Multispectroscopic and computational studies of interaction of bovine serum albumin, human serum albumin and bovine hemoglobin with bisacodyl

Interaction mechanism of oseltamivir phosphate with bovine serum albumin: multispectroscopic and molecular docking study

Oseltamivir phosphate (OP) is an antiviral drug with potential risks to human health due to overuse, leading to serious consequences such as gastrointestinal disturbances, abnormal neuropsychiatric symptoms, and sudden death. Therefore, gaining an in-depth understanding of its interaction with proteins is crucial. We investigated the interaction between OP and bovine serum albumin (BSA) utilizing multispectral methods (i.e., fluorescence, ultraviolet absorption, circular dichroism) combined with molecular docking techniques. Fluorescence spectroscopy indicated that OP quenched BSA fluorescence by forming the OP-BSA complex. The Stern-Volmer constants (KSV) between OP and BSA were determined to be 3.06 × 103 L/mol, 2.36 × 103 L/mol, and 1.86 × 103 L/mol at 293 K, 298 K, and 303 K, respectively. OP occupies exclusively one binding site on BSA, and the fluorescent probe displacement measurements revealed that this is BSA site I. Thermodynamic data (∆H, ∆S, and ∆G) obtained by fitting the van't Hoff equation were - 77.49 kJ/mol, -176.54 J/(mol∙K), and - 24.88 kJ/mol, respectively, suggesting that hydrogen bonding and van der Waals forces mainly participate in OP-BSA complex stabilization. Moreover, the reaction occurs spontaneously at room temperature. Synchronous fluorescence spectra indicated that OP interacts with tryptophan residue of BSA. The results of ultraviolet (UV) and 3D fluorescence spectroscopy indicated that the OP-BSA complex formation altered the microenvironment around amino acid residues. Circular dichroism spectra revealed that the addition of OP decreased the α-helix content of BSA by 7.13%. Docking analysis confirmed that OP binds to BSA site I through hydrogen bonding with amino acids VAL342, SER453, and ASP450. Finally, ADMET studies were conducted to explore the pharmacokinetics of OP as an antiviral drug.

Insight into the interaction of 5,6 epoxy-cholesterols with human serum albumin

5,6-Epoxy-cholesterols has been recently revealed to control metabolic pathway in breast cancer, which makes investigating their binding interaction with human serum albumin (HSA) an attractive field of research. The main aim of this article is to examine the binding interaction of 5,6 α-epoxy-cholesterol (5,6 α EC) and 5,6 β-epoxy-cholesterol (5,6 β- EC) with HSA using different spectroscopic methods and molecular modeling. These compounds interact with HSA via hydrophobic interactions and hydrogen bonds with binding constants 6.3 × 105 M-1 for 5,6 α-epoxy-cholesterol and 6.9 × 105 M-1 for 5,6 β-epoxy-cholesterol besides, the mechanism of the interaction can be attributed to static quenching. Circular dichroism data indicated that the α-helical content of HSA increased from 50.5 to 59.8 and 61.1 % after the addition of 5,6 α-ECs and 5,6 β-EC, respectively, with a ratio of 1:2. Thermodynamic analysis revealed that binding between 5,6-epoxy-cholesterols and HSA is spontaneous and entropy-driven. The molecular docking and esterase-like activity experiments were performed to envision a link between the experimental and theoretical results. The optimal binding site of 5,6-epoxy-cholesterols with HSA was located in subdomain IIA. Moreover, theoretical calculations were performed using the B3LYP function with the 6-311++G (d,p) basis set, indicating the HOMO-LUMO energy gap of 7.874 eV for 5,6 α-epoxy-cholesterol and 7.873 eV for 5,6 β-epoxy-cholesterol. The obtained findings are assumed to provide basic data for understanding the binding interactions of HSA with oxysterol compounds, which could help explore the pharmacokinetics and pharmacodynamics of oxysterol compounds.

In Vitro Hemoglobin Binding and Molecular Docking of Synthesized Chitosan-Based Drug-Carrying Nanocomposite for Ciprofloxacin-HCl Drug Delivery System

