Spectroscopic methodologies and computational simulation studies on the characterization of the interaction between human serum albumin and astragalin

Elucidating thyroid hormone transport proteins disruption by nitrophenols through computational and spectroscopic analysis

Thyroxine (T4), as a type of thyroid hormone (TH), is a key hormone in regulating human metabolism, growth and development, central nervous system functions, and energy balance. It relies on TH transport proteins to reach cells and exert its biological actions. However, the binding of nitrophenol pollutants to TH transport proteins prevents the delivery of thyroid hormones to cells, thereby inhibiting the effects of the hormones. This study combines spectroscopic experiments and computational simulations to explore the mechanism of nitrophenols' interference with TH transport proteins. Detailed information on the quenching mechanism, binding parameters, interaction forces, binding models, and conformational changes of nitrophenols (PNP), chlorinated nitrophenols (CNP), and brominated nitrophenols (BNP) with TH transport proteins is obtained through spectroscopic experiments. Nitrophenols are found to form hydrogen bonds with residues Lys15, Arg378, and Arg381, respectively, thereby displacing T4 at the binding site in the TH transport proteins. With an increasing number of halogen atoms, the affinity of halogenated nitrophenols for TH transport proteins intensifies. Computational simulations are used to further understand the binding modes and binding sites, providing molecular-level insights into the binding of NPs in the cavity of TH transport proteins. Theoretical evidence from molecular docking and molecular dynamics (MD) simulations supports the experimental findings.

Evaluation of the effects of amitraz on the enzyme activity and stability of lysozyme: Spectroscopic and MD simulation approach

The binding interaction of food preservatives and pesticides has emerged as a matter of paramount importance as it not only presents potential health hazards but also carries substantial consequences for food processing and preservation. Herein, the mechanism of interaction between lysozyme and Amitraz was explored through spectroscopic and computational techniques. Spectral investigations indicated the spontaneous nature and stability of the lysozyme-Amitraz complex. The corresponding CD and FT-IR studies proved the structural changes of lysozyme. The presence of amitraz led to a notable decrease in both the enzymatic activity and thermal stability of lysozyme. Molecular docking demonstrated the preferred mode of interaction, and molecular dynamics simulations confirmed the stability of the resultant complex. In conclusion, the alarming findings of the lysozyme-Amitraz interaction underscore its detrimental impact on food safety and human health. Accordingly, urgent measures are imperative to address and mitigate the potential hazards posed by such interactions in food production.

Spectroscopic and Molecular Docking Studies on the Influence of Inulin on the Interaction of Sophoricoside with Whey Protein Concentrate

The influence of inulin on the interaction of sophoricoside (Sop) with whey protein concentrate (WPC) was investigated using various spectroscopic methods, including fluorescence spectroscopy (intrinsic fluorescence, synchronous fluorescence, and three-dimensional fluorescence), ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular docking. Sop was found to quench the intrinsic fluorescence of WPC by a static mechanism, both with and without the addition of inulin, and to enhance the antioxidant capacity of the protein. The addition of inulin slightly increased the binding distance between WPC and Sop, while reducing the number of binding sites from two to one. Non-covalent interactions, predominantly van der Waals forces and hydrogen bonding, were maintained between Sop and the protein. Synchronous fluorescence spectroscopy revealed that Sop prevents the exposure of hydrophobic groups on tryptophan residues, leading to increased surface hydrophilicity of the WPC complex. This aligns with the decreased protein surface hydrophobicity measured by 8-Anilino-1-naphthalenesulfonic acid (ANS) binding assays. With inulin, the overall hydrophobicity of the protein was lower than in the system without inulin, suggesting that both inulin and Sop improve the solubility of WPC. Three-dimensional fluorescence spectral analysis showed a reduction in fluorescence intensity and a red shift in the presence of both Sop and inulin. FTIR spectroscopy indicated a slight increase in the secondary structure ordering of WPC following the addition of both Sop and inulin, suggesting structural stabilization under heating conditions. Molecular docking highlighted the potential for hydrogen bond formation between Sop and WPC.

