Binding studies of lophirone B with bovine serum albumin (BSA): Combination of spectroscopic and molecular docking techniques

Interaction of plant phenol vanillin with human hemoglobin: A spectroscopic and molecular docking study

Vanillin is a phenolic aldehyde widely used as a flavouring agent in the food industry. Vanillin has many health benefits and has gained attention in pharmacological industries also, due to its antioxidant properties and non-toxic nature. The interaction of vanillin with human hemoglobin (hHb), an abundant tetrameric heme protein, was investigated by several spectroscopic techniques and molecular modeling methods. UV-visible spectra showed that the binding of vanillin to hHb induces structural changes due to alterations in the micro-environment of hHb. Vanillin quenches the intrinsic fluorescence of hHb by the dynamic mechanism, which was confirmed by both temperature dependent and time resolved fluorescence studies. Vanillin binds spontaneously to hHb at a single site and the binding is stabilized by hydrogen bonds and hydrophobic interactions. The circular dichroism spectra showed that the binding of vanillin altered the secondary structure of hHb due to change in its alpha-helical content. Molecular docking identified the amino acids of hHb involved in binding to vanillin and also that the free energy change of the binding reaction is -5.5 kcal/mol. Thus, our results indicate that vanillin binds spontaneously to hHb at a single site and alters its secondary structure. This will help in understanding the potential use of vanillin and related antioxidants as therapeutic agents in various hematological disorders.

Biophysical studies of the binding of histone deacetylase inhibitor (Trichostatin-A) with bovine serum albumin

Trichostatin A (TSA), a potential radiomitigator in pre-clinical models, inhibits the class I and II mammalian histone deacetylase (HDAC) enzyme family preferentially. In the current study, the ADME assessment of TSA was explored in terms of its binding affinity for serum protein via spectroscopic and molecular docking techniques. Fluorescence spectroscopy was used to examine changes in the protein microenvironment, and affinity was quantified in terms of binding constant and stoichiometry. Post binding conformational changes were observed using circular dichroism (CD) and UV-Visible spectroscopy. Specific binding was visualized using molecular docking to support experimental studies. UV-vis spectra demonstrated a blue shift in the interaction of TSA to BSA. The calculated binding constants ranged from 3.10 to 0.78 x 10 5(M-1) and quenching constants from 2.75 to 2.15 x 104 (l mol-1), indicating TSA has a strong binding affinity for BSA. Based on the FRET theory, the distance between BSA (donor) and TSA (acceptor) was calculated to be 2.83 nm. The Stern-Volmer plot revealed (Ksv) static quenching. Thermodynamic parameters were calculated, and a negative ΔG value showed that the interaction is spontaneous. The CD spectra analysis further revealed a change in the protein's secondary structure, indicating TSA-BSA interaction. The molecular docking studies also indicated strong binding affinity of TSA with BSA. The results indicate that good bio-availability of TSA is possible because of the spontaneous and strong binding affinity with BSA.Communicated by Ramaswamy H. Sarma.

Green synthesis of zinc ferrite nanoparticles from Nyctanthes arbor-tristis: unveiling larvicidal potential, protein binding affinity and photocatalytic activities