Understanding the intermolecular interactions between antibiotic drugs and hemoglobin is crucial in biological systems. The current study aimed to investigate the preparation of chitosan/polysorbate-80/tripolyphosphate (CS-PS/TPP) nanocomposite as a potential drug carrier for Ciprofloxacin-HCl drug (CFX), intended for controlled release formulation and further used to interact with bovine hemoglobin. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis-differential thermal analysis (TGA-DTA), scanning electron microscopy (SEM), dynamic light scattering (DLS), and X-ray diffraction analyses were used to characterize the CS-PS/TPP nanocomposite and its CFX-loaded nanocomposite. The second series of biophysical properties were performed on the Ciprofloxacin-loaded CS-PS/TPP (NCFX) for interaction with bovine hemoglobin (BHb). The interactions of (CFX and NCFX) with redox protein hemoglobin were investigated for the first time through a series of in vitro experimental techniques to provide comprehensive knowledge of the drug-protein binding interactions. Additionally, the effect of inclusion of PS-80 on the CFX-BHb interaction was also studied at different concentrations using fluorescence spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and circular dichroism (CD) under physiological conditions. The binding process of CFX and NCFX was spontaneous, and the fluorescence of BHb was quenched due to the static mechanism formation of the (CFX/BHb) and (NCFX/BHb) complexes. Thermodynamic parameters ΔG, ΔH, and ΔS at various temperatures indicate that the hydrogen bonding and van der Waals forces play a major role in the CFX-BHb association.

Impact of Sinapic Acid on Bovine Serum Albumin Thermal Stability

The thermal stability of bovine serum albumin (BSA) in Tris buffer, as well as the effect of sinapic acid (SA) on protein conformation were investigated via calorimetric (differential scanning microcalorimetry-μDSC), spectroscopic (dynamic light scattering-DLS; circular dichroism-CD), and molecular docking approaches. μDSC data revealed both the denaturation (endotherm) and aggregation (exotherm) of the protein, demonstrating the dual effect of SA on protein thermal stability. With an increase in ligand concentration, (i) protein denaturation shifts to a higher temperature (indicating native form stabilization), while (ii) the aggregation process shifts to a lower temperature (indicating enhanced reactivity of the denatured form). The stabilization effect of SA on the native structure of the protein was supported by CD results. High temperature (338 K) incubation induced protein unfolding and aggregation, and increasing the concentration of SA altered the size distribution of the protein population, as DLS measurements demonstrated. Complementary information offered by molecular docking allowed for the assessment of the ligand binding within the Sudlow's site I of the protein. The deeper insight into the SA-BSA interaction offered by the present study may serve in the clarification of ligand pharmacokinetics and pharmacodynamics, thus opening paths for future research and therapeutic applications.

Recombinant expression and preliminary characterization of Peptidyl-prolyl cis/trans-isomerase Rrd1 from Saccharomyces cerevisiae

Sacchromycescerevisiae Peptidyl-prolylcis/trans-isomerase Rrd1 has been linked to DNA repair, bud morphogenesis, advancement of the G1 phase, DNA replication stress, microtubule dynamics and is also necessary for the quick decrease in Sgs1p levels in response to rapamycin. In present study, Rrd1 gene was amplified by standard PCR and subsequently cloned downstream to bacteriophage T7 inducible promoter and lac operator of expression vector pET21d(+). Additionally, immobilized metal affinity chromatography (IMAC) was used to purify the protein upto its homogeneity, and its homogeneous purity was further confirmed through western blotting. Size exclusion chromatography implies that Rrd1 is existing as monomer in its natural state. Foldwise Rrd1 protein belongs to PTPA-like protein superfamily. Rrd1 showed characteristic negative minima at 222 and 208 nm represent protein typically acquired α helix in the far-UV CD spectra. Fluorescence spectra showed properly folded tertiary structures of Rrd1 at physiological conditions. Rrd1protein can be identified from different species using a fingerprint created by PIPSA analysis. The protein's abundance could aid in its crystallization, biophysical characterization and identification of other-interacting partners of Rrd1 protein.

Study on the interaction of two quinazoline derivatives as novel PI3K/mTOR dual inhibitors and anticancer agents to human serum albumin utilizing spectroscopy and docking

Interactions of human serum albumin (HSA) with two structurally similar quinazoline derivatives, S₁ and S₂ , which are potential anticancer drugs acting on PI3K/mTOR targets, were investigated in vitro utilizing multiple spectroscopy as well as molecular docking. The fluorescence quenching study demonstrated that HSA fluorescence could be statically quenched by S₁ and S₂ through the formation of an HSA-drug complex. Furthermore, the details of the binding site number, binding constant, as well as the thermodynamic parameters, were estimated at 298, 303, and 310 K. The results revealed that hydrogen bond interactions, as well as van der Waals forces, were the predominant factors responsible for binding HSA to S₁ or S₂ . Synchronous fluorescence and ultraviolet (UV) absorption spectra suggested that S₁ and S₂ had little effect on the polarity of the microenvironment and conformation of HSA. Energy transfer from HSA to S₁ or S₂ most probably occurred. The docking study revealed that S₁ and S₂ were able to bind to the hydrophobic cavity that was located in the HSA subdomain IIA and formed varying numbers of hydrogen bonds with amino acid residues nearby. Due to the subtle difference in the chemical structure, the binding of S₁ and S₂ to HSA was slightly different.

