Mechanism evaluation of the interactions between eight flavonoids and γ-globulin based on multi-spectroscopy

Inhibitory effects and mechanisms of sorghum 3-deoxyanthocyanidins as a dual-target inhibitor against α-amylase and α-glucosidase

Sorghum 3-deoxyanthocyanidins (3-DAS) can potentially reduce postprandial hyperglycemia to treat type 2 diabetes, but its mechanisms remain unknown. Herein, the inhibitory effects of different 3-DAS and their structural analogs on α-amylase and α-glucosidase were investigated. Results showed that luteolinidin (LN) had more potent inhibitory effects. The related inhibitory mechanism was clarified by inhibition kinetics and multi-spectroscopy. Results indicated that LN could inhibit the activities of the two enzymes in a non-competitive and reversible mixed mode, along with altering the hydrophobic environment around the amino acid residues of enzymes. Besides, LN could statically quench the endogenous fluorescence of enzymes and reduce the content of the α-helix structure of the enzymes. Molecular docking analysis suggested that hydrogen bonding and Van der Waals forces were the primary interactions responsible for LN binding to the enzyme. These findings provide essential data support for high-value utilization of sorghum resources in food nutrition and healthcare.

Study on the synergistical effects of characteristic compounds in Osmanthus black tea against xanthine oxidase based on multispectral analysis combined with in silico studies

With the worldwide prevalence of hyperuricemia (HUA), safe and effective natural xanthine oxidase (XOD) inhibitors are in need. This research was aimed to reveal the promising XOD inhibitors in Osmanthus black tea. Here, the combination index (CI) values for TF3 and acteoside were below 0.9, confirming the synergistic inhibitory effects on XOD. Further research confirmed that TF3-acteoside was stronger in inducing static quenching of XOD fluorescence than TF3 or acteoside. Besides, the secondary structure of XOD was significant changed by TF3-acteoside, specifically a decrease in the content of α-Helix and random coil, accompanied by an increase in β-Sheet and β-Turn contents, ultimately its structural stability and rigidity was enhanced. Molecular docking and molecular dynamics simulation analysis verified that TF3-acteoside stably bound to XOD by multiple hydrogen bonds. This study will lay important theoretical basis for the advancement of novel XOD inhibitors and the application of osmanthus black tea in lowering uric acid (UA).

Structural and anti-ovarian cancer insights into the immunoglobulin G-glabridin nanocomplex

In this study, the formation of the immunoglobulin G-glabridin (IgG-GB) complex and nanocomplex was analyzed by assessing the structure, stability, solubility, and anticancer effects against the human epithelial ovarian cancer cell line, SKOV3. The hydrodynamic sizes of the prepared IgG-GB nanocomplex were 190.1 ± 25.68 nm (PDI: 0.19 ± 0.02), and the solubility levels of GB in the free and nanoformulated forms were 97.28 μg/mL and 368.95 ± 59.63 μg/mL, respectively. Additionally, the IgG-GB nanocomplex exhibited a slower and more sustained release of GB in a pH-sensitive manner. Spectroscopic measurements indicated logKb values of 4.01 and 4.66 for the IgG-GB complex and the IgG-GB nanocomplex, respectively. Furthermore, the main reaction type between IgG and GB was found to be hydrophobic forces, which led to the partial folding of IgG and nanoformulated IgG. Cellular assays demonstrated that the IC50 concentrations of GB, the IgG-GB complex, and the IgG-GB nanocomplex in ovarian cancer SKOV3 cells were 10.74, 10.05, and 6.39 μM, respectively, while these amounts were > 77.84 μM in normal epithelial FHC cells. Moreover, the IgG-GB nanocomplex resulted in increased membrane leakage, mitochondrial dysfunction, and upregulation of Bax/Bcl-2 and caspase-3, along with caspase-3 activity. In conclusion, an efficient IgG-GB nanocomplex was potentially prepared and developed as a selective anticancer system against ovarian cancer cells.