A comprehensive investigation of the nano-[Cu2-(DIP)2-EA] effects on HSA through spectroscopic procedures and computer simulations

In this research, the toxicity of nano-[Cu2-(DIP)2-EA], a metal nano-complex consisting of ellagic acid and bathophenanthroline ligands, on human serum albumin (HSA) at a protein level was investigated. Molecular docking simulations and spectral analyses were conducted in a simulated physiological environment at pH 7.4 to explore the interaction of nano-[Cu2-(DIP)2-EA] with HSA. The results represented an increase in albumin absorption upon exposure to nano-[Cu2-(DIP)2-EA], demonstrating significant interaction between the two compounds. Steady-state and time-resolved fluorescence measurements pointed out that nano-[Cu2-(DIP)2-EA] induced static quenching of the albumin's intrinsic fluorescence with a high binding affinity of approximately 106 mol/L in a 1:1 interaction ratio. The thermodynamic variables clarified that binding of nano-[Cu2-(DIP)2-EA] to albumin occurs spontaneously and primarily driven by van der Waals interactions and H-bonds. The results of the computer simulations and the binding displacement experiments utilizing the site markers warfarin and ibuprofen revealed that nano-[Cu2-(DIP)2-EA] binds to site I within the subdomain IIA of albumin. Circular dichroism analysis elaborated that nano-[Cu2-(DIP)2-EA] slightly perturbed the microenvironment around of tryptophan residues and diminished the α-helix structure stability to a negligible amount.

The potential impact of 6PPD and its oxidation product 6PPD-quinone on human health: A case study on their interaction with human serum albumin

6PPD and its oxidation product, 6PPD-quinone have garnered widespread attention due to their adverse effects on aquatic ecosystems and human health, and are recognized as emerging pollutants. In this study, we investigated the interaction mechanism between 6PPD/6PPD-quinone and human serum albumin (HSA) through various experiments. Experimental findings reveal that the IC50 values of 6PPD-quinone and 6PPD against HEK293T cells were 11.78 and 40.04 μM, respectively. Additionally, the cytotoxicity of these compounds was regulated by HSA, displaying an inverse correlation with their binding affinity to HSA. Furthermore, 6PPD/6PPD-quinone can spontaneously insert into site I on HSA, forming a binary complex that induces changes in the secondary structure of HSA. However, their effects on the esterase-like activity of HSA exhibit a dichotomy. While 6PPD activates the esterase-like activity of HSA, 6PPD-quinone inhibits it. Molecular docking analyses reveal that both 6PPD and 6PPD-quinone interact with many amino acid residues on HSA, including TRP214, ARG222, ARG218, ALA291, PHE211. The π electrons on the benzene rings of 6PPD/6PPD-quinone play pivotal roles in maintaining the stability of complexes. Moreover, the stronger binding affinity observed between 6PPD and HSA compared to 6PPD-quinone, may be attributed to the larger negative surface potential of 6PPD.

Probing the toxic effect of chlorpyrifos as an environmental pollutant on the structure and biological activity of lysozyme under physiological conditions

The pervasive use of pesticides like chlorpyrifos (CPY) has been associated with deleterious effects on biomolecules, posing significant risks to environmental integrity, public health, and overall ecosystem equilibrium. Accordingly, in this study, we investigated the potential binding interaction between the well-conserved enzyme, lysozyme (LSZ), and CPY through various spectroscopic techniques and molecular modeling. The UV-vis absorption and fluorescence experiments confirmed the complex formation and static quenching of the intrinsic fluorescence intensity. LSZ revealed a singular binding site for CPY, with binding constants around 105 M-1 across different temperature ranges. Analysis of thermodynamic parameters showed the spontaneous nature of the complexation process, while also revealing the pivotal role of hydrophobic interactions in stabilizing the LSZ-CPY system. According to circular dichroism and Fourier transform infrared studies, CPY binding changed the secondary structure of LSZ by boosting α-helix presence and reducing the levels of β-sheet and β-turn content. Further, CPY decreased the stability and activity of LSZ. Computational docking delineated the specific and highly preferred binding site of CPY within the structure of LSZ. Molecular dynamic simulation indicated the enduring stability of the LSZ/CPY complex and revealed structural modifications in the LSZ after binding with CPY. This research provides a detailed understanding of the intermolecular dynamics between CPY and LSZ, concurrently elucidating the molecular-level implications for the potential hazards of pesticides in the natural environment.

Acetylcholine Analog-Modified Albumin Nanoparticles for the Enhanced and Synchronous Brain Delivery of Saponin Components of Panax Notoginseng

BACKGROUND

Panax notoginseng saponins (PNS) are commonly used first-line drugs for treating cerebral thrombosis and stroke in China. However, the synchronized and targeted delivery of active ingredients in traditional Chinese medicine (TCM) poses a significant challenge for modern TCM formulations.

