Globular Protein Bovine Serum Albumin Research Articles

Concentration Dependence of Elastic and Viscoelastic Properties of Aqueous Solutions of Ficoll and Bovine Serum Albumin by Brillouin Light Scattering Spectroscopy.

The cellular environment is crowded with macromolecules of different shapes and sizes. The effect of this macromolecular crowding has been studied in a variety of synthetic crowding environments: two popular examples are the compact colloid-like Ficoll macromolecule and the globular protein bovine serum albumin (BSA). Recent studies have indicated that a significant component of bound or surface-associated water in these crowders reduces the available free volume. In this work, Brillouin light scattering experiments were performed on aqueous solutions of Ficoll 70 and Ficoll 400 with concentrations ranging from 1 to 35 wt % and BSA with concentrations of 1 to 27 wt %. From the dependence of spectral peak parameters on polymer concentration, we determined fundamental solution properties: hypersound velocity, adiabatic bulk modulus and compressibility, apparent viscosity, and hypersound attenuation. The existing theory that ignores intermolecular interactions can capture only the observed linear trends in the frequency shift up to a threshold concentration, beyond which a quadratic term accounting for intermolecular interactions is necessary. This likely indicates a transition from the dilute to semidilute regime. In the Ficoll solutions (but not BSA), we see evidence for a central mode, which is indicative of relaxation in the hydration shell of Ficoll.

Phase partitioning nature, interaction forces and thermodynamic parameters of triton X-100 and bovine serum albumin mixture: impacts of the composition of Na-salt

Herein, the assessment of interactions between a non-ionic surfactant (NIS) triton X-100 (TNX-100) and a globular protein bovine serum albumin (BSA) was explored through the determination of clouding nature in aqueous solution of sodium salts (Na-salts). Sodium chloride (NaCl), sodium acetate (NaOAc), sodium carbonate (Na2CO3), sodium oxalate (Na2Oxal), sodium sulphate (Na2SO4), and sodium phosphate (Na3PO4) have been chosen to assess their impacts on the clouding nature of TNX-100 + BSA mixture. The estimated cloud point (CP) values were noticed to be lowered with the enhancement of [Na-salts]. The lessening of CP values has been explained by the salting out effect of anions. The calculated standard Gibbs free energy change ( Δ G c o ) was positive at all examined conditions which illustrates the nonspontaneity of phase change. The standard enthalpy ( Δ H c o ) and entropy ( Δ S c o ) changes exhibited negative values at low contents of aq. Na-salts and positive values at high aq. Na-salts content. These consequences illustrate the presence of electrostatic interactions at low Na-salts concentration and hydrophobic interactions at high Na-salts concentration. Furthermore, enthalpy-entropy parameters were successfully computed and explained with proper clarification.

Developing targeted drug delivery carriers for breast cancer using glutathione-sensitive doxorubicin-coupled glycated bovine serum albumin nanoparticles

Incorporation of the nano-based carriers into drug delivery provides a promising alternative to overcome the limitations of the conventional chemotherapy. Doxorubicin (DOXO) is an effective chemotherapeutic drug widely used in chemotherapy for breast cancer treatment. A globular protein bovine serum albumin (BSA) holds great potential as carriers in pharmaceutical applications. This work is aimed at developing the DOXO-coupled glycated BSA nanoparticles via desolvation method for improving the capability of targeting the GLUT5 transporters over-expressed on breast cancer cells. Fructosamine assay and Fourier transform infrared spectroscopy were employed to determine the content of fructosamine structure and structural changes on the surfaces of nanoparticles, respectively. Additionally, the synthesized BSA nanoparticles were further characterized by electron microscopy and dynamic light scattering. Results revealed that the DOXO-coupled glycated BSA nanoparticles were spherically shaped with a hydrodynamic diameter of ~60.74 nm and a ζ-potential of ~ − 42.20 mV. Moreover, the DOXO release behavior of as-synthesized DOXO-coupled glycated BSA nanoparticles was examined under different conditions. Finally, the DOXO-coupled glycated BSA nanoparticles were found to exhibit cytotoxicity toward both MCF-7 and MDA-MB-231 cells. Our findings evidently suggested that the drug-coupled glycated BSA nanoparticles serve as the potential candidates for targeted drug delivery platform used in breast cancer therapy.