Environmental pollution, being a major concern worldwide, needs a unique and ecofriendly solution. To answer this, researchers are aiming in utilizing plant extracts for the synthesis of nanoparticles. These NPs synthesized using plant extracts provide a potential, environmentally benign technique for biological and photocatalytic applications. Especially, plant leaf extracts have been safe, inexpensive, and eco-friendly materials for the production of nanoparticles in a greener way. In this work, zinc ferrite nanoparticles (ZnFe2O4 NPs) were prepared using Nyctanthes arbor-tristis leaf extract by hydrothermal method, and its biological and photocatalytic properties were assessed. The synthesized ZnFe2O4 NPs were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR). X-ray diffraction confirmed the arrangement of the fcc crystal structure of the nanoparticles and that some organic substances were encapsulated within the zinc ferrite. According to the SEM analysis, the resulting nanoparticles got agglomerated and spherical in shape. The ZnFe2O4 nanoparticles are in their pure form, and all of their elemental compositions were shown by the energy-dispersive X-ray analysis (EDAX) spectrum. The FTIR results revealed that the produced nanoparticles contained distinctive functional groups. Fluorescence spectroscopy was used to examine the binding affinities between bovine serum albumin (BSA) and ZnFe2O4 nanoparticles in terms of protein binding, stability, and conformation. The interaction between BSA and ZnFe2O4 NPs was examined using steady-state and time-resolved fluorescence measurements, and it was evident that static quenching occurred. The ability of ZnFe2O4 nanoparticles to kill Culex quinquefasciatus (C. quinquefasciatus) larvae was evaluated. The synthesized NPs demonstrated a noteworthy toxic effect against the fourth instar larvae of C. quinquefasciatus with LC50 values of 43.529 µg/mL and LC90 values of 276.867 µg/mL. This study revealed the toxicity of green synthesized ZnFe2O4 NPs on mosquito larvae, proving that these NPs are good and effective larvicides. Furthermore, the ZnFe2O4 NPs were utilized for dye degradation of methylene blue under visible light treatment and achieved 99.5% degradation.

Characterization of the covalent binding of cyanidin-3-glucoside to bovine serum albumin and its inhibition mechanism for advanced nonenzymatic glycosylation reactions

Nonenzymatic glycosylation of proteins can generate advanced glycosylation end products, which are closely associated with the pathogenesis of certain chronic physiological diseases and aging. In this study, we characterized the covalent binding of cyanidin-3-glucoside (C3G) to bovine serum albumin (BSA) and investigated the mechanism by which this covalent binding inhibits the nonenzymatic glycosylation of BSA. The results indicated that the covalent interaction between C3G and BSA stabilized the protein's secondary structure. Through liquid chromatography-electrospray ionization tandem mass spectrometry analysis, we identified the covalent binding sites of C3G on BSA as lysine, arginine, asparagine, glutamine, and cysteine residues. This covalent interaction significantly suppressed the nonenzymatic glycosylation of BSA, consequently reducing the formation of nonenzymatic glycosylation products. C3G competitively binds to nonenzymatic glycosylation sites (e.g., lysine and arginine) on BSA, thereby impeding the glycosylation process and preventing the misfolding and structural alterations of BSA induced by fructose. Furthermore, the covalent attachment of C3G to BSA preserves the secondary structure of BSA and hinders subsequent nonenzymatic glycosylation events.

Exploring the interaction of a potent anti-cancer drug Selumetinib with bovine serum albumin: Spectral and computational attributes

The binding of drugs to plasma proteins determines its fate within the physiological system, hence profound understanding of its interaction within the bloodstream is important to understand its pharmacodynamics and pharmacokinetics and thereby its therapeutic potential. In this regard, our work delineates the mechanism of interaction of Selumetinib (SEL), a potent anti-cancer drug showing excellent effect against multiple solid tumors, with plasma protein bovine serum albumin (BSA), using methods such as absorption, steady-state fluorescence, time-resolved, fluorescence resonance energy transfer, Fourier transform infrared spectra (FTIR), circular dichroism (CD), synchronous and 3D-fluorescence, salt fluorescence, molecular docking and molecular dynamic simulations. The BSA fluorescence intensity was quenched with increasing concentration of SEL which indicates interactions of SEL with BSA. Stern-Volmer quenching analysis and lifetime studies indicate the involvement of dynamic quenching. However, some contributions from the static quenching mechanism could not be ruled out unambiguously. The association constant was found to be 5.34 × 105 M-1 and it has a single binding site. The Förster distance (r) indicated probable energy transmission between the BSA and SEL. The positive entropy changes and enthalpy change indicate that the main interacting forces are hydrophobic forces, also evidenced by the results of molecular modeling studies. Conformation change in protein framework was revealed from FTIR, synchronous and 3D fluorescence and CD studies. Competitive binding experiments as well as docking studies suggest that SEL attaches itself to site I (subdomain IIA) of BSA where warfarin binds. Molecular dynamic simulations indicate the stability of the SEL-BSA complex. The association energy between BSA and SEL is affected in the presence of different metals differently.

