Interaction study of pioglitazone with albumin by fluorescence spectroscopy and molecular docking

Interaction between the antioxidant compound safranal and α-chymotrypsin in spectroscopic fields and molecular modeling approaches

Among various herbal plants, saffron has been the subject of study in various medical and food fields. Among the compounds of saffron, safranal is one of them. Safranal is a monoterpene aldehyde. The precursor of safranal is called picrocrocin, whose hydrolysis leads to the production of safranal. picrocrocin has two sugar components and aglycone. sugar component was separated during the drying process of saffron and safranal is produced. Saffron is the cause of the saffron aroma. Previous studies have shown that safranal offers many benefits such as antioxidants, blood pressure regulation and anti-tumor qualities. On the other hand, α-Chy is an enzyme secreted by the pancreas into the intestine and then acts as an efficient protease. In this study, various methods, such as molecular dynamics (MD) simulation and molecular binding, and different spectroscopic techniques, as well as protein stability techniques, were used to investigate the possible interactions between safranal and α-Chy. UV spectroscopic studies were showing that the existence of safranal decreased α-Chy absorption intensity. safranal caused the intrinsic fluorescence of α-Chy to be quenched too. According to the Stern-Volmer equation, the interaction between safranal and α-Chy was of the static type. In thermodynamic calculations, the interaction between safranal and α-Chy was stabilized by hydrophobic forces. And it was found that this interaction continued spontaneously. These results were, thus, consistent with the Docking data simulation (with the negative ΔG° number and positive changes in enthalpy and entropy). The thermal stability of α-Chy was also measured, showing that its melting point was shifted to a higher threshold as a result of the interaction. also, MD simulation indicated that α-Chy became more stable in the presence of safranal. In this paper, all the results of the laboratory techniques were confirmed by molecular dynamic simulations, so the correctness of the results was confirmed. From this research, we hope to carefully observe the possible changes in the behavior and structure of the enzyme in the presence of safranal.Communicated by Ramaswamy H. Sarma.

Analysis of Binding Modes between Three Perfluorosulfonates and GPER Based on Computational Simulation and Multiple Spectral Methods

Perfluorinated compounds (PFCs) belong to a significant category of global environmental pollutants. Investigating the toxicological effects of PFCs within biological systems is of critical significance in various disciplines such as life sciences, environmental science, chemistry, and ecotoxicology. In this study, under simulated human physiological conditions (pH = 7.4), a combination of multiple spectroscopic techniques and computational simulations was employed to investigate the impact of perfluorinated compounds (PFCs) on the G protein-coupled estrogen receptor (GPER). Additionally, the research focused on exploring the binding modes and toxicological mechanisms between PFCs and GPER at the molecular level. All three perfluorinated sulfonic acids (PFSAs) can induce quenching of GPER fluorescence through static quenching and non-radiative energy transfer. Steady-state fluorescence calculations at different temperatures revealed apparent binding constants in the order of 106, confirming a strong binding affinity between the three PFSAs and GPER. Molecular docking studies indicated that the binding sites of PFSAs are located within the largest hydrophobic cavity in the head region of GPER, where they can engage in hydrogen bonding and hydrophobic interactions with amino acid residues within the cavity. Fourier transform infrared spectroscopy, three-dimensional fluorescence, and molecular dynamics simulations collectively indicate that proteins become more stable upon binding with small molecules. There is an overall increase in hydrophobicity, and alterations in the secondary structure of the protein are observed. This study deepens the comprehension of the effects of PFCs on the endocrine system, aiding in evaluating their potential impact on human health. It provides a basis for policy-making and environmental management while also offering insights for developing new pollution monitoring methods and drug therapies.