Cleavage of disulfide bonds used to reveal manifestation of tertiary structure in the Raman spectra of proteins

Raman spectroscopy is used in the study of the tertiary structure of proteins. The effect of cleavage of disulfide bonds (using DTT and TCEP agents) on the molecular structure and, hence, vibrational spectra is studied. Spectra of two globular proteins (chymotrypsin and bovine serum albumin) are compared with the spectra of the two proteins the structure of which is modified due to cleavage of disulfide bonds. Changes in spectral intervals of 500–550 and 2500–2620 cm-1 indicate disulfide bond breaking. Based on the comparative analysis of the spectral changes in the fingerprint region (in particular, amide I, amide III, tyrosine doublet, bands of disulfide bonds) and low-frequency region, we assume that spectral intervals of 140–470, 500–550, and 800–1000 cm-1 can be used in the study of changes of the tertiary structure.

Retrospective rationalization of disparities between the concentration dependence of diffusion coefficients obtained by boundary spreading and dynamic light scattering.

This study establishes the existence of substantial agreement between published results from traditional boundary spreading measurements (including synthetic boundary measurements in the analytical ultracenrifuge) on two globular proteins (bovine serum albumin, ovalbumin) and the concentration dependence of diffusion coefficient predicted for experiments conducted under the operative thermodynamic constraints of constant temperature and solvent chemical potential. Although slight negative concentration dependence of the translational diffusion coefficient is the experimentally observed as well as theoretically predicted, the extent of the concentration dependence is within the limits of experimental uncertainty inherent in diffusion coefficient measurement. Attention is then directed toward the ionic strength dependence of the concentration dependence coefficient ([Formula: see text]) describing diffusion coefficients obtained by dynamic light scattering, where, in principle, the operative thermodynamic constraints of constant temperature and pressure preclude consideration of results in terms of single-solute theory. Nevertheless, good agreement between predicted and published experimental ionic strength dependencies of [Formula: see text] for lysozyme and an immunoglobulin is observed by a minor adaptation of the theoretical treatment to accommodate the fact that thermodynamic activity is monitored on the molal concentration scale because of the constraint of constant pressure that pertains in dynamic light scattering experiments.

Complexity of the Role of Various Site-Specific and Selective Sudlow Binding Site Drugs in the Energetics and Stability of the Acridinedione Dye-Bovine Serum Albumin Complex: A Molecular Docking Approach.

Molecular docking (Mol.Doc) techniques were employed to ascertain the binding affinity of two resorcinol-based acridinedione dyes (ADR1 and ADR2) with the widely studied globular protein Bovine Serum Albumin (BSA) in the presence of site-selective binding drugs by Autodock Vina 4.2 software. Docking of various feasible conformers of ADR1 dye with BSA was found to be energetically more favored than ADR2 dye, even though both these dyes differ in the 9th position of the basic dye structure. Analysis of dyes with BSA establishes the location of dye in all of the binding sites of BSA, predominantly through conventional and nonconventional hydrogen-bonding (HB) interactions. The coexistence of hydrophobic interactions resulted in the stability of various conformers generated. The introduction of site I and site II (Sudlow site binding drugs) into ADR1-BSA and ADR2-BSA complexes effectively destabilizes the dye-protein complex; however, the drugs do not displace ADR dyes completely from their selective binding domains. Site II binding drugs effectively destabilize the binding ability of the dye-protein complex rather than site I drugs. However, docking of site I drug 3-carboxyl-4-methyl-5-propyl-2-furanpropanic acid (CMPF) largely destabilizes the ADR1-protein complex, whereas indomethacin (INDO) enhances the binding affinity of the ADR2-protein complex. Interestingly, simultaneous docking of ADR dyes to the BSA-drug complex results in larger stability of the protein-drug complex through HB interactions rather than hydrophobic interactions. Both ADR1 and ADR2 dyes predominantly occupy the Sudlow binding sites of BSA, and the introduction of either site I or site II binding drugs does not displace the dye efficiently from the corresponding binding sites, rather the drugs are effectively displaced toward other binding domains apart from their specific site-binding domains of BSA. Through Mol.Doc techniques, we authenticate that the interactions in host-guest complex systems involving competing ligands are established in depth, wherein the dye as well as the amino acid (AA) moieties in BSA act as both HB donor and acceptor sites apart from several hydrophobic interactions coexisting toward the stability.

