Globular Protein Bovine Serum Albumin Research Articles

Modified interactions among globular proteins below isoelectric point in the presence of mono-, di- and tri-valent ions: A small angle neutron scattering study

Both short range attraction and long range electrostatic repulsion exist among globular protein Bovine Serum Albumin in solution below its isoelectric point (pI≈4.8). At pD≈4.0, below pI, protein has a net positive surface charge although local charge inhomogeneity presents. Small angle neutron scattering study reveals that in the presence of both mono-(Na+) and di-(Ni2+) valent ions attractive interaction increases and repulsive interaction decreases with the increase of salt concentration. However, for tri-valent (Fe3+) ions, both attractive and repulsive interaction increases with increasing salt concentration but the relative strength of repulsion is more than the attraction.

Structure and interaction among protein and nanoparticle mixture in solution: Effect of temperature

Structure and interaction among globular protein bovine serum albumin (BSA) and silica nanoparticle mixtures in solutions have been studied using small angle neutron scattering technique by varying the solution temperature. Our study shows that in absence of nanoparticles and up to 70°C, an intermediate range repulsive and one long range attractive interaction potential between the proteins exist. Above that temperature, fractal structure forms. In presence of nanoparticles, fractal structures form even at room temperature by both the protein and nanoparticles. Fractal dimension increases with the increase of BSA concentration and solution temperature, and this temperature induced structural transition is irreversible.

Ionic Liquid Surfactant Mediated Structural Transitions and Self-Assembly of Bovine Serum Albumin in Aqueous Media: Effect of Functionalization of Ionic Liquid Surfactants.

The self-assembly of globular protein bovine serum albumin (BSA) has been investigated in aqueous solutions of ionic liquid surfactants (ILSs), 1-dodecyl-3-methyl imidazolium chloride, [C12mim][Cl], and its amide, [C12Amim][Cl], and ester, [C12Emim][Cl], functionalized counterparts. Dynamic light scattering (DLS) has provided insights into the alterations in hydrodynamic radii (D(h)) of BSA as a function of concentration of ILSs establishing the presence of different types of BSA-ILS complexes in different concentration regimes of ILSs. Isothermal titration calorimetry (ITC) has been exploited to quantify the ILSs interacting with BSA in dilute concentration regime of ILSs. The zeta-potential measurements shed light on changes in the charged state of BSA. The morphology of various self-assembled structures of BSA in different concentration regimes of ILSs have been explored using confocal laser scanning microscopy (CLSM) and scanning electron microscopy. The structural variations in ILSs have been found to produce remarkable effect on the nature and morphology of self-assembled structures of BSA. The presence of nonfunctionalized [C12mim][Cl] IL at all investigated concentrations has led to the formation of unordered large self-assembled structures of BSA. On the other hand, in specific concentration regimes, ordered self-assembled structures such as long rods and right-handedly twisted helical amyloid fibers have been observed in the presence of functionalized [C12Amim][Cl] and [C12Emim][Cl] ILSs, respectively. The nature of the formed helical fibers as amyloid ones has been confirmed using FTIR spectroscopy. Steady-state fluorescence and circular dichroism (CD) spectroscopy have provided insights into folding and unfolding of BSA as fashioned by interactions with ILSs in different concentration regimes supporting the observations made from other studies.

Sucralose Destabilization of Protein Structure.

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. The presence of sucralose in solution is found to destabilize the native structure of two model protein systems: the globular protein bovine serum albumin and an enzyme staphylococcal nuclease. The melting temperature of these proteins decreases as a linear function of sucralose concentration. We correlate this destabilization to the increased polarity of the molecule. The strongly polar nature is manifested as a large dielectric friction exerted on the excited-state rotational diffusion of tryptophan using time-resolved fluorescence anisotropy. Tryptophan exhibits rotational diffusion proportional to the measured bulk viscosity for sucrose solutions over a wide range of concentrations, consistent with a Stokes-Einstein model. For sucralose solutions, however, the diffusion is dependent on the concentration, strongly diverging from the viscosity predictions, and results in heterogeneous rotational diffusion.

