Mixture Of Bovine Serum Albumin Research Articles

Carrier-Guided Proteome Analysis in a High Protein Background: An Improved Approach to Host Cell Protein Identification.

Many shotgun proteomics experiments are negatively influenced by highly abundant proteins, such as those measuring residual host cell proteins (HCP) amidst highly abundant recombinant biotherapeutic or plasma proteins amidst albumin and immunoglobulins. While western blotting and ELISAs can reveal the presence of specific low abundance proteins from highly abundant background proteins, mass spectrometry approaches are required to define the low abundance protein composition in these scenarios. The challenge in detecting low abundance proteins in a high protein background by standard shotgun approaches is that spectra are often not triggered on their peptides in data dependent acquisition methods but rather on the highly abundant background peptides. Here, we use tandem mass tags (TMT) to introduce a carrier proteome approach to enhance the detection of proteins, such as from residual host cell proteomes amidst a highly abundant background. Using a mixture of bovine serum albumin (BSA) and E. coli as a mock high background/low abundance target protein formulation, we demonstrate proof-of-principle experiments allowing the improved detection of target proteins amidst a high protein background. While we observed significant coisolation interference, we mitigated it by using a spike-in interference detection TMT channel. Finally, we use the approach to identify 300 residual E. coli proteins from a protein A pulldown of a human IgG antibody, demonstrating that it may be applicable to analysis of HCPs in biotherapeutic protein formulations.

Phase separation, aggregation, and complexation of triton-X100 and bovine serum albumin mixture: A combined cloud point and UV–visible spectroscopic approaches

Phase separation and aggregation behaviour of triton X-100 (TX-100) and bovine serum albumin (BSA) mixture were investigated using cloud point and UV–visible spectroscopic techniques. The effects of various hydrotropes (HYTs) - namely, sodium salicylate (SS), sodium benzoate (SB), glycerol (Glyc), and 4-aminobenzoic acid (4-ABA) - on the cloud point (CP) of TX-100 + BSA were determined. The obtained CP values for the mixed system in the presence of HYTs followed the order:CPH2O+4−ABA<CPH2O+Glyc<CPH2O+SB<CPH2O+SS. The measured critical micellization concentration (CMC) values of the TX-100 + BSA mixture were found to be significantly altered with varying amounts of BSA. The calculated free energy of clouding and micellization indicated the non-spontaneous nature of the phase transition and the spontaneous association of the TX-100 + BSA mixture. The non-spontaneity of phase separation decreased with increasing concentrations of HYTs. The enumerated values of ∆Hco and ∆Sco were consistently recorded as negative and positive magnitudes, respectively, in all aqueous HYTs media. The clouding process occurred due to a combination of hydrophobic and electrostatic interactions. The binding constant of the mixed system was determined employing the UV–vis spectroscopic method using the Benesi-Hildebrand equation.

Triggered protein release from calcium alginate/chitosan gastro-resistant capsules

This work aimed to develop gastro-resistant capsules, based on alginate (Alg), as an oral delivery system for enhanced bioavailability of proteins. Bovine Serum Albumin (BSA), selected as a model protein, has been encapsulated inside calcium alginate capsules, which have been coated with a thin layer of chitosan (CHT) to improve its robustness and delivery profile. BSA and sodium alginate aqueous mixtures were characterized by optical microscopy and dynamic light scattering, suggesting that BSA and sodium alginate form water-in-water coacervate droplets by ionic complexation. Encapsulation of BSA-Alg colloidal dispersions was performed by introducing the BSA-Alg mixtures in CaCl2 solutions. Thus, calcium alginate capsules were formed, which were subsequently coated with CHT. Encapsulation of BSA achieved ≈99 % efficiency, the water content of capsules was ≈95 wt % and the amount of chitosan coating in wet capsules was <0.032 wt %. The stability of the capsules and the release of BSA were studied by several in vitro techniques, in simulated gastric and intestinal fluids. The addition of CHT as a coating material greatly improved the performance of the capsules, compared to that of capsules without CHT. The results of calcium alginate-chitosan capsules showed that they are stable in water at neutral pH and remain almost intact in simulated gastric fluid, but rapidly disintegrate when further treated with simulated intestinal fluid. These results demonstrated that calcium alginate-chitosan capsules can protect proteins from harsh gastric conditions and release their content at intestinal pH, demonstrating their potential application in the field of oral protein delivery.

