α2M) is an essential antiproteinase that is widely distributed in human plasma. The present study was aimed at investigating the binding of a potential therapeutic dietary flavonol, morin, with human α2M using a multi-spectroscopic and molecular docking approach. Recently, flavonoid-protein interaction has gained significant attention, because a majority of dietary bioactive components interact with proteins, thereby altering their structure and function. The results of the activity assay exhibited a 48% reduction in the antiproteolytic potential of α2M upon interaction with morin. Fluorescence quenching tests unequivocally confirmed quenching in the fluorescence of α2M in the presence of morin, conforming complex formation and demonstrating that the binding mechanism involves a dynamic mode of interaction. Synchronous fluorescence spectra of α2M with morin showed perturbation in the microenvironment around tryptophan residues. Furthermore, structural changes were observed through CD and FT-IR, showing alterations in the secondary structure of α2M induced by morin. FRET further supports the results of the dynamic mode of quenching. Moderate interaction is shown by binding constant values using Stern-Volmer's fluorescence spectroscopy. Morin binds to α2M at 298 K with a binding constant of 2.7 × 104 M-1, indicating the strength of the association. The α2M-morin system was found to have negative ΔG values, which suggests that the binding process was spontaneous. Molecular docking also reveals the different amino acid residues involved in this binding process, revealing that the binding energy is -8.1 kcal/mol.

Food Antioxidants and Their Interaction with Human Proteins

Common to all biological systems and living organisms are molecular interactions, which may lead to specific physiological events. Most often, a cascade of events occurs, establishing an equilibrium between possibly competing and/or synergistic processes. Biochemical pathways that sustain life depend on multiple intrinsic and extrinsic factors contributing to aging and/or diseases. This article deals with food antioxidants and human proteins from the circulation, their interaction, their effect on the structure, properties, and function of antioxidant-bound proteins, and the possible impact of complex formation on antioxidants. An overview of studies examining interactions between individual antioxidant compounds and major blood proteins is presented with findings. Investigating antioxidant/protein interactions at the level of the human organism and determining antioxidant distribution between proteins and involvement in the particular physiological role is a very complex and challenging task. However, by knowing the role of a particular protein in certain pathology or aging, and the effect exerted by a particular antioxidant bound to it, it is possible to recommend specific food intake or resistance to it to improve the condition or slow down the process.

Exploring the interaction of myricetin with human alpha-2-macroglobulin: biophysical and in-silico analysis

Myricetin (MYR) is a bioactive secondary metabolite found in plants that is recognized for its nutraceutical value and is an essential constituent of various foods and beverages. It is reported to exhibit a plethora of activities, including antioxidant, antimicrobial, antidiabetic, anticancer, and anti-inflammatory. Alpha-2-macroglobulin (α2M) is a major plasma anti-proteinase that can inhibit proteinases of both human and non-human origin, regardless of their specificity and catalytic mechanism. Here, we explored the interaction of MYR-α2M using various biochemical and biophysical techniques. It was found that the interaction of MYR brings subtle change in its anti-proteolytic potential and thereby alters its structure and function, as can be seen from absorbance and fluorescence spectroscopy. UV spectroscopy of α2M in presence of MYR indicated the occurrence of hyperchromism, suggesting complex formation. Fluorescence spectroscopy reveals that MYR reduces the fluorescence intensity of native α2M with a shift in the wavelength maxima. At 318.15 K, MYR binds to α2M with a binding constant of 2.4 × 10³ M^-1, which indicates significant binding. The ΔG value was found to be - 7.56 kcal mol^-1 at 298.15 K, suggesting the interaction to be spontaneous and thermodynamically favorable. The secondary structure of α2M does not involve any major change as was confirmed by CD analysis. The molecular docking indicates that Asp-146, Ser-172, Glu-174, and Tyr-180 were the key residues involved in α2M-MYR complex formation. This study contributes to our understanding of the function and mechanism of protein and flavonoid binding by providing a molecular basis of the interaction between MYR and α2M.

