Spectroscopic Technique-Based Comparative Investigation on the Interaction of Theaflavins with Native and Glycated Human Serum Albumin

Structure-activity relationship between gold nanoclusters and human serum albumin: Effects of ligand isomerization

The interactions between gold nanoclusters (AuNCs) and proteins have been extensively investigated. Nevertheless, the structure-activity relationship between gold nanoclusters and proteins in terms of ligand isomerization remained unclear. Here, interactions between Au25NCs modified with para-, inter- and ortho-mercaptobenzoic acid (p/m/o-MBA-Au25NCs) and human serum albumin (HSA) were analyzed. The results of the multispectral approach showed that all three gold nanoclusters bound to the site I in dynamic modes to increase the stability of HSA. There were significant differences in the binding intensity, thermodynamic parameters, main driving forces, and binding ratios between these three gold nanoclusters and HSA, which might be related to the existence forms of the three ligands on the surface of AuNCs. Due to the different polarities of AuNCs themselves, the impact of three AuNCs on the microenvironment of amino acid residues in HSA was also different. It could be seen that ligand isomerization significantly affected the interactions between gold nanoclusters and proteins. This work will provide theoretical guidance for ligand selection and biological applications of metal nanoclusters.

Structural and functional impacts of neonicotinoids analogues on Apis mellifera's chemosensory protein: Insights from spectroscopic and molecular modeling investigations

In the intricate web of ecological relationships, pollinators such as the Italian honeybee (Apis mellifera) play a crucial role in maintaining biodiversity and agricultural productivity. This study focuses on the interactions between three neonicotinoid compounds and the honeybee's chemosensory protein 3 (CSP3), a key player in their olfactory system. Employing advanced spectroscopic techniques and molecular modeling, we explore the binding dynamics and conformational changes in CSP3 upon exposure to these pesticides. The research reveals that all three neonicotinoids considerably quench CSP3's fluorescence through a dynamic and static mixing mechanism, indicating a strong binding affinity, predominantly driven by hydrophobic interactions. UV-visible absorption, synchronous fluorescence, and 3D fluorescence spectra support slight changes in the microenvironment around the aromatic amino acids of CSP3. Circular dichroism spectra indicate a reduction in CSP3's α-helix content, suggesting structural alterations. Molecular docking and dynamics simulations further elucidate the binding modes and stability of these interactions, highlighting the role of specific amino acids in CSP3's binding cavity. Findings provide critical insights into molecular mechanisms by which neonicotinoids may impair honeybee chemosensory function, offering implications for designing safer pesticides and understanding the broader ecological impact of these chemicals on pollinator health.

Investigation of steric hindrance effect on the interactions between four alkaloids and HSA by isothermal titration calorimetry and molecular docking

The binding of four alkaloids with human serum albumin (HSA) was investigated by isothermal titration calorimetry (ITC), spectroscopy and molecular docking techniques. The findings demonstrated that theophylline or caffeine can bind to HAS, respectively. The number of binding sites and binding constants are obtained. The binding mode is a static quenching process. The effects of steric hindrance, temperature, salt concentration and buffer solution on the binding indicated that theophylline and HSA have higher binding affinity than caffeine. The fluorescence and ITC results showed that the interaction between HSA and theophylline or caffeine is an entropy-driven spontaneous exothermic process. The hydrophobic force was the primary driving factor. The experimental results were consistent with the molecular docking data. Based on the molecular structures of the four alkaloids, steric hindrance might be a major factor in the binding between HSA and these four alkaloids. This study elucidates the mechanism of interactions between four alkaloids and HSA.

Probing the Interaction between Isoflucypram Fungicides and Human Serum Albumin: Multiple Spectroscopic and Molecular Modeling Investigations

To better understand the potential toxicity risks of isoflucypram in humans, The interaction between isoflucypram and HSA (human serum albumin) was studied through molecular docking, molecular dynamics simulations, ultraviolet-visible absorption, fluorescence, synchronous fluorescence, three-dimensional fluorescence, Fourier transform infrared spectroscopies, and circular dichroism spectroscopies. The interaction details were studied using the molecular docking method and molecular dynamics simulation method. The results revealed that the effect of isoflucypram on human serum albumin was mixed (static and dynamic) quenching. Additionally, we were able to obtain important information on the number of binding sites, binding constants, and binding distance. The interaction between isoflucypram and human serum albumin occurred mainly through hydrogen bonds and van der Waals forces. Spectroscopic results showed that isoflucypram caused conformational changes in HSA (human serum albumin), in which the α-helix was transformed into a β-turn, β-sheet, and random coil, causing the HSA structure to loosen. By providing new insights into the mechanism of binding between isoflucypram and human serum albumin, our study has important implications for assessing the potential toxicity risks associated with isoflucypram exposure.