Freezing-mediated formation of supraproteins using depletion forces

HypothesisLong-acting formulations such as microparticles, injectable depots and implantable devices can realize spatiotemporally controlled delivery of protein drugs to extend their therapeutic in vivo half-lives. To efficiently encapsulate the protein drugs into such drug delivery systems, (sub)micron-sized protein particles are needed. The formation of micronized supraproteins can be induced through the synergistic combination of attractive depletion forces and freezing. The size of the supraproteins can be fine-tuned from submicron to several microns by adjusting the ice crystallization rate through the freeze-quench depth, which is set by the target temperature.MethodsSupraprotein micron structures were prepared from protein solutions under various conditions in the presence and absence of nonadsorbing polyethylene glycol. Scanning electron microscopy and dynamic light scattering were employed to determine the sizes of the supraproteins and real-time total internal reflection fluorescent microscopy was used to follow the supraprotein formation during freezing. The protein secondary structure was measured before and after micronization by circular dichroism. A phase diagram of a protein–polyethylene glycol mixture was theoretically predicted to investigate whether the depletion interaction can elucidate the phase behavior.FindingsMicronized protein supraparticles could be prepared in a controlled manner by rapid freeze-drying of aqueous mixtures of bovine serum albumin, horseradish peroxidase and lysozyme mixed with polyethylene glycol. Upon freezing, the temperature quench initiates a phase separation process which is reminiscent of spinodal decomposition. This demixing is subsequently arrested during droplet phase separation to form protein-rich microstructures. The final size of the generated protein microparticles is determined by a competition between phase separation and cooling rate, which can be controlled by target temperature. The experimental phase diagram of the aqueous protein–polyethylene glycol dispersion aligns with predictions from depletion theory for charged colloids and nonadsorbing polymers.

A simple liquid chromatography method running in dual modes for quantification of short and medium chain fatty acids

Sample preparation is often a rate-limiting step in quantification of short chain and medium chain fatty acids (SFAs and MFAs) in biological samples. A novel liquid chromatography (LC) method with simple sample preparation is introduced in this report. The method is performed on a column packed with polyvinyl alcohol sorbents. In separation of a mixture of bovine serum albumin (BSA) with SFAs and MFAs, the protein is eluted in size-exclusion mode in the first part of the chromatogram. SFAs and MFAs are then eluted in the second part of the chromatogram in reverse-phase mode where fatty acids with longer carbon lengths are eluted at longer retention times. SFAs and MFAs are well resolved from each other without pre-column derivatization. The size-exclusion mode affords good tolerance to macromolecules in sample matrixes. The dual mode separation allows sample injections without complicated sample preparation steps, such as derivatization, extraction, evaporation, and reconstitution.

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.

Aggregation phenomena and physico-chemical properties of tetradecyltrimethylammonium bromide and protein (bovine serum albumin) mixture: Influence of electrolytes and temperature

It is important for biological, pharmaceutical, and cosmetic industries to understand how proteins and surfactants interact. Herein, the interaction of bovine serum albumin (BSA) with tetradecyltrimethylammonium bromide (TTAB) in different inorganic salts (KCl, K2SO4, K3PO4.H2O) has been explored through the conductivity measurement method at different temperatures (300.55 to 325.55 K) with a specific salt concentration and at a fixed temperature (310.55 K) using different salts concentrations. The extent of micelle ionization (α) and different thermodynamic parameters associated with BSA and TTAB mixtures in salt solutions were calculated. Evaluation of the magnitudes of ∆Hm0 and ∆Sm0 showed that the association was exothermic and primarily an enthalpy-operated process in all cases at lower contents of BSA, but the system became endothermic, and entropy driven in the presence of K3PO4.H2O at a relatively higher concentration of BSA. The enthalpy–entropy compensation variables were determined, which explained the types and nature of interactions between TTAB and BSA in salt media. Molecular docking analysis revealed that the main stabilizing factors in the BSA-TTAB complex are electrostatic and hydrophobic interactions. These findings aligned with the significant results obtained from the conductometry method regarding the nature and characteristics of binding forces observed between BSA and TTAB.