METHODS

Bovine serum albumin (BSA) was modified using 2-methacryloyloxyethyl phosphorylcholine (MPC), an analog of acetylcholine, and subsequently adsorbed the major PNS onto the modified albumin to produce MPC-BSA@PNS nanoparticles (NPs). This novel delivery system facilitated efficient and synchronized transport of PNS across the blood-brain barrier (BBB) through active transport mediated by nicotinic acetylcholine receptors.

RESULTS

In vitro experiments demonstrated that the transport rates of R1, Rg1, Rb1, and Rd across the BBB were relatively synchronous in MPC-BSA@PNS NPs compared to those in the PNS solution. Additionally, animal experiments revealed that the brain-targeting efficiencies of R1 + Rg1 + Rb1 in MPC-BSA@PNS NPs were 2.02 and 7.73 times higher than those in BSA@PNS NPs and the free PNS group, respectively.

CONCLUSIONS

This study presents a simple and feasible approach for achieving the targeted delivery of complex active ingredient clusters in TCM.

Change in thermal stability and molecular structure characteristics of whey protein beta-lactoglobulin upon the interaction with levamisole hydrochloride

The interaction between beta-lactoglobulin (BLG) and anthelmintic compounds including levamisole (LEV) is a matter of great concern as it not only poses potential health and environmental risks but also has significant implications for food processing and production. The mechanisms of LEV-BLG interaction were investigated through spectral and molecular modeling approaches. Fluorescence and UV-Visible investigations indicated the formation of a spontaneous and stable LEV-BLG complex. Structural changes of BLG were revealed by circular dichroism and Fourier transform infrared studies. The thermal stability of BLG increased in the presence of LEV. Molecular docking studies indicated the best mode of LEV-BLG interaction and molecular dynamics simulation confirmed the stability of the LEV-BLG complex. In conclusion, our study sheds light on the potential of BLG to interact with deleterious substances such as anthelmintic agents, thus highlighting the necessity of further research in this field to assure food safety and prevent any health hazards.

Structural alterations and inhibition of lysozyme activity upon binding interaction with rotenone: Insights from spectroscopic investigations and molecular dynamics simulation

The pervasive employment of pesticides such as rotenone on a global scale represents a substantial hazard to human health through direct exposure. Therefore, exploring the interactions between such compounds and body macromolecules such as proteins is crucial in comprehending the underlying mechanisms of their detrimental effects. The present study aims to delve into the molecular interaction between rotenone and lysozyme by employing spectroscopic techniques along with Molecular dynamics (MD) simulation in mimicked physiological conditions. The binding interaction resulted in a fluorescence quenching characterized by both dynamic and static mechanisms, with static quenching playing a prominent role in governing this phenomenon. The analysis of thermodynamic parameters indicated that hydrophobic interactions primarily governed the spontaneous bonding process. FT-IR and circular dichroism findings revealed structural alternations of lysozyme upon complexation with rotenone. Also, complexation with rotenone declined the biological activity of lysozyme, thus rotenone could be considered an enzyme inhibitor. Further, the binding interaction substantially decreased the thermal stability of lysozyme. Molecular docking studies showed the binding location and the key residues interacting with rotenone. The findings of the spectroscopic investigations were confirmed and accurately supported by MD simulation studies.

Synthesis and characterization of a novel Mannich base benzimidazole derivative to explore interaction with human serum albumin and antimicrobial property: experimental and theoretical approach