Adsorption and conformation variation of BSA protein with the size variation of the metallic nanoparticles in LB film

Abstract Adsorption and conformation variation of globular protein bovine serum albumin (BSA) on the surfaces of different sized gold nanoparticle Langmuir–Blodgett (LB) films have been studied by using atomic force microscopy, UV–vis and FTIR spectroscopy. Films of Au nanoparticles of different sizes were prepared on the quartz substrates by the LB method. Our study reveals that the protein adsorption increases on the nanoparticle covered quartz surfaces with the increase of the nanoparticle size. Moreover, modifications in the secondary conformations of the adsorbed protein occur on the surfaces of the nanoparticles in comparison with the bare quartz surface. Interparticle gap area and gap volume dependent protein adsorption and conformation variation have been proposed.

Deciphering the interaction of a model transport protein with a prototypical imidazolium room temperature ionic liquid: Effect on the conformation and activity of the protein

The present contribution reports the interaction of a prototypical surface-active room temperature ionic liquid (RTIL) viz., 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with a globular transport protein bovine serum albumin (BSA). The BSA–RTIL binding isotherm constructed from conductometric measurements is found to be well reproduced from fluorescence spectroscopy and thus revealing the various interaction zones as a function of the RTIL concentration. The present work delivers particular emphasis to delineate the denaturing action of RTIL on the native protein and in complementarity the effect of RTIL binding on functionality of BSA is explored in terms of esterase-like activity of BSA. The intrinsic time-resolved fluorescence decay and rotational-relaxation dynamics of the protein suggests swelling of the protein rather than aggregation during RTIL-induced denaturation. The result of molecular modeling based on blind docking simulation is found to abet the inferences drawn from experimental results reasonably well. The molecular modeling technique reveals the favorable binding location of the RTIL to be in the hydrophobic domain IIIA (drug site 2) of BSA. The thermodynamic parameters evaluated for the RTIL–BSA binding phenomenon also identifies the pivotal role of hydrophobic force in the interaction.

Protein-directed in situ synthesis of platinum nanoparticles with superior peroxidase-like activity, and their use for photometric determination of hydrogen peroxide

Platinum nanoparticles (Pt-NPs) with sizes in the range from 10 to 30 nm were synthesized using protein-directed one-pot reduction. The model globular protein bovine serum albumin (BSA) was exploited as the template, and the resulting BSA/Pt-NPs were studied by transmission electron microscopy, energy dispersive X-ray spectroscopy, and resonance Rayleigh scattering spectroscopy. The modified nanoparticles display a peroxidase-like activity that was exploited in a rapid method for the colorimetric determination of hydrogen peroxide which can be detected in the 50 μM to 3 mM concentration range. The limit of detection is 7.9 μM, and the lowest concentration that can be visually detected is 200 μM.

Interactions of bovine serum albumin with biological buffers, TES, TAPS, and TAPSO in aqueous solutions

The thermal stability of bovine serum albumin (BSA) in the aqueous solutions containing the biological buffers, N-[tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid (TES), N-[tris(hydroxylmethyl)methyl]-3-aminopropanesulfonic acid (TAPS), and N-[tris(hydroxymethyl)methyl]-3-amino-2-hydroxypropanesulfonic acid (TAPSO), was studied by using dynamic light scattering (DLS) at various temperatures and concentration ranges of buffers. It is found that the increase of the buffer concentration enhanced the thermal stability of protein BSA, and the stabilization tendency follows the order of TAPSO>TES≈TAPS. In this study, we have also investigated the interactions of BSA with TES, TAPS, and TAPSO by using various techniques, such as UV–vis absorption, fluorescence, and molecular docking. It is revealed that the main interactions between the studied buffers and the peptide moieties of proteins are electrostatic including hydrogen bonds. The results obtained from this series of studies confirmed that the biological buffers, TES, TAPS, and TAPSO can serve as good stabilizers for the globular protein BSA, in the aqueous solutions.

Albumin–furcellaran complexes as cores for nanoencapsulation

The possibility of using protein–polysaccharide complexes as cores for nanocapsules formation by sequential adsorption of polyelectrolytes were investigated. We selected the globular protein bovine serum albumin (BSA) and the natural anionic polysaccharide–furcellaran (FUR) and studied their complexation in the broad range of their concentration ratio and pH of the solutions. Analysing the zeta potential dependencies on these parameters, we selected optimal conditions for the core formation. The capsule shells were formed by the layer-by-layer adsorption of polyelectrolytes; polycation PDADMAC (polydiallyl dimethyl ammonium chloride) and polyanion PSS poly(sodium-4-styrene sulfonate). Depending on the shell thickness the size of the capsules was in the range of 60–80nm.