Quantitative extraction and concentration of cytochrome c by liquid–liquid phase separation of aqueous ionic liquids under microflow

In this study, phase separation of aqueous solutions of tetrabutylphosphonium trimethylbenzensulfonate ([P4444][TMBS]) under microflow is utilized for simultaneous target-selective extraction and separation. A microchannel with well structures at the bottom is fabricated in a poly(dimethysiloxane) (PDMS) device. A mixture of protein samples containing [P4444][TMBS] is flowed through the device while it is heated. A protein favorable to be distributed to [P4444][TMBS]-rich phase is selectively extracted and trapped in the well structure. As the separated [P4444][TMBS]-rich phase has a smaller volume, the target analyte is thus enriched. Herein, the selective extraction and concentration of cytochrome c from an aqueous mixture of bovine serum albumin, horseradish peroxidase, and azurin is examined. Quantitative concentrations are confirmed based on the volume ratio of each phase determined by color-information-based colorimetry. Precise selection and control of phase-separable materials enhance the versatility of liquid–liquid phase separation for the highly-sensitive detection of biomaterials and metal ions in small amounts of samples.

Stabilization of water-in-water emulsion upon solvent shifting

We report the stabilization of all-aqueous droplets upon addition of ethanol, which were further transformed into robust capsules. An all-aqueous emulsion consisting of dextran (Dex)-rich droplets in a polyethylene glycol (PEG)-rich continuous phase was used as templates. Addition of ethanol induced gelation of dextran, forming aggregated pellets of poor interest. However, this feature was prevented by initially adding bovine serum albumin (BSA) or positively charged silica particles so that in this case, stable droplets formed upon solvent addition, which no longer coalesced with time. An alternative method consisting of pouring concentrated Dex solution in a mixture of PEG, ethanol and BSA or particles, also afforded stable droplets. These stable droplets were further converted into robust capsules, using carbodiimide chemistry or silylation. We expect this method for preparing capsules to be of interest for various applications in the field of microencapsulation.

An amplification velocity-controlled PCR device for accurately detecting the initial content of target DNA templates

Taq DNA polymerase is the most widely used enzyme for PCR amplification and it contains 832 amino acids but no cysteines. Bovine serum albumin (BSA) is an 832-amino acid protein containing 35 cysteines, and at high temperature BSA can produce protein hydrogels through recombined disulfides and noncovalent bonds. When hydrogels are prepared using a mixture of Taq DNA polymerase and BSA, no disulfide bonds occur between them, and noncovalent bonds are the main forces holding together the Taq DNA polymerase with the hydrogels. During PCR amplification, temperature cycling can destroy the noncovalent bonds, thereby releasing Taq DNA polymerase from the hydrogels to synthesize DNA. The release rate, regulated through the variation of BSA concentration, allows for velocity-controlled amplification of DNA. As the amount of DNA products exceeds that of the Taq DNA polymerase released from hydrogels, a linear amplification replaces the exponential PCR amplification. When the amplification velocity begins to decrease, the time needed for reaching a plateau increase. This provides a broader detection window for the analysis of the end products, which correspond to the difference compared with the initial DNA concentration. The number of primers is continuously reduced with increasing cycles, which further causes a decline in the DNA amplification efficiency. The difference in the initial DNA template may cause a different consumption of primers, which can cause errors in the Ct values in the case of qPCR. Based on the slopes of the linear amplification curve, the Ct values can be calibrated to reduce this error, and a more accurate detection of the initial content of the target DNA can be implemented.