Generation of affinity maps for thiazolidinediones with human serum albumin using affinity microcolumns. I. Studies of effects by glycation on multisite drug binding

Human serum albumin (HSA) is known to undergo modifications by glucose during diabetes. This process produces glycated HSA that can have altered binding to some drugs. In this study, high-performance affinity microcolumns and competition studies were used to see how glycation affects the binding by two thiazolidinedione-class drugs (i.e., pioglitazone and rosiglitazone) at specific regions of HSA. These regions included Sudlow sites I and II, the tamoxifen and digitoxin sites, and a drug-binding site located in subdomain IB. At Sudlow site II, the association equilibrium constants (or binding constants) for pioglitazone and rosiglitazone with normal HSA were 1.7 × 105 M-1 and 2.0 × 105 M-1 at pH 7.4 and 37 °C, with values that changed by up to 5.7-fold for glycated HSA. Sudlow site I of normal HSA had binding constants for pioglitazone and rosiglitazone of 3.4 × 105 M-1 and 4.6 × 105 M-1, with these values changing by up to 1.5-fold for glycated HSA. Rosiglitazone was found to also bind a second region that had a positive allosteric effect on Sudlow site I for all the tested preparations of HSA (binding affinity, 1.1-3.2 × 105 M-1; coupling constant for Sudlow site I, 1.20-1.34). Both drugs had a strong positive allosteric effect on the tamoxifen site of HSA (coupling constants, 13.7-19.9 for pioglitazone and 3.7-11.5 for rosiglitazone). Rosiglitazone also had weak interactions at a site in subdomain IB, with a binding constant of 1.4 × 103 M-1 for normal HSA and a value that was altered by up to 6.8-fold with glycated HSA. Neither of the tested drugs had any significant binding at the digitoxin site. The results were used to produce affinity maps that described binding by these thiazolidinediones with HSA and the effects of glycation on these interactions during diabetes.

Characteristics and structure of a soy protein isolate-lutein nanocomplex produced via high-pressure homogenization

BACKGROUND

In recent years, nanocarriers for transporting active substances have attracted attention. This study was to explore the soy protein isolate (SPI) after high-pressure homogenization (HPH) (0, 30, 60, 90 and 120 MPa) as potential lutein carriers.

RESULTS

The load amount (LA) and encapsulation efficiency (EE) of the SPI-lutein nanocomplexes at a homogenization pressure of 60 MPa were the highest (2.32 mg mL^-1 and 92.85%, respectively), and the average particle size and ζ-potential of the SPI-lutein nanocomplexes were 192.1 nm and -30.06 mV, respectively. The DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydroxyl-antioxidant activities of the complex increased from 12.4% and 23.3% to 52.7% and 61.07%, respectively, after the protein was treated with HPH. The surface hydrophobicity of the SPI and the SPI-lutein nanocomplexes increased with increasing homogenization pressure treatment. Fourier transform-infrared spectrophotometry analyses suggested that the homogenization treatments resulted in partial unfolding of the protein molecules, and the addition of lutein can also lead to the change of protein secondary structure. The fluorescence emission of SPI was quenched by lutein through the static quenching mechanism. Fluorescence experiments revealed that SPI and lutein had the strongest binding ability through hydrophobic interaction at a homogenization pressure of 60 MPa.

CONCLUSION

After HPH, the combination of SPI and lutein was beneficial, and the stability of lutein also improved after the combination. This study is conducive to expanding the application of soybean protein in the food industry. © 2022 Society of Chemical Industry.

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.

Molecular insights into the interaction of 5-fluorouracil and Fe3O4 nanoparticles with beta-casein: An experimental and theoretical study

We investigated the potential carrier of milk beta-casein (β-CN) and its interactions with 5-fluorouracil (5-FU) and iron oxide nanoparticles (Fe₃O₄ NPs). We used different spectroscopic methods of fluorescence, UV-Visble, circular dichroism (CD), synchronous fluorescence, zeta potential assay, and computational studies to clarify the protein interaction with 5-FU and Fe₃O₄ NPs. The fluorescence data indicated both Fe₃O₄ NPs and 5-FU could quench the intrinsic fluorescence of β-CN. Fluorescence measurements showed that the single interaction of β-CN with 5-FU or Fe₃O₄ NPs was static, while reacted β-CN with both 5-FU and Fe₃O₄ NPs simultaneously showed a dynamic quenching. Synchronous fluorescence data in both tests revealed that the tryptophan (Trp) residue of β-CN had a dominant role in quenching and the polarity of its microenvironment more than tyrosine (Tyr) increased in interaction with 5-FU. All the binding sites and thermodynamic parameters were obtained at 25, 37, and 42 °C. The analysis of thermodynamic parameters and Job's plot techniques pointed to that both of these complexes with the 1:1 M ratio were exothermic (ΔH°<0) driven with the van der Waals and H-bonding interactions (in agreement with the docking results). The CD spectra in the region of far-UV and thermal denaturation study indicated minor changes in the secondary structure of β-CN in the presence of various concentrations of Fe₃O₄ NPs and 5-FU. Also, from the molecular dynamics (MD) analysis, as a result, the protein structure was stable during 100 ns. The outcomes highlighted that β-CN protein could form a great bind with 5-FU and Fe₃O₄ NPs ligands (supporting the zeta potential assay results) by independent binding sites. These results would be helpful insight to construct a potential magnetic nanocarrier β-CN base for 5-FU drug delivery.