Polymorphism in bovine serum albumin fibrils: morphology and statistical analysis

We investigate the self-assembly process of the globular protein bovine serum albumin (BSA) into fibrillar structures upon incubating the protein solution at high temperature (90 degreeC) and in an acidic environment (pH 2) for several days. The investigation is performed by atomic force microscopy (AFM) on the self-assembled fibrillar structures, adsorbed on mica substrates from a solution at different fibrillation time snapshots. A rigorous study of structural morphology reveals a sophisticated hierarchy of the BSA fibrils, where two major classes can be identified: flexible and rigid fibrils, with an order of magnitude of difference in their stiffness. Furthermore, each main class can be divided into two subclasses of thin and thick fibrils according to their average height. It is also shown that all types of flexible ribbon-like fibrils at some stage can wrap and close into nanotubes, that is into a rigid class of fibril. A precise statistical analysis of all the subclasses identified is developed throughout the manuscript. The determination of height and contour length distributions, persistence lengths, and other topological characteristics is carried out by processing the coordinates of BSA fibrils acquired from AFM imaging using in-house developed software. The resulting statistical analysis allows better understanding the fibrillation process and the structural properties of the BSA fibrils.

Dilational surface viscoelasticity of protein solutions. Impact of urea

The dilational surface rheology is applied to solutions of globular proteins (bovine serum albumin and β-lactoglobulin) in presence of urea. The kinetic dependencies of the dynamic dilational surface elasticity become non-monotonic if the denaturant concentration exceeds a certain critical value indicating the adsorption of unfolded protein molecules. The unfolding in the surface layer occurs at lower urea concentrations than in the bulk phase similar to the case of mixed solutions of the proteins and guanidine hydrochloride. At the same time, the influence of urea on the dilational surface rheological properties of protein solutions has some peculiarities. In particular, the high values of the dynamic surface elasticity close to equilibrium indicate the limited flexibility of unfolded BLG molecules in the surface layer.

Association of gold nanorods in water solutions: Influence of globular proteins

By absorption spectroscopy method optical properties of gold nanorods (10x38 nm) and their interaction with globular protein bovine hemoglobin and bovine serum albumin were investigated. Nanorods behavior was studied in water solution and in solution of 97 mM NaCl under ultrasound action during 90 min and results were then compared. In water solutions nanorods coagulation (aggregation) was observed with reduced optical density of the longitudinal plasmon band widening at lamda>800 nm. In NaCI solution absorption spectra evolution had complex character and was in some degree analogous to the result that was obtained for two-dimensional grids of gold nanoparticles when changing the distance between them. By interacting with serum albumin stabilization of colloid solution and dissociation of nanorods aggregates were observed.

Deciphering the role of pH in the binding of Ciprofloxacin Hydrochloride to Bovine Serum Albumin

The effect of the added fluoroquinolone, Ciprofloxacin Hydrochloride (CpH), on structural properties of Bovine Serum Albumin (BSA) was investigated by Circular Dichroism (CD), steady-state, time-resolved and Dynamic Light Scattering (DLS) spectroscopic approaches. The intrinsic fluorescence of the Tryptophan (Trp) amino acid residue in the globular protein BSA was made use of and the effect of pH at two different temperatures was thoroughly investigated. CD results indicate that CpH induces some structural changes in BSA and this has been well-supported by steady-state, lifetime and DLS data. The fluorescence intensity of Trp gradually decreases with the rise in concentration of CpH and we have conclusively proved that at pH 7.4 and 9.2, the mechanism of fluorescence quenching is mostly dynamic in nature, whereas at pH 4.5 mainly static quenching is operational. Thermodynamic parameters have been studied to rationalize the nature of binding of CpH to BSA, and we have concluded that hydrophobic and van der Waals forces play an important role in the process of drug-protein interaction at three different pH values. The lifetime of Trp was found to decrease with the rise in CpH concentration and the percentage reduction in lifetime was found to be a function of the pH of the medium under investigation.

