Secondary Structure Of Human Serum Albumin Research Articles

Investigation of the Interaction Between Human Serum Albumin and Antitumor Palladium(II) Complex Containing 1,10-Phenanthroline and Dithiocarbamate Ligands

The interaction between [Pd(But-dtc)(phen)]NO3 (where But-dtc = butyldithiocarbamate and phen = 1,10-phenanthroline) with HSA (Human Serum Albumin) was investigated by applying fluorescence, UV–Vis and circular dichroism techniques under physiological conditions. The results of fluorescence spectra indicated that the Pd(II) complex could effectively quench the fluorescence intensity of HSA molecules via static mechanism. The number of binding sites and binding constant of HSA–Pd(II) complex were calculated. Analysis of absorption titration data on the interaction between Pd(II) complex and HSA revealed the formation of HSA–Pd(II) complex with high-binding affinity. Thermodynamic parameters indicated that hydrophobic forces play a major role in this interaction. Furthermore, CD measurements were taken to explore changes in HSA secondary structure induced by the Pd(II) complex.

Interaction of Ifosfamide-Loaded Superparamagnetic Iron Oxide Nanoparticles with Human Serum Albumin—A Biophysical Study

Combined techniques like fluorescence, circular dichroism (CD), and Fourier transform infrared (FT-IR) were applied to study the interaction between ifosfamide-loaded superparamagnetic iron oxide nanoparticles (ISION) and human serum albumin (HSA) at physiological pH. The fluorescence results showed the existance of a static quenching mode for HSA-ISION interaction. The binding constant at 298 K was in the order of 105 M−1, showing high affinity occurred between ISION and HSA. The thermodynamic parameters obtained at three different temperatures (288, 298, and 308 K) indicated that the dominant binding forces are the electrostatic forces, for the values of the enthalpy change (ΔH°) and entropy change (ΔS°) were found to be −1.31 × 104 J · mol−1 and 55.4 J · mol−1 · K−1, respectively. Fluorescence resonance energy transfer (FRET) analysis revealed that the average binding distance (r) between Trp of HSA and ISION was 5.25 nm. The results of CD and FT-IR spectra demonstrated that the secondary structure of HSA was altered in the presence of ISION.

Spectroscopic Studies on the Interaction between Sulfadiazine and Human Serum Albumin

The interaction of sulfadiazine (SDZ) and human serum albumin (HSA) in phosphate buffer solution had been investigated using multi-spectroscopic methods. The inner filter effect was corrected. The quenching mechanism was determined to be static quenching according to the fluorescence measurement. The thermodynamic parameters (enthalpy change (ΔH) and entropy change (ΔS)) were calculated to be-9.70 KJ·mol-1 and 46.07 J·mol-1·K-1, respectively, which indicated that hydrogen bonds and hydrophobic interactions play the major role on driven the interaction of SDZ with HSA. SDZ binds in the vicinity of site I in HSA, and the binding distance was 1.93 nm. In addition, the effects of HSA secondary structure were quantitatively calculated by CD spectra.

Characterisation of interaction between food colourant allura red AC and human serum albumin: Multispectroscopic analyses and docking simulations

Binding interaction of human serum albumin (HSA) with allura red AC, a food colourant, was investigated at the molecular level through fluorescence, ultraviolet–visible, circular dichroism (CD) and Raman spectroscopies, as well as protein–ligand docking studies to better understand the chemical absorption, distribution and transportation of colourants. Results show that allura red AC has the ability to quench the intrinsic fluorescence of HSA through static quenching. The negative values of the thermodynamic parameters ΔG, ΔH, and ΔS indicated that hydrogen bond and van der Waals forces are dominant in the binding between the food colourant and HSA. The CD and Raman spectra showed that the binding of allura red AC to HSA induces the rearrangement of the carbonyl hydrogen-bonding network of polypeptides, which changes the HSA secondary structure. This colourant is bound to HSA in site I, and the binding mode was further analysed with the use of the CDOCKER algorithm in Discovery Studio.

