Changes Of Bovine Serum Albumin Research Articles

The Conformational Changes of Bovine Serum Albumin at the Air/Water Interface: HDX-MS and Interfacial Rheology Analysis.

The characterization and dynamics of protein structures upon adsorption at the air/water interface are important for understanding the mechanism of the foamability of proteins. Hydrogen-deuterium exchange, coupled with mass spectrometry (HDX-MS), is an advantageous technique for providing conformational information for proteins. In this work, an air/water interface, HDX-MS, for the adsorbed proteins at the interface was developed. The model protein bovine serum albumin (BSA) was deuterium-labeled at the air/water interface in situ for different predetermined times (10 min and 4 h), and then the resulting mass shifts were analyzed by MS. The results indicated that peptides 54-63, 227-236, and 355-366 of BSA might be involved in the adsorption to the air/water interface. Moreover, the residues L55, H63, R232, A233, L234, K235, A236, R359, and V366 of these peptides might interact with the air/water interface through hydrophobic and electrostatic interactions. Meanwhile, the results showed that conformational changes of peptides 54-63, 227-236, and 355-366 could lead to structural changes in their surrounding peptides, 204-208 and 349-354, which could cause the reduction of the content of helical structures in the rearrangement process of interfacial proteins. Therefore, our air/water interface HDX-MS method could provide new and meaningful insights into the spatial conformational changes of proteins at the air/water interface, which could help us to further understand the mechanism of protein foaming properties.

Investigating the Protective Role of Biochaga Drug on Structural Changes of Bovine Serum Albumin in the Presence of Methyl tert-butyl Ether.

The health benefits of natural products have a long history. Chaga (Inonotus obliques) is used in traditional medicine and is an essential antioxidant for protecting the body from oxidants. Reactive oxygen species (ROS) are produced routinely due to metabolic processes. However, environmental pollution factors such as methyl tert-butyl ether (MTBE) can increase oxidative stress in the human body. MTBE is widely used as a fuel oxygenator that can harm health. The widespread use of MTBE has posed significant threats to the environment by polluting environmental resources, including groundwater. This compound can accumulate in the bloodstream by inhaling polluted air, with a strong affinity for blood proteins. The primary mechanism of MTBE's harmful effects is ROS production. The use of antioxidants may help reduce MTBE oxidation conditions. The present study proposes that biochaga, as an antioxidant, can reduce MTBE damage in the bovine serum albumin (BSA) structure. This study investigated the role of different concentrations of biochaga in the structural change of BSA in the presence of MTBE by biophysical methods such as UV-Vis, fluorescence, FTIR spectroscopy, DPPH radical inhibition method, aggregation test, and molecular docking. Research at the molecular level is critical to investigate the structural change of proteins by MTBE and the protective effect of the ideal dose (2.5µg/ml) of biochaga. the results of spectroscopic examinations showed that the concentration of 2.5µg/ml of biochaga has the least destructive effect on the structure of BSA in the presence and absence of MTBE, and it can play as an antioxidant.

Mechanism evaluation of the interactions between bisphenol AP and bovine serum albumin based on multi-spectroscopy, wavefunction analysis, and molecular docking