Dielectric relaxation of ice in a partially crystallized poly(N-isopropylacrylamide)microgel suspension compared to other partially crystalized polymer-water mixtures.

A broadband dielectric spectroscopy study was conducted on a partially crystallized 10 wt% poly(N-isopropylacrylamide) [PNIPAM] microgel aqueous suspension to investigate the dielectric relaxation of ice in microgel suspensions. The measurements covered a frequency range of 10 mHz to 10 MHz and at temperatures ranging from 123 K to 273 K. Two distinct relaxation processes were observed at specific frequencies below the melting temperature. One is associated with the combination of the local chain motion of PNIPAM and interfacial polarization in the uncrystallized phase, while another is associated with ice. To understand the temperature-dependent behaviour of the ice relaxation process, the relaxation time of ice was compared with those observed in other frozen polymer water mixtures, including gelatin, poly-vinylpyrrolidone (PVP), and bovine serum albumin (BSA). For concentrations ≥ 10 wt%, the temperature dependence of the relaxation time of ice was found to be independent. Therefore, the study primarily focused on the 10 wt% data for easier comprehension of the ice relaxation process. It was found that the microgel and globular protein BSA had no significant effect on ice crystallization, while gelatin slowed down the crystallization process, and PVP accelerated it. To discuss the mechanism of the dielectric relaxation of ice, the trap-controlled proton transport model developed by Khamzin et al. [Chem. Phys., 2021, 541, 111040.] was employed. The model was used to discuss the dynamic heterogeneity of ice observed in this investigation, distinguishing it from the spatial heterogeneity of ice commonly discussed.

Structure and morphology of adsorbed protein (BSA) layer on hydrophilic silicon surface in presence of mono-, di- and tri-valent ions

Out-of-plane structure and surface morphology of the adsorbed thin films of globular protein bovine serum albumin (BSA) are investigated using X-ray reflectivity (XRR) and atomic force microscopy (AFM). BSA adsorption on hydrophilic silicon surface is done by dip coating method in absence and presence of mono- (Na + ), di- (Ca 2+ ) and tri- (La 3+ and Y 3+ ) valent ions in BSA solution for different salt concentrations. Unlike mono- and di-valent ions, BSA shows re-entrant phase transition for tri-valent ions like La 3+ and Y 3+ with their concentration variation. XRR study shows that the thickness of the adsorbed BSA layer slightly increases with the increase of mono- and di-valent ions concentration, while for tri-valent ions, considerable amount of thickness is obtained when the film is deposited from the condensed phase under re-entrant condensation and becomes relatively less with salt concentrations lower or higher than that particular salt concentration, however, thickness is again increased for higher salt concentration. Surface morphologies of the films are also modified with the variation of the salt type and their concentration. Thus, structural and morphological changes of the adsorbed protein layer on hydrophilic surface and the probable reason for such modifications are explored in the presence of different valent ions with their concentration variation. • BSA adsorption on hydrophilic surface is done in absence/presence of ions. • In presence of mono- and di-valent ions, bilayer-like structure is formed. • For tri-valent ions, concentration dependent structures are formed. • At turbid phase, tilted molecules are shifted vertically to form a trilayer-like structure. • Surface morphologies of adsorbed BSA films depend on salt type and concentration.

Globular protein assembly and network formation at fluid interfaces: effect of oil.

The formation of viscoelastic networks at fluid interfaces by globular proteins is essential in many industries, scientific disciplines, and biological processes. However, the effect of the oil phase on the structural transitions of proteins, network formation, and layer strength at fluid interfaces has received little attention. Herein, we present a comprehensive study on the effect of oil polarity on globular protein networks. The formation dynamics and mechanical properties of the interfacial networks of three different globular proteins (lysozyme, β-lactoglobulin, and bovine serum albumin) were studied with interfacial shear and dilatational rheometry. Furthermore, the degree of protein unfolding at the interfaces was evaluated by subsequent injection of disulfide bonds reducing dithiothreitol. Finally, we measured the interfacial layer thickness and protein immersion into the oil phase with neutron reflectometry. We found that oil polarity significantly affects the network formation, the degree of interfacial protein unfolding, interfacial protein location, and the resulting network strength. These results allow predicting emulsion stabilization of proteins, tailoring interfacial layers with desired mechanical properties, and retaining the protein structure and functionality upon adsorption.

