Studies on interactions of pentagalloyl glucose, ellagic acid and gallic acid with bovine serum albumin: A spectroscopic analysis

Ellagic acid-protein nano-complex inhibits tumor growth by reducing the intratumor bacteria and inhibiting histamine production

In recent years, there has been growing interest in understanding the role of bacteria within tumors and their potential as targets for cancer therapy. In this work, we developed an ellagic acid (EA) - endogenous protein (eP) nanocomposite (eP-EA) to target tumors by EPR (enhanced permeability and retention), kill bacteria within tumors to regulate anti-tumor immune responses. The potential mechanism of eP-EA treatment is associated with the reduced abundance and diversity of microorganisms within the tumor, culminating with an altered metabolism within the Tumor microenvironment (TME). Among them, the metabolite histamine that contributes to tumor progression, is significantly reduced in the TME after eP-EA treatment. We show that one possible mechanism by which these microbes promote tumor growth is through the production of histamine. This work suggests that the ellagic acid (EA)-protein nano complex can enhance cancer immunotherapy by targeting the intratumoral bacteria and reduce their production of histamine, delineating the potential relationship between intratumor bacteria and their impact on tumors. Our work suggests that the EA-protein nano complex can enhance cancer immunotherapy by targeting the intratumoral bacteria, suggesting the role of bacterial metabolites in contributing to tumor progression.

Preparation of soy protein isolate-ellagic acid conjugates through ultrasound-assisted metal-free Fenton reaction: Synthesis, structure, and functional properties

The grafting of polyphenols onto proteins possesses the potential to enhance their functional properties. In this study, ultrasound-assisted metal-free Fenton reaction grafting method (UMFM) was developed to efficiently prepare soy protein isolate (SPI)-ellagic acid (EA) conjugates. Under optimized conditions of 380 W, 50 °C, and 75 min, UMFM significantly improved the grafting degree of SPI with EA by 10.3 % and reduced the reaction time by 94.8 % compared to the conventional method. In addition, the results of reactive group content, multi-spectroscopy analysis, and surface hydrophobicity demonstrated the decrease in free amino and sulfhydryl groups contents, alterations in the secondary and tertiary structures of SPI, as well the ultrasonication-induced further unfolding of SPI structure, thereby facilitating the formation of covalent bonds between SPI and EA. Moreover, the functional properties of SPI, including thermal stability, emulsifying activity, and antioxidant properties, were significantly enhanced after conjugation with EA, especially in ultrasound-assisted conditions.

Gold nanoparticles decorated kaolinite mineral modified screen-printed electrode: Use for simple, sensitive determination of gallic acid in food samples

The current study offers the nanomolar quantification of gallic acid (GAL) based on gold nanoparticles (AuNps) and kaolinite minerals (KNT) modified on a screen-printed electrode (SPE). The electrochemical behavior of GAL was performed using differential pulse voltammetry (DPV) in Britton Robinson (BR) buffer solution at pH 2.0 as a supporting electrolyte. Under the optimized DPV mode parameters, the oxidation peak current of GAL (at 0.72 V vs Ag/AgCl) increased linearly in the range between 0.002 μmolL-1 and 40.0 μmolL-1 with a detection limit of 0.50 nmolL-1. The effect of common interfering agents was also investigated. Finally, the applicability of the proposed method was verified by quantification analysis of GAL in black tea and pomegranate juice samples.

Complexation of bovine lactoferrin with selected phenolic acids via noncovalent interactions: Binding mechanism and altered functionality

Noncovalent interactions of 4 selected phenolic acids, including gallic acid (GA), caffeic acid (CA), chlorogenic acid (CGA), and rosmarinic acid (RA) with lactoferrin (LF) were investigated. Compound combined with LF in the binding constant of CA > GA > RA > CGA, driven by van der Waals and hydrogen bonding for GA, and hydrophobic forces for others. Conformation of LF was affected at secondary and ternary structure levels. Molecular docking indicated that GA and CA located in the same site near the iron of the C-lobe, whereas RA and CGA bound to the C2 and N-lobe, respectively. Significantly enhanced antioxidant activity of complexes was found compared with pure LF, as demonstrated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis(2-ethylbenzothiazoline-6-sulfonate) (ABTS), and ferric reducing antioxidant power (FRAP) models. Caffeic acid, CGA, and RA significantly decreased the emulsifying stability index and improved foam ability of LF, and the effect of CA and RA was the most remarkable, respectively.

