Spectroscopic, thermodynamic and molecular docking studies of bovine serum albumin interaction with ascorbyl palmitate food additive.
ABSTRACT: Introduction: Ascorbyl palmitate (AP) is an example of natural secondary food antioxidant, which has been used for oxidative rancidity prevention in food industry. In this study, the interaction of AP with bovine serum albumin (BSA) was investigated. Methods: The mechanism of BSA interaction with AP was investigated using spectroscopic methods (UV-Vis, fluorescence). The thermodynamic parameters including enthalpy change (ΔH), entropy change (ΔS), and Gibb's free energy (ΔG) were calculated using Van't Hoff equation at different temperatures. Results: The experimental results showed that UV-Vis absorption spectra of BSA decreased upon increasing AP concentration, indicating that the AP can bind to BSA. Formation of the AP-BSA complex was approved by quenching of fluorescence and the quenching mechanism was found to be resultant from dynamic procedure. The positive values of both ΔH and ΔS showed that hydrophobic forces were the major binding forces. The negative value of ΔG demonstrated that AP interacts with BSA spontaneously. Molecular docking results confirmed that AP binds to BSA through hydrophobic forces. Conclusion: The attained results showed that AP can bind to BSA and effectively distributed into the bloodstream.
Project description:Exogenous drugs that are used as antidote against chemotheray, inflammation or viral infection, gets absorbed and interacts reversibly to the major serum transport protein i.e. albumins, upon entering the circulatory system. To have a structural guideline in the rational drug designing and in the synthesis of drugs with greater efficacy, the binding mechanism of an antineoplastic and anti-inflammatory drug Nordihydroguaiaretic acid (NDGA) with human and bovine serum albumins (HSA & BSA) were examined by spectroscopic and computational methods. NDGA binds to site II of HSA with binding constant (Kb) ~105 M-1 and free energy (ΔG) ~ -7.5 kcal.mol-1. It also binds at site II of BSA but with lesser binding affinity (Kb) ~105 M-1 and ΔG ~ -6.5 kcal.mol-1. The negative value of ΔG, ΔH and ΔS for both the albumins at three different temperatures confirmed that the complex formation process between albumins and NDGA is spontaneous and exothermic. Furthermore, hydrogen bonds and hydrophobic interactions are the main forces involved in complex formation of NDGA with both the albumins as evaluated from fluorescence and molecular docking results. Binding of NDGA to both the albumins alter the conformation and causes minor change in the secondary structure of proteins as indicated by the CD spectra.
Project description:Ellagic acid (EA), a natural polyphenol evidence several pharmacological benefits. The binding profile of EA with human serum albumin (HSA) has been explored and investigated by Isothermal titration calorimetry (ITC), circular dichroism (CD) spectroscopy, time-correlated single-photon counting (TCSPC), absorbance spectroscopy, steady-state fluorescence spectroscopy, and modelling studies. The ITC data analysis revealed the binding Constant (Ka), ΔH, ΔS and ΔG values to be 15.5×104M-1, -116.2±18.1 Kcal mol-1, -366 cal mol-1K-1 and -7.13 Kcal mol-1 respectively with a unique binding site at HSA. EA effectively quenched the intrinsic fluorescence of HSA by static quenching, whereas TCSPC data also revealed association of dynamic quenching also. Thermodynamic analysis confirmed that hydrophobic and mainly hydrogen bonding interaction played important role in stabilizing the HSA-EA complex. It further dictates the binding reaction to be enthalpy driven. The secondary structure of HSA was altered upon binding with EA. CD spectroscopic data indicated the fraction of alpha helicity to be decreased from 52% to 40% upon binding to EA. This study will provide an insight on evaluation of this bioactive interaction during transport and releasing efficiency at the target site in human physiological system since HSA is the most important carrier protein in blood serum.
Project description:In this study, the effect of preparation route of magnetic graphene oxide (mGO) on Reactive Black 5 (RB5) adsorption was investigated. The synthesis of mGO was achieved both with (i) impregnation method (mGOi nanoparticles), and (ii) co-precipitation (mGOp nanoparticles). After synthesis, the full characterization with various techniques (SEM, FTIR, XRD, DTA, DTG, VSM) was achieved revealing many possible interactions/forces of dye-composite system. Effects of initial solution pH, effect of temperature, adsorption isotherms and kinetics were investigated in order to conclude about the aforementioned effect of the preparation method on dye adsorption performance of the magnetic nanocomposites. The adsorption evaluation of the magnetic nanoparticles presented higher adsorption capacity of mGOp derivative (188 mg/g) and lower of mGOi (164 mg/g). Equilibrium experiments are also performed studying the effect of contact time (pseudo-first and -second order equations) and temperature (isotherms at 25, 45 and 65 °C fitted to Langmuir and Freundlich model). A full thermodynamic evaluation was carried out, calculating the parameters of enthalpy, free energy and entropy (ΔH⁰, ΔG⁰ and ΔS⁰).