Increasing the polarity of β-lapachone does not affect its binding capacity with bovine plasma protein

Despite ortho-quinones showing several biological and pharmacological activities, there is still a lack of biophysical characterization of their interaction with albumin - the main carrier of different endogenous and exogenous compounds in the bloodstream. Thus, the interactive profile between bovine serum albumin (BSA) with β-lapachone (1) and its corresponding synthetic 3-sulfonic acid (2, under physiological pH in the sulphonate form) was performed. There is one main binding site of albumin for both β-lapachones (n ≈ 1) and a static fluorescence quenching mechanism was proposed. The Stern-Volmer constant (KSV) values are 104 M-1, indicating a moderate binding affinity. The enthalpy (-3.41 ± 0.45 and - 8.47 ± 0.37 kJ mol-1, for BSA:1 and BSA:2, respectively) and the corresponding entropy (0.0707 ± 0.0015 and 0.0542 ± 0.0012 kJ mol-1 K-1) values indicate an enthalpically and entropically binding driven. Hydrophobic interactions and hydrogen bonding are the main binding forces. The differences in the polarity of 1 and 2 did not change significantly the affinity to albumin. In addition, the 1,2-naphthoquinones showed a similar binding trend compared with 1,4-naphthoquinones.

Characterization, modes of interactions with DNA/BSA biomolecules and anti-tumor activity of newly synthesized dinuclear platinum(II) complexes with pyridazine bridging ligand

Platinum-based drugs are widely recognized efficient anti-tumor agents, but faced with multiple undesirable effects. Here, four dinuclear platinum(II) complexes, [{Pt(1,2-pn)Cl}2(μ-pydz)]Cl2 (C1), [{Pt(ibn)Cl}2(μ-pydz)]Cl2 (C2), [{Pt(1,3-pn)Cl}2(μ-pydz)]Cl2 (C3) and [{Pt(1,3-pnd)Cl}2(μ-pydz)]Cl2 (C4), were designed (pydz is pyridazine, 1,2-pn is ( ±)-1,2-propylenediamine, ibn is 1,2-diamino-2-methylpropane, 1,3-pn is 1,3-propylenediamine, and 1,3-pnd is 1,3-pentanediamine). Interactions and binding ability of C1-C4 complexes with calf thymus DNA (CT-DNA) has been monitored by viscosity measurements, UV-Vis, fluorescence emission spectroscopy and molecular docking. Binding affinities of C1-C4 complexes to the bovine serum albumin (BSA) has been monitored by fluorescence emission spectroscopy. The tested complexes exhibit variable cytotoxicity toward different mouse and human tumor cell lines. C2 shows the most potent cytotoxicity, especially against mouse (4T1) and human (MDA-MD468) breast cancer cells in the dose- and time-dependent manner. C2 induces 4T1 and MDA-MD468 cells apoptosis, further documented by the accumulation of cells at sub-G1 phase of cell cycle and increase of executive caspase 3 and caspase 9 levels in 4T1 cells. C2 exhibits anti-proliferative effect through the reduction of cyclin D3 and cyclin E expression and elevation of inhibitor p27 level. Also, C2 downregulates c-Myc and phosphorylated AKT, oncogenes involved in the control of tumor cell proliferation and death. In order to measure the amount of platinum(II) complexes taken up by the cells, the cellular platinum content were quantified. However, C2 failed to inhibit mouse breast cancer growth in vivo. Chemical modifications of tested platinum(II) complexes might be a valuable approach for the improvement of their anti-tumor activity, especially effects in vivo.