Effects of Baicalein and Chrysin on the Structure and Functional Properties of β-Lactoglobulin

Two flavonoids with similar structures, baicalein (Bai) and chrysin (Chr), were selected to investigate the interactions with β-lactoglobulin (BLG) and the influences on the structure and functional properties of BLG by multispectral methods combined with molecular docking and dynamic (MD) simulation techniques. The results of fluorescence quenching suggested that both Bai and Chr interacted with BLG to form complexes with the binding constant of the magnitude of 10⁵ L·mol⁻¹. The binding affinity between BLG and Bai was stronger than that of Chr due to more hydrogen bond formation in Bai–BLG binding. The existence of Bai or Chr induced a looser conformation of BLG, but Chr had a greater effect on the secondary structure of BLG. The surface hydrophobicity and free sulfhydryl group content of BLG lessened due to the presence of the two flavonoids. Molecular docking was performed at the binding site of Bai or Chr located in the surface of BLG, and hydrophobic interaction and hydrogen bond actuated the formation of the Bai/Chr–BLG complex. Molecular dynamics simulation verified that the combination of Chr and BLG decreased the stability of BLG, while Bai had little effect on it. Moreover, the foaming properties of BLG got better in the presence of the two flavonoids compounds and Bai improved its emulsification stability of the protein, but Chr had the opposite effect. This work provides a new idea for the development of novel dietary supplements using functional proteins as flavonoid delivery vectors.

Probing the Role of Cu(II) Ions on Protein Aggregation Using Two Model Proteins

Copper is an essential trace element for human biology where its metal dyshomeostasis accounts for an increased level of serum copper, which accelerates protein aggregation. Protein aggregation is a notable feature for many neurodegenerative disorders. Herein, we report an experimental study using two model proteins, bovine serum albumin (BSA) and human serum albumin (HSA), to elucidate the mechanistic pathway by which serum albumins get converted from a fully folded globular protein to a fibril and an amorphous aggregate upon interaction with copper. Steady-state fluorescence, time-resolved fluorescence studies, and Raman spectroscopy were used to monitor the unfolding of serum albumin with increasing copper concentrations. Steady-state fluorescence studies have revealed that the fluorescence quenching of BSA/HSA by Cu(II) has occurred through a static quenching mechanism, and we have evaluated both the quenching constants individually. The binding constants of BSA-Cu(II) and HSA-Cu(II) were found to be 2.42 × 104 and 0.05 × 104 M-1, respectively. Further nanoscale morphological changes of BSA mediated by oligomers to fibril and HSA to amorphous aggregate formation were studied using atomic force microscopy. This aggregation process correlates with the Stern-Volmer plots in the absence of discernible lag phase. Raman spectroscopy results obtained are in good agreement with the increase in antiparallel β-sheet structures formed during the aggregation of BSA in the presence of Cu(II) ions. However, an increase in α-helical fractions is observed for the amorphous aggregate formed from HSA.

Probing the interaction between 7-geranyloxycoumarin and bovine serum albumin: Spectroscopic analyzing and molecular docking study

7-Geranyloxycoumarin (auraptene; AUR), as a potent phytochemical, is the naturally abundant prenyloxycoumarin found in many genera of the Rutaceae family. As the interaction with serum albumins may play a crucial role in identifying their pharmacological properties, we investigated AUR binding profile with bovine serum albumin (BSA) by experimental and computational methods. Binding constant, binding site, mode of binding, and the BSA structural change upon AUR addition, were studied. UV-vis spectroscopy results and fluorescence quenching analysis proposed that AUR can form the ground state complex with BSA. Meantime, thermodynamic parameters (negative ΔH and ΔS values) revealed that hydrogen bonds and van der Waals interactions play major role, as intermolecular forces, in the AUR-BSA complex formation. Synchronous fluorescence spectra and circular dichroism (CD) data showed that the secondary structure of BSA did not change significantly in the presence of AUR. Moreover, molecular docking results showed that AUR binds to the subdomain IIIB of BSA.

