Conformation Of HSA Research Articles

Studies of the Novel Bioactive Acridine‐1,3‐thiazolidin‐4‐one Derivatives With Human Serum Albumin Using Fluorescence Spectroscopy and Molecular Modelling

ABSTRACTIn this study, we employ spectroscopic, thermodynamic and molecular docking approaches to identify the mechanism by which thiazolidinone derivatives 4a–4d bind with human serum albumin. It has been suggested that the affinity of the interaction of derivatives 4a–4d with HSA is within the optimal range necessary for the transportation and distribution of compounds within the organism. The binding constant values for the derivative/HSA complexes were found to be 0.03–5.87 × 105 M−1. Both ΔH0 and ΔS0 values were negative, which indicates that binding occurs mainly through van der Waals forces and hydrogen bonding. The negative values calculated for ΔG0 indicate that the binding of derivatives 4a–4d with HSA is a spontaneous process. Our study also reveals that derivatives 4a–4d bind to the subdomain IB (Site III) of HSA and that this binding alters the conformation and thermodynamic stability of HSA. Molecular docking simulations suggest that the main binding forces are van der Waals interactions, hydrophobic interactions and hydrogen bonds. The studied compounds showed weak DPPH‐scavenging activity at all of the tested concentrations. The results suggest that compound 4b with a phenyl substituent at the nitrogen atom of the 1,3‐thiazolidin‐4‐one moiety can be considered the most potent antioxidant in the series.

Deciphering the spectroscopic and thermodynamic aspects of binding of biologically important antioxidants with the alkali induced state of human serum albumin.

Protein-ligand interactions are crucial for developing and identifying novel therapeutic targets. In this study, we investigate the interaction of the alkali induced state of human serum albumin (pH 11.2) with three hydroxycinnamic acid derivatives (HCDs), ferulic acid (FA), sinapic acid (SA) and trans-o-coumaric acid, which are biologically important antioxidants, and compare the outcomes with the results obtained at physiological pH (7.4). This study aims to explore the interaction of altered protein conformation with small molecules. Spectroscopic characterization methods show that the conformation of HSA and the ionic properties of HCDs are pH-dependent. Fluorescence, FRET and lifetime measurements reveal that the binding of HCDs with HSA is different at both pH 7.4 and 11.2. Despite the moderate binding of HCDs to HSA, circular dichroism and thermal denaturation studies report no conformational changes in HSA in the presence of HCDs. Isothermal titration calorimetry is employed to assess their binding based on structure and energetics using thermodynamic parameters. Standard molar enthalpy change (ΔH0m) and standard molar entropy change (ΔS0m) values vary with the change of pH from 7.4 to 11.2 with the contributions from the exothermicity and hydrophobicity of functional and aromatic groups of HCDs. Ferulic acid (FA) and sinapic acid (SA) binding to HSA is entropically driven, whereas trans-o-coumaric acid (CA) acid binding is enthalpically favourable. Our ITC studies also reveal that the involvement of -OH functional groups present in CA in binding with HSA is greater than that present in FA and SA at pH 11.2. Overall, this experimental study shows the comparable binding strength of HCDs to both the alkali-induced state of HSA and native HSA (pH 7.4). However, the mechanism of their binding is different.

Interaction of α‐Cembrenediol with Human Serum Albumin Based on Spectroscopic and Computational Analyses

