Structure Of Bovine Serum Albumin Research Articles

Insight into binding mechanism between three whey proteins and mogroside V by multi-spectroscopic and silico methods: Impacts on structure and foaming properties

In this work, the interaction mechanism, structure and foaming properties between three whey proteins (α-lactalbumin (ALa), β-lactoglobulin (BLg) and bovine serum albumin (BSA)) and Mogroside V (Mog) at pH 7.0 were systematically formulated via multi-spectroscopic analysis and silico methods. Mog quenched the fluorescence of three whey proteins in a static mode. Mog had greater binding affinity for ALa than that for BLg or BSA. Hydrogen bonds, van der Waals force and hydrophobic interaction acted as the primary driven forces in ALa/BLg/BSA-Mog system. Moreover, content of α-helix in ALa and β-sheet in BLg decreased after Mog addition, whereas there was no significant change in the secondary structure of BSA. In addition, hydrophobic crevice in ALa, “bottom of β-barrel” in BLg and interfacial region between two domains in BSA were the binding areas for Mog using molecular docking. Molecular dynamics (MD) simulation further demonstrated that the complex of ALa and Mog possessed the lowest binding free energy and most stable state. Furthermore, compared with single proteins, the foaming ability of protein/Mog complexes were improved. Especially, Ala-Mog attained the highest increase rate. Bubble morphology presented that three whey proteins containing Mog possessed compacter, smaller and even bubbles. This research could establish theoretical basis for the binding mechanism between different food proteins and low weight surfactants. Besides, whey protein-saponin complexes could be served as the novel food-grade foaming agents applied in food industry.

Antiglycation potential of plant based TiO2 nanoparticle in D-ribose glycated BSA in vitro.

Biosynthetic procedure is one of the best alternatives, inexpensive and ecologically sound for the synthesis of titanium dioxide (TiO2 ) nanoparticles using a methanolic extract of medicinal plant. The main prospect of this study was to investigate the antiglycation activity of the TiO2 nanoparticles (TNP) prepared by ethanolic leaf extract of the Coleus scutellarioides. In this study, biosynthesized TNP characterized with UV-Visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopyand scanning electron microscope. These TNP were further investigated with respect to their antiglycation property and it was checked in the mixture of d-ribose glycated bovine serum albumin (BSA) by measuring ketoamine, carbonyl content, Advanced glycation end products (AGEs) and aggregation of protein instigated by glycation process. The inhibitory effect of TNP to restore the structure of BSA in presence of d-ribose were also characterize by biophysical techniques mentioned above. Therefore, the findings of this study suggest repurposing of TNP for its antiglycation property that could be helpful in prevention of glycation instigated AGEs formation and structural loss of proteins.

Electrochemical and CD-spectroelectrochemical studies of the interaction between BSA and the complex [Cu(Bztpen)]2+, (Bztpen = (N-benzyl-N, N′, N′-tris (pyridin-2-ylmethyl) ethylenediamine)

In this work we report the electrochemical, spectroscopical and spectro-electrochemical studies of a model complex [CuΙΙ(Bztpen)]2+, (Bztpen = (N-benzyl-N,N′,N′-tris(pyridin-2-ylmethyl)ethylenediamine) in order to propose a methodology to evaluate the interaction of potential metal based anticancer agents during electron transfer processes, with transport proteins such as Bovine Serum Albumin (BSA). It was possible to establish a reversible electron transfer [CuΙΙ(Bztpen)]2+ +1e → [CuΙ(Bztpen)]+ and a weak interaction energy between BSA and [CuΙΙ(Bztpen)] and [CuΙ(Bztpen)] species, with no adsorption of protein over the electrode surface. Circular Dichroism (CD) Spectroelectrochemistry, not reported before, reveals no significant changes in BSA structure during the electron transfer [CuΙΙ(Bztpen)]2+ + 1e → [CuΙ(Bztpen)]+. CD experiments at variable temperature for BSA denaturalization in the absence and in the presence of [CuΙΙ(Bztpen)]2+, shown no change in thermodynamic parameters due to low interaction between the transport protein and copper complex.

A Novel Thermal-driven Self-assembly Method to Prepare Albumin Nanoparticles: Formation Kinetics, Degradation Behavior and Formation Mechanism.