Monitoring the Interaction between Thermally Induced Whey Protein and Anthocyanin by Fluorescence Quenching Spectroscopy

The color stability of anthocyanins was shown to improve with addition of whey proteins (WP). The goal of this study was to investigate the binding mechanisms of purple corn, grape and black carrot anthocyanin extracts to native and preheated WP (40-80 °C, 3.6 μM) at a pH of 3 using fluorescence quenching spectroscopy. The fluorescence spectra were collected with an excitation wavelength of 280 nm at 25 °C, 35 °C and 45 °C. The quenching data were analyzed by using the Stern-Volmer equation. The fluorescence intensity of WP decreased (up to 73%) and its λmax increased (by ~5 nm) with increasing anthocyanin concentration (0-100 μM). The quenching data showed that the interaction between anthocyanin extracts and WP was a static quenching process. Thermodynamic analysis showed their binding was mainly through hydrophobic interactions. Their binding affinity was higher for preheated WP than native WP and decreased gradually with increasing preheating temperature. Black carrot anthocyanin extract had the lowest binding affinity with WP, likely due to the larger molecular structure. These results help better understand the protection mechanism of native and preheated WP on anthocyanin color stability, expanding the application of anthocyanins as food colorants that better withstand processing and storage.

The long-term effects of Δ9-tetrahydrocannabinol on microtubule dynamicity in rats

Studies reported that Δ⁹-tetrahydrocannabinol (Δ⁹-THC) is an essential drug as an anti-cancer, neuroprotective, anti-inflammatory, and immune-modulatory agent. However, the mechanism by which Δ⁹-THC causes these events remains to be elucidated. We attempted to investigate the in vivo studies of Δ⁹-THC on brain microtubule dynamicity, and acetylcholinesterase (AChE) activity. The microtubule polymerization, secondary and tertiary structures of α/β-tubulins, as well as the AChE activity, were evaluated in the experimental groups. The significantly lowest optical density and initial rate of polymerization was observed in THC 3 mg/kg, THC 9 mg/kg, and THC 18 mg/kg treated groups. The content of secondary and tertiary structures of α/β-tubulins was significantly affected in treated groups. The AChE activity was significantly lower in treated groups in a dose-dependent manner. These data highlight the microtubule dynamicity as a molecular target for Δ⁹-THC, which affects memory dysfunction. However, Δ⁹-THC can be inhibited the AChE activity and provide an improved therapeutics for neurodegenerative diseases.

Investigating the interaction between three perfluorinated carboxylic acids and the G protein-coupled estrogen receptor: spectroscopic analyses and computational simulations

In this paper, perfluorinated compounds (PFCs), such as perfluorobutyric acid (PFBA), perfluorooctanoic acid (PFOA) and perfluorododecanoic acid (PFDoA), were selected as typical representatives of perfluorinated carboxylic acids (PFCAs) to study the effects of PFCAs on the G protein-coupled estrogen receptor (GPER). The interaction mechanism of the three types of PFCAs with the GPER was investigated using steady-state fluorescence spectroscopy, ultraviolet-visible spectroscopy, three-dimensional fluorescence spectroscopy, and Fourier transform infrared spectroscopy combined with molecular docking and molecular dynamics simulations. Among these techniques, steady-state fluorescence and ultraviolet-visible spectroscopic analyses showed that PFBA, PFOA and PFDoA quenched the endogenous GPER fluorescence by combined dynamic and static quenching and non-radiative energy transfer. The binding constants (K_a) of PFCAs on the GPER were all larger than 10⁵ L mol^-1, indicating that their affinity for the GPER was strong. Fourier transform infrared spectroscopy and three-dimensional fluorescence showed that the secondary structure of the GPER changed after binding to PFCAs. Thermodynamic analysis showed ΔG < 0, which indicated that the interaction between the GPER and PFCAs was spontaneous. For the binding of PFBA and PFOA to the GPER, ΔH > 0 and ΔS > 0, indicating that the interaction was mainly driven by hydrophobic forces; for the binding of PFDoA to the GPER, ΔH < 0 and ΔS < 0, suggesting that van der Waals force and hydrogen bonding were the main interaction forces. Molecular dynamics simulations suggested that the stability of the GPER-PFCA complexes was higher than that of the free GPER, and also that the structure and hydrophobicity of the GPER changed after binding to PFCAs. Molecular docking analysis showed that all three PFCAs could form hydrogen bonds with the GPER, which improved the stability of the complex.