Ellagic acid-loaded soy protein isolate self-assembled particles: Characterization, stability, and antioxidant activity

The limited water solubility and bioactivity of lipophilic phytochemicals may be enhanced by delivery systems. Ellagic acid (EA) has antioxidant and anti-inflammatory properties, but low solubility and instability limit its use in the food industry. In this study, the pH-shift method was applied to encapsulate EA with soy protein isolate (SPI). The interaction, encapsulation, and protective potential of the EA-loaded soy SPI complexes (SPI-EA) were investigated. The fluorescence spectra results suggest that the reaction between SPI and EA is spontaneous, with hydrophobic interactions predominating. Binding of EA molecules quenches the intrinsic fluorescence of SPI, mainly static quenching, with a binding site involved in the binding process. The ultraviolet (UV)-visible spectroscopy of the SPI-EA complexes included the characteristic absorption peaks of both SPI and EA, and the scanning electron microscopy images further indicated that the EA had been successfully embedded in SPI. Fourier transform infrared spectroscopy illustrates that EA has significantly changed the secondary structure of the SPI, primarily in the form of a decreased content of α-helix structures and an increased content of β-sheet and random coil structures. The encapsulation efficiency of EA was concentration-dependent, up to 81.08%. The addition of EA reduces the size of SPI particles (d < 155 nm). In addition, the SPI-EA complex showed up to 81.05% and 96.46% 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity. TGA showed that the degradation temperature of SPI-EA complex could be extended up to 300°C. And by encapsulation of EA, the loss of EA under the action of UV light, heat treatment, and high concentration of salt ion sensitive environment can be reduced. PRACTICAL APPLICATION: Ellagic acid (EA), a natural bioactive with low water solubility and stability, can be enhanced by forming an inclusion complex with soy protein isolate (SPI). SPI-EA complex has broad potential applications in the food, beverage, and pharmaceutical industries. Multiple spectral analyses have contributed to our understanding of the formation and interaction mechanisms of the SPI-EA complex under pH-driven conditions. Stability assays have also aided in the development of dietary resources for EA.

Tannin complexation with metal ions and its implication on human health, environment and industry: An overview

Tannins, also known as plant polyphenols (PPs), are secondary metabolites widely existing in higher plants and are a kind of natural renewable resource with wide distribution, variety and quantity. Tannin has become an important class of fine chemicals due to the easily modified molecular structure and the properties of antibacterial and antioxidant, combining with protein and complexing with metal ion. Besides being used for tanning leather, tannins are also widely used in wood adhesive, concrete water-reducing agents, oil drilling fluid viscosity-reducing agents, pharmaceutical, mineral processing, water treatment, gas desulfurization, metal anticorrosion, wood anticorrosion, printing and dyeing, liquor clarification, oil antioxidant, daily chemical products and other products preparation. There are two groups of tannins: condensed tannins (CTs) (flavonoid-derived proanthocyanidins) and hydrolysable tannins (HTs) (gallic acid ester-derived). Tannins can form complexes with metals through the ortho-dihydroxyphenolic group(s), especially with transition metals. The structure-activity relationships, stoichiometry, and origin of the insolubility of which were emphasized. Furthermore, this paper proposed an in-depth discussion of the associations of tannins-metal complexes in human health, environment and industries.

Molecular insights into α-glucosidase inhibition and antiglycation properties affected by the galloyl moiety in (-)-epigallocatechin-3-gallate

BACKGROUND

Diabetes mellitus poses a substantial threat to public health due to rising morbidity and mortality. α-Glucosidase is one of the key enzymes affecting diabetes. Herein, (-)-epigallocatechin-3-gallate (EGCG) and (-)-epigallocatechin (EGC) were applied to clarify the role of the galloyl moiety of tea polyphenols in the inhibition of glycation and α-glucosidase activity. The structure-activity relationship of the galloyl moiety in EGCG on α-glucosidase was investigated in terms of inhibition kinetics, spectroscopy, atomic force microscopy and molecular docking. A bovine serum protein-fructose model was employed to determine the effect of the galloyl moiety on glycation.