Study on the Mechanism of Interaction Between Tubeimoside I and Human Serum Albumin at Different Temperatures by Three-Dimensional Fluorescence Spectrum

Tubeimoside (TBMS), the bulb of Bolbostemma paniculatum (Maxim.) Franquet (Cucurbitaceae), is one of the traditional Chinese medicines often used for the treatment of tumors as well as for detoxication. Tubeimoside I (TBMS I) is one of the main active ingredients of TBMS, the mechanism of action of which remains unknown. Human serum albumin (HSA) is the most abundant carrier protein in blood circulation. Three-dimensional (3D) fluorescence spectra and the excitation-emission matrix of interaction between TBMS I and HSA were measured at different temper- atures. The results showed that HSA fluorescence was quenched by TBMS I through a static quenching mechanism. Also, the HSA fluorescence was quenched with the temperature increase from 283K to 353K. 3D spectral results revealed the changes in the secondary structure of HSA upon interaction with TBMS I.

Spectroscopic and molecular docking techniques study of the interaction between oxymetholone and human serum albumin

In this study, the binding of oxymetholone (OXM), a doping drug, to human serum albumin (HSA) was explored at pH 7.40 by spectroscopic methods including spectrofluorimetry, three dimensional excitation–emission matrix (3D EEM), UV–vis absorption, resonance rayleigh scattering (RRS) and molecular docking. The fluorescence results showed that there was a considerable quenching of the intrinsic fluorescence of HSA upon binding to OXM by static quenching mechanism. The Stern–Volmer quenching constants (KSV) between OXM and HSA at three different temperatures 295, 303, 308K, were obtained as 4.63×104, 3.05×104 and 1.49×104Lmol−1, respectively. Furthermore this interaction was confirmed by UV–vis spectrophotometric and RRS techniques. The binding site number, n, apparent binding constant, Kb, and corresponding thermodynamic parameters (ΔS, ΔH and ΔG) were measured at different temperatures. The Van der Waals and hydrogen-bond forces were found to stabilize OXM–HSA complex. The distance (r) between the donor and acceptor was obtained from Förster׳s theory of fluorescence resonance energy transfer (FRET) and found to be 1.67nm. The 3D EEM showed that OXM slightly changes the secondary structure of HSA. Furthermore, the molecular docking was employed for identification of drug binding sites and interaction of OXM with amino acid residues.

Study of Interaction between Human Serum Albumin and Miconazole Nitrate Using Multi-Spectroscopic Methods

The interaction of human serum albumin (HSA) and miconazole nitrate (MIN) had been studied by multi-spectroscopic methods. The inner filter effect was corrected before used the original data. The results indicated that MIN induced the fluorescence quenching of HSA was static quenching procedure. According to the Van’t Hoff equation, the interaction of HSA and MIN was determined by negative enthalpy change and positive entropy change, which showed that electrostatic forces were the major force in the binding process. The displacement experiments revealed that MIN binds in the vicinity of site I of HSA. The binding distance between Trp214 of HSA and MIN was 3.82 nm. Furthermore, the alternations of HSA secondary structure were calculated by FT-IR spectra. Upon formation of HSA-MIN complexes, the amount of α-helix structure reduced from 43.28% to 29.92%, β-sheet reduced from 22.59% to 18.79%, β-turn increased from 20.33% to 30.11% and random increased from 13.80% to 21.19%.

Spectroscopic and molecular simulation studies on the interaction of di-(2-ethylhexyl) phthalate and human serum albumin.

Di-(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in industrial production, but may have a potential health risk. In this study, the binding characteristics of DEHP with human serum albumin (HSA) in aqueous solution at pH 7.4 were determined using UV/vis absorption, fluorescence, Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD), along with a molecular simulation technique. Analysis of the fluorescence titration data at different temperatures suggested that the fluorescence quenching mechanism of HSA by DEHP was static. The calculated thermodynamic parameters indicated that hydrophobic forces played a predominant role in formation of the DEHP-HSA complex, but hydrogen bonds could not be omitted. Site marker competitive experiments and denaturation studies showed that the binding of DEHP to HSA primarily took place in subdomain IIA of HSA, and molecular docking results further corroborated the binding sites. The synchronous fluorescence, UV/vis absorption, FTIR and CD spectra revealed that the addition of DEHP induced changes in the secondary structure of HSA. Protein surface hydrophobicity (PSH) tests indicated that DEHP binding to HSA caused an increase in the PSH. Moreover, the effects of some metal ions on the binding constant of DEHP - HSA interaction were also investigated.