Effect of nanoscale surface topography on the adsorption of globular proteins

Protein adsorption is the initial step in the response of biological systems to artificial surfaces and thus a ubiquitous phenomenon in biomedicine and tissue engineering. Here, we investigate the adsorption of the three globular proteins myoglobin (MGB), thyroglobulin (TGL), and bovine serum albumin (BSA) at flat and nanorippled SiOx/Si and TiOx/Ti surfaces. Despite having lateral and vertical dimensions of only about 30 nm and less than 2 nm, respectively, these nanoripples influence protein adsorption and adsorption-induced protein denaturation in a highly protein- and material-specific way. Adsorption of small, positively charged MGB results in preferential protein alignment along the nanoripples on both oxide surfaces. The larger and strongly negatively charged TGL forms layers of similar thickness on all four surfaces except the nanorippled TiOx/Ti surface. Here, a smaller layer thickness is attributed to different denaturation states of the adsorbed proteins. Similarly, the smaller and less negatively charged BSA shows different degrees of denaturation on the flat and rippled SiOx/Si surfaces. Our results thus demonstrate that topographic surface features with vertical dimensions well below 10 nm may have a surprisingly strong effect on protein adsorption and thus need to be considered in the interaction of biological systems even with apparently flat surfaces.

Macromolecular Structure of a Commercial Humic Acid Sample

The molecular structure of a commercial sample of humic acids (HA) was investigated by membrane dialysis experiments (MD) and low-pressure size-exclusion chromatography (LP-SEC). MD showed that HA molecules were retained by dialysis membrane with a cut-off of 6–8 kDa, independently from HA concentration (15 or 150 mg L−1), NaHCO3 concentration (0.005–2.0 mol L−1), and from propan 2-ol (0–5 v/v %). SEC experiments at low pressure gave chromatograms with a broad peak, with an elution volume between those of the globular proteins bovine serum albumin (molecular weight = 66.5 kDa) and lysozyme from egg (molecular weight = 14.4 kDa). The pattern of the chromatogram did not vary with HA concentration, and second-run chromatograms of single eluted fractions showed relatively sharp peaks. From these data, we reveal that the commercial HA sample analysed has a macromolecular structure rather than being a supramolecular aggregate of relatively small molecules, as recently proposed for some samples of HA obtained from different sources.

Packing and dynamics of a protein solution approaching the jammed state.

The packing of proteins and their collective behavior in crowded media is crucial for the understanding of biological processes. Here we study the structural and dynamical evolution of solutions of the globular protein bovine serum albumin with increasing concentration via drying using small angle X-ray scattering and dynamic light scattering. We probe an evolving correlation peak on the scattering profile, corresponding to the inter-protein distance, ξ, which decreases following a power law of the protein volume fraction, φ. The rate of decrease in ξ becomes faster above a protein concentration of ∼200 mg ml-1 (φ = 0.15). The power law exponent changes from 0.33, which is typical of colloidal or protein solutions, to 0.41. During the entire drying process, we observe the development and the growth of two-step relaxation dynamics with increasing φ as revealed by dynamic light scattering. We find three different regimes of the dependence of ξ as a function of φ. In the dilute regime (φ < 0.22), protein molecules are far apart from each other compared to their size. In this case, the dynamics mainly corresponds to Brownian motion. At an intermediate concentration (0.22 < φ < 0.47), inter-protein distances become comparable to the size of protein molecules, leading to a preferential orientation of the ellipsoidal protein molecules along with a possible deformation. In this regime, the dynamics shows two distinct relaxation times. At a very high concentration (φ > 0.47), the system reaches a jammed state. Subsequently, the secondary relaxation time in this state becomes extremely slow. In this state, the protein molecules have approximately one hydration layer. This study contributes to the understanding of protein molecular packing in crowded environments and the phenomenon of density-driven jamming for soft matter systems.

Förster Resonance Energy Transfer-Mediated Globular Protein Sensing Using Polyelectrolyte Complex Nanoparticles.