RESULTS

The results indicated that the introduction of a galloyl moiety enhanced the capacity of EGCG to inhibit glycation and α-glucosidase activity. The IC50 value of EGC is approximately 2400 times higher than that of EGCG. Furthermore, the galloyl moiety in EGCG altered the microenvironment and secondary structure of α-glucosidase, resulting in a high binding affinity of EGCG to α-glucosidase. The binding constant of EGCG to α-glucosidase at 298 K is approximately 28 times higher than that of EGC.

CONCLUSION

Overall, the galloyl moiety of EGCG plays a crucial role in inhibiting glycation and α-glucosidase activity, which helps to enhance the molecular understanding of the structure and function of the polyphenol galloyl moiety in the science of food and agriculture. © 2023 Society of Chemical Industry.

Nickel chloride complexes with substituted 4'-phenyl-2',2':6',2″-terpyridine ligands: synthesis, characterization, anti-proliferation activity and biomolecule interactions

A series of Ni(II) sandwich-like coordinated compounds were synthesized by the reaction of nickel dichloride and ten 4'-(4-substituent phenyl)-2',2':6',2″-terpyridine ligands, and their structures were confirmed by elemental analysis, FT-IR, ESI-MS, solid state ultraviolet spectroscopy and X-ray single crystal diffraction analysis. Three human cancer cell lines and a normal human cell line were used for anti-proliferation potential study: human lung cancer cell line (A549), human esophageal cancer cell line (Eca-109), human liver cancer cells (Bel-7402) and normal human liver cells (HL-7702). The results show that these nickel complexes possess good inhibitory effects on the cancer cells, outperforming the commonly used clinical chemotherapy drug cisplatin. Especially, complexes 3 (-methoxyl) and 7 (-fluoro) have strong inhibitory ability against Eca-109 cell line with IC50 values of 0.223 μM and 0.335 μM, complexes 4 and 6 showed certain cell selectivity, and complex 6 can inhibit cancer cells and slightly poison normal cells when the concentration was controlled. The ability of these complexes binding to CT-DNA was studied by UV titration and CD spectroscopy, and CD spectroscopy was also used to study the secondary structural change of BSA under the action of the complexes. The binding of these complexes with DNA, DNA-Topo I and bovine serum protein has been simulated by molecular docking software, and the docking results and optimal binding conformation data showed that they interacted with DNA in the mode of embedded binding, which is consistent with the experimental results. These complexes are more inclined to move to the cleavage site when docking with DNA-Topo I, so as to play a role of enzyme cleavage, while BSA promotes the action of the complexes by binding to effective binding sites.

Exploring the binding mechanism and adverse toxic effects of degradation metabolites of pyrethroid insecticides to human serum albumin: Multi-spectroscopy, calorimetric and molecular docking approaches

Pyrethroid insecticides (PIs), a class of structurally similar non-persistent organic pollutants, can be degraded and metabolized to more toxic, and longer half-life products. In this study, the binding interaction mechanisms between human serum albumin (HSA) and the main degradation metabolites of PIs, 3-phenoxybenzoic acid (3-PBA) and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), were studied by theoretical simulation and experimental verification. Steady state fluorescence spectra showed that the fluorescence quenching mechanism was static. According to the binding constant, 4-F-3-PBA (1.53 × 105 L mol-1) was bound more strongly to HSA than 3-PBA (1.42 × 105 L mol-1) in subdomain ⅡA (site I). It was found by isothermal titration calorimetry that the metabolites and HSA spontaneously combined mainly through hydrogen bond and van der Waals interaction. Ultraviolet absorption spectra and circular dichroism spectra showed that the metabolites caused slight changes in the microenvironment and conformation of HSA. The above results were proved by molecular docking. The toxicity properties of the metabolites were further analyzed by software, and 4-F-3-PBA was found to be more toxic than 3-PBA. Considering the high exposure level of these metabolites in food, the environment and human body, it is necessary to further explore the toxicity of PIs metabolites.