Nanoparticles based on bovine serum albumin (BSA), which shares 76% homology with human serum albumin (HSA), have emerged as a promising candidate for the efficient delivery of anticancer drugs. Thermal-driven self-assembly is a novel organic solvent-free approach to produce albumin nanoparticles. In our previous study, some features of this nanoparticle such as drug loading efficiency, drug encapsulation efficiency and drug release kinetics have been evaluated. However, the formation mechanism that determines the above nanoparticle properties remains unclear. Here, we investigated the formation kinetics and mechanism using spectroscopic methods including fluorescence spectroscopy, circular dichroism (CD) and differential scanning calorimetry (DSC). We also applied chemical analysis methods that measured the content changes of albumin active groups and vanillin. To verify the covalent networks in the nanoparticles, trypsin and glutathione (GSH) were used separately to cleave the peptide bonds and disulfide bridges, and dynamic light scattering (DLS) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to analyze the degraded samples. BSA nanoparticles started to form at 10min and were completely formed at 120min. With the digestion of trypsin, more than 50% of the nanoparticles were degraded within 60min. CD spectra showed that α-helical structure of BSA decreased from 42.3% to 39.8% and 37.7% after heating for 10 and 60min, respectively. In the DSC thermogram, the melting peak of BSA nanoparticles was 229.14℃, which is about 12℃ higher than the physical mixture of BSA and vanillin, indicating that chemical reactions occurred during the nanoparticle formation and formed a new more stable substance. Moreover, the results of active group assay, GSH degradation and SDS-PAGE experiments also proved that disulfide bonds and peptide bonds were formed between BSA molecules, whereas Schiff bases were formed between BSA and vanillin molecules. Formation kinetics and degradation behavior are important properties to characterize albumin nanoparticles and should be paid attention to. Not only that, this study also provides an effective way to study the formation mechanism of protein-based nanodrug delivery systems.

Spectroscopic investigation on the interaction of direct yellow-27 with protein (BSA)

Direct yellow 27 (DY-27) interaction with bovine serum albumin (BSA) was investigated using multi-spectroscopic techniques to understand the toxicity mechanism. Fluorescence quenching of BSA by DY-27 was observed as a result of the formation of a BSA-DY27 complex with a binding constant of 1.19 × 105 M−1 and followed a static quenching mechanism with a quenching constant Ksv of 7.25 × 104 M−1. The far UV circular dichroism spectra revealed the conformational changes in the secondary structure of BSA in the presence of DY-27. The calculated average lifetime of BSA is 6.04 ns and is nearly constant (5.99 ns) in the presence of dye and supports the proposed quenching mechanism. The change in free energy (ΔG) was calculated to be −28.96 kJ mol−1 and confirmed the spontaneity of the binding process. Further, docking studies have been conducted to gain more insights into the interactions between DY-27 and serum albumin.

Binding and mechanistic studies of 5-HT7 specific benzothiazolone derivatives with bovine serum albumin: Spectroscopic and in silico studies

Serotonin, commonly known as 5-Hydroxytryptamine, or 5-HT, is a neurotransmitter having a single amine group and is distributed throughout the peripheral nervous system (PNS) and central nervous system (CNS).It is involved in a variety of physiological and behavioural disorders, including severe depression, pain, schizophrenia, obesity, anxiety, etc. Fourteen serotonin receptor (5-HTR) subtypes are known, among which the 5-HT1A/5-HT7 subtypes are the most studied. Agonists of the 5-HT1AR/5-HT7R have neuroprotective properties, whilst antagonists are helpful in the therapy of neurological diseases. Four (arylpiperazinyl-butyl) benzothiazolone (APBBT) derivatives, abbreviated as L1-L4, which are well established ligands for serotonin receptors. The protein–ligand interaction analysis was performed to determine the extent to which the synthesized APBBT derivatives bind to serum proteins for transport to the target organ.The binding affinity of bovine serum albumin (BSA) was evaluated using a computational technique. An enzyme activity assay specific for esterase confirmed its potential tobecome a new marker for 5-HT7. The quenching of fluorescence and details about the change in protein’s confirmation were provided by synchronous fluorescence spectroscopy. In this study, different spectroscopic methodologies were used, which included UV–visible spectroscopy, fluorescence spectroscopy, and circular dichroism (CD) spectroscopy. An enzymatic activity assay was done to assess the binding affinities of four (arylpiperazinyl-butyl)benzothiazolone derivatives with bovine serum albumin. Finally, molecular docking was used to deduce the primary intermolecular forces involved in the binding process between the synthesisedAPBBT derivatives and the BSA structure. On the basis of Glide score, ligand L3 was the most efficient for Sudlow Site I, followed by L1 > L2 > L4. All studies indicated the effective binding of serotonin derivatives with BSA, thus showing the role of BSA in the transport and metabolism of serotonin derivatives.