Physico-chemical properties of the association of cetyltrimethylammonium bromide and bovine serum albumin mixture in aqueous-organic mixed solvents

Herein, we have investigated the association behavior of bovine serum albumin (BSA) and cetyltrimethylammonium bromide (CTAB) using the conductivity method in H2O and H2O + organic mixed solvents at different temperatures. The association phenomenon was detected from the deviation of the conductivity changes with enhancing the surfactant concentration and changes of numerous physico-chemical properties, such as CMC, α, β and thermodynamic variables (∆G0m, ∆H0m and ∆S0m). The values of CMC for the CTAB + BSA system in 10 % (v/v) solvents follow the trend: CMCwater < CMCwater+DMSO < CMCwater+AN < CMCwater+DX < CMCwater+DMF. The interaction of BSA with CTAB is notably influenced due to a change of temperature and extent of hydration of BSA and surfactant. The obtained values of –∆G0m manifest that the association of BSA and CTAB mixture is a spontaneous process, while the values of –∆G0m in presence of 10 % (v/v) aq. organic solvents come out in the given sequence: -∆Gmo (H2O + DMSO) > ∆Gmo (H2O + DMF) > -∆Gmo (H2O + DX) > -∆Gmo (H2O + AN). The H-bonding, ion-dipole, along with the hydrophobic interactions, are believed to be the binding interactions between BSA and CTAB in the study media.

Preparation of composite monoliths of quaternized chitosan and diatom earth for protein separation.

In this study, composite monoliths with porous structures were prepared using quaternized chitosan and diatom earth for protein separation. Quaternized chitosan (N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride) dissolved in water was mixed with diatom earth and crosslinked with glutaraldehyde under low-temperature conditions to form a cryogel. Interconnected porous monoliths were obtained after removing ice crystals from the cryogel. The monoliths adsorbed bovine serum albumin selectively from the solution mixture of bovine serum albumin and bovine ɤ-globulin, and bovine ɤ-globulin was recovered in the flow-through fraction. The adsorption selectivity was enhanced by changing the solution pH from 6.8 to 5.5. The adsorption of bovine serum albumin by the monolith was replicated at least five times following its washing with a buffer containing 400mM NaCl and subsequent regeneration with a 10mM acetate buffer. The composited monolith is a promising adsorbent for the removal of acidic proteins, such as serum albumin contamination in neutral proteins, for example, ɤ-globulins, in bioproduction processes.

Monitoring non-specific adsorption at solid-liquid interfaces by supercritical angle fluorescence microscopy.

Supercritical angle fluorescence (SAF) microscopy is a novel imaging tool based on the use of distance-dependent fluorophore emission patterns to provide accurate locations of fluorophores relative to a surface. This technique has been extensively used to construct accurate cellular images and to detect surface phenomena in a static environment. However, the capability of SAF microscopy in monitoring dynamic surface phenomena and changes in millisecond intervals is underexplored in the literature. Here, we report on a hardware add-on for a conventional inverted microscope coupled with a post-processing Python module that extends the capability of SAF microscopy to monitor dynamic surface adsorption in sub-second intervals, thereby greatly expanding the potential of this tool to study surface interactions, such as surface fouling and competitive surface adhesion. The Python module enables researchers to automatically extract SAF profiles from each image. We first assessed the performance of the system by probing the specific binding of biotin-fluorescein conjugates to a neutravidin-coated cover glass in the presence of non-binding fluorescein. The SAF emission was observed to increase with the quantity of bound fluorophore on the cover glass. However, a high concentration of unbound fluorophore also contributed to overall SAF emission, leading to over-estimation in surface-bound fluorescence. To expand the applications of SAF in monitoring surface phenomena, we monitored the non-specific surface adsorption of BSA and non-ionic surfactants on a Teflon-AF surface. Solution mixtures of bovine serum albumin (BSA) and nine Pluronic/Tetronic surfactants were exposed to a Teflon-AF surface. No significant BSA adsorption was observed in all BSA-surfactant solution mixtures with negligible SAF intensity. Finally, we monitored the adsorption dynamics of BSA onto the Teflon-AF surface and observed rapid BSA adsorption on Teflon-AF surface within 10s of addition. The adsorption rate constant (ka) and half-life of BSA adsorption on Teflon-AF were determined to be 0.419 ± 0.004s-1 and 1.65 ± 0.016s, respectively, using a pseudo-first-order adsorption equation.