Multi-spectroscopic studies of the interaction of new synthesized platin complex with human carrier protein of serum albumin

Previous reports have shown that protein-drug interaction helps to improve the pharmacokinetics of the drugs. Human serum albumin (HSA) is one of the basic components of blood plasma and it serves as a storage and carrier protein. In the present study, the interaction of a new synthesized Pt [iso]2 complex (cis - [Pt(NH₂-Isopentylamine)₂(Isopentylglycine)]NO₃₎ with HSA was studied using the spectroscopic methods of fluorescence and circular dichroic (CD) at two different temperatures of 25 and 37 °C. Analysis of the quenching mechanism via Stern-Volmer curve, determination of HSA binding parameters (0.65 × 10⁴ and 2.27 × 10⁴) and standard Gibbs free energy (-25.8, and 21.77) at 25 and 37 °C, respectively, carried out using fluorescence quenching data. Data analysis showed that the static mechanism has the main role in fluorescence quenching. Also, the number of protein binding sites for complex indicated one binding site at two temperatures of 25 and 37 °C. The secondary structure of protein in the presence of different concentrations of Pt(II) complex did not show any significant alterations. Whereas, thermal stability of the HSA was reduced in the presence of complex. Also, thermal analysis obtained the values of ΔG°₂₅ for HSA and HSA in presence of Pt [Iso]₂ 20, 13, respectively. According to the above results, we concluded that the new synthesized Pt complex can bind to the blood carrier protein of HSA and change the stability of it which can be considered in the design of new drugs.Communicated by Ramaswamy H. Sarma.

Multispectral and computational probing of the interactions between sitagliptin and serum albumin

The binding of sitagliptin (SIT), an anti-diabetic drug, to human and bovine serum albumin (HSA and BSA; main serum transport proteins) was investigated using various spectroscopic and molecular docking techniques. The fluorescence data demonstrated that SIT quenched inherent fluorescence of these proteins through the formation of SIT-HSA/BSA complexes. The number of binding sites was obtained (~1) and binding constant (K_b) and effective quenching constant (K_a) were calculated as 10⁴ for both systems. Based on thermodynamic parameters, the van der Waals forces and hydrogen bonding were the most important forces in the interactions between HSA/BSA and SIT, and the complex formation processes were spontaneous. The results of UV-vis absorption and FT-IR spectroscopic revealed that SIT induces small conformational changes in the structure of the proteins (HSA/BSA). The synchronous fluorescence (SF) spectroscopy demonstrated that the binding of SIT with HSA/BSA had no effect on the polarity around Trp and Tyr residues. The CD spectra showed changes in the secondary and tertiary structures of both proteins with a decrease in α-helices contents and an increase in β-turn structures. The molecular docking and spectroscopic data verified the binding mechanisms between SIT and HSA/BSA, and revealed that SIT completely fits into the hydrophobic cavity between domain II and domain III of these proteins.

Multi-spectroscopic and molecular dynamics simulations investigation of the binding mechanism of polybrominated diphenyl ethers to hen egg white lysozyme