α‐Cembrenediol exhibits a wide range of biological activities, including antibacterial, antitumor, and neuroprotective effects. However, knowledge of the absorption, transport, and release of α‐cembrenediol in drug metabolism within the body is currently limited. Therefore, we aimed to gain a comprehensive understanding of the in vivo transport, distribution, and elimination mechanisms of α‐cembrenediol and investigate the interaction between α‐cembrenediol and HSA. To this end, we utilized various methods including UV absorption spectroscopy, steady‐state fluorescence analysis, circular dichroism measurements, molecular docking studies, and molecular dynamics simulations. The results of the UV and fluorescence spectra clearly demonstrated that HSA interacts with α‐cembrenediol. Specifically, the fluorescence spectra results showed that at a temperature of 310 K, the fluorescence quenching constant (KSV) and binding constant (Kb) between HSA and α‐cembrenediol were determined to be 1.28 × 103 Lmol−1 and 218.27 Lmol−1, respectively. As the temperature was decreased from 310 K to 293 K, both KSV and Kb values increased, indicating the presence of a static quenching mechanism throughout the interaction process. Moreover, the results indicated the presence of a singular, specific binding site for α‐cembrenediol on HSA, as evidenced by an approximate count of one binding site at all three temperatures. Additionally, this binding process occurred spontaneously (ΔG < 0), with van der Waals interactions and hydrogen bonding as the primary driving forces (ΔH = −9.40 kJmol−1 and ΔS = −14.50 Jmol−1·K−1). The binding of α‐cembrenediol to Sudlow site I of HSA was confirmed through molecular docking, a combination of fluorescence probe substitution, and molecular dynamics simulation experiments. Moreover, the results demonstrated that α‐cembrenediol binding led to alterations in the structural conformation of HSA, as confirmed by three‐dimensional fluorescence, synchronous fluorescence, and circular dichroism spectra. This study offers crucial insights into the interaction between α‐cembrenediol and HSA, contributing to an improved understanding of the compound’s pharmacokinetic properties.

Exploring the In‐Vitro Antibacterial Activity and Protein (Human Serum Albumin, Human Hemoglobin and Lysozyme) Interaction of Hexagonal Silver Nanoparticle Obtained from Wood Extract of Wild Cherry Shrub

AbstractHere, the silver nanoparticles were synthesized using aqueous wood extract of cerasus macrocarpa (wild Cherry) shrub. This green synthesis method was both eco‐friendly and straightforward. The nanoparticles were characterized using FT‐IR, zeta potential, ultraviolet‐visible, TEM, and SEM‐EDX analysis. Green synthesized AgNPs demonstrated effective antibacterial activity against gram‐positive and gram‐negative bacteria (S. aureus and E. coli). Furthermore, fluorometric, circular dichroism and UV‐vis were used to study the interaction of green synthesized AgNPs with Human serum albumin (HSA (, Human hemoglobin (HHb), and Lysozyme (Lys) in simulated physiological conditions. The studies of interaction with HSA, HHb and Lys show good binding affinity for green synthesized silver nanoparticles; the binding affinity was found in the order Lys>HSA>HHb at 298.15 K. The results show that the native conformation of HSA, HHb, and Lys was preserved at the secondary structure level, which is crucial in providing insights into the side effects of newly synthesized drugs on their carriers. The fluorescence data represented that green synthesized AgNPs quench the intrinsic fluorescence of proteins through a static quenching procedure.

Indoxyl and p-cresol sulfate binding with human serum albumin

Protein bound uremic toxins are of intense interest because they accumulate in the blood compartment of patients suffering from kidney dysfunction, are poorly cleared by hemodialysis, and are associated with poor patient outcomes. In particular, high blood concentrations of indoxyl sulfate (IS) and p-cresol sulfate (PCS) are associated with both cardiovascular disease and increased inflammation. Limited work has been done to understand the interaction between HSA and IS or PCS, where the binding mechanism, preferred binding sites, and resulting conformation of HSA remain ill-defined. Using isothermal titration calorimetry, it was observed that both IS (Ka=10.06 ×103) and PCS (Ka=1.39 ×103) binding to HSA are enthalpy driven, with electrostatic interactions playing an important role. Saturation transfer difference NMR was used to verify IS or PCS interactions with HSA and to confirm, using warfarin and ibuprofen, that IS binds to Sudlow’s site I and site II whereas PCS only partially binds to site II. Circular dichroism and fluorescence spectroscopy results indicated that changes in the secondary and tertiary conformation of HSA occurred upon binding of IS or PCS. This fundamental physiochemical analysis of IS or PCS binding to HSA provides key parameters that will help in the development of materials that can directly compete with HSA for binding IS or PCS from blood, or compete for the albumin binding sites so as to displace IS or PCS, to enhance their clearance using commonly employed dialysis methods and perhaps lead to better patient outcomes.

