Fluorescence Of Human Serum Albumin Research Articles

Combined multispectroscopic and molecular docking investigation on the interaction between strictosamide and human serum albumin

The interaction between strictosamide (STM) and human serum albumin (HSA) was investigated by fluorescence spectroscopy, synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, circular dichroism spectroscopy and molecular modeling under physiological pH 7.4. STM effectively quenched the intrinsic fluorescence of HSA via static quenching. The binding site number n and apparent binding constant K(a) were determined at different temperatures by fluorescence quenching. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated as -3.01 kJ/mol and 77.75 J/mol per K, respectively, which suggested that the hydrophobic force played major roles in stabilizing the HSA-STM complex. The distance r between donor and acceptor was obtained to be 4.10 nm according to Förster's theory. After the addition of STM, the synchronous fluorescence and three-dimensional fluorescence spectral results showed that the hydrophobicity of amino acid residues increased and the circular dichroism spectral results showed that the α-helix content of HSA decreased (from 61.48% to 57.73%). These revealed that the microenvironment and conformation of HSA were changed in the binding reaction. Furthermore, the study of molecular modeling indicated that STM could bind to site I of HSA and the hydrophobic interaction was the major acting force, which was in agreement with the binding mode study.

Molecular interaction of PCB153 to human serum albumin: Insights from spectroscopic and molecular modeling studies

Polychlorinated biphenyls (PCBs) possessed much potential hazard to environment because of its chemical stability and biological toxicity. Here, we identified the binding mode of a representative compound, PCB153, to human serum albumin (HSA) using fluorescence and molecular dynamics simulation methods. The fluorescence study showed that the intrinsic fluorescence of HSA was quenched by addition of PCB153 through a static quenching mechanism. The thermodynamic analysis proved the binding behavior was mainly governed by hydrophobic force. Furthermore, as evidenced by site marker displacement experiments using two probe compounds, it revealed that PCB153 acted exactly on subdomain IIIA (site II) of HSA. On the other hand, the molecular dynamics studies as well as free energy calculations made another important contribution to understand the conformational changes of HSA and the stability of HSA-PCB153 system. Molecular docking revealed PCB153 can bind in a large hydrophobic activity of subdomain IIIA by the hydrophobic interaction and hydrogen bond interactions between chlorine atoms and residue ASN391. The present work provided reasonable models helping us further understand the transporting, distribution and toxicity effect of PCBs when it spread into human blood serum.

Mechanism of Interaction between Chrysin and Different Configurations of Human Serum Albumin

The mechanism of the interaction between Chrysin (CHR) and human serum albumin (HSA) was investigated using various spectroscopic techniques. It was found that CHR can induce HSA fluorescence emission quenching by static process. Additionally, HSA caused a significant red shift in the ultraviolet absorption of CHR. This indicated that binding with a protein can result in dissociation of the phenolic hydroxyl in CHR. HSA can also cause CHR fluorescence emission. The binding constants of CHR and HAS were calculated based on the fluorescence quenching and emission modes. The results obtained using these two methods were consistent. The binding constant (KA) values at pH 7.4 were (9.97±0.24)×10 4 1 , respectively; and the ratio of combination was 1:1. The binding constants decreased gradually with decreasing the pH value. This is related to conformational changes in the protein. The protein is partly denatured at pH 3.5, with the site II in the HSA opening chain. It was found that CHR was located at site I, which is in subdomain IIA of HAS. Based on molecular modeling, the mechanism of the interaction between CHR and HAS was investigated.

Investigation on the Binding Behavior of Ellagic Acid to Human Serum Albumin in Aqueous Solution

Ellagic acid (EA), one of the polyphenols in fruits and nuts, has pharmacological activity. To explore binding behavior of EA to protein, human serum albumin (HSA) was chosen and investigated by fluorescence spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and molecular modeling in aqueous solution. Fluorescence titration results indicated that EA effectively quenched the intrinsic fluorescence of HSA by static quenching and the binding process was spontaneous. According to the Scatchard equation, there was only one class of binding sites can bind to HSA, the binding constants at three different temperatures (298, 310 and 318 K) were 8.47 × 104, 7.39 × 104 and 6.00 × 104, respectively. It was found by FT-IR spectra that EA altered HSA secondary structure. Thermodynamic analysis showed that hydrophobic interaction and hydrogen bonds played an important role in stabilizing EA–HSA complex. A molecular docking study suggested that the HSA residues for EA binding located in sub-domain IIA.