The novel Mannich base benzimidazole derivative (CB-1), 1-((1H-benzo[d]imidazol-1-yl)(3-chlorophenyl)methyl)-3-phenylurea) has been designed and synthesized by reacting benzimidazole, 3-chloro benzaldehyde, and N-Phenyl urea. CB-1 has been characterized by UV- Visible, FTIR, and 1H NMR. CB-1 was explored to study the interaction with the most abundant blood protein which involved in the role of transport of molecules (drugs), human serum albumin (HSA). Fluorescence results are evident for the presence of both dynamic and static quenching mechanisms in the binding of CB-1 to HSA. Antimicrobial screening were carried out against three bacteria and three fungi pathogens employing disc diffusion method. Molecular docking using AutoDock Vina tool further confirms the experimental binding interactions obtained from fluorescence. Density functional theory (DFT) with B3LYP/6-311G++ basis set was used for correlating theoretical data and obtaining optimized structures of CB-1 along with reactants with molecular electrostatic potential (MEP) map and HOMO→LUMO energy gap calculation. HIGHLIGHTSThe novel Mannich base benzimidazole derivative (CB-1) has been designed and synthesized by Mannich reaction.CB-1 has been characterized by UV- Visible, FTIR, and 1H NMR.Fluorescence quenching reveals that HSA binds to CB-1 via aromatic residues, which is corroborated by molecular docking.Antifungal and antibacterial activity was evaluated in comparison to Nystatin and Gentamicin standard drugs, respectively.DFT calculations support experimental data and provide HOMO-LUMO energy gap.Communicated by Ramaswamy H. Sarma.

Potential Therapeutic Implication of Herbal Medicine in Mitochondria-Mediated Oxidative Stress-Related Liver Diseases

Mitochondria are double-membrane organelles that play a role in ATP synthesis, calcium homeostasis, oxidation-reduction status, apoptosis, and inflammation. Several human disorders have been linked to mitochondrial dysfunction. It has been found that traditional therapeutic herbs are effective on alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) which are leading causes of liver cirrhosis and hepatocellular carcinoma. The generation of reactive oxygen species (ROS) in response to oxidative stress is caused by mitochondrial dysfunction and is considered critical for treatment. The role of oxidative stress, lipid toxicity, and inflammation in NAFLD are well known. NAFLD is a chronic liver disease that commonly progresses to cirrhosis and chronic liver disease, and people with obesity, insulin resistance, diabetes, hyperlipidemia, and hypertension are at a higher risk of developing NAFLD. NAFLD is associated with a number of pathological factors, including insulin resistance, lipid metabolic dysfunction, oxidative stress, inflammation, apoptosis, and fibrosis. As a result, the improvement in steatosis and inflammation is enough to entice researchers to look into liver disease treatment. However, antioxidant treatment has not been very effective for liver disease. Additionally, it has been suggested that the beneficial effects of herbal medicines on immunity and inflammation are governed by various mechanisms for lipid metabolism and inflammation control. This review provided a summary of research on herbal medicines for the therapeutic implementation of mitochondria-mediated ROS production in liver disease as well as clinical applications through herbal medicine. In addition, the pathophysiology of common liver disorders such as ALD and NAFLD would be investigated in the role that mitochondria play in the process to open new therapeutic avenues in the management of patients with liver disease.

Spectrin: an alternate target for cytoskeletal drugs

Cytoskeletal drugs having enormous therapeutic potential act on the cytoskeletal components like actin, tubulin either by promoting polymerization or destabilizing the same. Here we present the interaction of the popular cytoskeletal drugs such as taxol, latrunculin and cytochalasin with spectrin, a huge protein with multi domains that forms the cytoskeletal network. Particularly, the actin binding domain of spectrin regulates the dynamics of the actin cytoskeleton. We followed the binding of these drugs to its actin binding domain and intact spectrin as well. These drugs bind with moderate affinity (K_b ∼ 10⁴ M^-1) and the interaction with actin binding domain is entropy driven and hydrophobic in nature as determined by Van't Hoff plot. The docking studies and molecular dynamics simulations further corroborate the experimental findings. Particularly the higher binding constants in the case of latrunculin and cytochalasin to the actin binding domain of spectrin suggest the binding sites are presumably located in its actin binding domain.Communicated by Ramaswamy H. Sarma.

Molecular Insight into the Binding of Astilbin with Human Serum Albumin and Its Effect on Antioxidant Characteristics of Astilbin

Astilbin is a dihydroflavonol glycoside identified in many natural plants and functional food with promising biological activities which is used as an antioxidant in the pharmaceutical and food fields. This work investigated the interaction between astilbin and human serum albumin (HSA) and their effects on the antioxidant activity of astilbin by multi-spectroscopic and molecular modeling studies. The experimental results show that astilbin quenches the fluorescence emission of HSA through a static quenching mechanism. Astilbin and HSA prefer to bind at the Site Ⅰ position, which is mainly maintained by electrostatic force, hydrophobic and hydrogen bonding interactions. Multi-spectroscopic and MD results indicate that the secondary structure of HSA could be changed because of the interaction of astilbin with HSA. DPPH radical scavenging assay shows that the presence of HSA reduces the antioxidant capacity of astilbin. The explication of astilbin–HSA binding mechanism will provide insights into clinical use and resource development of astilbin in food and pharmaceutical industries.