N-ethyl-2-pyrrolidinone substitution enhances binding affinity between tea flavoalkaloids and human serum albumin: Greatly influenced by esterization

Formation of catechins-human serum albumin (HSA) complex contributes to stably transporting catechins and regulating their bioavailability. Recently, a new class of catechins namely flavoalkaloids have been reported from tea. The unique structural modification with an N-ethyl-2-pyrrolidinone ring at catechins from these flavoalkaloids has raised our interest in their HSA binding affinity. Thus, we investigated the interaction between HSA and flavoalkaloids by molecular docking, UV-Vis spectroscopy (UV), fluorescence quenching approaches, and surface plasmon resonance (SPR). Thermodynamic parameters suggest that electrostatic forces contribute greatly to the interaction. The binding ability is affected by different ester group (galloyl or cinnamoyl) at 3-OH, N-ethyl-2-pyrrolidinone substituted position (C-6 or C-8), C-2, C-3 and C-5′'' configurations, and hydroxyl group numbers at B ring, among which the 3-O-cinnamoyl substitution and 5′''-R configuration present the strongest contributions. UV showed slight changes in the conformation and microenvironment of HSA during the binding process. The quenching and binding constants suggest that the quenching is a static type. The small KD values (1–20 μM) detected by SPR confirmed the strong binding affinities between HSA and flavoalkaloids. Present study will help us to understand the interaction mechanism between flavoalkaloids and HSA, shedding light on structural modification of common catechins to enhance the stability, bioavailability and bioactivities.

Analysis on the interaction and binding properties of daphnoretin and human serum albumin in the presence of cisplatin: multi-spectroscopic methods and docking simulation

The interaction between anticancer drugs and HSA may have a significant impact on the pharmacology and efficacy of drugs. Drugs change the binding properties of HSA by regulating the quenching mechanism, binding mode and binding affinity. In this study, the interactions of cisplatin (cDDP), HSA, and daphnoretin were elucidated by multi-spectroscopic analyses and docking simulation. Fluorescence quenching showed that cDDP could not change the static quenching mechanism of HSA-daphnoretin, but could enhance their binding affinity. Site competition experiments revealed that daphnoretin and cDDP both bound to site I, which was consistent with the results of molecular docking. Thermodynamic date indicated that cDDP and daphnoretin formed a more stable complex with HSA via hydrophobic, van der Waals interaction and hydrogen bond. Three-dimensional fluorescence and circular dichroism spectra showed that cDDP changed the conformation and micro-environment of HSA induced by daphnoretin. This work could provide valuable information for the binding properties and interaction among cDDP, daphnoretin and HSA, and put forward the possibility of using HSA as a multidrug carrier.

Spectroscopic Characterization of the Interaction between Dopamine and Human Serum Albumin

The interactions of HSA with DA have received great attention nowadays due to its significant effect in the biomedical field and overall health. The main aim of this work is to examine the interaction between DA and HSA at physiological conditions. Upon addition of DA to HSA, the fluorescence emission was quenched with quenching constant Kq = 1.32 × 109 L⋅mol−1⋅s−1 and the binding constant of DA with HSA is found to be K = 4.4 × 102 mainly indicating dynamic quenching. The HSA conformation was altered upon binding of DA to HSA with an increase in α-helix and a decrease in β-sheets suggesting unfolding of HSA secondary structure due to weak intermolecular interaction with HSA. In view of the evidence presented, it is important to understand the details of the interactions of HSA with DA which will be crucial in the design of new DA-inspired drugs and help revealing vital details to better understand the HSA’s role as a transporter for many drugs.

Investigation on the Interaction of Dabrafenib with Human Serum Albumin Using Combined Experiment and Molecular Dynamics Simulation: Exploring the Binding Mechanism, Esterase-like Activity, and Antioxidant Activity.