Three PBDEs (BDE25, BDE47, and BDE154) were selected to investigate the interactions between PBDEs and hen egg white lysozyme (HEWL) by molecular modeling, fluorescence spectroscopy, and FT-IR spectra. The docking results showed that hydrogen bonds were formed between BDE25 and residue TRP63 and between BDE47 and TRP63 with bond lengths of 2.178 Å and 2.146 Å, respectively. The molecular dynamics simulations indicated that van der Waals forces played a predominant role in the binding of three PBDEs to HEWL. The observed fluorescence quenching can be attributed to the formation of complexes between HEWL and PBDEs, and the quenching mechanism is a static quenching. According to Förster's non-radiative energy transfer theory, the binding distances r were < 7 nm, indicating a high probability of energy transfer from HEWL to the three PBDEs. The synchronous fluorescence showed that the emission maximum wavelength of tryptophan (TRP) residues emerged a red-shift. FT-IR spectra indicated that BDE25, BDE47 and BDE154 induced the α-helix percentage of HEWL decreased from 32.70% ± 1.64% to 28.27% ± 1.41%, 27.50% ± 1.38% and 29.78% ± 1.49%, respectively, whereas the percentage of random coil increased from 26.67% ± 1.33% to 27.60% ± 1.38%, 29.18% ± 1.46% and 30.59% ± 1.53%, respectively.

Experimental and theoretical investigations on the interaction of l-methionine molecules with α-chymotrypsin in the aqueous solution using various methods

l-Methionine (l-Met) is one of the necessary amino acids that play unparalleled roles, influencing both the protein structure and metabolism. Understanding the interactions between proteins and small molecules can be realized by various perspectives, and this is significant for the progression of basic sciences and drug development. In this study, the variations in the stability, function, and structure of α-Chymotrypsin (α-Chy) in the presence of l-Met were investigated using spectroscopic and computational approaches. The results of the UV-vis absorption demonstrated that α-Chy had a maximum peak at 280 nm due to the Trp residue. Hyperchromism shift was seen in the presence of l-Met. Ground state system was formed in the presence of l-Met, as confirmed by the fluorescence studies. Fluorescence variations also revealed static quenching. The CD spectra also represented the alteration of the enzyme with an increase in the α-helix and a decrease in the β-sheet. The activity of α-Chy was incremented in the presence of l-Met. Therefore, l-Met served as an activator. Molecular docking results also indicated a negative amount for the Gibbs free energy of the binding of l-Met to the enzyme. α-Chy became more stable in the presence of l-Met, based on the molecular dynamics simulation.

Insight of the Interaction between 2,4-thiazolidinedione and Human Serum Albumin: A Spectroscopic, Thermodynamic and Molecular Docking Study

Thiazolidinedione derivatives (TZDs) have attracted attention because of their pharmacological effects. For example, certain TZDs have been reported to ameliorate type II diabetes by binding and activating PPARs (peroxisome proliferator-activated receptors). Nonetheless, no information is available on the interaction between the heterocyclic 2, 4-thiazolidinedione (2,4-TZD) moiety and serum albumin, which could affect the pharmacokinetics and pharmacodynamics of TZDs. In this study, we investigated the binding of 2,4-TZD to human serum albumin (HSA). Intrinsic fluorescence spectroscopy revealed a 1:1 binding stoichiometry between 2,4-TZD and HSA with a binding constant (Kb) of 1.69 ± 0.15 × 103 M-1 at 298 K. Isothermal titration calorimetry studies showed that 2,4-TZD/HSA binding was an exothermic and spontaneous reaction. Molecular docking analysis revealed that 2,4-TZD binds to HSA subdomain IB and that the complex formed is stabilized by van der Waal's interactions and hydrogen bonds. Molecular dynamics simulation confirmed the stability of the HSA-TZD complex. Further, circular dichroism and 3D fluorescence studies showed that the global conformation of HSA was slightly altered by 2,4-TZD binding, enhancing its stability. The results obtained herein further help in understanding the pharmacokinetic properties of thiazolidinedione.

Molecular design and synthesis of new dithiocarbazate complexes; crystal structure, bioactivities and nano studies

The syntheses of a new set of metal complexes MoO2L'(CH3OH), VOL'(CH3O)(CH3OH), , , SnL'Cl2 and SnL'I2 with a new ligand (L = (2,2'(disulfanediylbis((ethylthio)methylene)bis(hydrazin-2-yl-1-ylidene)bis(methanylylidene)) diphenol; L' = S-ethyl-3-(2-hydroxyphenyl)methylenedithiocarbazate are described along with characterization by elemental analysis, mass spectrometry, spectroscopic (IR, 1H- and 13C-NMR) and TGA techniques. The crystal structures of compounds were determined by single crystal X-ray diffraction analysis and compared to powder X-ray diffraction (PXRD) patterns of the nano complexes obtained using ultrasonic methods. The PXRD results indicate that the compounds synthesized by ultrasonic methods have high crystallinity. The compounds were evaluated in an in vitro cytotoxicity study with two human cancer cell lines. The results of this study revealed that all complexes exhibit good cytotoxic activity when compared to the clinical drug, cisplatin. Interaction of the samples with human serum albumin (HSA) was investigated using fluorescence spectrophotometric methods and the Stern-Volmer quenching constant (K SV) and free energy changes (ΔG) were calculated at 298 K. The fluorescence quenching method is used to determine the number of binding sites (n) and association constants (K a) at the same temperatures.

