Studies on the interaction between benzophenone and bovine serum albumin by spectroscopic methods

Spectroscopic analysis to identify the binding site for Rifampicin on Bovine Serum Albumin

This article reports the interaction of rifampicin, one of the important antituberculosis drugs, with Bovine Serum Albumin (BSA). Herein, we have monitored the fluorescence properties of tryptophan (Trp) residue in BSA to understand the interactions between protein and rifampicin. Fluorescence intensity of BSA was quenched tremendously upon interacting with the drug. Using steady state and time-resolved spectroscopic tools the static and dynamic nature of quenching have been characterised. Time correlated single photon counting technique confirmed that out of two lifetime components ∼6.2 ns and ∼2.8 ns of BSA, the rifampicin has affected only the shorter lifetime component a lot that was assigned to Trp-213 residue. Hence, it was thought that the drug must have been located near to the amino acid residue. Molecular docking studies have revealed the structural information of drug-protein complex which supported the above conjecture, confirming the nearest tryptophan as Trp-213 to the complexing rifampicin molecule.

Investigation on the interaction of food colorant Sudan III with bovine serum albumin using spectroscopic and molecular docking methods

Sudan III is a coloring agent used in chemical industries and food additives. This article uses spectroscopic and molecular docking methods to investigate the interaction of Sudan III with bovine serum albumin (BSA) under a physiological condition. Spectroscopic analysis of the emission quenching revealed that the quenching mechanism of BSA by Sudan III was static. The binding sites and constants of Sudan III-BSA complex were observed to be from 0.72 and 6.41 × 10² L·mol^-1 to 0.69 and 5.83 × 10² L·mol^-1 at 298 and 310 K, respectively. The enthalpy change (ΔH) and entropy change (ΔS) revealed that van der Waals forces and hydrogen bonds stabilized the Sudan III-BSA complex. Energy transfer from tryptophan to Sudan III occurred by a fluorescence resonance energy transfer mechanism, and the r distance (3.32 nm) had been determined. The results of UV-Vis absorption, synchronous, three-dimensional fluorescence, and circular dichroism spectra showed that Sudan III induced conformational changes of BSA. Molecular docking studies revealed that Sudan III situated within subdomain IIA of BSA. A study on the interaction between Sudan III and BSA was of fundamental importance for providing more information about the potential toxicological effect of chemicals at the molecular level.

Spectroscopy study and co-administration effect on the interaction of mycophenolic acid and human serum albumin

Mycophenolic acid (MPA), an immunosuppressor, is always administered in combination with several drugs in clinical therapy, which may alter the binding of MPA to human serum albumin (HSA) and could influence its pharmacological activities. Thus, this study evaluated the interaction between HSA and MPA, as well as investigated the effect of co-administrated drugs on the MPA-protein binary system using fluorescence spectroscopy. Results revealed that MPA has a strong capability to quench the fluorescence of HSA, and the acting forces for the binding are hydrogen bonds and van der Waals forces. Competition on combined administration showed that balofloxacin significantly affects the MPA-HSA interaction, as reflected by the remarkable decrease in fluorescence intensity. Furthermore, cefminox sodium has competitive capability with MPA to some extent, whereas methyl prednisone and amlodipine besylate have a minor influence on the binary system. However, simvastatin has no appreciable effect on the MPA-HSA interaction. In addition, three-dimensional fluorescence spectra and circular dichroism spectroscopy, which were employed to determine the conformation, showed that the binding of MPA with HSA can induce conformation changes in HSA.