Probing HSA-ionic liquid interactions by spectroscopic and molecular docking methods

Herein, we report the interaction of synthesized pyrrolidinium based ionic liquid, N-butyl-N-methyl-2-oxopyrrolidinium bromide (BMOP) with human serum albumin (HSA). The BMOP was characterized by using 1H NMR, 13C NMR and FT-IR techniques. The critical micelle concentration (cmc) of BMOP was confirmed by surface tension, conductivity and contact angle measurements. The interactions between HSA and BMOP were studied by steady-state and time-resolved fluorescence, UV–visible, FT-IR spectroscopic and molecular docking methods. The steady-state fluorescence spectra showed that BMOP quenched the fluorescence of HSA through combined quenching mechanism. Corresponding thermodynamic parameters viz. Gibbs free energy change (ΔG), entropy change (ΔS) and enthalpy change (ΔH) illustrated that the binding process was spontaneous and entropy driven. It is also suggested that hydrophobic forces play a key role in the binding of BMOP to HSA. In addition, the pyrene probe analysis again suggests the involvement of hydrophobic interaction in HSA–BMOP complex formation. Surface tension profile showed that the cmc value of BMOP in the presence of HSA is higher than the cmc value of pure BMOP. The FT-IR results show a conformational change in the secondary structure of HSA upon the addition of BMOP. The molecular docking result indicated that BMOP binds with HSA at hydrophobic pocket domain IIA with hydrophobic and hydrogen bond interactions in which hydrophobic interactions are dominating.

Spectroscopic investigations of the interaction of the anti‑hypertension drug valsartan with human serum albumin.

The aim of the present study was to investigate the interaction between valsartan, an anti-hypertension drug, and human serum albumin (HSA) using spectroscopic techniques, including fluorescence, ultraviolet-visible absorption, synchronous fluorescence and circular dichroism (CD). The results demonstrated that valsartan and HSA form a complex and that a static quenching mechanism occurs. In addition, the binding constant and the number of binding sites for valsartan on HSA were analyzed. Hydrophobic interactions and hydrogen bonds were the predominant forces in the association reaction based on thermodynamic parameters. The distance between the donor (HSA) and the acceptor (valsartan) was 1.994 nm as derived from Forster's theory. Alterations in the secondary structure of HSA in the presence of valsartan were assessed using synchronous fluorescence and CD. This study provides an enhanced understanding of the pharmacodynamic effects of valsartan on the physiologically important protein HSA.

Comparison of the interaction between three anthocyanins and human serum albumins by spectroscopy

Anthocyanin is an important kind of water-soluble pigment existing widely in plants, and has various health benefits to human body. The number and location of the hydroxyl groups of the parent nucleus of Anthocyanins have significant effects on their activities. This research employed different spectroscopic methods (i.e. fluorescence spectroscopy, UV–vis absorbance, three-dimensional fluorescence spectra and circular dichroism (CD)) to investigate the mutual interactions between three differently substituted B-ring hydroxyl groups (Pelargonidin-3-O-glucoside, P3G; Cyanidin-3-O-glucoside, C3G and Delphinidin-3-O-glucoside, D3G) and human serum albumin (HSA) under physiological pH conditions. The calculated thermodynamic parameters and the spectrum showed that P3G, C3G and D3G could result in quenching of the intrinsic fluorescence. The comparison result of the strength of comprehensive binding parameter Y (i.e. Y=lg( Ka×E×n/r)), which was used to reflect the extent of interaction of Anthocyanin–HSA system, was YD3G>YC3G>YP3G. Moreover, the secondary structure of HSA was changed in the presence of P3G/C3G/D3G. The α-helix percentage of P3G–HSA increased while that of C3G/D3G–HSA decreased. Overall, these results showed that the number of B-ring –OH in each molecule played an important role in the interaction of these anthocyanins with HSA.

Binding and Molecular Dynamics Studies of 7-Hydroxycoumarin Derivatives with Human Serum Albumin and Its Pharmacological Importance