Effect of Cu2+ and Al3+ on the interaction of chlorogenic acid and caffeic acid with serum albumin

Despite the phenolic acids' health benefits, their interactions with proteins are still unclear. In this study, the interactions of Bovine Serum Albumin (BSA) with chlorogenic acid (CHA), caffeic acid (CA), and their Al³⁺, Cu²⁺ complexes were studied by using circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and UV/Vis spectroscopy. It was found that esterification of carboxyl group of CA with quinic acid increased the binding affinities for BSA. After chelating with Cu²⁺ and Al³⁺, both CHA and CA exhibited high binding affinities for BSA. CHA could form CHA-Cu₂ and CHA-Al₂ complex with Cu²⁺ and Al³⁺. The result of CD spectroscopy demonstrated that the binding of CHA and Al³⁺ with BSA contributed to the folding of BSA secondary structure. In addition, with the presence of CHA, binding with Al³⁺ could also induce changes in BSA conformation. The binding sites of both CHA and CA were closed to Trp213.

Insight into the interaction between tannin acid and bovine serum albumin from a spectroscopic and molecular docking perspective

In this study, the interaction mechanism of bovine serum albumin (BSA) with tannic acid (TA) was investigated by spectroscopic and computational approaches and further validated using circular dichroism (CD), differential scanning calorimetry (DSC) and molecular docking techniques. The fluorescence spectra showed that TA bound to BSA and underwent static quenching at a single binding site, which was consistent with the molecular docking results. And the fluorescence quenching of BSA by TA was dose-dependent. Thermodynamic analysis indicated that hydrophobic forces dominated the interaction of BSA with TA. The results of circular dichroism showed that the secondary structure of BSA was slightly changed after coupling with TA. Differential scanning calorimetry showed that the interaction between BSA and TA improved the stability of the BSA-TA complex, and the melting temperature increased to 86.67 °C and the enthalpy increased to 264.1 J g^-1 when the ratio of TA to BSA was 1.2 : 1. Molecular docking techniques revealed specific amino acid binding sites for the BSA-TA complex with a docking energy of -12.9 kcal mol^-1, which means the TA is non-covalently bound to the BSA active site.

Hydrogen bond-driven assembly of coral-like soy protein isolate-tannic acid microcomplex for encapsulation of limonene

BACKGROUND

The encapsulation of flavor and aroma compounds has great potential in foods, while effective preparation in the food industry is still a great challenge. Inspired by leather tanning, tannic acid (TA) was used for deep crosslinking through hydrogen bond-driven assembly on soy protein isolate for encapsulating limonene with a high loading ratio.

RESULTS

The added TA changed the protein structure and formed a limonene-loaded microcomplex. The morphology of these microcomplexes changed from smooth to rough, followed by the formation of smooth nanoparticle aggregates, by changing the amount of TA. The encapsulation efficiency and loading ratio were increased from 0.78% and 4.30% to 59.32% and 45.78% after increasing TA from 1.875 to 60 mg mL^-1 . The result of confocal laser scanning microscopy indicated that limonene is evenly distributed in microcomplexes. Additionally, the results of thermal stability demonstrated protection of limonene by soy protein-tannic acid microcomplex.

CONCLUSION

It is suggested that the added TA improved the encapsulation efficiency and loading ratio. Limonene is loaded in the complex in two ways. The present research provides a new and easy path for the preparation of the non-thermal soy protein aroma carrier. © 2022 Society of Chemical 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.

Insights into the interaction of cyclooxygenase and lipoxygenase with natural compound 3,4',5,7-Tetrahydroxyflavone based on multi-spectroscopic and metabolomics

Hypoxia induce right ventricular dysfunction in human heart, but the molecular mechanism remains limited. As known, cyclooxygenases (COX) and lipoxygenases (LOX) play a key role in the cardiovascular system under hypoxia. 3,4',5,7-Tetrahydroxyflavone (THF), which widely exists in a variety of plants and vegetables, is famous for good ability to relieve cardiac injury, but the mechanism remains to be further understood. In this study, we firstly estimated the preventive role of THF against hypoxia-induced right ventricular dysfunction. Metabolomics analysis showed there were differential metabolites involved in above process, which helped us to screen the crucial regulated enzymes of these metabolites. Molecular docking and multi-spectroscopic revealed the molecular mechanism of interaction between THF and COX/LOX. Results suggested that THF bound to COX/LOX through static quenching and these bindings were driven by hydrogen bonds. After binding with THF, the secondary structure of COX/LOX was changed. In general, this study indicated that THF inhibited COX/LOX by spontaneously forming complexes with them.