Protein-polymer conjugation via ligand affinity and photoactivation of glutathione S-transferase

A photoactivated, site-selective conjugation of poly(ethylene glycol) (PEG) to the glutathione (GSH) binding pocket of glutathione S-transferase (GST) is described. To achieve this, a GSH analogue (GSH-BP) was designed and chemically synthesized with three functionalities: (1) the binding affinity of GSH to GST, (2) a free thiol for polymer functionalization, and (3) a photoreactive benzophenone (BP) component. Different molecular weights (2 kDa, 5 kDa, and 20 kDa) of GSH-BP modified PEGs (GSBP-PEGs) were synthesized and showed conjugation efficiencies between 52% and 76% to GST. Diazirine (DA) PEG were also prepared but gave conjugation yields lower than for GSBP-PEGs. PEGs with different end-groups were also synthesized to validate the importance of each component in the end-group design. End-groups included glutathione (GS-PEG) and benzophenone (BP-PEG). Results showed that both GSH and BP were crucial for successful conjugation to GST. In addition, conjugations of 5 kDa GSBP-PEG to different proteins were investigated, including bovine serum albumin (BSA), lysozyme (Lyz), ubiquitin (Ubq), and GST-fused ubiquitin (GST-Ubq) to ensure specific binding to GST. By combining noncovalent and covalent interactions, we have developed a new phototriggered protein–polymer conjugation method that is generally applicable to GST-fusion proteins.

Investigation on the interaction of pyrene with bovine serum albumin using spectroscopic methods

This paper was designed to investigate the interaction of pyrene with bovine serum albumin (BSA) under physiological condition by spectroscopic methods. Spectroscopic analysis of the emission quenching revealed that the quenching mechanism of BSA by pyrene was static. The binding sites and constants of pyrene-BSA complex were observed to be 1.20 and 2.63×10(6) L mol(-1) at 298 K, respectively. The enthalpy change (ΔH) and entropy change (ΔS) revealed that van der Waals forces and hydrogen bonds stabilized the pyrene-BSA complex. Energy transfer from tryptophan to pyrene occurred by a FRET (fluorescence resonance energy transfer) mechanism, and the distance (r=2.72 nm) had been determined. The results of synchronous, three-dimensional fluorescence, and circular dichroism spectra showed that the pyrene induced conformational changes of BSA.

Molecular interactions of benzophenone UV filters with human serum albumin revealed by spectroscopic techniques and molecular modeling

Benzophenone (BP)-type UV filters have been widely used in many personal care products to protect human from UV exposure. Their dermal applications can cause direct human health risk following accumulation in bloodstream. Few studies have addressed whether BP-type UV filters could bind and alter the structure and function of human serum albumin (HSA), the major carrier protein in plasma. Four benzophenones, BP-1, BP-2, BP-3 and BP-8 were selected to investigate their potentially toxic interactions with HSA and the intrinsic binding mechanism using combined spectroscopies and molecular docking techniques. Four benzophenones significantly quench the intrinsic fluorescence of HSA via static mode. The competitive binding fluorescence assay and molecular docking both revealed that the benzophenones bind at site II of HSA. Their binding constants range from 1.91 × 10(4)M(-1) to 12.96 × 10(4)M(-1) at 296 K. BP-8 interacts with HSA mainly through hydrogen bonding interactions and van der Waals interactions, while hydrophobic interactions and electrostatic interactions are dominant for interactions between BP-1, BP-2, BP-3 and HSA. Molecular docking revealed that the changes in structural moiety and hydrophobicity of four benzophenones account for their different binding affinities. As further revealed by circular dichroism and time-resolved fluorescence decay, these benzophenones cause global and local structural changes of HSA, which illustrates their potential toxicity to cause structural damage of HSA. Two degradation products of BP-3 have higher binding affinities to HSA, suggesting higher potencies in causing adverse effects on human health.