Stabilization of insect cell membranes and soluble enzymes by accumulated cryoprotectants during freezing stress

Most multicellular organisms are freeze sensitive, but the ability to survive freezing of the extracellular fluids evolved in several vertebrate ectotherms, some plants, and many insects. Here, we test the coupled hypotheses that are perpetuated in the literature: that irreversible denaturation of proteins and loss of biological membrane integrity are two ultimate molecular mechanisms of freezing injury in freeze-sensitive insects and that seasonally accumulated small cryoprotective molecules (CPs) stabilize proteins and membranes against injury in freeze-tolerant insects. Using the drosophilid fly, Chymomyza costata, we show that seven different soluble enzymes exhibit no or only partial loss of activity upon lethal freezing stress applied invivo to whole freeze-sensitive larvae. In contrast, the enzymes lost activity when extracted and frozen invitro in a diluted buffer solution. This loss of activity was fully prevented by adding low concentrations of a wide array of different compounds to the buffer, including C. costata native CPs, other metabolites, bovine serum albumin (BSA), and even the biologically inert artificial compounds HistoDenz and Ficoll. Next, we show that fat body plasma membranes lose integrity when frozen invivo in freeze-sensitive but not in freeze-tolerant larvae. Freezing fat body cells invitro, however, resulted in loss of membrane integrity in both freeze-sensitive and freeze-tolerant larvae. Different additives showed widely different capacities to protect membrane integrity when added to invitro freezing media. A complete rescue of membrane integrity in freeze-tolerant larvae was observed with a mixture of proline, trehalose, and BSA.

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.

In situ visualization of combined membrane fouling behaviors using multi-color light sheet fluorescence imaging: A study with BSA and dextran mixture

The understanding of fouling behaviors and mechanism is critical for membrane fouling that is a bottleneck for the sustainable application of membrane technology. Therefore, it is essential to develop new analytical tools that can in situ characterize membrane fouling processes during filtration. In this work, we demonstrate a capability of high-resolution large-scale in situ visualization that can rapidly differentiate foulants and their temporal-spatial-distributions on/in/over the membrane matrix during filtration process based on multi-color light sheet fluorescence imaging platform. The rapid-evolving fouling process of different foulants were directly monitored and analyzed during the ultrafiltration of bovine serum albumin (BSA), dextran and their mixture solutions. Inner adsorption was found to play a more critical role for dextran-induced fouling on polymeric membranes compared with BSA-induced fouling. During the ultrafiltration of BSA/dextran mixture solutions, BSA was directly observed as the major contributor to the decrease of permeate flux, which could be employed as a complementary evidence for the interfacial free energy calculations during membrane fouling and vice versa. This work provides new insights into combined membrane fouling process and offers a highly-sensitive, non-invasive characterization tool for a wide range of explorations in membrane-based processes and interfacial processes. In situ large-scale characterization of combined membrane fouling behaviors Strong relations between flux decline rate and foulant distributions in/on membrane Direct observation of key foulant in combined fouling process Facilitation of exploring interfacial processes (dynamic and thermodynamic)

Modes of interaction and thermodynamic behavior of aggregation of CTAB + BSA mixtures in diols media: effects of diols composition and temperature

The micellization of cetyltrimethylammonium bromide (CTAB) and bovine serum albumin (BSA) mixture has been studied conductometrically in aq. solutions of different diols (1,2-propanediol (1,2-PrD), 2,3-butanediol (2,3-BD), and 1,5-pentanediol (1,5-PD)) media over the temperature range from 298.15 K to 323.15 K to gain insight into the mode and degree of interaction amongst the investigated constituents. The critical micelle concentration (cmc) values of the CTAB + BSA mixtures were attained initially low but enhanced with the rise in temperature in all the media studied. The values of the CTAB + BSA mixtures in the different diols media followed the order: The degree of micelle ionization (α) increased with increasing carbon chain length of diols and temperature. The Gibbs free energy () values associated with the micellization of the CTAB + BSA mixture were negative and revealed a lowering of the spontaneity of micellization with increasing carbon chain length of the diols. The enthalpy () and entropy () changes of micellization revealed that the micellization was exothermic and mainly an enthalpy-controlled process in aq.1,2-PrD and 2,3-BD media while the process being endothermic, and entropy controlled in the 1,5-PD medium. The contribution of the solvent to the thermodynamic parameters was assessed from free energy of transfer (), enthalpy of transfer (), and entropy of transfer () values. The enthalpy–entropy compensation parameters were also studied and discussed with proper reasoning.