Project description:The molecule, 1,2-Bis(2-benzimidazolyl)-1,2-ethanediol (BBE) is known to act as a selective inhibitor of poliovirus, rhinovirus, Candida albicans, several bacterial species, and is easily synthesized by Phillips reaction. The interaction of BBE with BSA and the effects of its binding on the conformation and unfolding/refolding pathways of the protein were investigated using multispectroscopic techniques and molecular modeling. The binding studies indicate that BSA has one high affinity BBE binding site with association constant 6.02±0.05×10(4) M(-1) at 298 K. By measuring binding at different temperatures, we determined the changes in enthalpy (ΔH = -15.13±2.15 kJ mol(-1)), entropy (ΔS = 40.87±7.25 J mol(-1) K(-1)) and free energy (ΔG( = )26.78±1.02) of interaction, which indicate that the binding was spontaneous and both enthalpically and entropically driven. Based on molecular modeling and thermodynamic parameters, we proposed that the complex formation involved mainly hydrophilic interaction such as hydrogen bonding between hydroxyl groups of ethane-1,2-diol fragment with Tyr410 and benzimidazole sp(2) nitrogen atom with Ser488 and hydrophobic interaction between phenyl ring of one benzimidazole of the ligand and hydrophobic residues namely, Ile387, Cys391, Phe402, Val432 and Cys437. The sequential unfolding mechanism of BSA, site-specific marker displacement experiments and molecular modeling showed that the molecule preferably binds in subdomain IIIA. The BBE binding to BSA was found to cause both secondary and tertiary structural alterations in the protein as studied by intrinsic fluorescence, near-UV and far-UV circular dichroism results. The unfolding/refolding study showed that BBE stabilized native to intermediate states (N⇌I) transition of the protein by ∼2 kJ mol(-1) without affecting the intermediate to unfolded states (I⇌U) transition and general mechanism of unfolding of BSA.
Project description:Interaction of a pharmacologically important flavonoid, pinostrobin (PS) with the major transport protein of human blood circulation, human serum albumin (HSA) has been examined using a multitude of spectroscopic techniques and molecular docking studies. Analysis of the fluorescence quenching data showed a moderate binding affinity (1.03 × 10(5) M(-1) at 25°C) between PS and HSA with a 1∶1 stoichiometry. Thermodynamic analysis of the binding data (ΔS = +44.06 J mol(-1) K(-1) and ΔH = -15.48 kJ mol(-1)) and molecular simulation results suggested the involvement of hydrophobic and van der Waals forces, as well as hydrogen bonding in the complex formation. Both secondary and tertiary structural perturbations in HSA were observed upon PS binding, as revealed by intrinsic, synchronous, and three-dimensional fluorescence results. Far-UV circular dichroism data revealed increased thermal stability of the protein upon complexation with PS. Competitive drug displacement results suggested the binding site of PS on HSA as Sudlow's site I, located at subdomain IIA, and was well supported by the molecular modelling data.
Project description:Sodium benzoate (SB) is widely used as a preservative in food industry, and bovine serum albumin (BSA) is a major carrier protein similar to human serum albumin (HSA), the study of the binding between the two has great significance on human health. In this paper, we systematically investigated the binding of SB and BSA under the simulated physiological conditions combining with various common analytical methods, e.g., fluorescence, UV-vis absorption, synchronous fluorescence and circular dichroism (CD) spectra, as well as molecular docking method. The fluorescence quenching measurements were respectively carried out at 298 K, 303 K and 308 K using the Stern-Volmer method. The results reveal that ground state SB-BSA complex was formed within the binding constants from 2.02?×?104 to 7.9?×?103 M-1. Meanwhile, the negative values of ?H 0 (-?43.92 kJ mol-1) and ?S 0 (-?111.6 J mol-1 K-1) demonstrated that both the hydrogen binding interaction and van der Waals forces contributed to stabilizing the SB-BSA complex. The site marker competitive experiments show that the SB and BSA bound at site I. Furthermore, the experimental results of UV-vis absorption, synchronous fluorescence and CD spectra indicate that the binding of SB and BSA may change the conformation of BSA. In addition, the molecular docking experiment suggests that hydrogen bond was formed in the interaction between SB and BSA.