On-line screening and verification of haptens in Xiangdan injection combining chemical analysis with activity detection

Xiangdan injection (XDI), as a well-known traditional Chinese medicine injection, is of great significance to treat cardiovascular and cerebrovascular diseases. The haptens causing allergic reactions are urged to be detected due to the adverse reaction. In this study, an efficient approach was established to rapidly identify and screen potential haptens in XDI for the first time by combining high performance liquid chromatography-diode array detector-electrospray ionization-ion trap-time of flight-mass spectrometry with human serum albumin-fluorescence detector (HPLC-DAD-ESI-IT-TOF-MS-HSA-FLD). 21 compounds were identified according to their mass spectrum or comparison with reference substances and 8 salvianolic acids in XDI showed interactions with HSA in varying degrees. After that, surface plasmon resonance (SPR) was applied to screen the compounds showing specific affinity with human serum albumin (HSA). Subsequently, active systemic anaphylaxis (ASA) in guinea pigs was carried out to verify the sensitization of active compounds, In the meantime the serum IgE level before and after challenge was measured by the enzyme-linked immunosorbent assay (ELISA). Ultimately, it was tested that salvianolic acid C had a strong sensitization, in addition, lithospermic acid, rosmarinic acid and salvianolic acid B had potential sensitization. This study suggest that the on-line method provides rapid preliminary searching for haptens in XDI, combined with SPR and ASA, offering an efficient, rapid and comprehensive approach to screen haptens.

Evaluation the binding of chlorogenic acid with bovine serum albumin: Spectroscopic methods, electrochemical and molecular docking

Chlorogenic acid(CGA) is the common active phenolic acid in Chinese medicinal materials such as honeysuckle and eucommia. It is a class of small molecules with multiple activities such as antioxidant, inhibiting cancer cells, lowering blood sugar and lowering blood pressure. In this paper, UV-vis spectroscopy, fluorescence spectroscopy, circular dichroism, molecular dynamics simulation and cyclic voltammetry (CV) electrochemical analysis were used to investigate the mechanism about interaction between CGA and BSA. Based on fluorescence quenching analysis, CGA quenched the inherent fluorescence of BSA remarkably through a static mechanism. The obtained value of binding constant (K_b = 5.75 × 10⁵ L·mol^-1) revealed a high binding affinity between CGA and BSA. The simulated molecular docking showed that hydrophobic force were also involved in the interaction between BSA and CGA. This paper also investigate the effect of temperature and metal ions on the binding of CGA and BSA. When the temperature increased, the binding of BSA and CGA was destroyed. Metal ions affect both the structure of BSA and the combination of BSA and CGA. By studying the mechanism of CGA interaction with BSA, we elucidated the storage and transport mechanism of CGA in vivo under simulated human environment and temperature conditions.

Study on the Interaction Mechanism of Theaflavin with Whey Protein: Multi-Spectroscopy Analysis and Molecular Docking

The interaction mechanism of whey proteins with theaflavin (TF1) in black tea was analyzed using multi-spectroscopy analysis and molecular docking simulations. The influence of TF1 on the structure of bovine serum albumin (BSA), β-lactoglobulin (β-Lg), and α-lactoalbumin (α-La) was examined in this work using the interaction of TF1 with these proteins. Fluorescence and ultraviolet-visible (UV-vis) absorption spectroscopy revealed that TF1 could interact with BSA, β-Lg and α-La through a static quenching mechanism. Furthermore, circular dichroism (CD) experiments revealed that TF1 altered the secondary structure of BSA, β-Lg and α-La. Molecular docking demonstrated that the interaction of TF1 with BSA/β-Lg/α-La was dominated by hydrogen bonding and hydrophobic interaction. The binding energies were -10.1 kcal mol^-1, -8.4 kcal mol^-1 and -10.4 kcal mol^-1, respectively. The results provide a theoretical basis for investigating the mechanism of interaction between tea pigments and protein. Moreover, the findings offered technical support for the future development of functional foods that combine tea active ingredients with milk protein. Future research will focus on the effects of food processing methods and different food systems on the interaction between TF1 and whey protein, as well as the physicochemical stability, functional characteristics, and bioavailability of the complexes in vitro or in vivo.

Nutritive Value of Active Volatile Components of Anacardiaceae Mango and Their Effects on Carrier Proteins Function

The effects of mango active volatile components (VOCs) on protein function were investigated from the perspective of nutrient transport. The active volatile components of five varieties of mango were analyzed by headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS). The interaction mechanism between active volatile components and three carrier proteins was discussed by fluorescence spectroscopy, molecular docking and dynamic simulation. The results showed that there were 7 active components in the five mango varieties. The aroma components represented by 1-caryophyllene and β-pinene were selected for further study. The interaction between VOCs small molecules and proteins is a static binding process, and its main force is hydrophobic interaction. The results of molecular simulation and spectral experiments showed that the binding ability of 1-caryophyllene and β-pinene to β-Lg was strong, so mango VOCs could possess a certain nutritional value in dairy products, expanding its application in dairy products in the food industry.