Dabrafenib is a novel targeted antimelanoma drug. The present work explored the binding mechanism of dabrafenib-human serum albumin (HSA) and the effect on the esterase-like activity and antioxidant activity of HSA by using 19F NMR, spectroscopy methods, and molecular dynamics simulation. The results of 19F NMR, fluorescence, and time-resolved fluorescence spectroscopy revealed that dabrafenib spontaneously binds to the subdomain IIIA of the HSA by hydrophobic action and forms a static complex. The binding affects the esterase-like activity of HSA but not its antioxidant activity. According to the results of molecular dynamics simulation, dabrafenib interacts with Arg410 and Tyr411, which are the key residue associated with the esterase-like activity of HSA. Meanwhile, dabrafenib does not interact with Cys34, the key residue associated with the antioxidant activity of HSA. The results of circular dichroism spectroscopy and molecular dynamics simulation show that the conformation of HSA is not affected by the binding of dabrafenib. This study can provide useful information for understanding the pharmacokinetic properties of dabrafenib.

Probing the interaction of anticancer drug temsirolimus with human serum albumin: molecular docking and spectroscopic insight

The binding interaction between temsirolimus, an important antirenal cancer drug, and HSA, an important carrier protein was scrutinized making use of UV and fluorescence spectroscopy. Hyper chromaticity observed in UV spectroscopy in the presence of temsirolimus as compared to free HSA suggests the formation of complex between HSA and temsirolimus. Fluorescence quenching experiments clearly showed quenching in the fluorescence of HSA in the presence of temsirolimus confirming the complex formation and also confirmed that static mode of interaction is operative for this binding process. Binding constant values obtained through UV and fluorescence spectroscopy reveal strong interaction; temsirolimus binds to HSA at 298 K with a binding constant of 2.9 × 104 M−1implying the strength of interaction. The negative Gibbs free energy obtained through Isothermal titration calorimetry as well as quenching experiments suggests that binding process is spontaneous. Molecular docking further provides an insight of various residues that are involved in this binding process; showing the binding energy to be -12.9 kcal/mol. CD spectroscopy was retorted to analyze changes in secondary structure of HSA; increased intensity in presence of temsirolimus showing changes in secondary structure of HSA induced by temsirolimus. This study is of importance as it provides an insight into the binding mechanism of an important antirenal cancer drug with an important carrier protein. Once temsirolimus binds to HSA, it changes conformation of HSA which in turn can alter the functionality of this important carrier protein and this altered functionality of HSA can be highlighted in variety of diseases.

Insights into the effect of N-acetyl-L-cysteine-capped CdTe quantum dots on the structure and activity of human serum albumin by spectroscopic techniques

Quantum dots (QDs) are a kind of nanostructured semiconductor crystals with the size range of 1–10nm. Their unique photophysical properties and potential toxicity to human health have aroused wide concern of scientists and general public. However, the interaction mechanism of QDs on human serum albumin (HSA, the vital protein in human blood) from both structural and functional perspectives is rarely reported. In the present work, effects of N-acetyl-L-cysteine-capped CdTe quantum dots with fluorescence emission peak at 612nm (QDs-612) on the conformation and function of HSA were investigated by spectroscopic methods, molecular docking study and esterase activity assay. The hydrophobic interaction between HSA and QDs-612 was spontaneous with the binding constants calculated to be 6.85×105Lmol−1 (298K) and 8.89×105Lmol−1 (308K). The binding of QDs-612 to HSA induced the static quenching of fluorescence and the changes of secondary structure and microenvironment of Tyr-411 residue, which resulted in serious decrease on the hydrolysis of substrate p-nitrophenylacetate in esterase activity assay of HSA. This work confirms the possibility on direct interaction of QDs-612 with HSA and obtains a possible mechanism of relationship between conformation and function of HSA.