Human serum albumin (HSA) is one of the most widely studied proteins and is an important plasma protein responsible for binding and transport of many exogenous and endogenous drugs. Coumarin derivatives play a critical role as anticancer, antidiabetic, anticoagulant, and analgesic agents. Here we have studied the cytotoxic activity of 7-hydroxycoumarin derivatives (7HC-1, 7HC-2, and 7HC-3) on mouse macrophage (RAW 264.7) cell lines. These studies revealed that 7-hydroxycoumarin derivatives caused an increased inhibition in growth of inflamed macrophages in a concentration-dependent manner with an IC50 of 78, 63, and 50 μM. Further studies, using fluorescence, circular dichroism spectroscopy, molecular docking, and molecular dynamics methods, show binding of 7HC (umbelliferone) derivatives with HSA at physiological pH 7.2. The binding constant of 7HC derivatives with HSA obtained from fluorescence emission was found to be K7HC-1 = 4.6 ± 0.01 × 10(4) M(-1), K7HC-2 = 1.3 ± 0.01 × 10(4) M(-1), and K7HC-3 = 7.9 ± 0.01 × 10(4) M(-1) which corresponds to -6.34 kcal/mol, -5.58 kcal/mol, and -6.65 kcal/mol of free energy. In contrast, the binding of these coumarin derivatives (7HC-1, 7HC-2, and 7HC-3) was almost negligible with α-1-glycoprotein (AGP). Circular dichroism (CD) studies revealed a decreased α-helix content with an increase in the β-sheets and random coils in HSA upon interaction with coumarin derivatives, suggesting a partial unfolding of the HSA secondary structure. Site probe studies with phenylbutazone (Site I) and ibuprofen (Site II) indicated that 7HC derivatives specifically bind to sub domains IIIA and IIIB of HSA which is further corroborated by molecular dynamics and docking studies suggesting that binding is specific in nature. The values of free energies and binding constants coincide for both experimental and in silico analysis and suggest that there are hydrophobic interactions when coumarin derivatives bind to HSA. Molecular dynamics studies showed that the HSA-coumarin complex reaches an equilibration state at around 3.5 ns which indicates that the HSA-coumarin complexes were stable. Thus these interactions play a central role in development of coumarin derivative-inspired drugs.

Interaction of human serum albumin with Fe(III)–deferasirox studied by multispectroscopic methods

The interaction between the iron complex of deferasirox (Fe(III)–DFX) and human serum albumin (HSA) was studied by fluorescence, UV–vis absorption and circular dichroism (CD) spectroscopy. Binding constants, number of binding sites and binding distance (r) were calculated. Fluorescence data at different temperatures revealed that the fluorescence intensity of HSA is decreased in the presence of Fe(III)–DFX complex, and the fluorescence quenching was the result of the formation of the Fe(III)–DFX–HSA complex, therefore the quenching mechanism was static. The binding constant (Ka) for the interaction was 104, and the number of binding site was obtained ~1. The thermodynamic parameters including enthalpy (∆H), entropy (∆S) and Gibb׳s free energy (∆G) changes were calculated according to the van׳t Hoff equation. These data suggested that hydrophobic interaction was the dominant intermolecular force in stabilizing the complex and the association process was spontaneous. The interaction of HSA with Fe(III)–DFX was also confirmed by UV–vis absorption spectra. The quantitative analysis data of CD spectra showed significant alterations of HSA secondary structure in the presence of Fe(III)–DFX complex in aqueous solution with reduction of α-helices content and increase of β-turn structure.

Investigation of the interaction between patulin and human serum albumin by a spectroscopic method, atomic force microscopy, and molecular modeling.

The interaction of patulin with human serum albumin (HSA) was studied in vitro under normal physiological conditions. The study was performed using fluorescence, ultraviolet-visible spectroscopy (UV-Vis), circular dichroism (CD), atomic force microscopy (AFM), and molecular modeling techniques. The quenching mechanism was investigated using the association constants, the number of binding sites, and basic thermodynamic parameters. A dynamic quenching mechanism occurred between HSA and patulin, and the binding constants (K) were 2.60 × 104, 4.59 × 104, and 7.01 × 104 M−1 at 288, 300, and 310 K, respectively. Based on fluorescence resonance energy transfer, the distance between the HSA and patulin was determined to be 2.847 nm. The ΔG 0, ΔH 0, and ΔS 0 values across various temperatures indicated that hydrophobic interaction was the predominant binding force. The UV-Vis and CD results confirmed that the secondary structure of HSA was altered in the presence of patulin. The AFM results revealed that the individual HSA molecule dimensions were larger after interaction with patulin. In addition, molecular modeling showed that the patulin-HSA complex was stabilized by hydrophobic and hydrogen bond forces. The study results suggested that a weak intermolecular interaction occurred between patulin and HSA. Overall, the results are potentially useful for elucidating the toxigenicity of patulin when it is combined with the biomolecular function effect, transmembrane transport, toxicological, testing and other experiments.