CD, UV, and In Silico Insights on the Effect of 1,3-Bis(1'-uracilyl)-2-propanone on Serum Albumin Structure.

1,3-diaryl-2-propanone derivatives are synthetic compounds used as building blocks for the realization not only of antimicrobial drugs but also of new nanomaterials thanks to their ability to self-assemble in solution and interact with nucleopeptides. However, their ability to interact with proteins is a scarcely investigated theme considering the therapeutic importance that 1,3-diaryl-2-propanones could have in the modulation of protein-driven processes. Within this scope, we investigated the protein binding ability of 1,3-bis(1′-uracilyl)-2-propanone, which was previously synthesized in our laboratory utilizing a Dakin–West reaction and herein indicated as U2O, using bovine serum albumin (BSA) as the model protein. Through circular dichroism (CD) and UV spectroscopy, we demonstrated that the compound, but not the similar thymine derivative T2O, was able to alter the secondary structure of the serum albumin leading to significant consequences in terms of BSA structure with respect to the unbound protein (Δβ-turn + Δβ-sheet = +23.6%, Δα = −16.7%) as revealed in our CD binding studies. Moreover, molecular docking studies suggested that U2O is preferentially housed in the domain IIIB of the protein, and its affinity for the albumin is higher than that of the reference ligand HA 14−1 (HDOCK score (top 1–3 poses): −157.11 ± 1.38 (U2O); −129.80 ± 6.92 (HA 14−1); binding energy: −7.6 kcal/mol (U2O); −5.9 kcal/mol (HA 14−1)) and T2O (HDOCK score (top 1–3 poses): −149.93 ± 2.35; binding energy: −7.0 kcal/mol). Overall, the above findings suggest the ability of 1,3-bis(1′-uracilyl)-2-propanone to bind serum albumins and the observed reduction of the α-helix structure with the concomitant increase in the β-structure are consistent with a partial protein destabilization due to the interaction with U2O.

Molecular mechanism of two functional protein structure changes under 2,3-butanedione-induced oxidative stress and apoptosis effects in the hepatocytes

Food security has become closely watched with the occurrence of a series of food safety incidents in recent years. The widespread adoption of 2,3-butanedione (BUT), as a food additive, is an unpreventable significant risk factor to food security. Based on this, mouse hepatocyte AML-12 cells and two functional proteins (bovine serum albumin and lysozyme) were utilized as targeted receptors to study the adverse effects of BUT at the cellular and molecular levels. Results suggested that BUT could disrupt the redox balance of AML-12 cells, reducing glutathione (GSH) activity fell to 87.18 %, which cannot offset the production of reactive oxygen species (ROS). Meanwhile, the increasement of lipid peroxidation and malondialdehyde (MDA) levels were observed. The mitochondrial membrane function was also abnormal due to the excessive accumulation of ROS and eventually leads to cell apoptosis and death. At the molecular level, the exposure of BUT could alter the skeleton and secondary structure of bovine serum albumin (BSA) and lysozyme (LYZ), and it could statically quench the intrinsic fluorescence of proteins. The combined experiments confirmed proved the potentially toxic effects of BUT accumulation on the detoxification organ, providing theoretical support for the liver diseases caused by BUT exposure, and a reference for the risk assessment of occupational exposure of BUT.

Analysis of bovine serum albumin unfolding in the absence and presence of ATP by SYPRO Orange staining of agarose native gel electrophoresis

An attempt was made to specifically stain unfolded proteins on agarose native gels. SYPRO Orange is routinely used to detect unfolded protein in differential scanning fluorimetry, which is based on the enhanced fluorescence intensity upon binding to the unfolded protein. We demonstrated that this dye barely bound to the native proteins, resulting in no or faint staining of the native bands, but bound to and stained the unfolded proteins, on agarose native gels. Using bovine serum albumin (BSA), it was shown that staining did not depend on whether BSA was thermally unfolded in the presence of SYPRO Orange or stained after electrophoresis. On the contrary, SYPRO Orange dye stained protein bands in the presence of sodium dodecylsulfate (SDS) due to incorporation of the dye into SDS micelles that bound to the unfolded proteins. This staining resulted in detection of new, intermediately unfolded structure of BSA during thermal unfolding. Such intermediate structure occurred at higher temperature in the presence of ATP.