Arsenic trioxide binding to serum proteins

Arsenic trioxide (ATO) also known as Trisenox, is an anticancer chemotherapeutic drug which has been used in treating diagnosed and relapsed patients with acute promyelocytic leukemia (APL). Serum albumin is the most abundant of the proteins in blood plasma and is the major transporter for delivering several drugs in vivo. The current study was designed to evaluate the potential ability of human and bovine serum albumin for delivering arsenic trioxide. Therefore, interaction of arsenic trioxide with HSA and BSA was investigated in aqueous solution at physiological conditions using a constant protein concentration and various drug contents. FTIR and UV–Vis spectroscopic methods were used to analyze arsenic trioxide and protein binding modes, the binding constants and the effect of drug complexation on HSA and BSA stability and conformation. Results of this study showed that drug complexation altered protein conformation by major reduction of α-helix and increase of turn structure which is indicative of a partial protein destabilization. Structural analysis revealed that arsenic trioxide bind HSA and BSA with overall binding constants of KATO-HSA=1.07 (±0.01)×104M−1 and KATO-BSA=1.27(±0.02)×104M−1. It could be concluded that serum albumins can be considered as good carriers for delivering arsenic trioxide to target tissue.

Study of the interaction between two newly synthesized cyclometallated platinum (II) complexes and human serum albumin: Spectroscopic characterization and docking simulation

This study describes HSA binding properties of two cyclometalated platinum (II) complexes with non-leaving lipophilic ligands; deprotonated 2-phenylpyridine (ppy): C1 and deprotonated benzo [h]quinolone (bhq): C2, using UV–vis, fluorescence and circular dichroism (CD) spectroscopy. The absorption spectra of HSA decreased in the presence of increasing concentration of these complexes, reflecting HSA structural alteration after drug׳s binding. Also the thermodynamic parameters (ΔG, ΔH and ΔS) that obtained from Trp fluorescence study revealed that the interaction between these complexes and HSA were spontaneous. In addition, C1 with flexible chemical structure indicated significantly higher fluorescence quenching and binding affinity to HSA than C2 which possesses a higher structural rigidity. The ANS fluorescence results also indicated that two Pt (II) complexes were competing for binding to the hydrophobic regions of HSA. Moreover, CD results demonstrated that C2 complex induced alteration of HSA conformation to more significant extent compared to C1. The molecular docking results revealed the involvement of π–π stacking and hydrophobic interaction between these complexes and the protein. Overall, this study may highlight the significance of structural flexibility in designing of future anticancer Pt (II) complexes with improved binding affinity for HSA.

Insight into the binding mechanism of imipenem to human serum albumin by spectroscopic and computational approaches.

The mechanism of interaction between imipenem and HSA was investigated by various techniques like fluorescence, UV.vis absorbance, FRET, circular dichroism, urea denaturation, enzyme kinetics, ITC, and molecular docking. We found that imipenem binds to HSA at a high affinity site located in subdomain IIIA (Sudlow's site I) and a low affinity site located in subdomain IIA.IIB. Electrostatic interactions played a vital role along with hydrogen bonding and hydrophobic interactions in stabilizing the imipenem.HSA complex at subdomain IIIA, while only electrostatic and hydrophobic interactions were present at subdomain IIA.IIB. The binding and thermodynamic parameters obtained by ITC showed that the binding of imipenem to HSA was a spontaneous process (ΔGD⁰(D)= -32.31 kJ mol(-1) for high affinity site and ΔGD⁰(D) = -23.02 kJ mol(-1) for low affinity site) with binding constants in the range of 10(4)-10(5) M(-1). Spectroscopic investigation revealed only one binding site of imipenem on HSA (Ka∼10(4) M(-1)). FRET analysis showed that the binding distance between imipenem and HSA (Trp-214) was optimal (r = 4.32 nm) for quenching to occur. Decrease in esterase-like activity of HSA in the presence of imipenem showed that Arg-410 and Tyr-411 of subdomain IIIA (Sudlow's site II) were directly involved in the binding process. CD spectral analysis showed altered conformation of HSA upon imipenem binding. Moreover, the binding of imipenem to subdomain IIIA (Sudlow's site II) of HSA also affected its folding pathway as clear from urea-induced denaturation studies.