Measurement of the thickness of ultra-thin adsorbed globular protein layers with dual-polarisation interferometry: a comparison with neutron reflectivity

Dual-polarisation interferometry (DPI) was used to investigate the effectiveness of the random sequential adsorption (RSA) model to describe the adsorption of the globular proteins bovine serum albumin (BSA) and transferrin at the silicon/water interface. DPI provided an almost real-time view of dynamic protein adsorption. The results showed that initial BSA adsorption followed the Langmuir kinetic model below a protein concentration of 0.5 mg ml−1 and the random sequential adsorption kinetic model of particle deposition at and above 0.5 mg ml−1. At long adsorption times the predicted t−1/2 scaling law for the dependence of the surface coverage on time as the globular particles approached the 2-D jamming limit was observed for BSA over 3 logarithms in time and for transferrin over 4 logarithms. Furthermore, BSA adsorption was used as a model system to compare measurements of surface coverage and layer thickness as measured by DPI and neutron reflectivity (NR) at a pulsed spallation source (SURF at ISIS). The analysis of the DPI data based on a simplified single-layer model was capable of accurately determining the overall protein layer thicknesses over a large concentration range for these ultra-thin adsorbed layers (thickness ≤7 nm, surface coverage 0–3.5 mg m−2). NR required a two-layer model to cover the same concentration range. NR data modelling showed non-uniform density distributions of adsorbed BSA over the high surface coverage range, clearly indicating changes of protein conformation with concentration. Differences in equilibrium thicknesses between the DPI and NR techniques are discussed.

Comparative assessment of structural and biological properties of biomimetically coated hydroxyapatite on alumina (α‐Al2O3) and titanium (Ti‐6Al‐4V) alloy substrates

Previous reports have shown the use of hydroxyapatite (HAp) and related calcium phosphate coatings on metal and nonmetal substrates for preparing tissue-engineering scaffolds, especially for osteogenic differentiation. These studies have revealed that the structural properties of coated substrates are dependent significantly on the method and conditions used for coating and also whether the substrates had been modified prior to the coating. In this article, we have done a comparative evaluation of the structural features of the HAp coatings, prepared by using simulated body fluid (SBF) at 25 degrees C for various time periods, on a nonporous metal substrate titanium-aluminium-vanadium (Ti-6Al-4V) alloy and a bioinert ceramic substrate alpha-alumina (alpha-Al(2)O(3)), with and without their prior treatment with the globular protein bovine serum albumin (BSA). Our analysis of these substrates by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectrometry showed significant and consistent differences in the quantitative and qualitative properties of the coatings. Interestingly, the bioactivity of these substrates in terms of supporting in vitro cell adhesion and spreading, and in vivo effects of implanted substrates, showed a predictable pattern, thus indicating that some coated substrates prepared under our conditions could be more suitable for biological/biomedical applications.

Protein diffusion in crowded electrolyte solutions

We report on a combined cold neutron backscattering and spin-echo study of the short-range and long-range nanosecond diffusion of the model globular protein bovine serum albumin (BSA) in aqueous solution as a function of protein concentration and NaCl salt concentration. Complementary small angle X-ray scattering data are used to obtain information on the correlations of the proteins in solution. Particular emphasis is put on the effect of crowding, i.e. conditions under which the proteins cannot be considered as objects independent of each other. We thus address the question at which concentration this crowding starts to influence the static and in particular also the dynamical behaviour. We also briefly discuss qualitatively which charge effects, i.e. effects due to the interplay of charged molecules in an electrolyte solution, may be anticipated. Both the issue of crowding as well as that of charge effects are particularly relevant for proteins and their function under physiological conditions, where the protein volume fraction can be up to approximately 40% and salt ions are ubiquitous. The interpretation of the data is put in the context of existing studies on related systems and of existing theoretical models.

Effect of proteins on the self-assembly of multiring structural ZrO 2 nanodisks

Compared to the air–water interfacial zirconia film with regularly multiring structure self-assembled by using zirconium(IV) butoxide as precursor, sodium dodecyl sulfonate (SDS) as template and gelatin (G) as stabilizer, another kind of multiring structural ZrO 2 nanodisks has been prepared in the presence of the globular protein bovine serum albumin (BSA). X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS), etc. have been used to characterize morphologies, high ordered structures and components for the assembled ZrO 2 film. Results show that both G and BSA could help to assemble multiring structural ZrO 2 films. The difference is that the multiring nanodisk assembled with BSA seems to be relatively defective compared to the product prepared with G, due to the better ability of G to stabilize the micelles of surfactant templates. Remarkably, this self-assembly method may be widely applied in preparing many functional metal oxide nanofilms and proteins will play important roles in assembling well ordered structures inside those films.