Unveiling interaction mechanisms between myricitrin and human serum albumin: Insights from multi-spectroscopic, molecular docking and molecular dynamic simulation analyses

Myricitrin is a natural polyhydroxy flavonoid and is mainly derived from the bark and leaves of the Chinese Bayberry tree (Myrica rubra). It has different pharmacological activities, including antioxidative, anti-inflammatory, hypoglycemic, antiviral, liver protection and cholagogue properties, and may be added to foods, pharmaceuticals, and cosmetic products for antioxidant purposes. In this study, the interaction mechanism between myricitrin and human serum albumin (HSA) was investigated using spectroscopic methods, molecular docking techniques, and molecular dynamic simulations. We showed that the HSA/myricitrin interaction exhibited a static fluorescence quenching mechanism, and that binding processes were spontaneous in nature, with the main forces exemplified by hydrogen bonding, hydrophobic interactions, and electrostatic interactions. Fluorescence spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, synchronous fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy, micro-Fourier transform infrared spectroscopy (micro-FTIR), and circular dichroism (CD) spectroscopy showed that myricitrin binding altered the HSA conformation to some extent. Competitive binding and molecular docking studies showed that the preferred binding of myricitrin on HSA was in the sub-structural domain IIA (Site I); molecular dynamic simulations revealed that myricitrin interacted with HSA to produce a well stabilized complex, and it also generated a conformational change in HSA. The antioxidant capacity of the HSA-myricitrin complex was reduced when compared with free myricitrin. The identification of HSA-myricitrin binding mechanisms provides valuable insights for the application of myricitrin to the food and pharmaceutical industries.

Interaction between laccase and diethylstilbestrol based on multispectral and chromatography analyses

Diethylstilbestrol (DES) is a synthetic form of oestrogen that does not easily degrade in the environment and can be harmful to human health. Herein, the mechanism of the interaction between laccase and DES was investigated by various spectroscopic means and high-performance liquid chromatography (HPLC). The results of fluorescence experiments showed that the quenching of intrinsic fluorescence of laccase by DES was due to a static quenching, forming a binding site. According to the Förster non-radiative energy transfer theory (FRET), the action distance R₀ between DES and laccase was 4.708 nm, r was 5.81 nm, and the energy transfer efficiency E was 22.08%, respectively. Both UV-Vis absorption spectra and FT-IR spectra indicated changes in the conformation and surroundings of the enzyme and changed in the secondary structure of laccase. Multispectral synthesis showed that the interaction of laccase with DES caused a change in the secondary structure of laccase. The degradation experiments showed that laccase could degrade DES, and the DES content decreased with time. This study provides a new theoretical basis and experimental method for further research on the reaction mechanism of the laccase degradation of DES. It may also provide a reference basis for human biological and environmental safety evaluations.

Polysaccharides from mulberry (Morus alba L.) leaf prevents obesity by inhibiting pancreatic lipase in high-fat diet induced mice

Pancreatic lipase (PL) is a key enzyme related to the prevention and treatment of obesity. The aim of the study was to evaluate the inhibitory effects of mulberry leaf polysaccharides (MLP) on PL and possible interaction mechanism, inhibition on lipid accumulation in vitro and in vivo. The results revealed that MLP had obvious inhibitory effects on PL (P < 0.05). The interaction of MLP-PL complexes was in a spontaneous way driven by enthalpy, and hydrogen bonds were the main factors in the binding. MLP could significantly inhibit the development of lipid accumulation in HepG2 cells (P < 0.05). Furthermore, consumption of high-fat diet containing MLP showed protective effects on liver and adipose tissue damages in mice, and inhibited the lipid absorption in digestive tract. MLP also significantly reduced the increased expression level of pancreatic digestive enzymes (P < 0.05). The study indicated that the anti-obesity effect of MLP might be caused by inhibition of lipid absorption via reducing PL activity.