5,2′-Dibromo-2,4′,5′-trihydroxydiphenylmethanone Inhibits LPS-Induced Vascular Inflammation by Targeting the Cav1 Protein

Vascular inflammation is directly responsible for atherosclerosis. 5,2′-Dibromo-2,4′,5′-trihydroxydiphenylmethanone (TDD), a synthetic bromophenol derivative, exhibits anti-atherosclerosis and anti-inflammatory effects. However, the underlying pathways are not yet clear. In this study, we first examined the effects of TDD on toll-like receptor-4 (TLR4) activity, the signaling receptor for lipopolysaccharide (LPS), and found that TDD does not inhibit LPS-induced TLR4 expression in EA.hy926 cells and the vascular wall in vivo. Next, we investigated the global protein alterations and the mechanisms underlying the action of TDD in LPS-treated EA.hy926 cells using an isobaric tag for the relative and absolute quantification technique. Western blot analysis revealed that TDD inhibited NF-κB activation by regulating the phosphorylation and subsequent degradation IκBα. Among the differentially expressed proteins, TDD concentration-dependently inhibited Caveolin 1(Cav1) expression. The interaction between Cav1 and TDD was determined by using biolayer interference assay, UV-vis absorption spectra, fluorescence spectrum, and molecular docking. We found that TDD can directly bind to Cav1 through hydrogen bonds and van der Waals forces. In conclusion, our results showed that TDD inhibited LPS-induced vascular inflammation and the NF-κB signaling pathway by specifically targeting the Cav1 protein. TDD may be a novel anti-inflammatory compound, especially for the treatment of atherosclerosis.

Insight on the microscopic binding mechanism of bisphenol compounds (BPs) with transthyretin (TTR) based on multi-spectroscopic methods and computational simulations

Thyroid hormones are involved in numerous physiological processes as regulators of metabolism, regulating organ growth, and mental state. Bisphenol compounds (BPs) are recognized as chemicals that interfere with endocrine balance. Because BPs have a similar structure to thyroxine, they can compete for binding to thyroid protein and disrupt the normal physiological activity of the thyroid system. In this study, three typical bisphenol compounds were selected to explore the interaction between BPs and TTR by computer simulations and multi-spectroscopic methods. The results revealed that BPs quenched the endogenous fluorescence of TTR via the combination of static quenching and non-radiative energy transfer, and the van der Waals forces and hydrogen bonding played a synergistic role in the binding process of BPs and TTR. Furthermore, the three-dimensional fluorescence spectroscopy, UV-vis spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy, which were employed to determine the conformation of protein, revealed that binding of BPs with TTR could induce conformational changes in TTR. In addition, the binding sites and the residues surrounding the BPs within the TTR were determined through molecular docking and molecular dynamics simulation. Therefore, this work provides new insights into the interaction between BPs and TTR to evaluate the potential toxicity of BPs.

Spectroscopic and in silico insight into the interaction between dicofol and human serum albumin

Dicofol, a broad-spectrum acaricide, has garnered considerable attention because of the potential harm to the environment and various organisms. Herein, this study applied spectroscopic and in silico methods to understand the interaction between human serum albumin (HSA) and dicofol. Fluorescence experiments demonstrated that dicofol formed a stable complex and the binding process occurred in Suldow's site I of HSA. Its binding constant was 2.26 × 10⁵ M^-1 at 298 K. Van der Waals forces and hydrogen bond were primarily facilitated the interaction between dicofol and HSA (ΔH < 0, ΔS < 0) according to thermodynamic experiments. Additionally, 3D fluorescence and circular dichroism (CD) spectra revealed a few conformational changes in HSA due to dicofol. Molecular docking analysis indicated that dicofol interacted with Ser192, Gln196, Leu481, Arg218, Leu238, and Phe211 via van der Waals forces and formed a hydrogen bond with His242. Molecular dynamics (MD) simulation showed that Lys195 and Arg218 residues contributed greater energy for forming the HSA-dicofol complex. MD simulation analysis also showed that dicofol can affect the HSA structure with a reduction in α-helix. This research is desired to facilitate a new perspective on the toxicity mechanism of dicofol in the human body.