Removal of stabilizers from human serum albumin by adsorbents and dialysis used in blood purification

INTRODUCTION

Human serum albumin (HSA) is a monomeric multi-domain protein that possesses an extraordinary binding capacity. It plays an important role in storing and transporting endogenous substances, metabolites, and drugs throughout the human circulatory system. Clinically, HSA is used to treat a variety of diseases such as hypovolemia, shock, burns, hemorrhage, and trauma in critically ill patients. Pharmaceutical-grade HSA contains the stabilizers sodium caprylate and N-acetyltryptophanate to protect the protein from oxidative stress and to stabilize it for heat treatment which is applied for virus inactivation.

MATERIAL AND METHODS

The aim of this study was to determine if the two stabilizers can be depleted by adsorbent techniques. Several, adsorbents, some of them are in clinical use, were tested in batch and in a dynamic setup for their ability to remove the stabilizers. Furthermore, the removal of the stabilizers was tested using a pediatric high flux dialyzer.

RESULTS

The outcome of this study shows that activated charcoal based adsorbents are more effective in removal of N-acetylthryptophanate, whereas polystyrene based adsorbents are better for the removal of caprylate from HSA solutions. An adsorbent cartridge which contains a mix of activated charcoal and polystyrene based material could be used to remove both stabilizers effectively. After 4 hours treatment with a high flux dialyzer, N-acetyltryptophanate was totally removed whereas 20% of caprylate remained in the HSA solution.

Association of iminium and alkanolamine forms of the benzo[c]phenanthridine alkaloid chelerythrine with human serum albumin: photophysical, thermodynamic and theoretical approach

Association of isoforms of chelerythrine (CHL) with HSA.

The mechanism and conformational changes of polybrominated diphenyl ethers to TTR by fluorescence spectroscopy, molecular simulation, and quantum chemistry

Free energy contribution of amino acid LYS (B and D chains) and PDBEs was analyzed combining quantum chemistry and molecular modeling.

Characterization of colchicine binding with normal and glycated albumin: In vitro and molecular docking analysis

The transport of more than 90% of the drugs viz. anticoagulants, analgesics, and general anesthetics in the blood takes place by albumin. Hence, albumin is the prime protein needs to be investigated to find out the nature of drug binding. Serum albumin molecules are prone to glycation at elevated blood glucose levels as observed in diabetics. In this piece of work, glycation of bovine serum albumin (BSA) was carried out with glyceraldehyde and characterized by molecular docking and fluorometry techniques. Glycation of BSA showed 25% loss of free amino groups and decreased protein fluorescence (60%) with blue shift of 6 nm. The present study was also designed to evaluate the binding of colchicine (an anti-inflammatory drug) to native and glycated BSA and its ability to displace 8-analino-1-nephthalene sulfonic acid (ANS), from the BSA-ANS complex. Binding of ANS to BSA showed strong binding (K_a = 4.4 μM) with native conformation in comparison to glycated state (K_a = 8.4 μM). On the other hand, colchicine was able to quench the fluorescence of native BSA better than glycated BSA and also showed weaker affinity (K_a = 23 μM) for glycated albumin compared with native state (K_a = 16 μM). Molecular docking study showed that both glyceraldehyde and colchicine bind to common residues located near Sudlow's site I that explain the lower binding of colchicine in the glycated BSA. Based on our results, we believe that reduced drugs-binding affinity to glycated albumin may lead to drugs accumulation and precipitation in diabetic patients.