Interaction mechanism of benzophenone-type UV filters on bovine serum albumin: Insights from structure-affinity relationship

Benzophenone (BP)-type UV filters can cause structural changes of carrier protein in plasma. The binding process of five BP-type UV filters with bovine serum albumin (BSA) was investigated by multiple characterization methods, along with their structure-affinity relationship involving the structure of the five BP-type UV filters and their binding affinity for BSA. The BP-type UV filters investigated bound to BSA spontaneously, and altered conformation of BSA. The binding constants and number of binding sites between BP-type UV filters and BSA were 10³-10⁶ M^-1 and 0.82-1.26, respectively. These BP-type UV filters and BSA interacted with the same binding forces and went through the similar binding process, suggesting that the benzophenone skeleton structure was primarily responsible for the BP-type UV filters and BSA binding, and changes in the structure of the BSA. The BP-type UV filters with hydroxyl substituent (BP-1 and BP-9) and non-polar molecules (BP-6) had a high affinity for binding BSA and had a greater impact on BSA conformation.

Explore the Interaction between Ellagic Acid and Zein Using Multi-Spectroscopy Analysis and Molecular Docking

With the increasing interest in value-added maize products, the interaction of zein with bioactive molecules to become more nutritional and beneficial to human health has gained a lot of attention. To broaden the application of ellagic acid (EA) in maize flour products, we investigated the interaction between zein and EA. The fluorescence quenching type of zein interacting with EA was mainly static quenching through hydrophobic interaction, as demonstrated by quenching behavior modeling, and ultraviolet-visible spectroscopy confirmed the formation of zein–EA complexes. Synchronous fluorescence spectroscopy showed that EA reduced the polarity of zein around tyrosine residues, which were exposed to a more hydrophobic microenvironment. Meanwhile, circular dichroism suggested that EA noticeably changed the secondary structure of zein, which was mainly reflected in the increase of α-helix and β-sheet content and the decrease of random coil content. Finally, the molecular docking simulation found that zein could have five active sites binding to EA and there was hydrogen bond interaction besides hydrophobic interaction. The findings of this study provided a basis for a theory for the interaction mechanism between zein and EA, which could be essential for developing value-added plant-derived protein products using EA as a functional component.

Interaction of bovine serum albumin with ellagic acid and urolithins A and B: Insights from surface plasmon resonance, fluorescence, and molecular docking techniques

Human serum albumin (HSA) shows the sequence homology and structural similarity with bovine serum albumin (BSA). Therefore, here, the interaction of natural phenolic antioxidants, ellagic acid (ELA), and its derivatives-urolithins A (ULA) and B (ULB)-with BSA was investigated. The results of surface plasmon resonance (SPR) indicated a high affinity of ELA, ULA, and ULB to BSA, with KD value < 1 × 10-6 M. The KD values of binding of the studied compounds to BSA increased with temperature, revealing a reduction in affinity with an increase in temperature. Fluorescence data showed that the quenching of BSA by tested compounds occurred via a static quenching. However, the affinity of ELA for BSA was higher than that of ULA and ULB, which may be because of the presence of a large number of hydroxyl groups in its structure. The assessment of the antioxidant activity of BSA and BSA-ELA/ULA/ULB complexes using the DPPH assay indicated that the DPPH scavenging activity of BSA increased after complex formation with ELA/ULA/ULB in the following order: BSA-ELA > BSA-ULA > BSA-ULB > BSA, which was due to their structural differences. The results of the docking analysis were in agreement with the experimental results.

Functionalization of sweet potato leaf polyphenols by nanostructured composite β-lactoglobulin particles from molecular level complexations: A review

Sweet potato leaf polyphenols (SPLPs) have shown potential health benefits in the food and pharmaceutical industries. Nowadays, consumption of SPLPs from animal feeds to foodstuff is becoming a trend worldwide. However, the application of SPLPs is limited by their low bioavailability and stability. β-lactoglobulin (βlg), a highly regarded whey protein, can interact with SPLPs at the molecular level to form reversible or irreversible nanocomplexes (NCs). Consequently, the functional properties and final quality of SPLPs are directly modified. In this review, the composition and structure of SPLPs and βlg, as well as methods of molecular complexation and mechanisms of formation of SPLPsβlgNCs, are revisited. The modified functionalities of SPLPsβlgNCs, especially protein conformational structures, antioxidant activity, solubility, thermal stability, emulsifying, and gelling properties including allergenic potential, digestibility, and practical applications are discussed for SPLPs future development.