Probing the interaction mechanism of tigecycline with γ-globulin and hemoglobin in the absence and presence of amikacin

The interaction mechanism of tigecycline with γ-globulin and hemoglobin in the absence and presence of amikacin was investigated through multipectral, molecular docking and molecular dynamics simulation. The results show that tigecycline and γ-globulin/hemoglobin forms a ground state complex without or with amikacin. The presence of amikacin slightly increases the binding constant of tigecycline to γ-globulin/hemoglobin, but all are of moderate binding affinity, at 104 L mol-1. The equilibrium fraction of unbound tigecycline fu is >90 %, but the presence of amikacin reduces the free concentration of tigecycline in γ-globulin and hemoglobin. Whether amikacin is present or not, the interaction between tigecycline and γ-globulin/hemoglobin is a synergistic interaction driven by enthalpy and entropy. Non-covalent forces are primarily hydrophobic interactions, but also include electrostatic forces and hydrogen bonds. In the presence of amikacin, the effect of tigecycline on the skeleton structure of γ-globulin/hemoglobin is more significant. The effect of tigecycline and/or amikacin on the secondary structure of γ-globulin/hemoglobin is not significant, while the secondary structure changes in different systems are not the same. Molecular docking shows that γ-globulin/hemoglobin-tigecycline (first)-amikacin ternary system is the most stable. Molecular dynamics simulation explores the stability and dynamic behavior of γ-globulin/hemoglobin-tigecycline complex without or with amikacin.

Interactions Between Silver Nanoparticles and Culture Medium Biomolecules with Dose and Time Dependencies

The interaction between silver nanoparticles (AgNPs) and molecules producing coronas plays a key role in cytotoxicity mechanisms. Once adsorbed coronas determine the destiny of nanomaterials in vivo, their effective deployment in the biomedical field requires a comprehensive understanding of the dynamic interactions of biomolecules with nanoparticles. In this work, we characterized 40 nm AgNPs in three different nutritional cell media at different molar concentrations and incubation times to study the binding mechanism of molecules on surface nanoparticles. In addition, their cytotoxic effects have been studied in three cell lineages used as tissue regeneration models: FN1, HUV-EC-C, RAW 264.7. According to the data, when biomolecules from DMEM medium were in contact with AgNPs, agglomeration and precipitation occurred. However, FBS medium proteins indicated the formation of coronas over the nanoparticles. Nonetheless, little adsorption of molecules around the nanoparticles was observed when compared to DMEM supplemented with 10% FBS. These findings indicate that when nanoparticles and bioproteins from supplemented media interact, inorganic salts from DMEM contribute to produce large bio-coronas, the size of which varies with the concentration and time. The static quenching mechanism was shown to be responsible for the fluorescence quenching of the bioprotein aggregates on the AgNPs surface. The calculated bioprotein-nanoparticle surface binding constants were on the order of 105 M-1 at 37 °C, with hydrophobic interactions driven by enthalpy and entropy playing a role, as confirmed by thermodynamic analysis. Cytotoxicity data showed a systematic degrowth in the viable cell population as the number of nanoparticles increased and the diameter of coronas decreased. Cytotoxic intervals associated with half decrease of cell population were established for AgNPs molar concentration of 75 µM for 24 h and 50 µM for 48 h. In summary, through the cytotoxicity mechanism of bio-coronas we are able to manipulate cells' expansion rates to promote specific processes, such inflammatory mechanisms, at different time instants.

The interaction of cinchonine and immunoglobulin G and the development of a nanocomplex with improved anti-breast cancer activity

In this study we evaluated the interaction of cinchonine (Cin) and immunoglobulin G (IgG). Then, Cin-IgG nanoparticles (NPs) were synthesized and characterized. Finally, the anticancer effects of free Cin and Cin-IgG NPs on MCF-7 breast cancer (BC) cells were evaluated. The results of spectroscopy measurements show that the IgG-Cin complex's quenching mechanism is static and the structure of IgG was partially changed following interaction with Cin. The prepared Cin-IgG NPs display a hydrodynamic size of 190 nm with a PDI of 0.269, a zeta potential of -38.05 mV, an EE% of 72.38 %, a LC% of 5.41 %, and a pH-sensitive drug release behavior. In the cellular assay, it was found that the calculated IC50 concentrations of Cin, IgG NPs, and Cin-IgG NPs are 66.4 ± 5.39, >100, and 29.2 ± ± 4.11 μM, respectively, in MCF-7 BC cells. Finally, Cin-IgG NPs induce a greater effect on the overexpression of the Bax/Bcl-2 ratio and downregulation of PI3K/p-AKT compared to the free drug. In conclusion, this study shows that Cin has the potential to bind IgG as a human plasma protein, and its complexation into a NP form with IgG can boost its anti-BC effects.