Application of molecular modelling and spectroscopic approaches for investigating the binding of tanshinone IIA to human serum albumin

The interaction of tanshinone IIA and human serum albumin (HSA) has been characterised by molecular modelling, fluorescence, Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopic methods. The results of molecular modelling suggested that tanshinone IIA located within the binding pocket of subdomain IIA of HSA is held mainly by hydrophobic forces. Fluorescence titration revealed that tanshinone IIA could quench the intrinsic fluorescence of HSA. The binding constants at three temperatures (296, 303, and 310)K are (6.42·104, 1.54·105, and 4.35·105)dm3·mol−1, respectively. In addition, the studies of CD spectroscopy and FT-IR spectroscopy showed that the binding of tanshinone IIA to HSA changed molecular conformation of HSA.

Complexation of HSA with different forms of antimony (Sb): An application of fluorescence spectroscopy

Antimony (Sb) pollution has been of a great environmental concern in some areas in China. Sb enters human body via drinking water, inhalation and food chain, unavoidably interacts with human serum albumin (HSA) in blood plasma, and consequently does harm to human health. The harmful effects of Sb on human health depend on the Sb species and their binding ability to HSA. In the present study, binding of three forms of Sb with HSA was investigated by excitation-emission matrix (EEM) spectroscopy. All of antimony potassium tartrate, antimony trichloride and potassium pyroantimonate quenched fluorescence of HSA. Values of conditional stability constant Ka (×105/M) for Sb and HSA systems were 8.13–9.12 for antimony potassium tartrate, 2.51–4.27 for antimony trichloride and 3.63–9.77 for potassium pyroantimonate. The binding constant Kb (×104/M) values of HSA with antimony potassium tartrate, antimony trichloride and potassium pyroantimonate were 0.02–0.07, 3.55–5.01, and 0.07–1.08, respectively. There was one independent class of binding site for antimony trichloride towards HSA. There was more than one Sb binding site and negative cooperativity between multiple binding sites for potassium pyroantimonate and antimony potassium tartrate towards HSA. The binding ability of HSA to complex Sb followed the order: antimony trichloride>potassium pyroantimonate>antimony potassium tartrate.

Fluorescence spectroscopy of osthole binding to human serum albumin

The interaction of human serum albumin (HSA) with osthole was investigated by fluorescence spectroscopy. Osthole can quench the fluorescence of HSA and the quenching mechanism is a static process. The binding site number n and apparent binding constant K were measured at different temperatures. The thermodynamic parameters ΔH0, ΔG0 and ΔS0 were calculated at different temperatures. The results indicated that electrostatic forces played a major role in the interaction of osthole with HSA. Results of osthole synchronous fluorescence and UV absorption spectra showed that the microenvironment and conformation of HSA were changed.

Binding Effect of Common Ions to Human Serum Albumin in the Presence of Norfloxacin: Investigation with Spectroscopic and Zeta Potential Approaches

In this work, the toxic influence of metallic ions (Al3+, Cu2+, Mg2+, Pb2+) on human serum albumin (HSA) in the absence and presence of norfloxacin (NRF) was studied by spectroscopic approaches [fluorescence quenching, synchronous fluorescence, three-dimensional fluorescence, circular dichroism, resonance light scattering (RLS) and zeta potential techniques] under simulated physiological conditions. Fluorescence spectroscopy revealed that these metallic ions and NRF can quench the HSA fluorescence, and this quenching effect became more significant when both ion and drug are present together. The binding constants and binding sites of metal ions with HSA in the absence and presence of NRF were determined, based on the fluorescence quenching results. Ion aggregation gives rise to an enhancement of the RLS intensity for HSA and the critical induced aggregation concentration (C CIAC) of the ions, causing HSA aggregation for binary and ternary systems. The zeta potential measurements indicate a combination of electrostatic and hydrophobic interactions between ion, NRF and HSA and the formed micelle-like clusters. These data illustrated that NRF has an effect on the interaction between HSA and metal ions, with relevance for various toxicological and therapeutic processes.

Binding of Dioxopromethazine Hydrochloride with Human Serum Albumin and Its Effect on the Conformation of the Protein

The interaction between dioxopromethazine hydrochloride (DPZ) and human serum albumin (HSA), in vitro, was investigated by means of fluorescence, absorption and circular dichroism (CD) spectroscopy. The results obtained from analysis of the fluorescence spectra indicate that DPZ has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching mechanism. The HSA–DPZ binding distance was determined to be less than 7 nm, suggesting that energy transfer from HSA to DPZ may occur. The thermodynamic parameters of the interaction between DPZ and HSA were measured according to the van’t Hoff equation. The negative enthalpy change (ΔH0) and positive entropy change (ΔS0) values indicate that hydrophobic and electrostatic interactions play major roles in the binding between DPZ and HSA. The binding process was a favorable process in which the Gibbs energy change (ΔG0) is negative. The results of displacement experiments suggested that DPZ is located in site I of HSA within subdomain IIA. In addition, the results of absorption, synchronous fluorescence and CD spectra show that binding of DPZ with HSA can induce conformational changes in HSA.