Polyelectrolyte complex nanoparticles (PEC NPs) are synthesized using two oppositely charged polyelectrolytes, i.e., anionic poly(sodium 4-styrene sulfonate) (PSS) and cationic poly(diallyldimethylammoniumchloride), at molar mixing ratios (n–/n+) of ≈0.4, 0.67, 0.75, and 1.5 by applying consecutive centrifugation to modify the optical property of PSS. However, for n–/n+ ≈ 0.75, PEC NPs exhibit a larger blue shift and a specific emission peak occurs at ≈278 nm for the 225 nm excitation. The mechanism of such modification of PSS emission after complex formation is proposed. This specific emission by PEC NPs nearly matches with the optical absorption wavelength of globular proteins. The emission intensity of PEC NPs is therefore quenched in the presence of globular proteins (bovine serum albumin, human serum albumin, lysozyme, and hemoglobin) through resonance energy transfer between the donor (PEC NPs) and acceptor (globular proteins). The spectral overlap integral and the variation of the separation distance from 1.8 to 2.5 nm between the donor and acceptor confirm the resonance energy transfer. Sensing of proteins by the PEC NPs is possible within the detection limit of 5 nM and therefore such PEC NPs can be used as an efficient and promising protein sensing material.

Electric Field Deformation of Protein-Coated Droplets in Thin Channels.

High-strength droplet interfaces are attractive for many applications, specifically in cases where droplets are channeled through fluidic devices and manipulated by electromagnetic fields. Using models and experiments, we study the deformation of droplets and capsules with protein interfaces in an electric field in thin and wide electrode gaps. Proteins are chosen from candidates expected to display qualitatively different interfacial interactions and strengths: a globular protein (bovine serum albumin), a reversible cross-linking peptide (AFD4), and a hydrophobin (cerato ulmin). Dilute protein additives can lead to over 1 order of magnitude stronger oil-water interfaces than those stabilized by small surfactants. We develop small deformation models to evaluate a protein membrane's interfacial elasticity, notably accounting for the electric field perturbation encountered in a gap and a careful treatment of a generalized elastic interface with both surface tension and interfacial elasticity. Results indicate that globular proteins, which typically have comparable surface tension and interfacial elasticity, can be modeled well by this generalized elastic interface. We further find that when in a gap, droplets and capsules migrate toward one electrode, deform asymmetrically, exhibit polar spreading on the electrode, and predictably stretch more than in the infinite gap scenario at constant field strength.

Photophysical study of the interaction between ZnO nanoparticles and globular protein bovine serum albumin in solution and in a layer-by-layer self-assembled film

In this study, we investigated the spectroscopic properties of the water-soluble globular protein bovine serum albumin (BSA) while interacting with zinc oxide (ZnO) semiconductor nanoparticles (NPs) in aqueous medium and in a ZnO/BSA layer-by-layer (LbL) self-assembled film fabricated on poly (acrylic acid) (PAA)-coated quartz or a Si substrate via electrostatic interactions. BSA formed a ground state complex due to its interaction with ZnO NPs, which was confirmed by ultraviolet–visible absorption, and steady state and time-resolved fluorescence emission spectroscopic techniques. However, due to its interaction with ZnO, the photophysical properties of BSA depend significantly on the concentration of ZnO NPs in the mixed solution. The quenching of the fluorescence intensity of BSA in the presence of ZnO NPs was due to the interaction between ZnO and BSA, and the formation of their stable ground state complex, as well as energy transfer from the excited BSA to ZnO NPs in the complex nano-bioconjugated species. Multilayer growth of the ZnO/BSA LbL self-assembled film on the quartz substrate was confirmed by monitoring the characteristic absorption band of BSA (280 nm), where the nature of the film growth depends on the number of bilayers deposited on the quartz substrate. BSA formed a well-ordered molecular network-type morphology due to its adsorption onto the surface of the ZnO nanostructure in the backbone of the PAA-coated Si substrate in the LbL film according to atomic force microscopic study. The as-synthesized ZnO NPs were characterized by field emission scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering techniques.

Structures and interactions among globular proteins above the isoelectric point in the presence of divalent ions: A small angle neutron scattering and dynamic light scattering study

Small angle neutron scattering study reveals that at pD ≈ 7.0, above the isoelectric point of the globular protein Bovine Serum Albumin (BSA), in the presence of different divalent ions (Mg2+, Ca2+, Sr2+ and Ba2+), the short-range attractive interaction remains nearly constant and the intermediate-range repulsive interaction decreases with increasing salt concentration up to a certain concentration value but after that remains unchanged. However, for the monovalent ion (Na+), repulsive interaction decreases gradually up to 1 M salt concentration. Dynamic light scattering study shows that for all ions, diffusion coefficient of BSA decreases with increasing salt concentration and then nearly saturates.