Pharmacological Profile of Nigella sativa Seeds in Combating COVID-19 through In-Vitro and Molecular Docking Studies

COVID-19 infection is associated with elevated oxidative stress, systemic hyper-inflammatory responses, endothelial dysfunction, and red blood cell membrane deformability. Nigella sativa extract is widely used in alternative and complementary medicine systems in a large population, due to its highly therapeutic, economic, natural, and safe nature. The aim of this study was to evaluate the effect of N. sativa extract on oxidative stress, hemolysis, proteolysis, and glycation through in vitro studies, as well as to find out its anti-viral potential against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) using in silico studies. N. sativa seed extract (at 600 µg/mL) displayed 67.33% scavenging activity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test, and 70.28% hydrogen peroxide reducing activity. N. sativa exhibited anti-proteolytic activity by decreasing heat-induced denaturation of bovine serum albumin (BSA) and egg albumin by 63.14% and 57.95%, respectively, and exhibited anti-proteinase potential of 66.28% at 600 μg/mL. In addition, heat-induced hemolysis and hypersalinity-induced hemolysis were inhibited by 57.86% and 61.7%, respectively, by the N. sativa seeds. N. sativa also inhibited browning intensity by 56.38%, and percent aggregation index by 51.38%, amyloid structure by 48.28%, and AGE-specific fluorescence by 52.18%, thereby protecting the native structure of BSA from glycation. The binding interactions between bioactive molecules of N. sativa seed with SARS-CoV-2 spike glycoprotein were proven by using in silico molecular docking tools. The functional amino acids involved in the interactions are Asp467, Thr108, Thr114, Ile468, Asn234, Gln155, Glu465, Arg466, Gly232, and Ile233, indicating the inhibiting property of N. sativa on SARS-CoV-2. Finally, we may infer that phytoconstituents of N. sativa seeds have the potential to protect against the spike protein of SARS-CoV-2. Studies on N. sativa seeds might act as a path to develop a potent alternative therapy against viral infections, especially COVID-19 infection, in the future. However, the limitations linked with the use of natural products are also needed to be considered in this regard.

Effect of solvent and additives on the electrospinnability of BSA solutions

Electrospun nanofibrous membranes have attracted the interest of the scientific community over the past decades due to their unique properties (e.g., high surface area, enzyme encapsulation high efficiency in filtering). Among the most promising membranes are those derived from natural polymers, which are not based on fossil fuels and most of them are highly biocompatible. In this regard, this study is focused on the development and characterization of electrospun nanofibrous membranes of bovine serum albumin (BSA) with potential applications in several fields, from tissue engineering to advanced filtering. Although the globular structure of BSA hinders the generation of nanofibers, some previous studies have succeeded in its electrospinning. However, they made use of either toxic reagents or co-electrospinning with synthetic polymers, which resulted in poorer biocompatibility. To prevent this, the present study explores the impact of non-hazardous reagents on the formation of BSA nanofibers. As a result, it was observed that the addition of ethanol (EtOH) in the solvent mixture and the thermal denaturation of BSA favored the electrospraying of nanoparticles (∼ 300 nm). It was also noticed that the presence of hydroxypropyl methylcellulose (HPMC) favors the formation of nanofibers (∼ 60 nm). However, bead formation was found in these membranes. This work contributes to clarifying the influence of solvents and surfactants when proteins are electrospun, enabling the manufacture of bio-based nanofibrous mats with applications in different fields (e.g., filtering, biomaterials, active packaging).

A Survey of Gasoline Ameliorator, Methyl-Tert-Butyl Ether (MTBE) on Bovine Serum Albumin: A Spectroscopy and Molecular Dynamic Simulation Study.