Interactive Associations of Drug–Drug and Drug–Drug–Drug with IIA Subdomain of Human Serum Albumin

Owing to advantageous biochemical and pharmacological properties of human serum albumin (HSA), HSA-based drug carrier is playing an increasing role in the clinical setting. Since the IIA subdomain of HSA is a big hydrophobic cavity, we proposed that HSA delivers multiple drugs simultaneously docking on the IIA subdomain and that drugs may influence each other's binding affinity to albumin when cobinding the HSA IIA subdomain. Therefore, we studied the interactive association of drugs with the IIA subdomain of HSA by fluorescence spectroscopy and X-ray crystallography, in order to elucidate the molecular mechanism and behavior of drugs cobinding the IIA subdomain of HSA, and develop a universal structure-based model for HSA carrier design. We solved HSA-fatty acid-cinnamic acid, HSA-fatty acid-cinnamic acid-indometacin and HSA-fatty acid-cinnamic acid-indometacin-lamivudine complex structures, respectively. HSA complex structures and fluorescence quenching of HSA revealed that different drugs can regulate binding sites, binding mode and binding affinity of each other. For example, indometacin renders cinnamic acid to make reposition, and decreases binding affinity of HSA for cinnamic acid, but increases binding affinity of itself to HSA. Lamivudine makes cinnamic acid and indometacin to bind new subsites. Cinnamic acid-indometacin enhances binding affinity of lamivudine, and cinnamic acid-lamivudine increases binding affinity of indometacin, but indometacin-lamivudine decreases binding affinity of cinnamic acid to HSA. The study provided a biochemical basis for structure-guided development of HSA delivery system.

Probing the influences of urea on the interaction of sinomenine with human serum albumin by steady-state fluorescence

The binding of sinomenine to human serum albumin (HSA) in aqueous solution in the absence and presence of urea has been studied by fluorescence and the three-dimensional (3D) fluorescence at pH 7.40. Subdomain IIA binding site of human serum albumin (HSA) was characterized by examining the change in HSA fluorescence. The quenching rate constants and binding constants were calculated in the absence and presence of the denaturant. The results point to a static quenching mechanism operating in the complexes. However, the binding ability of sinomenine to denatured HSA is weaker than that of sinomenine to native HSA. Denaturation of HSA in the presence of urea is almost complete at [urea]⩾8.0M. Upon unfolding, two fluorescence peaks were observed. One peak was assigned to the fluorescence of Trp-214 residue in a polar environment, and the other peak was assigned to the fluorescence of tyrosine residues. Compared to the free HSA, the HSA-sinomenine complex is more stable in the presence of urea.

Study the interaction between CdTe@glutathione and human serum albumin

In this paper, glutathione (GSH) modified CdTe quantum dots (CdTe@GSH QDs) were synthesized in an aqueous solution. Then, the binding of the CdTe@GSH QDs to human serum albumin (HSA) was studied using the fluorescence spectroscopy. The quenching mechanism was investigated in terms of the association constants and basic thermodynamic parameters. The fluorescence data revealed that CdTe@GSH QDs could quench the intrinsic fluorescence of human serum albumin by a static quenching mechanism. Furthermore, alteration of the secondary protein structure in the presence of the QDs was confirmed by synchronous fluorescence spectra.

Influence of stearic acids on resveratrol-HSA interaction

The interaction between the natural polyphenol resveratrol and human serum albumin (HSA), the most abundant transport protein in plasma, has been studied in the absence and in the presence of up to six molecules of stearic acids (SA) pre-complexed with the protein. The study has been carried out by using the intrinsic fluorescence of both HSA and resveratrol. Protein and polyphenol fluorescence data indicate that resveratrol binds to HSA with an association constant k(a) = (1.10 ± 0.14) × 10(5) M(-1) and (1.09 ± 0.02) × 10(5) M(-1), respectively, whereas Job plot evidences the formation of an equimolar protein/drug complex. Low SA content associated with HSA does not affect significantly the structural conformation of the protein and its interaction with resveratrol, whereas high SA content induces conformational changes in the protein, and reduces resveratrol binding affinity. The photostability of resveratrol in the different samples changes in the order: buffer < (high [SA]/HSA) < HSA < (low [SA]/HSA). The results on (SA/HSA)-resveratrol samples highlight the ability of the protein to bind hydrophobic and amphiphilic ligands and to protect from degradation an important antioxidant molecule under biologically relevant conditions.