Network-supported and adaptable binding efficacy for flexible and multi-functionalized chitosan/phenolic carbaldehyde hydrogels

A thoughtful strategy has been intended to control the hydrogel networking to assess the binding efficacy of multifunctional hydrogel. The processing of two distinct network-supported hydrogels has portrayed to express the operating interactions involved during co-existence with solvents, small molecules, biomolecules, etc. Herein, chitosan has separately functionalized in semisynthetic approaches with 4-hydroxyisopthalaldehyde (ChDA) and 2-hydroxybenzene-1,3,5-tricarbaldehyde (ChTA) to construct different gel networks. The disposition of gel networks ChDA adapts more flexible chain or spine, whereas ChTA possesses restricted movements within gel networks. The gel networks of hydrogels have a significant role in their distinct physical activities. Their gel-bonding elucidations have performed to establish the variation in mechanical, swelling photophysical properties, etc. Remarkable self-fluorescence behaviors are used as a tool for binding study. Distinctive gel networks and their flexibility have investigated against self-fluorescence, UV-Vis, and FTIR against small molecule, Boron trifluoride and biomolecule, and Bovine serum albumin. Hydrogel/BF3 shows variation in fluorescence due to the disposition of gel networks. Hydrogel/BSA quenching of fluorescence at three different temperatures provides the binding constant and Stern-Volmer quenching constant. Theoretical DFT and docking studies successfully established the flexibility against binding study. The controlling of cross-linking or functionalization is very crucial for the development of hydrogel-mediated applications.

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.

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.

Hantzsch-Like Synthesis, DNA Photocleavage, DNA/BSA Binding, and Molecular Docking Studies of Bis(sulfanediyl)bis(tetrahydro-5-deazaflavin) Analogs Linked to Naphthalene Core

The cyclocondensation reaction of aldehydes with dimedone and bis(6-aminopyrimidin-4-one) in acetic acid led to the formation of the corresponding bis(pyrimido[4,5-b]quinoline-4,6-diones) which are known as bis(sulfanediyl)bis(tetrahydro-5-deazaflavin) analogs in a single step. Also, bis(pyrimido[4,5-b]quinoline-4,6-diones) which are linked to naphthyl core via phenoxymethyl linkage is prepared. The interactions of the synthesized compounds with DNA and bovine serum albumin (BSA) were studied. Gel electrophoresis assay was used to show the capability of the compounds to photocleave the supercoiled pBR322 plasmid DNA in UV-A (365 nm). Besides, the most photocleavable compound, bis(tetrahydropyrimido[4,5-b]quinoline-4,6-dione) linked to pyridin-3-yl at position-5 exhibits good binding affinities toward CT-DNA and BSA as supported by UV/VIS spectral studies. In addition to the experimental findings, a molecular docking simulation was performed to collect detailed binding data for this compound to both biomolecules.

Biophysical Characterization of the Interaction between a Transport Human Plasma Protein and the 5,10,15,20-Tetra(pyridine-4-yl)porphyrin

The interaction between human serum albumin (HSA) and the non-charged synthetic photosensitizer 5,10,15,20-tetra(pyridine-4-yl)porphyrin (4-TPyP) was evaluated by in vitro assays under physiological conditions using spectroscopic techniques (UV-vis, circular dichroism, steady-state, time-resolved, synchronous, and 3D-fluorescence) combined with in silico calculations by molecular docking. The UV-vis and steady-state fluorescence parameters indicated a ground-state association between HSA and 4-TPyP and the absence of any dynamic fluorescence quenching was confirmed by the same average fluorescence lifetime for HSA without (4.76 ± 0.11 ns) and with 4-TPyP (4.79 ± 0.14 ns). Therefore, the Stern-Volmer quenching (K_SV) constant reflects the binding affinity, indicating a moderate interaction (10⁴ M^-1) being spontaneous (ΔG°= -25.0 kJ/mol at 296 K), enthalpically (ΔH° = -9.31 ± 1.34 kJ/mol), and entropically (ΔS° = 52.9 ± 4.4 J/molK) driven. Binding causes only a very weak perturbation on the secondary structure of albumin. There is just one main binding site in HSA for 4-TPyP (n ≈ 1.0), probably into the subdomain IIA (site I), where the Trp-214 residue can be found. The microenvironment around this fluorophore seems not to be perturbed even with 4-TPyP interacting via hydrogen bonding and van der Waals forces with the amino acid residues in the subdomain IIA.