Methyl-Tert-Butyl Ether (MTBE) as a gasoline modifier is frequently added to fuels and used in plenty of worldwide applications. MTBE biodegradation in groundwater occurs slowly and produces water miscibility; therefore, it causes diverse environmental and human health concerns. The interaction of MTBE with bovine serum albumin (BSA) as a model protein at physiological conditions is investigated to illustrate the possible interactions of MTBE with the body's proteins. Uv-visible, fluorescence, circular dichroism (CD) spectroscopy methods, and molecular modeling were used to analyze the MTBE's effect on BSA structure and dynamics. The constant protein concentration and various MTBE contents were used for possible interactions. The protein structural analysis shows that MTBE binds to BSA via positive enthalpy and entropy via hydrophobic interactions. Molecular docking shows the participation of several amino acids in the MTBE-BSA interaction. The CD spectroscopy results show that the BSA structure was not changed in the MTBE concentrations utilized in the study. Molecular dynamics (MD) simulation results suggest that MTBE can slightly change protein structure in the last 50ns. Comparing experimental and MD simulation results demonstrated that the BSA secondary structure was maintained in the low concentration of the MTBE. The entropy and enthalpy parameters asserted the hydrophobic interaction was the major force in the interaction between the BSA and MTBE.

Inducing the formation of a colloidal albumin carrier of curcumin

The administration and delivery of pharmaceuticals faces a variety of well-known obstacles that result in limited biocompatibility and bioavailability. Efforts to improve these properties have often employed serum albumin, primarily due to its inherent biocompatibility and its ability to enhance the circulation times of pharmaceuticals. In this work, we have adapted a nanoparticle-formulation protocol, to produce a protein carrier of curcumin with bovine serum albumin. This was achieved by using a near-equimolar protein:curcumin ratio instead of the abundance of curcumin that would be normally used in a nanoparticle formulation. Photometric and quantitative analysis of this carrier showed an increased curcumin content in the produced aqueous solutions following the homogenization of bovine serum albumin (water) and curcumin (dichloromethane) phases. Albumin fluorescence studies indicated curcumin association near a tryptophan residue, without excluding the possibility of additional sites. Circular dichroism provided strong evidence of this association through the induced circular dichroism effect and showed that the secondary structure of bovine serum albumin was effectively maintained. Overall, this work presented a new means of facilitating the association of increased levels of curcumin with bovine serum albumin, which could potentially be used to generate additional non-covalent albumin carriers for pharmaceutical compounds.

Mechanistic interaction studies of synthesized ZIF-8 nanoparticles with bovine serum albumin using spectroscopic and molecular docking approaches

Numerous studies have shown that nanosized zeolitic imidazolate framework particles (ZIF-8 NPs) serve as promising vehicles for pH-responsive drug delivery. An understanding of their interaction with serum proteins present in physiological systems will thus be of critical importance. In this work, monodisperse ZIF-8 NPs with an average size of 60 nm were synthesized at room temperature and characterized for their various physicochemical properties. Bovine serum albumin (BSA) was used as model serum protein for various interaction studies with ZIF-8 NPs. Spectroscopic techniques such as UV–visible and fluorescence spectroscopy indicated the formation of a ground-state complex with a binding constant of the order 103 M−1 and a single binding site. Steady-state and time-resolved fluorescence spectroscopy confirmed the mechanism of quenching to be static. Conformational changes in the secondary structure of BSA were observed using CD and FT-IR spectroscopies. Binding sites were explored using molecular docking studies.

Exciton-tryptophan coupling pulse behaviour along with corona formation, binding analysis, and interaction study of ZnO nanorod-serum albumin protein bioconjugate.

The bioconjugate of bovine serum albumin (BSA) and zinc oxide nanorods (ZnO NRs) is investigated to explore the behaviour of the tryptophan (Trp)-exciton coupling and corona formation. The pulse like nature of the coupled system between Trp of BSA and exciton of ZnO NRs has been observed after analysis of the optical parameters such as refractive index, susceptibility, and optical dielectric constant. The time constant for tryptophan, exciton surface binding (t1 ) and reorganization (t2 ) are found to be (t1 ) 8 min, 7 min and (t2 ) 150 min, 114.5 min, respectively. The close proximity binding of BSA with ZnO NRs via tryptophan as well as exciton is responsible for bioconjugate formation. The aggregated structure of BSA is observed from small-angle X-ray scattering study in interaction with ZnO NRs. The change in secondary structure and tertiary deformation of the serum protein have been studied from Fourier transform infrared and emission quenching analyses. The number of binding sites (n) signified to the enhancement of the cooperative binding. The binding has been found to be endothermic and favoured using unfavourable positive enthalpy with a favourable entropy change from the result of the isothermal titration calorimetry.