Comprehensive analysis of the anti-glycation effect of peanut skin extract

Advanced glycation end-products (AGEs) are produced during protein glycation and associated with diabetic complications. Peanut skin is rich in procyanidins, which may be used as an inhibitor of glycation. This study evaluated the potential anti-glycation effect of peanut skin extract (PSE) and dissected the underlying mechanism. PSE could effectively inhibit the formation of AGEs in BSA-Glc and BSA-MGO/GO models, with 44%, 37% and 82% lower IC₅₀ values than the positive control (AG), respectively. The inhibitory effect of PSE on BSA glycation might be ascribed to its binding interaction with BSA, attenuated formation of early glycation products and trapping of reactive dicarbonyl compounds. Notably, PSE showed a remarkably stronger inhibitory effect on Amadori products than AG. Furthermore, three new types of PSE-MGO adducts were formed as identified by UPLC-Q-TOF-MS. These findings suggest that PSE may serve as an inhibitor of glycation and provide new insights into its application.

The study on the interactions of two 1,2,3-triazoles with several biological macromolecules by multiple spectroscopic methodologies and molecular docking

1-(4-chlorophenyl)-5-phenyl-1H-1,2,3-triazole (CPTC) and 5-(3-chlorophenyl) -1-phenyl-1H-1,2,3-triazole (PCTA) are two new derivatives of 1,2,3-triazole. Their structural and spectral properties were characterized by density functional theory calculations (DFT). The binding properties of CPTC or PCTA with several typical biomacromolecules such as human serum albumin (HSA), bovine hemoglobin (BHb), human immunoglobulin (HIgG) or DNA were investigated by molecular docking and multiple spectroscopic methodologies. The different parameters including binding constants and thermodynamic parameters for CPTC/PCTA-HSA/BHb/HIgG/DNA systems were obtained based on various fluorescence enhancement or quenching mechanisms. The results of binding constants indicated that there were the strong interactions between two triazoles and four biological macromolecules due to the higher order of magnitude between 10³ and 10⁵. The values of thermodynamic parameters revealed that the binding forces for these systems are mainly hydrophobic interactions, electrostatic force, or hydrogen bond, respectively, which are in agreement with the results of molecular docking to a certain extent. Moreover, the information from synchronous, 3D fluorescence and UV-Vis spectroscopies proved that two compounds CPTC and PCTA could affect the microenvironment of amino acids residues of three kinds of proteins. Based on the above experimental results, a comparison of the interaction mechanisms for CPTC/PCTA-proteins/DNA systems have been performed in view of their different molecular structures, which is beneficial for the further research in order to design them as the novel drugs.

Effects of theaflavins on the structure and function of bovine lactoferrin

In this study, theaflavins were used to interact with bovine lactoferrin (bLF) to observe the effects of theaflavins on the structure and functionality of bLF. Spectral experiments verified that theaflavins were able to interact with bLF by a static quenching method. The circular dichroism experiment further showed that the combination of theaflavins would lead a certain change in the structure of bLF. By comparing the calculated data of the spectral experiment and the degree of structural change after bLF binding to theaflavins, the theaflavin-3, 3'-digallate (TFDG), which had the strongest effect on the structure of bLF, was selected to explore its influence on effects of bLF functionality. Conclusions were drawn from iron binding, enzyme-linked immunosorbent and in vitro simulated digestion experiments-the addition of TFDG had a certain effect on the functionality of bLF.

Non-enzymatic glycation of human serum albumin modulates its binding efficacy towards bioactive flavonoid chrysin: A detailed study using multi-spectroscopic and computational methods

The non-enzymatic glycation of plasma proteins by reducing sugars have important consequences on the conformational and functional properties of protein. The formation of advanced glycation end products (AGEs) is responsible for cell death and other pathological conditions. We have synthesized the glycated human serum albumin (gHSA) and characterized the same by using differential spectroscopic measurements. The aim of the present study is to determine the effect of glycation on the binding of human serum albumin (HSA) with bioactive flavonoid chrysin, which possesses anti-cancer, anti-inflammatory and anti-oxidant activities. The interaction of chrysin with HSA and gHSA was studied using multi-spectroscopic, molecular docking and molecular dynamics (MD) simulation techniques. Chrysin quenched the intrinsic fluorescence of both HSA and gHSA by static quenching mechanism. The value of the binding constant (K_b) for the interaction of HSA-chrysin complex (4.779 ± 0.623 × 10⁵ M^-1 at 300 K) was found to be higher than that of gHSA-chrysin complex (2.206 ± 0.234 × 10⁵ M^-1 at 300 K). Hence, non-enzymatic glycation of HSA significantly reduced its binding affinity towards chrysin. The % α-helicity of HSA was found to get enhanced upon binding with chrysin, and minimal changes were observed for the gHSA-chrysin complex. Site marker probe studies indicated that chrysin binds to subdomain IIA and IIIA of both HSA and gHSA. The results from molecular docking and MD simulation studies correlated well with the experimental findings. Electrostatic interactions followed by hydrogen bonding and hydrophobic interactions played major roles in the binding process. These observations may have some useful insights into the field of pharmaceutics.