Probing the biomolecular (DNA/BSA) interaction by new Pd(II) complex via in-depth experimental and computational perspectives: synthesis, characterization, cytotoxicity, and DFT approach

Scientists should not forget that the rate of death as a result of cancer is far more than that of other diseases like influenza or coronavirus (COVID-19), so the research in this field is of cardinal significance. Therefore, a new and hydrophilic palladium(II) complex of the general formula [Pd(bpy)(proli-dtc)]NO₃, in which bpy and proli-dtc are 2,2'-bipyridine and pyrroline dithiocarbamate ligands, respectively, was synthesized and characterized utilizing spectral and analytical procedures. Density functional theory (DFT) calculation was also performed with B3LYP method in the gas phase. The DFT and spectral analysis specified that the Pd(II) atom is found in a square-planar geometry. HOMO/LUMO analysis, quantum chemical parameters and MEP surface of the complex were investigated to acquire an intuition about the nature of the compound. Partition coefficient and water solubility determination showed that both lipophilicity and hydrophilicity of the compound are more than cisplatin. The 50% inhibition concentration (IC₅₀) value was evaluated against K562 cancer cells, the obtained result has revealed a promising cytotoxic effect. DNA and BSA binding of the complex were explored through multi-spectroscopic (UV–Vis, fluorescence, FRET, and CD) and non-spectroscopic (gel electrophoresis, viscosity and docking simulation) techniques. The obtained findings demonstrated that the complex strongly interacts with CT-DNA by hydrophobic interactions and possesses medium interaction with BSA via hydrogen bond and van der Waals forces, thus BSA could efficiently carry out complex transportation. Furthermore, the results of docking simulation agree well with the experimental findings. In conclusion, the new Pd(II) complex has cytotoxic activity and could interact with DNA and BSA effectively.

Interaction between Caffeic Acid Phenethyl Ester (CAPE) and Protease: Monitoring by Spectroscopic and Molecular Docking Approaches

The interaction of one anticancer drug (caffeic acid phenethyl ester, CAPE) with three proteases (trypsin, pepsin and α-chymotrypsin) has been investigated with multispectral methods and molecular docking. As an active components in propolis, the findings are of great benefit to metabolism, design and stuctural modification of drugs. The results show that CAPE has an obvious ability to quench the trypsin, pepsin, or α-chymotrypsin fluorescence mainly through a static quenching procedure. Trypsin has the largest binding affinity to CAPE, and α-chymotrypsin has the smallest binding affinity to CAPE. The data obtained from thermodynamic parameters and molecular docking prove that the spontaneously interaction between CAPE and each protease is mainly due to a combination of Van der Waals (vdW) force and hydrogen bond (H-bond), controlled by enthalpy-driven process. The binding force, strength, position, and the number of H-bond are further obtained from the results of molecular docking. Through ultraviolet spectroscopy, dynamic light scattering (DLS) and circular dichroism (CD) experiments, the change in the protease secondary structure induced by CAPE was observed. Additionally, the addition of protease had a positive impact on the antioxidative activity of CAPE, and α-chymotrypsin has the greatest impact on the removal of DPPH free radicals by CAPE.

Backbone and side chain-linker tunability among dithiocarbamate, ester and amide in sequence-defined oligomers: Synthesis and structure-property-function relationship

Structural diversity and tunable properties achieved by the defined monomeric sequence are the trademarks of a sequence-defined polymer. Herein, we report a modular synthetic platform where, in addition to the...

Revealing the binding properties between resorcinol and DNA

Resorcinol (1,3-dihydroxybenzene) is a common coupling agent in permanent hair dyes, and has arrested people's attention for its potential hazard to human health. However, the action mechanism of resorcinol and human DNA has not been elucidated. In this research, the binding properties between resorcinol and calf thymus DNA (ct-DNA) were studied for the first time through various spectral and molecular docking techniques. Spectral studies showed that the initial fluorescence quenching of resorcinol against DNA was a static one. The result of ΔH < 0 and ΔS > 0 was produced from thermodynamic experimental data, therefore it could be concluded that electrostatic force was the major driving force, while binding constant K_b was 1.56 × 10⁴  M^-1 at 298 K. The electrostatic binding network between resorcinol and ct-DNA was established explicitly through competitive substitution analysis and other spectral approaches. The results of FT-IR absorption spectra indicated that resorcinol had bound to the DNA phosphate skeleton. Molecular docking clearly revealed that binding occurred between hydroxyl groups of resorcinol and phosphorus oxygen bonds (P-O) of the DNA skeleton. These findings may deepen our understanding of the action mechanism between resorcinol and ct-DNA and provide some useful data on the effect of resorcinol on human diseases.