Complexation of ellagic acid with α-lactalbumin and its antioxidant property

Ellagic acid possesses numerous bioactivities such as antioxidant activity and anti-inflammatory effect. In this work, the binding interaction between ellagic acid and α-lactalbumin was investigated by multi-spectroscopy and the results suggested that ellagic acid could change the conformation of α-lactalbumin. Chromatographic analysis proved the interaction of α-lactalbumin with ellagic acid taken place in less than 30 min and this interaction was stable. Computer simulations showed that both aromatic clusters Ⅰ and Ⅱ of α-lactalbumin were active sites for ellagic acid. Interestingly, both the results of molecular docking and molecular dynamics simulations suggested that ellagic acid tended to bind to aromatic cluster Ⅱ rather than aromatic cluster Ⅰ. Moreover, α-lactalbumin could enhance the antioxidant property of ellagic acid, indicating that the solubility of ellagic acid might be improved by combining α-lactalbumin. Overall, this work suggested that α-lactalbumin exhibited binding affinity for ellagic acid and enhanced its antioxidant property.

In Vitro and In Silico Interaction Studies with Red Wine Polyphenols against Different Proteins from Human Serum

Previous reports have shown that consumption of wine has several health benefits; however, there are different types of wine. In the present study, red wines were investigated for their compositions of active ingredients. The interaction of each component in terms of its binding mode with different serum proteins was unraveled, and the components were implicated as drug candidates in clinical settings. Overall, the study indicates that red wines have a composition of flavonoids, non-flavonoids, and phenolic acids that can interact with the key regions of proteins to enhance their biological activity. Among them, rutin, resveratrol, and tannic acid have shown good binding affinity and possess beneficial properties that can enhance their role in clinical applications.

Dietary polyphenols inhibit plasma protein arabinosylation: Biomolecular interaction of genistein and ellagic acid with serum albumins

The mode of interaction of polyphenolic compounds like genistein (GTN) and ellagic acid (EGA) with human and bovine serum albumin (HSA and BSA, respectively) was found to differ significantly. Stern-Volmer (SV) analysis of the fluorescence quenching data revealed that the binding strength of EGA (1.9 ± 0.09 × 105 M-1) to HSA is about one order of magnitude higher than GTN (2.24 ± 0.06 × 104 M-1). While the static quenching of HSA fluorescence was found to proceed through simple Stern-Volmer (SV) mechanism, a quenching sphere-of-action model was indispensable for BSA. Temperature dependent fluorescence along with a series of other biophysical experiments and ensemble docking calculation revealed that EGA and GTN bind to the serum proteins primarily through the entropy driven process. The α-helical content and the microenvironment near Trp residue of HSA and BSA did not show any appreciable change due to the binding of either GTN or EGA. Interestingly, both GTN and EGA were found to inhibit the formation of advanced glycated end (AGE) product of serum proteins up to the extent of 70-90% within 12-24 h. Relatively moderate binding propensity along with the anti-glycation ability of the polyphenols confirmed that GTN and EGA can be used either as an alternative or towards development of suitable drugs in the prevention of many diabetic-related complications.

Pentagalloyl Glucose-Laden Poly(lactide-co-glycolide) Nanoparticles for the Biomechanical Extracellular Matrix Stabilization of an In Vitro Abdominal Aortic Aneurysm Model