Impacts of photoaging on the interactions between graphene oxide and proteins: Mechanisms and biological effect

Graphene oxide (GO) are subjected to photoaging in aquatic environment, and inevitably enter biota and then interact with proteins. Here, the interactions of pristine and photoaged GO with two typical proteins (bovine serum albumin (BSA) and lysozyme) were systematically investigated. Due to long term photoirradiation (1–3 day), the lateral size of GO decreased greatly, and the oxygen-containing groups decreased as well while the graphitic carbon contents increased. Compared to pristine GO, the photoaged GO displayed stronger binding affinities with both proteins, which was mainly attributed to the increased binding sites as a result of smaller lateral size and increased hydrophobicity. The photoaging effect was more obvious for the negatively charged BSA, because hydrogen bonding and van der Waals force were mainly involved in the enthalpy-driven interactions between them. While, the strong electrostatic attraction between the positively charged lysozyme and GO diminished the photoaging effect. Analyses of synchronous, three-dimensional fluorescence spectra and fibrillation experiments intensified that the photoaged GO induced more serious changes in conformational structure of BSA and exhibited stronger inhibition on fibrillation of BSA compared to pristine GO. This study provided novel insights into the increased ecological risks of GO as a result of photoaging.

Characterization of plasmatic proteins adsorption on poly(styrene sodium sulfonate) functionalized silicone surfaces

Proteins adsorption occurs spontaneously on biomaterial upon insertion within the body. The resulting protein layer influences biomaterial biocompatibility through enhanced bio-integration or, on the contrary, adverse reactions. Furthermore, upon adsorption, proteins can undergo modifications of their structure and, ultimately, their physicochemical properties and activity. Hence, the understanding of protein adsorption on implanted materials appears essential, as exemplified by silicone breast prostheses that might lead to serious health issues.Surface modifications with a bioactive polymer, poly(styrene sodium sulfonate)-polyNaSS, on a hydrophobic silicone surface that composes breast implants, have been successfully performed under UV irradiation by a radical surface polymerization. This strategy enhances cell biocompatibility and antibacterial features. Although detailed insights related to the mechanism are still scarce, polyNaSS is supposed to promote changes in the conformation and/or orientation of adsorbed plasma proteins, reducing the odd for a biofilm to form.The present work addresses more in-depth structural investigations of the adsorbed state of two plasma proteins: Bovine Serum Albumin (BSA), as a model protein, and fibronectin (FN), for its role in cell adhesion. Using Atomic force microscopy (AFM), we report that polyNaSS showed no significant impact on the BSA structure conversely to the FN one. However, imaging findings with AFM clearly outlined a change in the structural organization of FN, going from a nano fibrillar assembly with an average length of 130 nm to a globular one when the surface was grafted. Thus, it is highlighted that polyNaSS interacts specifically with FN. In addition, cell spreading assay of L929 fibroblasts on FN-coated surfaces with optical microscopy indicated no significant impact of the change in FN structure upon fibroblasts adhesion, which displayed active elongated shapes. The present features are crucial for understanding the cell adhesion mechanism induced by surface modification.

Ultrasonic-assisted foam fractionation for recovering bovine serum albumin from aqueous solution: Structure and function evaluation

In this work, a technology of ultrasonic-assisted foam fractionation had been used to recover bovine serum albumin (BSA) from its aqueous solution. First, the operation parameters (e.g., height ratio of liquid phase and foam phase, aperture size of gas distributor and gas flow rate) of foam fractionation were optimized. Subsequently, ultrasonic treatment was assembled into foam fractionation operation. Experimental results indicated that the surface excess of BSA molecules first increased and then decreased with increasing ultrasonic intensity from 0 W/cm2 to 75 W/cm2. Considering enrichment ratio and recovery percentage of BSA, the suitable intensity of ultrasonic treatment was 45 W/cm2. Fourier transform infrared (FTIR) spectroscopy and SDS-PAGE analysis suggested that ultrasonic-assisted foam fractionation could not only destroy the intramolecular covalent bonds within BSA, but also prevent the oxidation of free sulfhydryl groups. The circular dichroism spectroscopy showed that the secondary structure of BSA had become loose and well-ordered after suffering foam fractionation with assistance of ultrasonic treatment. Ultrasound wave contributed to inhibiting the formation of BSA aggregates in foam fractionation. Furthermore, the surface hydrophobicity, emulsibility, and foaming property of BSA could be effectively maintained by assembling ultrasonic treatment into foam fractionation.