• Interaction behaviors between bisphenol AP (BPAP) and bovine serum albumin (BSA) were investigated by fluorescence, UV-Vis, Fourier transform infrared, and circular dichroism spectroscopies. • Explicit topology of BPAP was theoretically analyzed by electrostatic potential and wavefunction analysis methods. • To acquire clearer perspective, the molecular docking indicated that BPAP was steadily located in the hydrophobic cavity of BSA with two hydrogen bonds. • These insights potentially clarify the transportation and binding mechanism of BPAP by BSA, and present a better understanding about the toxicity assessment of BPAP in humans. The hazardous effects of bisphenol compounds on organisms have attracted wide attention. Hence, elaborating of the specific binding mode of emerging contaminants to macromolecules provides a pivotal insight into the interaction mechanism. In the present study, the structure changes of bovine serum albumin (BSA) upon binding with bisphenol AP (BPAP) were explored via multi-spectroscopies under simulated physiological conditions. Stern-Volmer calculation showed BPAP quenched the endogenous fluorescence of BSA by static quenching. Thermodynamic results with respect to temperatures indicate that the van der Waals force and hydrogen bond interactions play a pivotal role in BSA-BPAP complex formation. Circular dichroism and Fourier transform infrared spectroscopies also quantitatively confirm the secondary structural changes of the complex. Explicit topological analysis was theoretically conducted by the wavefunction analysis method. Electrostatic potential map pinpointed the global surface minimum and maximum of BPAP, which correspond to −26.86 and 52.50 kcal mol −1 around oxygen atom and hydrogen atom, respectively. To acquire clearer perspective, local orbital localizer and electron localization function were calculated to visually represent the electron delocalization in BPAP. More specifically, molecular docking indicated that BPAP was located in the hydrophobic cavity of BSA. Herein, the experimental and theoretical results reveal BPAP and BSA interaction mechanism in detail. These insights have great value in warning the toxicity assessment of BPAP on BSA in humans and wildlife.

A mutispectroscopic study on the structure–affinity relationship of the interactions of bisphenol analogues with bovine serum albumin

Bisphenol A (BPA) is a recognized endocrine-disrupting chemical (EDC), and its analogues also exert negative effects on health. The structure–affinity relationship between the structures of nine bisphenol (BP) analogues and the conformational changes of bovine serum albumin (BSA) was studied by various characterization methods and molecular docking. BPs including BPA and its analogues, bisphenol B (BPB), bisphenol C (BPC), bisphenol AP (BPAP), bisphenol M (BPM), bisphenol P (BPP), bisphenol Z (BPZ), diethylstilbestrol (DES) and dienestrol (DS) interacted with BSA. At the concentration of 3.85 × 10−5 mol l−1, DS was found to lead to 64% quenching, while BPAP, BPM and DES quenched 60%, 59% and 55% of BSA fluorescence, respectively. The values of ΔH (−19.31–135.42 kJ mol−1) and ΔS (12.52–495.63 J mol−1 K−1) indicated that hydrophobic interactions and hydrogen bonds played important roles in the binding process. The binding constants of DS (8.87 × 104 l mol−1), DES (3.05 × 104 l mol−1), BPAP (1.52 × 104 l mol−1), BPC (1.16 × 104 l mol−1) and BPM (1.10 × 104 l mol−1) to BSA were greater than that of BPA (1.18 × 103 l mol−1) to BSA, indicating that they may exert more negative effects than BPA. The molecular structure differences of these BPs partly affected their ability to bind to BSA. The binding constants of BPB/BPP to BSA were smaller due to the steric hindrance of ethyl and benzene ring. BPs with conjugated double bond structures (DS and DES) and benzene ring structures (BPM, BPP, BPAP) had a greater influence on the conformation of BSA.

Spontaneous Fibrillation of Bovine Serum Albumin at Physiological Temperatures Promoted by Hydrolysis-Prone Ionic Liquids.

This study highlights the role of time-dependent hydrolysis of ionic liquid anion, [BF4]-, of ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate, [C2mim][BF4], which results in ever-changing pH conditions. Such pH changes along with the ionic interactions bring conformational changes in bovine serum albumin (BSA), leading to the formation of amyloid fibers at 37 °C without external control of pH or addition of electrolyte. The fibrillation of BSA occurs spontaneously with the addition of IL; however, the highest growth rate has been observed in aqueous solution of 10% IL (v/v %) among investigated systems. Thioflavin T (ThT) fluorescence emission has been employed to monitor the growth and development of β-sheet content in amyloid fibrils. The structural alterations in BSA have also been investigated using intrinsic fluorescence measurements. Circular dichroism (CD) measurements confirmed the formation of amyloid fibrils. Transmission electron microscopy (TEM) has been explored to establish the morphologies of BSA fibrils at different intervals of time, whereas atomic force microscopy (AFM) has established the helically twisted nature of grown amyloid fibrils. The docking studies have been utilized to understand the insertion of IL ions in different domains of BSA, which along with decreased pH cause the unfolding and growth of BSA into amyloid fibrils. It is expected that the results obtained from this study would help to understand the impact of IL containing [BF4]- anion on protein stability and aggregation along with providing a new platform to control the formation of amyloid fibrils and other biomaterials driven via ionic interactions and alterations in pH.