Comparative analysis of the interaction mechanism of γ-globulin and hemoglobin with spherical and rod-shaped gold nanoparticles

The interaction mechanism of spherical gold nanoparticles (AuNPs) and rod-shaped gold nanoparticles (AuNRs) with γ-globulin and hemoglobin was comprehensively and comparatively analyzed. γ-Globulin and hemoglobin have high affinity with AuNPs, and with two different types of binding sites on AuNRs surface. Except hemoglobin interaction with the first binding site of AuNRs, the interaction between γ-globulin/hemoglobin and AuNPs/AuNRs is the spontaneous, endothermic and entropy-driven process, and hydrophobic interaction plays a dominant role. The molecular adsorption mechanism of γ-globulin/hemoglobin on AuNPs and AuNRs surface conforms to Langmuir model and Freundlich model, respectively. The kinetic molecular mechanism between them conforms to the pseudo-second-order model, and chemisorption is the rate-limiting step. AuNPs result in the loosening and unfolding of γ-globulin backbone. AuNRs have no significant effect on γ-globulin backbone. AuNPs/AuNRs result in no significant changes in hemoglobin structure and heme group microenvironment. AuNPs/AuNRs decrease the hydrophobicity of Trp microenvironment of γ-globulin, but there is an intramolecular energy transfer from Trp residue to Tyr residue of hemoglobin. The β-sheet of γ-globulin and the α-helix of hemoglobin reduce by increasing concentrations of AuNPs/AuNRs. Molecular docking is suggesting that the specific amino acid residues of γ-globulin and hemoglobin interaction with AuNPs/AuNRs, and validates the experimental results.

Anti-Inflammatory and Antioxidant Pyrrolo[3,4-d]pyridazinone Derivatives Interact with DNA and Bind to Plasma Proteins-Spectroscopic and In Silico Studies

From the point of view of the search for new pharmaceuticals, pyridazinone derivatives are a very promising group of compounds. In our previous works, we have proved that newly synthesized ligands from this group have desirable biological and pharmacokinetic properties. Therefore, we decided to continue the research evaluating the activity of pyrrolo[3,4-dpyridazinone derivatives. In this work, we focused on the interactions of five pyridazinone derivatives with the following biomolecules: DNA and two plasma proteins: orosomucoid and gamma globulin. Using several of spectroscopic methods, such as UV-Vis, CD, and fluorescence spectroscopy, we proved that the tested compounds form stable complexes with all biomacromolecules selected for analysis. These findings were also confirmed by the results obtained by molecular modeling. All tested pyridazinone derivatives bind to the ctDNA molecule via groove binding mechanisms. All these molecules can also be bound and transported by the tested plasma proteins; however, the stability of the complexes formed is lower than those formed with serum albumin.

The 2-hydroxy-3-(4-aryl-1-piperazinyl)propyl Phthalimide Derivatives as Prodrugs—Spectroscopic and Theoretical Binding Studies with Plasma Proteins

Many publications in databases deal with the interactions of new drugs with albumin. However, it is not only albumin that is responsible for binding pharmaceutical molecules to proteins in the human body. There are many more proteins in plasma that are important for the study of the ADME pathway. Therefore, in this study, we have shown the results of the interactions between the plasma proteins albumin, orosomucoid, and gamma globulins and non-toxic anti-inflammatory phthalimide analogs, which due to the promising obtained results, may be potential candidates in the group of analgesic and anti-inflammatory drugs. Using spectroscopic methods and molecular modeling, we showed that all four tested compounds form complexes with the analyzed proteins. The formation of a complex with proteins raises the pharmacological efficacy of the drug. Therefore, the obtained results could be a step in the study of the pharmacokinetics and pharmacodynamics of new potential pharmaceuticals.

Exploring the interactions of naringenin and naringin with trypsin and pepsin: Experimental and computational modeling approaches

Naringenin and naringin are two natural compounds with important health benefits, whether as food or drug. It is necessary to study the interactions between naringenin/naringin and digestive proteases, such as trypsin and pepsin. In this study, the bindings of naringenin and naringin to trypsin and pepsin were investigated using multi-spectroscopy analysis and computational modeling approaches. Fluorescence experiments indicate that both naringenin and naringin can quench the intrinsic fluorescence of trypsin/pepsin via static quenching mechanism. Naringin binds trypsin/pepsin in a more firmly way than naringenin. Thermodynamic analysis reveals that the interactions of naringenin/naringin and trypsin/pepsin are synergistically driven by enthalpy and entropy, and the major driving forces are hydrophobic, electrostatic interactions and hydrogen bonding. Synchronous fluorescence spectroscopy, circular dichroism spectroscopy and FT-IR show that naringenin/naringin may induce microenvironmental and conformational changes of trypsin and pepsin. Molecular docking reveals that naringenin binds in the close vicinity of the active site (Ser-195) of trypsin and Asp-32 (the catalytic activity of pepsin) appears in naringin-pepsin system. The direct interactions between naringenin or naringin and catalytic amino acid residues will inhibit the catalytic activity of trypsin and pepsin, respectively. The results of molecular dynamic simulation validate the reliability of the docking results.