Project description:Malodorous rivers are among the major environmental problems of cities in developing countries. In addition to the unpleasant smell, the sediments of such rivers can act as a sink for pollutants. The excessive amount of ammonia nitrogen (NH3-N) in rivers is the main factor that causes the malodour. Therefore, a suitable method is necessary for sediment disposition and NH3-N removal in malodorous rivers. The sediment in a malodorous river (PS) in Beijing, China was selected and modified via calcination (PS-D), Na+ doping (PS-Na) and calcination-Na+ doping (PS-DNa). The NH3-N removal efficiency using the four sediment materials was evaluated, and results indicated that the NH3-N removal efficiency using the modified sediment materials could reach over 60%. PS-DNa achieved the highest NH3-N removal efficiency (90.04%). The kinetics study showed that the pseudo-second-order model could effectively describe the sorption kinetics and that the exterior activated site had the main function of P sorption. The results of the sorption isotherms indicated that the maximum sorption capacities of PS-Na, PS-D and PS-DNa were 0.343, 0.831 and 1.113 mg g-1, respectively, and a high temperature was favourable to sorption. The calculated thermodynamic parameters suggested that sorption was a feasible or spontaneous (ΔG < 0), entropy-driven (ΔS > 0), and endothermic (ΔH > 0) reaction.
Project description:The binding interaction between bovine serum albumin (BSA) and sodium salt of risedronic acid (RSN) was studied by using the FT-IR (Fourier transform infrared), UV-Vis (ultraviolet-visible), fluorescence (emission and synchronous), CD (circular dichroism) spectrometric, and computational (molecular docking) techniques at 289, 297, and 305?K temperatures with physiological buffer of pH 7.40. The conformational and secondary structural changes observed for BSA from CD spectra and by curve fitting procedure were applied to Fourier self-deconvolution in FT-IR spectra. The formation of a BSA-RSN complex was confirmed from UV-Vis spectroscopy. The static type of quenching shown for RSN to BSA was verified from Stern-Volmer and modified Stern-Volmer equations. The binding constant of order 105 was obtained to be confirming that there exists a strong binding interaction between BSA and RSN. Synchronous fluorescence shows that the microenvironment of tryptophan was altered, not tyrosine of BSA; in addition to this, the distance between tryptophan of BSA and RSN was found out from Forster's theory of nonradiation energy transfer. The interaction between BSA and RSN mainly occurred as a result of hydrogen bonds and van der Waals forces, the process is exothermic and spontaneous, and it was achieved through van 't Hoff equation. This interaction was affected by the presence of biologically active Fe2+, Ni2+, Ca2+, Mg2+, and Cd2+ ions and was also studied. The subdomain IIIA of BSA involved with RSN interaction was authenticated from molecular docking analysis.
Project description:This study investigated the interaction between eupatorin and bovine serum albumin (BSA) using ultraviolet-visible (UV-vis) absorption, fluorescence, synchronous fluorescence, circular dichroism (CD) spectroscopies, and molecular modeling at pH 7.4. Results of UV-vis and fluorescence spectroscopies illustrated that BSA fluorescence was quenched by eupatorin via a static quenching mechanism. Thermodynamic parameters revealed that hydrophobic and electrostatic interactions played major roles in the interaction. Moreover, the efficiency of energy transfer, and the distance between BSA and acceptor eupatorin, were calculated. The effects of eupatorin on the BSA conformation were analyzed using UV-vis, CD, and synchronous fluorescence. Finally, the binding of eupatorin to BSA was modeled using the molecular docking method.
Project description:Five different activated carbons (ACs) have been prepared from dried date pits using air and phosphoric acid as activating agents. The used phosphoric acid:date pit ratio dictated the characteristics of the prepared ACs; the equivalent BET-nitrogen surface area varied from 794 m²/g for a ratio of 5:1, to 1707 m²/g for a ratio of 2:1, whereas the micropore volume changed in value from 0.24 cm³/g for the 5:1 ratio to 0.59 cm³/g for the 2:1 ratio. The prepared ACs were tested to remove 4-chlorophenol (4-CP) from aqueous solutions by means of batch adsorption process. The prepared 2:1 AC exhibited the highest uptake with a maximum of 525 mg/g. Equilibrium pH studies showed that 4-CP removal was pH dependent; the maximum uptake occurred at an equilibrium pH value of 5.5. Dynamic studies showed that 4-CP uptake on 2:1 AC is rapid, with 80% of the maximum uptake achieved during the first 40 min. Both surface adsorption and intraparticle diffusion were identified to be effective adsorption mechanisms. Kinetic studies indicated a pseudo second-order reaction. Results of equilibrium adsorption experiments showed that the adsorption of the 4-CP on 2:1 AC is best described by the Langmuir model. The thermodynamics parameters of the adsorption (ΔG⁰, ΔH⁰, and ΔS⁰) were determined by studying the adsorption equilibrium at different temperatures. The values of these parameters indicated the spontaneous and endothermic nature of the adsorption phenomenon of 4-CP on the prepared ACs.