Whey protein-polyphenol conjugates and complexes: Production, characterization, and applications

Whey proteins are widely used as functional ingredients in various food applications owing to their emulsifying, foaming, and gelling properties. However, their functional attributes are limited in some applications because of the dependence of their performance on pH, mineral levels, and temperature. Several approaches have been investigated to enhance the functional performance of whey proteins by interacting them with polyphenols via covalent bonds (conjugates) or non-covalent bonds (complexes). The interaction of the polyphenols to the whey proteins alters their molecular characteristics, techno-functional attributes, and biological properties. Analytical methods for characterizing the properties of whey protein-polyphenol complexes and conjugates are highlighted, and a variety of potential applications within the food industry are discussed, including as antioxidants, emulsifiers, and foaming agents. Finally, areas for future research are highlighted.

Investigation of the binding properties between levamlodipine and HSA based on MCR-ALS and computer modeling

Levamlodipine (LEE) is a drug commonly used for antihypertensive treatment in clinical therapy. The overlapping fluorescence spectra of LEE and human serum albumin (HSA) cause some trouble in analysis of interactions between them by using the classic fluorescence method. Here, the multivariate curve resolution-alternating least squares (MCR-ALS) approach was used to overcome this disadvantage. Meanwhile, the binding properties of LEE-HSA complex were then explored through computer modeling. The MCR-ALS results suggested that LEE-HSA complex was present in the mixture solution of LEE and HSA. This conclusion was then confirmed by the Stern-Volmer equation and time-resolved fluorescence experiment. The binding constant (K_a) was 2.139 × 10⁴ L·mol^-1 at 298 K. LEE was located close to the Trp-214 residue of HSA, with van der Waals forces and hydrogen bonding as main driving forces for this interaction. LEE can alter the conformation of HSA, in which the content of α-helix reduced from 57.2% to 52.3%. The Pi-Alkyl interactions contributed to maintaining the stability of the LEE-HSA complex. The results of molecular dynamics simulations showed that LEE-HSA complex was formed within 5 ns, and the particle size (R_g) of HSA was altered by the binding reaction. This study would promote better understanding of the transportation and distribution mechanisms of LEE in the human body.

Biophysical study of phloretin with human serum albumin in liposomes using spectroscopic methods

The ability of drugs to diffuse through the lipid bilayer of cell membranes is important for their metabolism, distribution, and efficacy. In this study, the interaction between phloretin and human serum albumin (HSA) in an L-egg lecithin phosphatidylcholine (PC) liposome suspension was investigated by fluorescence and absorbance spectroscopy. The spectroscopic and fluorescence quenching experiments show that phloretin molecules penetrated into the lumen of the liposome. The partition coefficient of phloretin in the PC liposome suspensions was calculated from fluorescence quenching measurements. The results show that phloretin efficiently quenches the intrinsic fluorescence of HSA through a combination of dynamic and static quenching. The values of Gibbs free energy, and the enthalpy and entropic change in the binding process of phloretin with HSA in the PC liposome suspensions were negative, suggesting that the binding process of phloretin and HSA was spontaneous. Hydrogen bonding and van der Waals force interactions play an important role in the interaction between the two molecules. In addition, binding of phloretin to HSA in liposome suspensions was investigated by synchronous fluorescence spectroscopy.

Inhibition and molecular mechanism of diosmetin against xanthine oxidase by multiple spectroscopies and molecular docking

Studying the inhibition and molecular mechanism of diosmetin against xanthine oxidase helps to develop natural product xanthine oxidase inhibitors.