Interactions between hydroxylated polycyclic aromatic hydrocarbons and serum albumins: Multispectral and molecular docking analyses

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) can bind to serum albumin and influence their distribution and elimination in organisms. Herein, multispectral analysis and molecular docking methods were used to investigate the binding mechanism of two OH-PAHs, 1-hydroxyphenanthrene (1-OHPhe) and 9-hydroxyphenanthrene (9-OHPhe), with two homologous serum albumins, human serum albumin (HSA) and bovine serum albumin (BSA). The quenching constants of HSA with 1-OHPhe and 9-OHPhe were much larger than those for BSA. Energy transfer from the tryptophan (Trp) residues in HSA to 1-OHPhe and 9-OHPhe was more probable than from Trp in BSA. The interactions of 1-OHPhe and 9-OHPhe with Trp in HSA and BSA altered the microenvironment of Trp. Molecular docking results revealed that the binding modes and binding forces of 1-OHPhe and 9-OHPhe with HSA and BSA were different. The two OH-PAHs were used as fluorescent probes to analyze the microenvironmental hydrophobicities of HSA and BSA, which were distinctly different. The structural difference between HSA and BSA induced significant variations in their binding behavior with 1-OHPhe and 9-OHPhe. Moreover, HSA was more susceptible to 1-OHPhe and 9-OHPhe than BSA. This work suggests that the differences between the two serum albumins should be considered in related studies.

Study of Competitive Displacement of Curcumin on α-zearalenol Binding to Human Serum Albumin Complex Using Fluorescence Spectroscopy

α-zearalenol (α-ZOL) is a mycotoxin with a strong estrogen effect that affects the synthesis and secretion of sex hormones and is transported to target organs through human serum albumin (HSA). Additionally, it has been reported that curcumin can also bind to HSA with high affinity at the same binding site as α-ZOL. Additionally, several studies reported that reducing the bound fraction of α-ZOL contributes to speeding up the elimination rate of α-ZOL to reduce its hazard to organs. Therefore, to explore the influence of a nutrition intervention with curcumin on α-ZOL effects, the competitive displacement of α-ZOL from HSA by curcumin was investigated using spectroscopic techniques, ultrafiltration techniques and HPLC methods. Results show that curcumin and α-ZOL share the same binding site (subdomain IIA) on HSA, and curcumin binds to HSA with a binding constant of 1.12 × 10⁵ M⁻¹, which is higher than that of α-ZOL (3.98 × 10⁴ M⁻¹). Ultrafiltration studies demonstrated that curcumin could displace α-ZOL from HSA to reduce α-ZOL’s binding fraction. Synchronous fluorescence spectroscopy revealed that curcumin could reduce the hydrophobicity of the microenvironment of an HSA–α-ZOL complex. This study is of great significance for applying curcumin and other highly active foodborne components to interfere with the toxicokinetics of α-ZOL and reduce its risk of its exposure.

Modulation of the binding ability to biomacromolecule, cytotoxicity and cellular imaging property for ionic liquid mediated carbon dots

For the preparation of carbon dots (CDs), a variety of carbon sources and synthetic protocols are available which endow CDs with variable and unpredictable properties. In the present study, three CDs were developed with ionic liquid 1-butyl-3-methylimidazolium dicyanamide as the precursor through ethanol-thermal and hydrothermal strategies, termed as E-CDs and H-CDs, respectively. The features of these carbon dots, i.e., their physicochemical and optical properties, their interactions with bovine serum albumin (BSA) as well as their imaging capability were investigated with respect to the CDs prepared with microwave assisted approach (W-CDs). E-CDs and H-CDs were demonstrated to exhibit similar framework structures and optical properties, and they exhibited larger particle-sizes than that of W-CDs. In addition, the increase of ethanol-thermal and hydrothermal reaction time strengthened the quantum yields of the CDs and promoted their binding capability with BSA. E-CDs and H-CDs showed similar cytotoxicity on normal (LX-2) and cancer (SK-Hep-1) cells. We further found that these CDs may readily enter the cells within 5 min, while the fluorescence of hydrophilic E-CDs and H-CDs was very weak with respect to that of hydrophobic W-CDs in cell imaging. On the other hand, all the CDs exhibited little impact on the level of intracellular reactive oxygen species. The present study is conducive to guide the preparation of suitable carbon dots for different application scenarios.