Comprehensive investigation of binding of some polycyclic aromatic hydrocarbons with bovine serum albumin: Spectroscopic and molecular docking studies

The interactions of phenanthrene (PHTN), fluorene (FLRN) and fluoranthene (FLRT) as polycyclic aromatic hydrocarbons (PAHs) with bovine serum albumin (BSA) were explored employing spectroscopic approaches and molecular docking simulations. Based on fluorescence quenching analysis FLRT showed higher binding affinity to BSA comparing with PHTN and FLRN. PHTN/FLRN/FLRT quenched the intrinsic fluorescence of BSA in the form of the mixed mechanism. Synchronous fluorescence spectroscopy, UV–Vis and circular dichroism spectroscopy demonstrated that presence of PHTN/FLRN/FLRT induced conformational alterations in BSA molecules. Based on the Förster resonance energy transfer (FRET) theory, the binding distances between the donor (BSA) and the acceptor (PHTN/FLRN/FLRT) were 3.85, 2.34 and 2.69 nm, respectively. Molecular docking simulations of 16 EPA priority PAHs were carried out to disclose their preferred binding modes. Docking analysis demonstrated that PAHs were bound to BSA stronger as the number of aromatic rings increased. Moreover, the results revealed the role of differences in the location of aromatic rings in PAHs on their interactions with BSA despite equivalent number of aromatic rings. Van der Waals forces dominated the formation of the.BSA-PAHs complexes. Most studied PAHs were bound to the IIIB region of BSA; however, the sterically bulky PAHs like benzo[g,h,i]perylen and indeno[1,2,3cd]pyrene were located in the IIIA and IIB regions of BSA. Naproxen, the co-crystalized ligand, was redocked to the crystal structure of BSA and root mean square deviation value was found to be 1.96 Å highlighting the predictive accuracy of the docking protocol.

Probing multifunctional azure B conjugated gold nanoparticles with serum protein binding properties for trimodal photothermal, photodynamic, and chemo therapy: Biophysical and photophysical investigations

Multimodal or combination therapy has been considered as a powerful approach for treatment of complex diseases like cancer. The fascinating physicochemical and optoelectronic properties of gold nanoparticles make them potential candidate for cancer therapeutic and diagnostic applications. Herein, we design a multifunctional nanosystem by conjugating a photosensitizer, Azure B (AB) with citrate reduced gold nanoparticles (CI-Au NPs) through non-covalent interactions. The conjugation of AB with CI-Au NPs was confirmed through UV–Visible absorption spectroscopy and Fourier Transform Infra-red (FT-IR) spectroscopy. The morphology, size, and charge of the prepared nano-conjugates (AB@CI-Au NPs) were determined by transmission electron microscopy (TEM), Dynamic light scattering (DLS), and zeta potential measurements. The proficiency of AB@CI-Au NPs for cancer photo-therapies was demonstrated by evaluating their potential for photothermal heating and singlet oxygen generation in solution upon Visible laser (635 nm, 500 mW/cm2) irradiation. The AB@CI-Au NPs display superior heating efficiency than CI-Au NPs alone or free AB, and offer better photostability as well as singlet oxygen generation rate compared to free photosensitizer. The interaction of AB@CI-Au NPs with Calf thymus DNA (Ct-DNA) and transport protein Bovine Serum Albumin (BSA) were studied using various biophysical techniques including Circular dichroism, UV–Visible and fluorescence spectroscopic studies. AB@CI-Au NPs show intercalative binding with Ct-DNA by inducing local perturbations in double helical structure and hence can exert chemotherapeutic action by targeting DNA. AB@CI-Au NPs also display moderate binding with BSA without any adverse effect on BSA structure, which is desirable for significant biodistribution and pharmacokinetics of AB@CI-Au NPs. Also, in vitro cytotoxicity of the AB@CI-Au NPs with and without laser irradiation (635 nm, 500 mW/cm2) was demonstrated using the hepatocellular carcinoma (HepG2) cell lines. Our findings through photophysical and biophysical studies strongly recommend the exploitation of AB@CI-Au NPs nanoconjugates as a multifunctional probe for trimodal anticancer therapy.