Self-assembled nanostructures from amphiphilic globular protein–polymer hybrids

Amphiphilic globular protein–polymer hybrids, consisting of poly(methyl methacrylate) (PMMA) as hydrophobic tail and globular protein as hydrophilic head, are prepared by the end-functional PMMA covalently binding to the primary amino groups of bovine serum albumin (BSA) in the phosphate buffer saline (PBS)/acetone mixture solvents at pH 5. The self-assembly behaviors of amphiphilic BSA–PMMA hybrids are explored in aqueous solution by the dynamic light scatter (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The self-assembled morphologies of the amphiphilic BSA–PMMA hybrids are controlled by the length of hydrophobic PMMA chains. The amphiphilic BSA–PMMA hybrids with the longer hydrophobic PMMA chains self-assembled into spherical vesicles and elongated tubular vesicles, and conversely, they self-assembled into micelles. A vesicle consists of BSA as two outer hydrophilic layers and PMMA as hydrophobic wall. Amphiphilic globular protein–polymer hybrids consist of PMMA as hydrophobic tail and globular protein BSA as hydrophilic head. Amphiphilic globular protein–polymer hybrids self-assembled into micelles or vesicles in phosphate buffer saline. The self-assembled morphology of amphiphilic protein–polymer hybrids was controlled by adjusting the length of hydrophobic chains.

Mode of action of betaine on some amino acids and globular proteins: Thermodynamic considerations

The interactions of the amino acids glycine, l-alanine, dl-α-amino-n-butyric acid, l-valine, and l-leucine have been studied based on values of apparent molar volume (V2,m,ϕ) and apparent molar compressibility (Ks,2,m,ϕ) in 1mol·kg−1 and 2mol·kg−1 aqueous betaine solutions at T=298.15K. These thermodynamic quantities have been calculated from density and sound velocity measurements. Isothermal titration calorimetry has been employed to determine the values of enthalpies of interaction of aqueous solutions of these amino acids with betaine. These data have been further used to calculate values of infinite dilution standard partial molar volumes (V2,mo), standard partial molar isentropic compressibilities (Ks,2,mo) and limiting enthalpies of dilution (ΔdilHmo) of these amino acids in aqueous betaine solutions. The standard partial molar volumes of transfer (ΔtrV2,mo), isentropic compressibilities of transfer (ΔtrKs,2,mo) and enthalpies of dilution of transfer Δtr(ΔdilHom) of amino acids from water to aqueous betaine solutions have been calculated from the measured data in order to understand possible intermolecular interactions such as ion-ion, ion-polar, hydrophilic-hydrophobic and hydrophobic-hydrophobic group interactions. The contributions of the end groups {(NH3+, COO−), CH2 groups and the other alkyl chains of the amino acids to V2,mo} have also been determined. The interactions of betaine with the globular proteins α-lactalbumin and bovine serum albumin have also been studied. Such studies are important in obtaining information on the action of osmolytes on proteins and their constituents and establishing possible correlations.

Strong Isotope Effects on Effective Interactions and Phase Behavior in Protein Solutions in the Presence of Multivalent Ions.

In this article, we have studied the influence of the isotopic composition of the solvent (H2O or D2O) on the effective interactions and the phase behavior of the globular protein bovine serum albumin in solution with two trivalent salts (LaCl3 and YCl3). Protein solutions with both salts exhibit a reentrant condensation phase behavior. The condensed regime (regime II) in between two salt concentration boundaries (c* < cs < c**) is significantly broadened by replacing H2O with D2O. Within regime II, liquid-liquid phase separation (LLPS) occurs. The samples that undergo LLPS have a lower critical solution temperature (LCST). The value of LCST decreases significantly with increasing solvent fraction of D2O. The effective protein-protein interactions characterized by small-angle X-ray scattering demonstrate that although changing the solvent has negligible effects below c*, where the interactions are dominated by electrostatic repulsion, an enhanced effective attraction is observed in D2O above c*, consistent with the phase behavior observed. As the LCST-LLPS is an entropy-driven phase transition, the results of this study emphasize the role of entropy in solvent isotope effects.

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.