Aggregation and thermodynamic study of bovine serum albumin + cationic surfactant mixture in short chain alcoholic media: Effect of composition and temperature

To improve the application of surfactants and polymers, the knowledge of the interaction of surfactant with polymer is essential. Therefore, the interaction of bovine serum albumin (BSA) with a typical cationic surfactant, tetradecyltrimethylammonium bromide (TTAB) was investigated using the conductivity measurement method in aq. alcohols solutions having numerous alcohols concentrations at definite temperature (310.55 K) and the same alcohols concentration at variable temperatures (300.55–323.55 K). The types and extent of interactions between BSA and TTAB have been detected from the variation of critical micelle concentration (CMC) for the studied system. The CMC has been achieved from the plots of conductivity against TTAB concentration. One CMC was achieved for the TTAB + BSA mixture in all aq. alcohols media. The CMC values experience a change with the variation of alcohol contents and temperature of the study medium. The extent of micelle ionization (α), counter ions binding (β), and thermodynamic variables such as free energy (ΔGm0), enthalpy (ΔHm0) and entropy (ΔSm0) of micellization were computed from the standard thermodynamic formulae and demonstrated in detail. The ΔGm0 values were found negative which pointed out the spontaneous attitude of the aggregation process. Here, the intrinsic enthalpy gain (ΔHm0,∗) and the compensation temperature (Tc) were also evaluated and explained. The estimated parameters reveal the presence of interaction among the studied components which is dependent on solvent composition and temperature.

Phase stability of aqueous mixtures of bovine serum albumin with low molecular mass salts in presence of polyethylene glycol

The stability of bovine serum albumin (BSA) solutions against phase separation caused by cooling the system is studied under the combined influence of added poly(ethylene glycol) (PEG) and alkali halide salts in water as solvent. The phase stability of the system depends on the concentration of the added PEG and its molecular mass, the concentration of the low molecular mass electrolyte and its nature, as also on the pH of the solution. More specifically, the addition of NaCl to the BSA-PEG mixture promotes phase separation at pH=4.0, where BSA carries the net positive charge in aqueous solution, and it increases the stability of the solution at pH=4.6, i.e., near the isoionic point of the protein. Moreover, at pH=4.6, the cloud-point temperature decreases in the order from NaF to NaI and from LiCl to CsCl. The order of the salts at pH=4.0 is exactly reversed: LiCl and NaF show the weakest effect on the cloud-point temperature and the strongest decrease in stability is caused by RbCl and NaNO3. An attempt is made to correlate these observations with the free energies of hydration of the added salt ions and with the effect of adsorption of salt ions on the protein surface on the protein–protein interactions. Kosmotropic salt ions decrease the phase stability of BSA-PEG-salt solutions at pH<pI, while exactly the opposite is true at pH=pI.

Assembly behaviour and thermodynamics of the mixture of cetyltrimethylammonium bromide and bovine serum albumin in aqueous and aqua-ethylene glycol mixed solvents media at several temperatures

The aggregation of the mixture of cetyltrimethylammonium bromide (CTAB) and bovine serum albumin (BSA) in aqueous and aq. ethylene glycol (EG) media has been carried out conductometrically at numerous temperatures. Conductivity values of CTAB have been changed with the concentration of CTAB and the values also experience a change with the presence of BSA, change of BSA concentration, variation of EG contents as well as the experimental temperatures. The critical micelle concentration (CMC) and the extent of micelle dissociation (α) were evaluated graphically plotting the specific conductivity against the CTAB concentration. The CTAB aggregation happens lately in the appearance of BSA. Also, the CMC values of CTAB + BSA experience an upsurge with the rise of BSA contents. The CMC values of the mixture of CTAB and BSA have been obtained to be higher in extents in aq. EG solution in contrast to water medium. In all of the circumstances inspected, the micellisation of the CTAB + BSA mixture is spontaneous (negative ΔG 0 m values). Depending on the ΔH0 m and ΔS0 m values for the CTAB + BSA mixture, the recommended forces between CTAB and BSA are electrostatic interaction (hydrogen bonding and ion-dipole interactions) and hydrophobic interactions.