Study of proteinous and micellar microenvironment using donor acceptor charge transfer fluorosensor N,N-dimethylaminonaphthyl-(acrylo)-nitrile

Interaction of charge transfer fluorophore N,N-dimethylaminonaphthyl-(acrylo)-nitrile (DMANAN) with globular proteins Human Serum Albumin (HSA) and Bovine Serum Albumin (BSA) brings forth a marked change in the position and intensity of band maxima both in case of absorption and fluorescence spectra. Spectroscopic approach has been elaborately implemented to explore the binding phenomena of the probe with HSA and BSA and it is found that the extent of binding of the probe to both serum albumins is similar in nature. Steady state fluorescence anisotropy values, fluorescence quenching study using acrylamide quencher and Red Edge Excitation Shift (REES) help in drawing reliable conclusions regarding the location of the probe molecule within the hydrophobic cavity of the proteins. An increase in fluorescence lifetime of the probe molecule solubilized in both the proteinous media also indicate that the probe is located at the motionally restricted environment inside the hydrophobic cavity of proteins and hence non-radiative channels are less operative than in the bulk water. Similarly, the variation of position and intensity of the emission maxima of DMANAN solubilized in micellar medium of Sodium Dodecyl Sulphate (SDS) also predicts well the critical micellar concentration (CMC) and polarity of micellar microenvironment.

Characterization of Globular Protein Solutions by Dynamic Light Scattering, Electrophoretic Mobility, and Viscosity Measurements

In this work, physicochemical properties of two globular proteinsbovine serum albumin (BSA) having a molecular weight of 67 kDa and human serum albumin (HSA) having a molecular weight of 69 kDawere characterized. The bulk characteristics of these proteins involved the diffusion coefficient (hydrodynamic radius), electrophoretic mobility, and dynamic viscosity as a function of protein solution concentration for various pH values. The hydrodynamic radius data suggested an association of protein molecules, most probably forming compact dimers. Using the hydrodynamic diameter and the electropheretic mobility data allowed the determination of the number of uncompensated (electrokinetic) charges on protein surfaces. The electrophoretic mobility data were converted to zeta potential values, which allowed one to determine the isoelectric point (iep) of these proteins. It was found to be at pH 5.1 for both proteins, in accordance with previous experimental data and theoretical estimations derived from amino acid composition and p K values. To determine further the stability of protein solutions, dynamic viscosity measurements were carried out as a function of their bulk volume concentration for various pH values. The intrinsic viscosity derived from these measurements was interpreted in terms of the Brenner model, which is applicable to hard spheroidal particles. It was found that the experimental values of the intrinsic viscosity of these proteins were in good agreement with this model when assuming protein dimensions of 9.5 x 5 x 5 nm3 (prolate spheroid). The possibility of forming linear aggregates of association degree higher than 2 was excluded by these measurements. It was concluded that the combination of dynamic viscosity and dynamic light scattering can be exploited as a convenient tool for detecting not only the onset of protein aggregation in suspensions but also the form and composition of these aggregates.

Non-Newtonian behavior of concentrated emulsions stabilized with globular protein in the presence of nonionic surfactant

Changes in the rheological properties of a model concentrated oil-in-water emulsion stabilized with globular protein (bovine serum albumin) upon the addition of nonionic surfactant polyoxyethylene (20) sorbitan monooleate (Tween 80) are studied. Non-Newtonian behavior is typical of the emulsions in question; moreover, they are characterized by the existence of yield stress. At stresses above the yield stress, the viscosity drops not immediately but after the intermediate Newtonian region at the flow curve. For all systems studied, the total flow curve is exhibited with the minimum Newtonian viscosity that is adequately described by the Cross formula. An increase in the Tween 80 concentration leads to a decrease in the viscosity of emulsion. Two threshold phenomena on the concentration dependences of rheological properties are revealed: at low concentration of added nonionic surfactant, the yield stress drops abruptly, whereas the viscosity lowers considerably with an increase in surfactant concentration to 1 × 10−3 mol/l and the emulsion becomes unstable. The effects observed can be explained by the gradual displacement of high-molecular-weight stabilizer from interfacial layers and its replacement by nonionic surfactant.