Influence of MLS laser radiation on erythrocyte membrane fluidity and secondary structure of human serum albumin

The biostimulating activity of low level laser radiation of various wavelengths and energy doses is widely documented in the literature, but the mechanisms of the intracellular reactions involved are not precisely known. The aim of this paper is to evaluate the influence of low level laser radiation from an multiwave locked system (MLS) of two wavelengths (wavelength = 808 nm in continuous emission and 905 nm in pulsed emission) on the human erythrocyte membrane and on the secondary structure of human serum albumin (HSA). Human erythrocytes membranes and HSA were irradiated with laser light of low intensity with surface energy density ranging from 0.46 to 4.9 J cm−2 and surface energy power density 195 mW cm−2 (1,000 Hz) and 230 mW cm−2 (2,000 Hz). Structural and functional changes in the erythrocyte membrane were characterized by its fluidity, while changes in the protein were monitored by its secondary structure. Dose-dependent changes in erythrocyte membrane fluidity were induced by near-infrared laser radiation. Slight changes in the secondary structure of HSA were also noted. MLS laser radiation influences the structure and function of the human erythrocyte membrane resulting in a change in fluidity.

Differential interactions and structural stability of chitosan oligomers with human serum albumin and α-1-glycoprotein

Chitosan is a naturally occurring deacetylated derivative of chitin with versatile biological activities. Here, we studied the interaction of chitosan oligomers with low degree of polymerization such as chitosan monomer (CM), chitosan dimer (CD), and chitosan trimer (CT) with human serum albumin (HSA) a major blood carrier protein and α-1-glycoprotein (AGP). Since, HSA and AGP are the two important plasma proteins that determine the drug disposition and affect the fate of distribution of drugs. Fluorescence emission spectra indicated that CM, CD, and CT had binding constants of KCM = 6.2 ± .01 × 105 M−1, KCD = 5.0 ± .01 × 104 M−1, and KCT = 1.6 ± .01 × 106 M−1, respectively, suggesting strong binding with HSA. However, binding of chitooligomers with AGP was insignificant. Thermodynamic and molecular docking analysis indicated that hydrogen bonds and also hydrophobic interaction played an important role in stabilizing the HSA-chitooligomer complexes with free energies of −7.87, −6.35, and −8.4 Kcal/mol for CM, CD, and CT, respectively. Further, circular dichroism studies indicated a minor unfolding of HSA secondary structure, upon interaction with chitooligomers, which are supported with fluctuations of root mean square deviation (RMSD) and radius of gyration (Rg) of HSA. Docking analysis revealed that all three chitooligomers were bound to HSA within subdomain IIA (Site I). In addition, RMSD and Rg analysis depicted that HSA-chitooligomer complexes stabilized at around 4.5 ns. These results suggest that HSA might serve as a carrier in delivering chitooligomers to target tissues than AGP which has pharmacological importance.

Exploring the binding of 4-thiothymidine with human serum albumin by spectroscopy, atomic force microscopy, and molecular modeling methods

The interaction of 4-thiothymidine (S4TdR) with human serum albumin (HSA) was studied by equilibrium dialysis under normal physiological conditions. In this work, the mechanism of the interaction between S4TdR and human serum albumin (HSA) was exploited by fluorescence, UV, CD circular, and SERS spectroscopic. Fluorescence and UV spectroscopy suggest that HSA intensities are significantly decreased when adding S4TdR to HAS, and the quenching mechanism of the fluorescence is static. Also, the ΔG, ΔH, and ΔS values across temperature indicated that hydrophobic interaction was the predominant binding force. The CD circular results show that there is little change in the secondary structure of HSA except the environment of amino acid changes when adding S4TdR to HSA. The surface-enhanced Raman scattering (SERS) shows that the interaction between S4TdR and HSA can be achieved through different binding sites which are probably located in the II A and III A hydrophobic pockets of HSA which correspond to Sudlow’s I and II binding sites. In addition, the molecular modeling displays that S4TdR–HSA complex is stabilized by hydrophobic forces, which result from amino acid residues. The atomic force microscopy results revealed that the single HSA molecular dimensions were larger after interaction of 4-thiothymidine. This work would be useful to understand the state of the transportation, distribution, and metabolism of the anticancer drugs in the human body, and it could provide a useful biochemistry parameter for the development of new anti-cancer drugs and research of pharmacology mechanisms.