The suppression of abdominal aortic aneurysm (AAA) growth by nonsurgical therapy is currently not an option, and AAA is considered an irreversible destructive disease. The formation and development of AAA is associated with the progressive deterioration of the aortic wall. Infiltrated macrophages and resident vascular smooth muscle cells oversecrete matrix metalloproteinases (MMPs), which cause the loss of crucial aortic extracellular matrix (ECM) components, thus weakening the aortic wall. Stabilization of the aortic ECM could enable the development of novel therapeutic options for preventing and reducing AAA progression. In the present work, we studied the biochemical and biomechanical interactions of pentagalloyl glucose (PGG) on mouse C2C12 myoblast cells. PGG is a naturally occurring ECM-stabilizing polyphenolic compound that has been studied in various applications, including vascular health, with promising results. With its known limitations of systemic administration, we also studied the administration of PGG when encapsulated within poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs). Treatment with collagenase and elastase enzymes was used to mimic a pathway of degenerative effects seen in the pathogenesis of human AAA. PGG and PLGA(PGG) NPs were added to enzyme-treated cells in either a suppressive or preventative scenario. Biomolecular interactions were analyzed through cell viability, cell adhesion, reactive oxygen species (ROS) production, and MMP-2 and MMP-9 secretion. Biomechanical properties were studied through atomic force microscopy and quartz crystal microbalance with dissipation. Our results suggest that PGG or PLGA(PGG) NPs caused minor to no cytotoxic effects on the C2C12 cells. Both PGG and PLGA(PGG) NPs showed reduction in ROS and MMP-2 secretion if administered after enzymatic ECM degradation. A quantitative comparison of Young's moduli showed a significant recovery in the elastic properties of the cells treated with PGG or PLGA(PGG) NPs after enzymatic ECM degradation. This work provides preliminary support for the use of a pharmacological therapy for AAA treatment.

How hydrophilic group affects drug-protein binding modes: Differences in interaction between sirtuins inhibitors Tenovin-1/Tenovin-6 and human serum albumin

Introduction of hydrophilic groups can improve the solubility of leading drugs but inevitably affect their interaction with proteins. This study selected sirtuin inhibitors Tenovin-1 (T1) and Tenovin-6 (T6) as drug models to determine differences in binding mode to human serum albumin (HSA). T1 and T6 quenched the endogenous fluorescence of HSA via static quenching mechanism. Introduction of hydrophilic groups greatly reduced the binding constant, i.e., from 1.302 × 10⁴ L mol^-1 for the HSA-T6 system to 0.128 × 10⁴ L mol^-1 for the HSA-T1 system. HSA-T1 system was mainly driven by electrostatic interactions while that of HSA-T6 system was hydrophobic interaction and both systems were spontaneous reactions. Site marker experiments and molecular docking indicated that both systems mainly bound to the hydrophobic site I of HSA. Molecular dynamics (MD) simulation analysis further revealed that Tyr148, Tyr150 and Arg257 residues played a key role in this recognition process for both systems. In particular, T6 maintained additional several hydrogen bonds with the surrounding residues. T1 had almost no effect on the esterase-like activity of HSA, but T6 inhibited the hydrolysis of p-NPA. Furthermore, differential scanning calorimetry (VP-DSC), circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy confirmed that HSA in the T6 system undergone a more significant conformational transition than that in the T1 system.

Typical organic pollutant-protein interactions studies through spectroscopy, molecular docking and crystallography: A review

With the development of industry and human society, more attention was paid for the toxic effects of organic pollutants that are closely related to human daily life. Previous studies mainly focused on the dose-response relationship and cytotoxic effects of pollutants to organisms，while little research focused on pollutant-protein interactions at molecular level. However, the binding of organic pollutants to biomolecules, especially proteins like transporters, membrane receptor and nuclear receptors, is often the first step of toxic effects. It can make a series of endocrine disrupting and genotoxic effects through cell signaling pathway by binding specific target proteins including serum albumin, thyroid transporter, estrogen receptor, androgen receptor, and aryl hydrocarbon receptor. Thus, the research of interactions between organic pollutants and proteins is helpful and necessary to understand the distribution, metabolism and toxicity mechanism of compounds in organisms at the molecular level. This paper reviewed the latest research progress of the interaction types of persistent organic pollutants (POPs), emerging pollutants and some other pollutants with targeted proteins. In addition, we summarized several main experimental techniques for studying pollutant-protein interactions including ultraviolet/visible absorption spectrometry (UV-vis), fluorescence, infrared spectrometry, circular dichroic spectra (CD), molecular docking and X-ray crystallography. This review contributes to the molecular mechanism of the interaction between organic pollutants and biomolecules.