Inhibition of Iron Release from Donkey Spleen Ferritin through Malt-Derived Protein Z-Ferulic Acid Interactions

Protein-small molecule interactions naturally occur in foodstuffs, which could improve the properties of protein and small molecules. Meanwhile, they might affect the bioavailability and nutritional value of proteins. Ferritin, as an iron-storage protein, has been a focus of research. However, the complexity of foodstuffs enables the interaction between ferritin and food components, especially polyphenols, which can induce iron release from ferritin. Thus, the application of ferritin in food is limited. Inspired by the natural-occurring, strong protein-polyphenol interactions in beer, to inhibit the iron release of ferritin, the malt-derived protein Z (PZ) was chosen to interact with ferulic acid (FA), an abundant reductant in malt, beer, and other foodstuffs. The analysis of the interaction between PZ and FA was carried out using fluorescence spectroscopy, the results of which suggest that one PZ molecule can bind with 22.11 ± 2.13 of FA, and the binding constant is (4.99 ± 2.13) × 10⁵ M^-1. In a molecular dynamics (MD) simulation, FA was found to be embedded in the internal hydrophobic pocket of PZ, where it formed hydrogen bonds with Val-389 and Tyr-234. As expected, compared to iron release induced by FA, the iron release from donkey spleen ferritin (DSF) induced by FA decreased by 86.20% in the presence of PZ. Meanwhile, based on the PZ-FA interaction, adding PZ in beer reduced iron release from DSF by 40.5% when DSF:PZ was 1:40 (molar ratio). This work will provide a novel method of inhibiting iron release from ferritin.

Interaction of Synthetic Pyrethroid Insecticide Deltamethrin with Human Alpha-2-Macroglobulin: Spectroscopic and Molecular Docking Studies

Background:

Deltamethrin (DLM) is a commercial insecticide of the synthetic pyrethroid family that is used to control disease-causing insects and vectors. When humans are exposed to the fumes or aerosols of DLM, it enters the body via cuticular absorption and reacts with proteins and other biomolecules.

Objective:

Alpha-2-macroglobulin (α2M) is a serum proteinase inhibitor that also carries out receptor- mediated endocytosis of extracellular substances. This study was done to decipher the structural and functional alterations of α2M by DLM.

Method:

Various spectroscopic techniques, including UV absorption and fluorescence spectroscopy, binding studies, and molecular docking, were used to characterize the interaction of DLM with α2M. The affinity constant was calculated from the Stern-Volmer equation using fluorescence data.

Results:

The UV-Vis and fluorescence spectral studies indicated the formation of a complex between α2M and DLM. Thermodynamically, the interaction was found to be spontaneous with ΔG = -4.23 kcal/mol. CD spectra suggested a change in the secondary structure of the protein from β to α helical content with increasing concentration of DLM. The molecular docking study by Autodock Vina established the interaction of DLM with Glu-926, Ala-1103, Ala-1108, Val-1116, Asn-1159, Glu-1220, Leu-1261, Thr-1272, Ile-1390, Pro-1391, Lys-1393, Val-1396, Lys-1397, Thr-1408, Glu-1409, Val-1410, Ser-1411, Ser-1412, and Asn-1413 with an improved docking score of -6.191 kcal/mol. The binding was carried out in the vicinity of the receptor-binding domain at the C-terminal of α2M.

Conclusion:

The decrease in the functional activity and structural changes of protein after binding with DLM has a significant effect on human α2M. The information may be useful for exploring the role of DLM in a clinical chemistry laboratory.

Interaction of Human Alpha-2-Macroglobulin with Pesticide Aldicarb Using Spectroscopy and Molecular Docking

BACKGROUND

Aldicarb is a carbamate pesticide commercially used in potato crop production. Once it enters human body, it interacts with diverse proteins and other substances.

OBJECTIVE

Aldicarb is toxic to human health and it is also a cholinesterase inhibitor, which prevents the breakdown of acetylcholine in synapse. Human alpha-2-macroglobulin (α2M), is a large tetrameric glycoprotein of 720 kDa with antiproteinase activity, found abundantly in plasma.

METHODS

In the present study, the interaction of aldicarb with alpha-2-macroglobulin was explored utilizing various spectroscopic techniques and molecular docking studies.

RESULTS

UV-vis and fluorescence spectroscopy suggests the formation of a complex between aldicarb and α2M apparent by increased absorbance and decreased fluorescence with static quenching mode. CD spectroscopy indicates a slight change in the structure of alpha-2-macroglobulin. Docking studies confirm the interaction of aldicarb with Pro- 1391, Leu-1392, Lys-1393, Val-1396, Lys- 1397, Thr-1408, Glu-1409, Val-1410, Asp-282 and Glu-281 in the receptor binding domain at the C-terminal of the alpha 2 macroglobulin.