Bovine serum albumin refolding at acid solution by small angle neutron scattering

A series of study of the conformational change of bovine serum albumin (BSA) induced by pH and additive has been conducted by small angle scattering (SANS) technique. The unfolding process occur by increasing the solvent acidity of the buffer. The previous work from SANS scattering profile shows that BSA unfolded into a cylinder-like structure at pH 2. In this work, the role of sorbitol in refolding process of BSA in acid solution was studied. Sorbitol, at concentrations from 0 to 3 M, led to the progressive restoration of BSA globular structure. The SANS scattering data show the conformational change from cylinder-like structure of pure BSA at pH 2 undergo to ellipsoid-like structure in the addition of 3M sorbitol. In the absence, 1M and 2M sorbitol, the SANS scattering profile of BSA fitted to flexible cylinder model. Meanwhile in the present of 3M sorbitol, it fitted to triaxial ellipsoid model. These results are confirmed with ab initio low-resolution shape calculation model analysis using GNOM and DAMMIN obtaining the three-dimensional structure model.

Ribosylation induced structural changes in Bovine Serum Albumin: understanding high dietary sugar induced protein aggregation and amyloid formation

Non-enzymatic glycation of proteins is believed to be the root cause of high dietary sugar associated pathophysiological maladies. We investigated the structural changes in protein during progression of glycation using ribosylated Bovine Serum Albumin (BSA). Non enzymatic attachment of about 45 ribose molecules to BSA resulted in gradual reduction of hydrophobicity and aggregation as indicated by red-shifted tryptophan fluorescence, reduced ANS binding and lower anisotropy of FITC-conjugated protein. Parallely, there was a significant decrease of alpha helicity as revealed by Circular Dichroism (CD) and Fourier transformed-Infra Red (FT-IR) spectra. The glycated proteins assumed compact globular structures with enhanced Thioflavin-T binding resembling amyloids. The gross structural transition affected by ribosylation led to enhanced thermostability as indicated by melting temperature and Transmission Electron Microscopy. At a later stage of glycation, the glycated proteins developed non-specific aggregates with increase in size and loss of amyloidogenic behaviour. A parallel non-glycated control incubated under similar conditions indicated that amyloid formation and associated changes were specific for ribosylation and not driven by thermal denaturation due to incubation at 37 °C. Functionality of the glycated protein was significantly altered as probed by Isothermal Titration Calorimetry using polyphenols as substrates. The studies demonstrated that glycation driven globular amyloids form and persist as transient intermediates during formation of misfolded glycated adducts. To the best of our knowledge, the present study is the first systematic attempt to understand glycation associated changes in a protein and provides important insights towards designing therapeutics for arresting dietary sugar induced amyloid formation.

Mechanistic interaction of triflate based noscapine ionic liquid with BSA: Spectroscopic and chemoinformatics approaches