Spectroscopic and molecular docking studies on the interaction of human serum albumin with copper(II) complexes

Two osazone based ligands, butane-2,3-dione bis(2'-pyridylhydrazone) (BDBPH) and hexane-3,4-dione bis(2'-pyridylhydrazone) (HDBPH), were synthesized out of the 2:1M Schiff base condensation of 2-hydrazino pyridine respectively with 2,3-butanedione and 3,4-hexanedione. The X-ray crystal structures of both the ligands have been determined. The copper(II) complex of HDBPH has also been synthesized and structurally characterized. HDBPH and its copper(II) complex have thoroughly been characterized through various spectroscopic and analytical techniques. The X-ray crystal structure of the copper complex of HDBPH shows that it is a monomeric Cu(II) complex having 'N₄O₂' co-ordination chromophore. Interaction of human serum albumin (HSA) with these ligands and their monomeric copper(II) complexes have been studied by various spectroscopic means. The experimental findings show that the ligands as well as their copper complexes are good HSA binders. Molecular docking investigations have also been done to unravel the mode of binding of the species with HSA.

Assessment of the interaction procedure between Pt(IV) prodrug [Pt(5,5'-dmbpy)Cl4 and human serum albumin: Combination of spectroscopic and molecular modeling technique

In this study, a cytotoxic Pt(IV) complex [Pt(5,5'-dmbpy)Cl₄ (5,5'-dmbpy is 5,5'-dimethyl-2,2'-bipyridine) was selected to investigate its affinity to human serum albumin (HSA) by spectroscopy and molecular docking methods. This complex has a bidentate nitrogen donor ligand with four chloride anions attached to a Pt(IV) metal in a distorted octahedral environment. The fluorescence data showed this complex quench the intrinsic fluorescence of HSA through a static quenching mechanism. The binding constant (K_b) and the number of binding sites (n) were obtained based on the results of fluorescence measurements. UV-vis, circular dichroism spectroscopy, and three-dimensional fluorescence spectroscopy proved that the Pt(IV) complex could slightly change the secondary structure of protein. Thermodynamic parameters show that the Pt(IV) complex binds to HSA through electrostatic and Vander Waals interactions with one binding site. The molecular docking results confirmed the spectroscopic results and showed that Pt(IV) complex is embedded into subdomain IIA of protein. The aim of this study is to describe the performance of effective anti-cancer drugs when faced with proteins such as HSA.

Assessment of the Dissociation Energetics of Some Selected Ligand Drugs Bound on Human Serum Albumin by Differential Scanning Calorimetry

Drug-protein binding may play a role in the thermal energetics of protein denaturation and could lead to the determination of its equilibrium dissociation parameter. The aim of this study was to assess the energetics of a drug that was bound to human serum albumin (HSA) during thermal denaturation. Drugs that were bound at a single high-affinity primary binding site on HSA, including diazepam and ibuprofen, were employed. Commercial HSA was treated with charcoal to remove stabilizers and adjusted to 20% w/v in a pH 7.4 buffered solution. Serial concentrations of individual drugs up to 0.16 mmole/g-protein were added to the cleaned HSA solutions whereas diazepam was added to a commercial HSA solution. Samples were subjected to differential scanning calorimetry (DSC) set to run from 37 to 90°C at 3.0°C/min. Binding of the drug slightly increased the denaturing temperature of the cleaned HSA due to a shift in the equilibrium toward the native protein bound with the drug. Diazepam depressed the denaturing temperature of the commercial HSA by competing with the stabilizers already bound to the primary site of the HSA. This yielded not only the HSA-stabilizer but also the HSA-diazepam type complexes that exhibited a different denaturation process. A rational approximation of the Lumry-Eyring protein denaturation model was used to treat the DSC endotherms. The approximated scheme: [Formula: see text] was successfully fitted to the data. It was used to determine the dissociation parameters for diazepam and ibuprofen bound to the HSA. These results were comparable to those obtained from other methods.

Graphene–polyglycerol–curcumin hybrid as a near-infrared (NIR) laser stimuli-responsive system for chemo-photothermal cancer therapy

The aim of this study is to develop a nano graphene–polyglycerol–curcumin hybrid capable of simultaneous co-delivery of chemotherapeutic drug and cytotoxic heat to cancer cells by near infrared (NIR) laser irradiation.

The effect of spermine on the structure, thermal stability and activity of bovine pancreatic trypsin

This work studied the interaction between spermine and trypsin at pH 8.0.