Mechanistic and conformational studies on the interaction of food dye amaranth with human serum albumin by multispectroscopic methods

The mechanism of interaction between food dye amaranth and human serum albumin (HSA) in physiological buffer (pH 7.4) was investigated by fluorescence, UV–vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. Results obtained from analysis of fluorescence spectra indicated that amaranth had a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The negative value of enthalpy change and positive value of entropy change elucidated that the binding of amaranth to HSA was driven mainly by hydrophobic and hydrogen bonding interactions. The surface hydrophobicity of HSA increased after binding with amaranth. The binding distance between HSA and amaranth was estimated to be 3.03nm and subdomain IIA (Sudlow site I) was the primary binding site for amaranth on HSA. The results of CD and FT-IR spectra showed that binding of amaranth to HSA induced conformational changes of HSA.

Determination of Mercury (II) Ion Concentrations in Human Serum Albumin Using Fluorescence Spectroscopy and Multivariate Regression Analysis

Human serum albumin (HSA) is a protein responsible for the transportation and delivery of drug molecules, fatty acids, and metabolites to various targets and the removal of waste products from the body. However, the binding of heavy metal ions, including mercury (II) (Hg(II)), can adversely affect HSA physiological properties with deleterious health consequences. The volatility of Hg at room temperature precludes the use of conventional flame, graphite furnace, or inductively couple atomic absorption spectroscopy for routine analysis of Hg in most research and medical laboratories. This study reports the first potential utility of fluorescence spectroscopy and multivariate regression analysis for the determination of Hg(II) concentration in HSA samples. The results of Fourier transform infrared (FT-IR) spectroscopy indicated the binding of Hg(II) at HSA amide I and amide II sites. Also, the binding of Hg(II) with HSA resulted in a decreased HSA ultraviolet (UV)-visible absorption and dramatic quenching of HSA fluorescence emission. The developed multivariate partial least squares regression (PLSR) model from Hg(II)–HSA fluorescence emission data was able to predict the Hg(II) concentration in HSA samples, with a root mean square percent relative error of prediction of 6.59%. The simplicity, low cost, and robustness of this method makes it a promising alternative method for rapid determination of Hg(II) concentration in biological specimens.

A novel 4-(tetrahydro-2-furanmethoxy)-N-octadecyl-1,8-naphthalimide based blue emitting probe: Solvent effect on the photophysical properties and protein detection

A novel 4-(tetrahydro-2-furanmethoxy)-N-octadecyl-1,8-naphthalimide (4-TN1) blue emitting fluorophore was synthesized for solvent polarity probing and protein detection. The effect of various solvents on absorption and fluorescence spectra of 4-TNI was investigated. By comparison with other derivatives with heterocyclic electron-donating groups, 4-TNI had the advantage of higher fluorescence quantum yield. The bathochromic shift observed in absorption and fluorescence spectra of 4-TNI with increasing solvent polarity indicates that the transitions involved are pi --> pi*. The normalized transition energy value E(T)N showed some scattering when plotted versus deltav. According to the quantum mechanics second order perturbation method, the ground and excited state dipole moments of 4-TNI were calculated as 3.91 and 7.12 D, respectively. Density functional calculations were also used to obtain the ground and excited state dipole moments. The result was consistent with the experimental values. Binding of TNI with human serum albumin (HSA) was studied. Fluorescence data revealed that quenching of HSA fluorescence by 4-TNI was due to the formation of a 4-TNI-HSA complex. Hydrogen bonds and hydrophobic interactions are the driving force of complex formation. 4-TNI fluorescence was found to be very sensitive to quenching by HSA. Therefore, a new spectrofluorimetric method for detection of HSA in Tris-HCl buffer solution (pH 7.4) was developed. The linear range of the calibration curve was 0.1-14.2 x 10(-6) M for HSA, with a detection limit (3sigma) of 1.37 x 10(-10) M. The method was applied to determination of total protein in clinical samples of human serum and the results were in good agreement with the data obtained by using Coomassie Brilliant Blue G-250 colorimetry.