Novel Self-assembly Endows Human Serum Albumin Nanoparticles with an Enhanced Antitumor Efficacy

Protein-based nanomedicine plays an important role in tumor chemotherapy due to their merits in bioavailability, biocompatibility, biodegradability, and low toxicity. In this study, we developed a novel method of preparing human serum albumin (HSA) nanoparticles for targeted delivery of paclitaxel (PTX) to tumors. HSA-PTX nanoparticles (NPs-PTX) were fabricated via unfolding of HSA in appropriate solution to expose more hydrophobic domains and consequent self-assembling into nanoparticles with added PTX. Via this self-assembly method, a desirable particle size (around 120 nm), a high drug loading (>20%), and a high encapsulation efficiency (near 100%) were obtained. PTX dispersed as an amorphous state in NPs-PTX and the secondary structures of HSA were maintained. In a cytotoxicity study, NPs-PTX displayed an enhanced cytotoxicity in MCF-7 and A549 cells. Confocal microscopy and flow cytometry revealed that the uptake of NPs-PTX was mediated by secreted protein acidic and rich in cysteine and "caveolar" transport. In H22 tumor-bearing mice, NPs-PTX displayed an increasing and everlasting tumor distribution, leading to slower tumor growth and longer mice survival than PTX. Therefore, this novel self-assembly method offers a much easier method to prepare PTX nanoparticles, provides better antitumor efficacy in vitro and in vivo, and more importantly, sets up a delivery platform for other hydrophobic drugs to improve their effectiveness in cancer therapy.

A new ternary copper(II) complex derived from 2-(2′-pyridyl)benzimidazole and glycylglycine: Synthesis, characterization, DNA binding and cleavage, antioxidation and HSA interaction

A new ternary copper(II)–dipeptide complex [Cu(glygly)(HPB)(Cl)]⋅2H2O (glygly=glycylglycine anion, HPB=2-(2′-pyridyl)benzimidazole) has been synthesized and characterized. The DNA interaction of the complex was studied by spectroscopic methods, viscosity, and electrophoresis measurements. The antioxidant activity was also investigated using the pyrogallol autoxidation assay. Besides, the interaction of the complex with human serum albumin (HSA) in vitro was examined by multispectroscopic techniques. The complex partially intercalated to CT-DNA with a high binding constant (Kb=7.28×105M−1), and cleaved pBR322 DNA efficiently via an oxidative mechanism in the presence of Vc, with the HO· and O2- as the active species, and the SOD as a promoter. Furthermore, the complex shows a considerable SOD-like activity with the IC50 value of 3.8386μM. The complex exhibits desired binding affinity to HSA, in which hydrogen bond or vander Waals force played a major role. The alterations of HSA secondary structure induced by the complex were confirmed by UV–visible, CD, synchronous fluorescence and 3D fluorescence spectroscopy.

Study of the Enantioselective Interaction of Diclofop and Human Serum Albumin by Spectroscopic and Molecular Modeling Approaches In Vitro

In this contribution, the enantioselective interactions between diclofop (DC) and human serum albumin (HSA) were explored by steady-state and 3D fluorescence, ultraviolet-visible spectroscopy (UV-vis), and molecular modeling. The binding constants between R-DC and HSA were 0.9213 × 10(5), 0.9118 × 10(5), and 0.9009 × 10(5) L · mol(-1) at 293, 303, 313 K, respectively. Moreover, the binding constants of S-DC for HSA were 1.4766 × 10(5), 1.2899 × 10(5), and 1.0882 × 10(5) L · mol(-1) at 293, 303, and 313 K individually. Such consequences markedly implied the binding between DC enantiomers and HSA were enantioselective with higher affinity for S-DC. Steady-state fluorescence study evidenced the formation of DC-HSA complex and there was a single class of binding site on HSA. The thermodynamic parameters (ΔH, ΔS, ΔG) of the reaction clearly indicated that hydrophobic effects and H-bonds contribute to the formation of DC-HSA complex, which was in excellent agreement with molecular simulations. In addition, both site-competitive replacement and molecular modeling suggested that DC enantiomers were located within the binding pocket of Sudlow's site II. Furthermore, the alterations of HSA secondary structure in the presence of DC enantiomers were verified by UV-vis absorption and 3D fluorescence spectroscopy. This study can provide important insight into the enantioselective interaction of physiological protein HSA with chiral aryloxyphenoxy propionate herbicides and gives support to the use of HSA for chiral pesticides ecotoxicology and environmental risk assessment.