In the present era, Ionic liquids (ILs) are showing great importance in many fields of research. Apart from those applications, researchers have grown their interest in pharmaceutical applications of ionic liquids. Proteins play a vital role in the study of various in vitro and in vivo studies to understand the action of a drug. A little disturbance induced by a drug in the microenvironment of proteins can alter their natural three dimensional structure. It has been observed that the interaction of ILs with blood proteins (BSA and HSA) is providing useful information in the manufacture of active pharmaceutical ILs and drug delivery. In the present study, an attempt was made to investigate the interaction between BSA (Bovine Serum Albumin) and [Pip-Nos] Triflate, a Noscapine (alkaloid) based ionic liquid, using UV–visible absorption spectra, fluorescence spectra, circular dichroism, and chemoinformatics studies. UV spectra showed a rise in intensity with a small red shift proving the BSA-IL complex formation. According to fluorescence spectra, static quenching of the BSA was observed on the addition of IL. The conformational changes of bovine serum albumin were analyzed with the help of CD analysis. The moderate binding was observed as a result of all the spectroscopic assays in correlation with molecular modeling studies. [Pip-Nos]OTf displayed optimal binding to the BSA protein with a molecular docking score of −343.71 kJ/mol. The molecular dynamics simulation study showed the stable binding of [Pip-Nos]OTf with BSA through RMSD 1–2.2 Å, Rg score of 26.1–26.5 Å and RMSF 0.4–7 Å. MM/PB (GB) SA binding energy calculations revealed the involvement of large binding energy along with a high static number of hydrogen bonds in complexation. These spectroscopic and chemoinformatics assays report the potency of [Pip-Nos]OTf and an important futuristic role in cancer therapeutics.

Investigation of the binding interactions between 17α-ethinylestradiol with bovine serum albumin by multispectroscopy

To understand the effect of 17α-ethinylestradiol (EE2) on the conformation changes of bovine serum albumin (BSA), the binding mechanisms of EE2 with BSA were investigated by fluorescence spectroscopy, time-resolved fluorescence spectroscopy, synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, UV–visible spectroscopy, circular dichroism (CD) spectroscopy and molecular docking. The quenching constants, binding constants, the number of binding sites, thermodynamic parameters, binding distance and the secondary structure changes of BSA were determined. The results of fluorescence quenching experiment suggested that the fluorescence quenching of BSA by EE was due to the formation of complex through static quenching, which was also confirmed by time-resolved fluorescence measurements. The thermodynamic parameters indicated that the binding of EE2 to BSA was driven mainly by van der Waals forces and hydrogen bonding. The conformation alterations of BSA upon EE2 binding were studied by UV–vis spectroscopy and CD spectroscopy. The results of site marker competitive experiments and molecular docking showed that the binding sites of EE2 were mainly located within site I in the subdomain IIA of BSA.

Investigation of the binding interactions between dimethyl phthalate and its metabolite with bovine serum albumin by multispectroscopy.

To understand the behavior of dimethyl phthalate (DMP) and realize the effect of DMP and its metabolite, monomethyl phthalate (MMP), on the conformation changes of bovine serum albumin (BSA), the interaction mechanisms of DMP and MMP with BSA were investigated by multispectroscopy and molecular docking. The results of the fluorescence quenching experiment showed that the fluorescence quenching of BSA by DMP and MMP was due to the formation of a complex though static quenching, which was also confirmed by time-resolved fluorescence measurements. The binding constants were 8.06 × 104 M-1 and 4.74 × 104 M-1 for DMP-BSA and MMP-BSA, respectively, and the number of binding sites were 1.20 (DMP) and 1.18 (MMP). The thermodynamic parameters showed different binding forces for DMP and MMP with BSA. The binding of DMP to BSA was driven mainly by hydrophobic interactions and hydrogen bonding, and MMP bound to BSA by van der Waals forces and hydrogen bonding, which were in accordance with the results from the molecular docking. The conformation and structural alterations of BSA upon DMP or MMP binding were studied by UV-vis spectroscopy, circular dichroism spectroscopy and synchronous fluorescence spectroscopy. The presence of metabolite did not change the quenching mechanism but decreased the binding affinity of DMP toward BSA as well as shortened the binding distance, which may be attributed to the competition between DMP and MMP for binding to BSA. This study revealed the combined effects of DMP and its metabolite on BSA at the molecular level.