Synthesis, characterization and interaction studies of copper based drug with Human Serum Albumin (HSA): Spectroscopic and molecular docking investigations

A new water soluble copper(II) complex, [Cu(glygly)(ssz)(H2O)]⋅6H2O, 1 derived from dipeptide (glycyl glycine anion) and sulfasalazine was synthesized and characterized by elemental analysis (CHN), molar conductance measurements and spectroscopic methods (IR, UV–vis, ESI-MS). The complex 1 is non-ionic in nature and possess octahedral geometry around Cu(II) metal ion. The interaction of complex 1 with Human Serum Albumin (HSA) was investigated under physiological condition in Tris–HCl buffer solution at pH 7.4 by means of various spectroscopic methods (fluorescence, CD and FTIR) and molecular docking technique. The results of fluorescence titration revealed that the complex 1 strongly quench the intrinsic fluorescence of HSA through a static quenching procedure. Binding constants (Kb) and the number of binding sites (n≈1) were calculated using modified Stern–Volmer equations. The thermodynamic parameters ΔG at different temperatures were calculated subsequently the value of ΔH and ΔS was also calculated which revealed that the hydrophobic and hydrogen bonding interactions play a major role in HSA–complex 1 association. The distance r between donor (HSA) and acceptor (complex 1) was obtained according to fluorescence resonance energy transfer and the alterations of HSA secondary structure induced by complex 1 were confirmed by FT-IR and CD measurements.

Interaction of virstatin with human serum albumin: spectroscopic analysis and molecular modeling.

Virstatin is a small molecule that inhibits Vibrio cholerae virulence regulation, the causative agent for cholera. Here we report the interaction of virstatin with human serum albumin (HSA) using various biophysical methods. The drug binding was monitored using different isomeric forms of HSA (N form ∼pH 7.2, B form ∼pH 9.0 and F form ∼pH 3.5) by absorption and fluorescence spectroscopy. There is a considerable quenching of the intrinsic fluorescence of HSA on binding the drug. The distance (r) between donor (Trp214 in HSA) and acceptor (virstatin), obtained from Forster-type fluorescence resonance energy transfer (FRET), was found to be 3.05 nm. The ITC data revealed that the binding was an enthalpy-driven process and the binding constants K a for N and B isomers were found to be 6.09×105 M−1 and 4.47×105 M−1, respectively. The conformational changes of HSA due to the interaction with the drug were investigated from circular dichroism (CD) and Fourier Transform Infrared (FTIR) spectroscopy. For 1∶1 molar ratio of the protein and the drug the far-UV CD spectra showed an increase in α- helicity for all the conformers of HSA, and the protein is stabilized against urea and thermal unfolding. Molecular docking studies revealed possible residues involved in the protein-drug interaction and indicated that virstatin binds to Site I (subdomain IIA), also known as the warfarin binding site.

Interaction of cyproheptadine hydrochloride with human serum albumin using spectroscopy and molecular modeling methods

The interaction between cyproheptadine hydrochloride (CYP) and human serum albumin (HSA) was investigated by fluorescence spectroscopy, UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and molecular modeling at a physiological pH (7.40). Fluorescence of HSA was quenched remarkably by CYP and the quenching mechanism was considered as static quenching since it formed a complex. The association constants Ka and number of binding sites n were calculated at different temperatures. According to Förster's theory of non-radiation energy transfer, the distance r between donor (human serum albumin) and acceptor (cyproheptadine hydrochloride) was obtained. The effect of common ions on the binding constant was also investigated. The effect of CYP on the conformation of HSA was analyzed using FT-IR, synchronous fluorescence spectroscopy and 3D fluorescence spectra. The thermodynamic parameters ΔH and ΔS were calculated to be -14.37 kJ mol(-1) and 38.03 J mol(-1) K(-1), respectively, which suggested that hydrophobic forces played a major role in stabilizing the HSA-CYP complex. In addition, examination of molecular modeling indicated that CYP could bind to site I of HSA and that hydrophobic interaction was the major acting force, which was in agreement with binding mode studies.

Combined fluorescence spectroscopy and molecular modeling studies on the interaction between harmalol and human serum albumin

The interaction between harmalol and human serum albumin (HSA) has been studied by fluorescence spectroscopy and molecular modeling methods. The intrinsic fluorescence of HSA was quenched by harmalol, which was rationalized in terms of the static quenching mechanism. The binding parameters, quenching constants and conformation changes were determined by fluorescence quenching method. The thermodynamic parameters, calculated from the temperature dependence of binding constants (i.e., ΔH°=-62.7 kJ mol⁻¹ and ΔS°=-119.3J mol⁻¹ K⁻¹), indicated the major role of van der Waals force and hydrogen bonding in binding process. Site marker competitive experiments revealed that harmalol binds to both the IIA and IIIA sub-domains of HSA with a slight preference toward sub-domain IIA. Finally, the binding of harmalol to HSA was modeled by molecular docking and molecular dynamic simulation methods. Excellent agreement was found between the experimental and theoretical results with respect to the mechanism of binding and binding constants. Molecular dynamic simulation revealed that HSA does not have a significant conformational change when it binds with harmalol.