Molecular Dynamics Simulations of Human Serum Albumin and Role of Disulfide Bonds

Atomistic molecular dynamics simulations of human serum albumin in the presence and absence of disulfide bonds are presented. Simulations of 70 ns duration provide information on the relevance of disulfide bonds in the dynamics and structural conformation of HSA. Significant conformational changes are observed in the absence of disulfide bonds after 35 ns that could impact the functionality and stability of the protein. Changes in the secondary structure, hydrogen bonds, B factors, and cross-correlations reveal which disulfide bonds are important for keeping the secondary and tertiary structure and dynamics of the protein (e.g., Cys168-Cys177, Cys278-Cys289) and which have little effect on the local structure and dynamics (e.g., Cys200-Cys246, Cys461-Cys477). Removing all disulfide bonds in the protein appears to be a practical prescreening tool for identifying disulfide bonds relevant to structure and dynamics. In the absence of disulfide bonds, certain hydrogen bonds and correlated motions vanish, affecting the structure of neighboring residues. The structure of the primary binding sites of HSA is partially affected when disulfide bonds are removed. For the native structure, simulations clearly reveal the conformational changes that allow the only free cysteine to be exposed on the protein surface to form intermolecular disulfide bonds; this information could not be resolved from the static crystal structure alone. The absence of specific disulfide bonds could lead to partially unfolded structures; such structures are known to be prone to protein aggregation. Removing disulfide bonds could have similar consequences in other proteins of interest, such as immunoglobulin G.

Synthesis of biological active thiosemicarbazone and characterization of the interaction with human serum albumin

The synthesis of a new biological active reagent, 2-((1,4-dihydroxy)-9,10-anthraquinone) aldehyde thiosemicarbazone (DHAQTS), was designed. The interaction between DHAQTS and HSA was studied by fluorescence spectroscopy in combination with molecular modeling under simulation of physiological conditions. According to the results of fluorescence measurements, the quenching mechanism was suggested to be static. The thermodynamic parameters are calculated by van't Hoff equation, which demonstrated that hydrophobic interactions are the predominant intermolecular forces stabilizing the complex. The number of binding sites (n) was calculated. Through the site marker competitive experiment, DHAQTS was confirmed to be located in site I of HSA. The binding distance r=2.83nm between the donor HSA and acceptor DHAQTS was obtained according to Förster's non-radiative energy transfer theory. The three-dimensional fluorescence spectral results showed the conformation and microenvironment of HSA changed in the presence of DHAQTS. The effects of common ions on the binding of DHAQTS to HSA were also evaluated. The experimental results were in agreement with the results obtained via a molecular docking study.

Effect of ageing of human serum albumin in vitro on surface hydrophobicity and binding sites of metronidazole

The fluorescence characteristic of the “alkaline-ageing” process was performed. The quenching of the aged form of human serum albumin (AHSA) fluorescence by acrylamide (Ac) was smaller than that of native HSA, in contrast to the negatively charged anion iodide quencher. The comparison of quenching of fluorescence probes ANS and DNSA bound to aged and native forms of HSA allows for the conclusion that “alkaline-ageing process” causes an increase of hydrophobicity within the binding site located in subdomain IIA. This conclusion was confirmed by the F coefficients calculated for the emission fluorescence spectra of A- and N-forms of HSA excited at 295 nm and 275 nm which show that the increase of hydrophobicity is more significant within tyrosyl than within tryptophanyl residues. The binding constants metronidazole–HSA as well as the number of the class of binding sites were determined by the use of the Scatchard and Klotz-plot analysis. Ageing of HSA causes an increase of the quenching constant determined from the Stern–Volmer equation for λ ex 275 nm. However ageing does not affect the K Q value for λ ex 295 nm. The influence of ageing of human serum albumin on its surface hydrophobicity was also studied with the use of 8-anilino-1-naphthalenesulfonic acid (ANS) as the fluorescence probe. At the ANS fluorescence excitation wavelength λ ex 360 nm the change in surface hydrophobicity is not observed for both N- and A-forms of HSA. The increase of surface hydrophobicity of the A-form in comparison with that of the native form at λ ex 295 nm indicates that within subdomain IIA an alteration of HSA conformation takes place.