DISCUSSION

In this work, aldicarb is shown to bind with alpha 2-macroglobulin at receptor binding domain which is the binding site for various extracellular and intracellular ligand too. Also, affecting the functional activity of the protein may lead to further physiological consequences.

CONCLUSION

It is possible that aldicarb binds and compromises antiproteinase activity of α2M and binding properties by inducing changes in the secondary structure of the protein.

Antipsychotic clozapine binding to alpha-2-macroglobulin protects interacting partners against oxidation and preserves the anti-proteinase activity of the protein

In this study, the interaction between clozapine, an atypical antipsychotic drug, and alpha-2-macroglobulin (α₂M), a multipurpose anti-proteinase, was investigated under simulated (patho) physiological conditions using multiple spectroscopic techniques and molecular modeling. It was found that α₂M binds clozapine with a moderate affinity (the binding constant of 0.9 × 10⁵ M^-1 at 37 °C). The preferable binding site for both clozapine's atropisomers was revealed to be a large pocket at the interface of C and D monomer subunits of the protein. Hydrogen bonds and the hydrophobic effect were proposed as dominant forces in complex formation. The binding of clozapine did not induce significant conformational change of the protein, as confirmed by virtually unaltered α₂M secondary structure and anti-proteinase activity. However, both clozapine and α₂M shielded each other from the deleterious influence of strong oxidants: sodium hypochlorite and 2,2'-azobis-2-methyl-propanimidamide dihydrochloride (AAPH). Moreover, clozapine in a concentration range that is usually targeted in the plasma during patients' treatment effectively protected the anti-proteinase activity of α₂M under AAPH-induced free radical overproduction. Our results suggest that the cooperation between α₂M and clozapine may be a path by which these two molecules synergistically protect neural tissue against injury caused by disturbed proteostasis or oxidative stress.

Binding interaction of sheep alpha-2-macroglobulin and tannic acid: A spectroscopic and thermodynamic study

Tannic acid is a polyphenol found in plant species commonly consumed by ruminants. It works as an important molecule in plant defense system to fight against environmental stressors. Tannic acid has number of effects on animals and humans. An attempt has been made to study the interaction of tannic acid with alpha-2-macroglobulin (α₂M). α₂M is a large tetrameric glycoprotein which function as a key serum anti-proteinase under physiological conditions. In the present study we explored the tannic acid-α₂M interaction by number of spectroscopic techniques such as UV, fluorescence, CD and FTIR along with isothermal titration calorimetry. CD and FT-IR spectroscopy were mainly used to study the secondary structural change induced in the antiproteinase. Analysis of activity shows the antiproteolytic potential of protein was compromised. Data of UV spectroscopy shows formation of α₂M-tannic acid complex. The thermodynamic signatures of this interaction reveals hydrogen bonding played a major role in the binding of α₂M-tannic acid. Analysis of CD and FTIR results suggest a minor conformational change in α₂M on tannic acid binding. Overall, tannic acid induces subtle conformation change in α₂M structure resulting the loss of its proteinase inhibitory activity.

Exploration of interaction of canthaxanthin with human serum albumin by spectroscopic and molecular simulation methods

The interaction between the food colorant canthaxanthin (CA) and human serum albumin (HSA) in aqueous solution was explored by using fluorescence spectroscopy, three-dimensional fluorescence spectra, synchronous fluorescence spectra, UV-vis absorbance spectroscopy, circular dichroism (CD) spectra and molecular docking methods. The thermodynamic parameters calculated from fluorescence spectra data showed that CA could result in the HSA fluorescence quenching. From the K_SV change with the temperature dependence, it was concluded that HSA fluorescence quenching triggered by CA is the static quenching and the number of binding sites is one. Furthermore, the secondary structure of HSA was changed with the addition of CA based on the results of synchronous fluorescence, three-dimensional fluorescence and CD spectra. Hydrogen bonds and van der Waals forces played key roles in the binding process of CA with HSA, which can be obtained from negative standard enthalpy (ΔH) and negative standard entropy (ΔS). Furthermore, the conclusions were certified by molecular docking studies and the binding mode was further analyzed with Discovery Studio. These conclusions can highlight the potential of the interaction mechanism of food additives and HSA.