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

Theaflavin is a kind of multi-pharmacological and health beneficial black tea factor. The aim of this study is to investigate the mechanisms by which theaflavin interacts with glycosylated and non-glycosylated serum albumins and compares their binding properties. Fluorescence and ultraviolet spectra indicated that theaflavin interacted with native and glycated human serum albumin through a static quenching mechanism and had a higher degree of quenching of human serum albumin. The thermodynamic parameters revealed that the combinations of theaflavin with native and glycated human serum albumin were a spontaneous endothermic reaction, and the hydrophobic force was a major driving force in the interaction process. Zeta potential, particle size, synchronous fluorescence, three-dimensional fluorescence spectroscopy and circular dichroism further clarified the effect of theaflavin on the conformation of human serum albumin structure were more pronounced. In addition, site competition experiments and molecular docking technique confirmed that the binding sites of theaflavin on both native and glycated human serum albumin were bound at site II. This study had investigated the effects of glycation on the binding of HSA with polyphenols and the potential nutriology significance of these effects.

Molecular mechanism of the interaction between resveratrol and trypsin via spectroscopy and molecular docking

Mechanism of the interaction between resveratrol and trypsin and its effect on their biological activity.

Regulating the alky chain length of fatty acid-didanosine prodrugs and evaluating its role in albumin binding

Rational design of prodrugs for efficient albumin binding shows distinct advantages in drug delivery in terms of drug availability, systemic circulation, and potential targeting effect. And fatty acids are good candidates due to their high affinity to albumin. However, how the alkyl chain length of fatty acids affects the binding dynamics between prodrugs and albumin, despite its importance, is still unclear. In the present study, three prodrugs of didanosine (DDI) and fatty acids were designed and synthesized to evaluate the effect of the alkyl chain length on prodrug-albumin binding process, including capric acid-didanosine (CA-DDI), myristic acid-didanosine (MA-DDI), and stearic acid-didanosine (SA-DDI). The binding dynamics between these prodrugs with bovine serum albumin (BSA) were studied by fluorometry, circular dichroism (CD), UV analysis, and molecular docking. It turned out that DDI itself showed poor binding affinity to BSA. In contrast, CA-DDI, MA-DDI, and SA-DDI demonstrated significantly improved binding affinity. Interestingly, the binding affinity between DDI prodrugs and BSA was correlated with the alkyl chain length of fatty acids, and the binding constant significantly increased with the extension of alkyl chain length (K_CA-DDI = 5.86 × 103 M^-1, K_MA-DDI = 8.57 × 103 M^-1, and K_SA-DDI = 11.42 × 103 M^-1 at 298 K).

Domain-Specific Association of a Phenanthrene-Pyrene-Based Synthetic Fluorescent Probe with Bovine Serum Albumin: Spectroscopic and Molecular Docking Analysis

In this report, the interaction between a phenanthrene-pyrene-based fluorescent probe (PPI) and bovine serum albumin (BSA), a transport protein, has been explored by steady-state emission spectroscopy, fluorescence anisotropy, far-ultraviolet circular dichroism (CD), time-resolved spectral measurements, and molecular docking simulation study. The blue shift along with emission enhancement indicates the interaction between PPI and BSA. The binding of the probe causes quenching of BSA fluorescence through both static and dynamic quenching mechanisms, revealing a 1:1 interaction, as delineated from Benesi-Hildebrand plot, with a binding constant of ∼10⁵ M^-1, which is in excellent agreement with the binding constant extracted from fluorescence anisotropy measurements. The thermodynamic parameters, ΔH°, ΔS°, and ΔG°, as determined from van't Hoff relationship indicate the predominance of van der Waals/extensive hydrogen-bonding interactions for the binding phenomenon. The molecular docking and site-selective binding studies reveal the predominant binding of PPI in subdomain IIA of BSA. From the fluorescence resonance energy transfer study, the average distance between tryptophan 213 of the BSA donor and the PPI acceptor is found to be 3.04 nm. CD study demonstrates the reduction of α-helical content of BSA protein on binding with PPI, clearly indicating the change of conformation of BSA.