Interaction of an amino-functionalized ionic liquid with enzymes: a fluorescence spectroscopy study

The interaction of an amino-functionalized ionic liquid, 1-(2-aminoethyl)-3-butylimidazolium bromide ([NH(2)C(2)C(4)im]Br) with two enzymes, pepsin and papain was investigated using fluorescence spectroscopic technique. It is found that [NH(2)C(2)C(4)im]Br has strong ability to quench the intrinsic fluorescence of pepsin and papain. Quenching mechanisms are considered as static quenching for papain and dynamic quenching for pepsin, respectively. The binding constants and the number of binding sites (n) of [NH(2)C(2)C(4)im]Br to papain were calculated at different temperatures. The thermodynamic parameters such as free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS), were calculated by thermodynamic equations. The values of ΔG, ΔH and ΔS suggest that interaction of [NH(2)C(2)C(4)im]Br with the two enzymes is spontaneous. Hydrogen bonding and van der Waals interactions play important roles in the binding process of [NH(2)C(2)C(4)im]Br to papain. However, hydrophobic interaction is the main driving force for the interaction of [NH(2)C(2)C(4)im]Br with pepsin. The results of three-dimensional fluorescence spectra show that [NH(2)C(2)C(4)im]Br has no obvious effects on the polypeptide structures of the two enzymes. Additionally, the [NH(2)C(2)C(4)im]Br-containing system can slightly increase the activities of the two enzymes.

Investigation on the site-selective binding of bovine serum albumin by erlotinib hydrochloride

The purpose of this study was to investigate the site-selective binding of erlotinib hydrochloride (ET), a targeted anticancer drug, to bovine serum albumin (BSA) through 1H NMR, spectroscopic, thermodynamic, and molecular modeling methods. The fluorescence quenching of BSA by ET was a result of the formation of BSA-ET complex with high binding affinity. The site marker competition study combined with isothermal titration calorimetry experiment revealed that ET binds to site II of BSA mainly through hydrogen bond and van der Waals force. Molecular docking was further applied to define the specific binding site of ET to BSA. The conformation of BSA was changed in the presence of ET, revealed by synchronous fluorescence, circular dichroism, and three-dimensional fluorescence spectroscopy results. Further, NMR analysis of the complex revealed that the binding capacity contributed by the aromatic protons in the binding site of BSA might be greater than the aliphatic protons. An animated interactive 3D complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:26.

Spectroscopic studies on the interaction of bovine serum albumin with surfactants and apigenin

The binding of apigenin (Ap) to bovine serum albumin (BSA) has been studied using the methods of fluorescence spectroscopy and UV-vis absorption spectroscopy. The spectroscopic analysis of the quenching mechanism indicates that the quenching constants are inversely correlated with the temperatures and the quenching process could result from a static interaction. The type of interaction force was discussed and the binding site of Ap was in site I (subdomain IIA) of BSA. The thermodynamic parameters ΔH and ΔS are -42.02kJ mol(-1) and -48.31J mol(-1)K(-1), respectively and the negative ΔG implying that the binding interaction was spontaneous. The distance r between BSA and Ap was calculated according to Förster's theory and the value is 3.44nm. The synchronous and three-dimensional fluorescence spectra show that the binding of Ap to BSA could lead to the changes in the conformation and microenvironment of BSA. At the same time, the effects of ionic surfactants on the interaction of Ap and BSA have also been investigated.

The binding characteristics of the interaction between 3-(2-cyanoethyl) cytosine and human serum albumin

The binding characteristics of the interaction between 3-(2-cyanoethyl) cytosine (CECT) and human serum albumin (HSA) were investigated using fluorescence, UV absorption spectroscopic and molecular modeling techniques under simulative physiological conditions. The intrinsic fluorescence intensity of HSA was decreased with the addition of CECT. The fluorescence data handled by Stern-Volmer equation proved that the quenching mechanism of the interaction between CECT and HSA was a static quenching procedure. The binding constants evaluated utilizing the Lineweaver-Burk equation at 17, 27 and 37 °C, were 2.340 × 10(4), 2.093 × 10(4) and 1.899 × 10(4) L mol(-1), respectively. The thermodynamic parameters were calculated according to van't Hoff equations. Negative enthalpy (ΔH) and positive entropy (ΔS) values indicated that both hydrogen bond and hydrophobic force played a major role in the binding process of CECT to HSA, which was consistent with the results of the molecular modeling study. In addition, the effect of other ions on the binding constant of CECT-HSA was examined.