Investigation of Conformational Changes of Bovine Serum Albumin upon Binding with Benzocaine Drug: a Spectral and Computational Analysis

Benzocaine drug (BZC) is an active component of various nonprescription drugs and used for numb teething treatments. The interaction of BZC with bovine serum albumin (BSA) has been studied using fluorescence, synchronous fluorescence, UV-Vis, circular dichroism (CD), and molecular docking analysis. The results revealed that BZC has a strong affinity to quench the intrinsic fluorescence of BSA in terms of a static quenching mechanism under physiological conditions. The fluorescence quenching data revealed that the quenching constants are (KSV) 4.10, 3.30, and 2.35 × 104 L mol−1 at 298, 304, and 310 K, respectively. The binding constants (Kb) at three different temperatures (298, 304, and 310 K) were found to be 6.02, 3.72, and 1.10 × 105 L mol−1, respectively. The thermodynamic parameters ∆H° and ∆S° have been estimated to be − 70.67 and − 128.9 J mol−1 K−1, respectively, thereby, indicating that hydrogen bonding and Van der Waals forces play major role in the interaction of BSA–BZC. Moreover, the negative values of ΔG° − 32.30, − 31.50, − 30.68 kJ mol−1 at 298, 304, 310 K, respectively, indicate the spontaneity of the interaction. FRET analysis proved high probability of energy transfer from BSA to the drug molecule. Molecular docking and displacement studies indicated that BZC was bound to the Sudlow’s site II through hydrogen bonding and Van der Waals interactions.

Characterization of the binding mechanism and conformational changes of bovine serum albumin upon interaction with aluminum-maltol: a spectroscopic and molecular docking study.

The widespread use of aluminum in the treatment of drinking water, food, agriculture and pharmaceuticals has greatly increased the risk of human exposure to excess aluminum, which is a serious health hazard to human beings. In our previous work, serum albumin was reported to have a specific affinity for aluminum. However, the mechanism of binding of aluminum to serum albumin was unclear. In this work, the interaction between bovine serum albumin (BSA) and aluminum-maltol (Al-Mal) was studied by molecular docking and spectroscopic analysis. The results show that the combination of Al-Mal and BSA is a spontaneous endothermic reaction. The binding force is mainly related to the hydrophobic force and hydrogen bonding; when the ratio of BSA to Al-Mal was 1 : 10, the random coils of BSA increased by 47.6%. In addition, the hydrophobicity of BSA was enhanced after combining with Al-Mal. This study can provide a theoretical evidence for the binding mechanism of food-borne aluminum and serum albumin.

Insights into the structural changes of bovine serum albumin in ethanolammonium laurate based surface active ionic liquids

Ionic liquids (ILs) owing to their unique and tunable physicochemical properties have found profound applications in the biomedical and pharmaceutical field. Since ILs are widely used as solubilizing and stabilizing agents for biomolecules. It is important to explore their effect on proteins. Surface active ionic liquids (SAILs) due to their higher surface activity and tunable property have emerged as new task specific ILs and found to have superior properties than conventional ionic surfactants. In this work, we have synthesized and characterized two novel ethanolammonium based SAILs, namely, (n-butylethanolammonium laurate [NBEA][LAU] and tert-butylethanolammonium laurate [TBEA][LAU]). The self-assembling behavior of the SAILs in pure water was examined by tensiometry and conductometry. The structural changes occurring in BSA as the consequence of interactions with SAILs at pH 7.4 and T = 298.15 K were explored using steady-state and life time fluorescence, UV–Visible and far UV circular dichroism(CD) spectroscopy and isothermal titration calorimetry (ITC). The results from surface tension and conductivity measurements give the values of critical micelle concentration (cmc) of the BSA-SAIL complex formation. The CD spectroscopy gives information on the secondary structure alterations of BSA-SAIL complex, which is further confirmed by ITC data. The dynamic quenching effect in tryptophan fluorescence of BSA is significant as evidenced by lifetime measurements. Overall, the present work highlights the conformational changes the protein can undergo upon interacting with SAILs.

Conductance Changes in Bovine Serum Albumin Caused by Drug-Binding Triggered Structural Transitions.