Spectroscopic and computational studies on the binding interaction between gallic acid and Pin1

Gallic acid (GA) is a natural ingredient in functional foods, which has various health-promoting and antitumour effects. Peptidyl-prolyl cis/trans isomerase Pin1 plays an important role in preventing the development of some malignant tumours. However, whether there was an interaction between Pin1 and GA remains unknown. In this work, the binding information of GA and Pin1 was investigated systematically using multiple spectral and computational methods. GA bound to Pin1 directly with moderate binding affinity in the order of 10⁴  mol/L, therefore decreasing the activity of Pin1. Also, the binding process of GA to Pin1 was driven through weak van der Waals forces, hydrogen bonds, and electrostatic forces. In addition, the important residues Lys63, Arg68, and Arg69 played a significant role in maintaining the binding stability between Pin1 and GA. Interestingly, GA reduced the activity of Pin1 by affecting its conformational characteristics. Our present work showed that GA binds to Pin1 and inhibits its activity, affecting its structural and functional properties, which may contribute to the therapy of Pin1-related diseases.

Exploring the toxic effects and mechanism of methoxylated polybrominated diphenyl ethers (MeO-PBDEs) on thyroxine-binding globulin (TBG): Synergy between spectroscopic and computations

The interaction mechanism between thyroxine-binding globulin (TBG) and three methoxylated polybrominated diphenyl ethers (MeO-PBDEs) was analyzed by steady-state fluorescence, ultraviolet-visible (UV-visible) spectroscopy, circular dichroism (CD), molecular docking and molecular dynamics simulation methods. The results of the molecular docking technique revealed that 2'-MeO-BDE-3, 5-MeO-BDE-47, and 3-MeO-BDE-100 combined with TBG at the active site. The steady-state fluorescence spectra displayed that MeO-PBDEs quenched the endogenous fluorescence of TBG through static quenching mechanism, and complex formation between MeO-PBDEs and TBG was further indicated by UV-vis spectroscopy. The thermodynamic quantities showed that the binding process is spontaneous, and the major forces responsible for the binding are hydrogen bonding and hydrophobic interactions, which are consistent with the results of molecular docking to a certain extent. The results of CD confirmed that the secondary structure of TBG was changed after combining with MeO-PBDEs. The dynamic simulation results illustrated that the protein structure is more compact and changes in the secondary structure of TBG after binding to MeO-PBDEs. Additionally, we also utilized the molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) method to analyze the binding free energy of TBG and MeO-PBDEs. The results suggest that van der Waals force plays an essential role in the combination.

Probing the Interaction between Human Serum Albumin and 9-Hydroxyphenanthrene: A Spectroscopic and Molecular Docking Study

9-Hydroxyphenanthrene (9-OHPhe), the representative hydroxyl metabolite of phenanthrene, has generated increasing concern as it is potentially hazardous to organisms. Herein, multispectroscopic and molecular docking techniques were applied to investigate the molecular interaction of human serum albumin (HSA) with 9-hydroxyphenanthrene (9-OHPhe) under simulated physiological conditions. Steady-state fluorescence and time-resolved fluorescence spectral analysis showed that 9-OHPhe quenched HSA fluorescence through a mixed static and dynamic process. HSA can bind with 9-OHPhe to form a 1:1 complex, with binding constants of 1.28 × 10⁵, 1.36 × 10⁵, and 1.26 × 10⁵ L·mol^-1 at 298.15, 303.15, and 308.15 K, respectively. The strong binding between HSA and 9-OHPhe is spontaneous and entropy-driven. Molecular docking indicated that the optimal binding site of 9-OHPhe with HSA was located in the IA subdomain of HSA. Thermodynamic analysis and molecular docking results suggested that hydrophobic interactions and hydrogen bond force dominated the binding process of HSA with 9-OHPhe. Specifically, 9-OHPhe formed hydrophobic interactions with LEU134, LEU139, ILE142, LEU154, PHE157, ALA158, and TYR161 and formed a 1.86 Å hydrogen bond with LEU135. Circular dichroism spectral analysis showed that the α-helical content of HSA decreased from 52.3 to 50.9% after adding 9-OHPhe with a ratio of 1:1. The obtained results are hoped to provide basic data for understanding the potential effects of the hydroxyl metabolites of PAHs on functional biomacromolecules.