Interaction of ergosterol with bovine serum albumin and human serum albumin by spectroscopic analysis

This study was designed to examine the interactions of ergosterol with bovine serum albumin (BSA) and human serum albumin (HSA) under physiological conditions with the drug concentrations in the range of 2.99-105.88 μM and the concentration of proteins was fixed at 5.0 μM. The analysis of emission spectra quenching at different temperatures revealed that the quenching mechanism of HSA/BSA by ergosterol was the static quenching. The number of binding sites n and the binding constants K were obtained at various temperatures. The distance r between ergosterol and HSA/BSA was evaluated according to Föster non-radioactive energy transfer theory. The results of synchronous fluorescence, 3D fluorescence, FT-IR, CD and UV-Vis absorption spectra showed that the conformations of HSA/BSA altered in the presence of ergosterol. The thermodynamic parameters, free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) for BSA-ergosterol and HSA-ergosterol systems were calculated by the van't Hoff equation and discussed. Besides, with the aid of three site markers (for example, phenylbutazone, ibuprofen and digitoxin), we have reported that ergosterol primarily binds to the tryptophan residues of BSA/HSA within site I (subdomain II A).

Study on the interaction between isoniazid and bovine serum albumin by fluorescence spectroscopy: the effect of dimethylsulfoxide

The investigation of the binding between isoniazid (or isonicotinic acid hydrazide, INH) and serum albumin is of crucial importance to reveal the reason of resistant Mycobacterium tuberculosis strains towards INH and to increase the anti-tuberculous activity of INH. The interaction between INH and bovine serum albumin (BSA) was studied by fluorescence, UV and FT-IR spectroscopy methods. The analysis of the emission quenching at different temperatures revealed that the quenching mechanism corresponds to a static process and, as consequence; a complex INH-BSA is formed. The modified Stern-Volmer quenching constant K (a) and the corresponding thermodynamic parameters ΔH, ΔG and ΔS were calculated. The distance, r, between donor (BSA) and acceptor (INH) was calculated to be 2.14 nm based on Förster's non-radiative energy transfer theory (FRET). The results obtained on the basis of fluorescence study of BSA solutions at the presence of dimethylsulfoxide (DMSO) were discussed in terms of the hydration properties and competitive intermolecular interactions between BSA and solvent components. The dependence of binding constant on the concentration of added DMSO as a solvent component showed non monotonous behavior. The conformational changes of BSA and its secondary structure alterations at the presence of INH were revealed.

Exploring the binding mechanism of ondansetron hydrochloride to serum albumins: spectroscopic approach

The mechanism of interaction of ondansetron hydrochloride (OND) to serum albumins [bovine serum albumin (BSA) and human serum albumin (HSA)] was studied for the first time employing fluorimetric, circular dichroism, FTIR and UV-vis absorption techniques under the simulated physiological conditions. Fluorimetric results were utilized to investigate the binding and conformational characteristics of protein upon interaction with varying concentrations of the drug. Higher binding constant values revealed the strong interaction between the drug and protein while the number of binding sites close to unity indicated single class of binding site for OND in protein. Thermodynamic results revealed that both hydrogen bond and hydrophobic interactions played a major role in stabilizing drug-protein complex. Site marker competitive experiments indicated that the OND bound to albumins at subdomin II A (Sudlow's site I). Further, the binding distance between OND and serum albumin was calculated based on the Förster's theory of non-radioactive energy transfer and found to be 2.30 and 3.41 nm, respectively for OND-BSA and OND-HSA. The circular dichroism data revealed that the presence of OND decreased the α-helix content of serum albumins. 3D-fluorescence results also indicated the conformational changes in protein upon interaction with OND. Further, the effects of some cations have been investigated in the interaction of drug to protein.