Proteins, due to their binding selectivity, are promising candidates for fabricating nanoscale bio-sensors. However, the influence of structural change on protein conductance caused by specific protein-ligand interactions and disease-induced degeneration still remains unknown. Here, we excavated the relationship between circular dichroism (CD) spectroscopy and conductive atomic force microscopy (CAFM) to reveal the effect of the protein secondary structures changes on conductance. The secondary structure of bovine serum albumin (BSA) was altered by the binding of drugs, like amoxicillin (Amox), cephalexin (Cefa), and azithromycin (Azit). The CD spectroscopy shows that the α-helical and β-sheet content of BSA, which varied according to the molar ratio between the drug and BSA, changed by up to 6%. The conductance of BSA monolayers in varying drug concentrations was further characterized via CAFM. We found that BSA conductance has a monotonic relation with α-helical content. Moreover, BSA conductance seems to be in connection with the binding ability of drugs and proteins. This work elucidates that protein conductance variations caused by secondary structure transitions are triggered by drug-binding and indicate that electrical methods are of potential application in protein secondary structure analysis.

Spectroscopic study of conformation changes of bovine serum albumin in aqueous environment

The secondary structural changes of bovine serum albumin (BSA) aqueous solutions with and without calcium cations were investigated by attenuated total reflection-Fourier transform infrared (ATR-FTIR) technology. The spectra of BSA solution and BSA dry powder were mainly reflected the formation of hydrogen bonds between water and BSA. Further investigation indicated that the concentrations of calcium cations in BSA aqueous solution also affected the secondary structural change of the protein. Amide I band was red shifted and amide II band was blue shifted in aqueous environment compared with the dry BSA powder, and the addition of calcium cations further changed the amide bands position, which led to the change of the secondary structure. The result was coinciding with the Raman spectroscopy.

Characterization of the binding and conformational changes of bovine serum albumin upon interaction with antihypertensive olmesartan medoxomil

The interaction of bovine serum albumin (BSA) with the olmesartan medoxomil (OLM) was investigated by different spectroscopic and linear sweep voltammetric techniques under experimentally optimised physiological conditions. The alteration of functional properties of BSA when quenched by OLM was illustrated by the continuous decrease of the fluorescence intensity of BSA upon addition of OLM. The quenching constants (Ksv) obtained were 0.71 × 104, 1.3 × 104 and 2.1 × 104 Lmol−1 at 288, 298 and 308 K respectively. The binding mechanism was dynamic type quenching. The value of K is of the order of 104, indicating that a long-lasting interaction exists between OLM and BSA. The positive values of ΔH0 and ΔS0 suggested the hydrophobic interactions play the major roles in the binding reaction. The conformational change of BSA after binding with OLM was demonstrated by the synchronous, FTIR and 3-D fluorescence spectral results. The effects of some common metal ions and site probes on binding of BSA– OLM were also investigated.

Stimuli-responsive nanoparticles by thermal treatment of bovine serum albumin inside its complexes with chondroitin sulfate

We combine electrostatic polysaccharide/protein complexation with subsequent thermal denaturation of proteins to produce chondroitin sulfate/bovine serum albumin nanoparticles that do not lose their integrity at neutral and basic pH. Light scattering at a wide angular range shows that nanoparticle size (radius of gyration and hydrodynamic radius) and molar mass may be tuned by the CS/BSA mass ratio while the irreversible protein-protein contacts upon temperature treatment endow the complexes with properties of nanogels. These nanoparticles respond to changes of pH by reversing their surface charge at pH 5.3 while their size responds to the solution ionic strength and pH. The conformational changes of bovine serum albumin upon thermal treatment are confirmed by spectroscopy methods. The ability of the nanoparticles to encapsulate bioactive substances is demonstrated by loading the nutraceutical β-carotene. The methodology of this work may be applied to other polysaccharide/protein systems to produce multi-functional stimuli-responsive nanoparticles for nanodelivery in food science and biomedical applications.

Esterase activity and conformational changes of bovine serum albumin toward interaction with mephedrone: Spectroscopic and computational studies.