Molecular interaction studies of trimethoxy flavone with human serum albumin.

BackgroundHuman serum albumin (HSA) is the most abundant protein in blood plasma, having high affinity binding sites for several endogenous and exogenous compounds. Trimethoxy flavone (TMF) is a naturally occurring flavone isolated from Andrographis viscosula and used in the treatment of dyspepsia, influenza, malaria, respiratory functions and as an astringent and antidote for poisonous stings of some insects.Methodology/Principal FindingsThe main aim of the experiment was to examine the interaction between TMF and HSA at physiological conditions. Upon addition of TMF to HSA, the fluorescence emission was quenched and the binding constant of TMF with HSA was found to be KTMF = 1.0±0.01×103 M−1, which corresponds to −5.4 kcal M−1 of free energy. Micro-TOF Q mass spectrometry results showed a mass increase of from 66,513 Da (free HSA) to 66,823 Da (HAS +Drug), indicating the strong binding of TMF with HSA resulting in decrease of fluorescence. The HSA conformation was altered upon binding of TMF to HSA with decrease in α-helix and an increase in β-sheets and random coils suggesting partial unfolding of protein secondary structure. Molecular docking experiments found that TMF binds strongly with HSA at IIIA domain of hydrophobic pocket with hydrogen bond and hydrophobic interactions. Among which two hydrogen bonds are formed between O (19) of TMF to Arg 410, Tyr 411 and another one from O (7) of TMF to Asn 391, with bond distance of 2.1 Å, 3.6 Å and 2.6 Å, respectively.Conclusions/SignificanceIn view of the evidence presented, it is imperative to assign a greater role of HSA's as a carrier molecule for many drugs to understand the interactions of HSA with TMF will be pivotal in the design of new TMF-inspired drugs.

In vitro study on the interaction between thiophanate methyl and human serum albumin

Thiophanate methyl (MT) is one of the widely used fungicides to control important fungal diseases of crops, which has led to potential toxicological risk to public health. Several different transport proteins exist in blood plasma, but albumin only is bound by a wide diversity of xenobiotics reversibly with high affinity. We studied the interaction of MT with human serum albumin by using spectroscopic methods including fluorescence quenching technology, UV and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The result of fluorescence titration revealed that MT could quench the intrinsic fluorescence of HSA. The binding process was exothermic and spontaneous, as indicated by the thermodynamic analyses. In addition, the studies of FT-IR spectroscopy showed that the binding of MT to HSA changed molecular conformation of HSA. The results obtained from molecular modeling showed that the interaction between MT and HSA was dominated by hydrophobic force, and there was also hydrogen bond interaction between the pesticide and the residues of HSA, which was in good agreement with the result of binding mode.

Spectroscopic studies on binding of Puerarin to human serum albumin

The interaction between Puerarin with human serum albumin has been studied for the first time by spectroscopic methods including fluorescence quenching technology, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The results of fluorescence titration revealed that Puerarin can strongly quench the intrinsic fluorescence of HSA by static quenching and there is a single class of binding site on HSA. In addition, the studies of CD spectroscopy and FT-IR spectroscopy showed that the binding of Puerarin to HSA changed slightly molecular conformation of HSA. Furthermore, the thermodynamic functions Δ H 0 and Δ S 0 for the reaction were calculated to be −9.067 kJ mol −1 and 54.315 J mol −1 K −1 according to van’t Hoff equation. These data suggested that both hydrogen bond and hydrophobic interaction play a major role in the binding of Puerarin to HSA, which is in good agreement with the result of molecular modeling study.