The present work is a brief overview of the effect of psychostimulant drug mephedrone hydrochloride (4MMC) on a transport protein, bovine serum albumin (BSA). The binding effect of 4MMC on BSA has been investigated by using UV-visible, steady-state fluorescence, time-resolved fluorescence, fluorescence resonance energy transfer, Fourier transform infrared, circular dichroism, and molecular docking method. 4-Methylmephedrone quenched the intrinsic fluorescence of BSA by static quenching mechanism, which was further confirmed by time-resolved fluorescence. The absorption spectrum of BSA in the presence of various concentrations of 4MMC reveals the change in the absorption bands of BSA-4MMC complex. The binding constant between 4MMC and BSA was calculated to be of the order of 104 Lmol-1 . The thermodynamic parameters such as molar enthalpy change (∆H), molar Gibbs free energy change (∆G), and molar entropy contribution (∆S) were obtained by the van't Hoff equation. The values obtained suggested that the binding mechanism was entropic driven and the major forces involved are hydrophobic in nature. The fluorescence resonance energy transfer result indicates the high probability of energy transfer from Trp residue of BSA to the 4MMC (r=2.01nm). Fourier transform infrared and CD results showed that 4MMC induced secondary structural changes in BSA. The esterase-like activity of BSA in presence of 4MMC further validated our CD results, confirming the distortion and change in functionality of protein upon binding with 4MMC. Molecular docking analysis showed that 4MMC principally bind at the II site (subdomain IIIA) of BSA.

Investigation on the conformational changes of bovine serum albumin in a wide pH range from 2 to 12

The conformation of bovine serum albumin largely depends on its microenvironment pH and affects its physical functions and applications. In this study, we investigated the effects of pH (wide range 2–12) on the conformation of bovine serum albumin based on spectroscopic signals by various spectroscopic means including fluorescence, synchronous fluorescence, resonance light scattering, UV-visible absorption, and circular dichroism. The changes in spectroscopic signals, such as peak position and intensity, showed that the structure of bovine serum albumin varied significantly with pH. The conformation of bovine serum albumin was compact at pH 6–7, as indicated by the largest peak position values and peak intensities in the fluorescence, synchronous fluorescence, and RLS spectra. The structure of bovine serum albumin became loose in the acidic or alkaline environment, as indicated by the decreased peak position values and peak intensities. The microenvironment of the amino acid residues of bovine serum albumin also varied with pH, as indicated by the changing peak position values. At pH 7, the hydrophobicity of the tyrosine and tryptophan residues was the weakest, as indicated by the minimum synchronous fluorescence signals. In addition, the secondary structure of bovine serum albumin, especially α-helix, varied with pH. The content of α-helix reached the maximum value of 68% at pH 6–8, whereas it decreased in the acidic or alkaline environment. The study provides valuable details for studying the physiological function and applications of serum albumins.

INTERACTION OF COPPER OXIDE NANOPARTICLES WITH BOVINE SERUM ALBUMIN BY SPECTROSCOPIC STUDIES

Objective: Since structural changes of adsorbed protein are necessary for cellular uptake of nanoparticles (NPs) it is of prime importance to know about structural changes of bovine serum albumin (BSA) when it interacts with CuO NPs–a potential new antitumor drug.Methods: CuO NPs prepared by sol-gel technique were characterized by x-ray diffraction (XRD) and tunneling electron microscope (TEM) techniques. The conformational changes induced by CuO NPs on BSA were studied by various spectroscopic techniques such as steady state and time-resolved fluorescence measurements. The changes in fluorescence emission parameters such as fluorescence intensity, fluorescence emission maximum and lifetimes of fluorescent residues in BSA were studied.Results: XRD analysis showed the average particle size as 32 nm. The TEM micrograph showed particles of different size varying from 10 to 45 nm. Fluorescence quenching was confirmed due to a decrease in fluorescence intensity of CuO NPs–BSA complex. The analysis of lifetime measurements indicated BSA contained two tryptophan (trp) residues that fluoresced in different environments. Static quenching mechanism was confirmed by time-resolved measurements when BSA interacted with CuO NPs.Conclusion: Minor structural changes of BSA protein were observed during the interaction studies.