Bovine Serum Albumin System Research Articles

Potential inhibitory effect of highland barley protein hydrolysates on the formation of advanced glycation end-products (AGEs): A mechanism study

Advanced glycation end products (AGEs) can be caused during a glycoxidation reaction. This reaction is associated with complications of diabetes and the consequences of health problems. Therefore, we are exploring the prohibitory effect of highland barley protein hydrolysates (HBPHs) on AGE formation. Herein, first extracted the protein from highland barley with various pH conditions and then hydrolyzed using four different proteolytic enzymes (flavourzyme, trypsin, papain, pepsin) under different degrees of hydrolysis. We assessed three degrees of hydrolysates (lowest, middle, highest) of enzymes used to characterize the antioxidant activity and physicochemical properties. Among all the hydrolysates, flavourzyme-treated hydrolysates F-1, F-2, and F-3 indicated the high ability to scavenge DPPH (IC50 values of 0.97 %, 0.63 %, and 0.90 %), structural and functional properties. Finally, the inhibitory effect of the most active hydrolysates F-1, F-2, and F-3 against the AGEs formation was evaluated in multiple glucose-glycated bovine serum albumin (BSA) systems. Additionally, in a BSA system, F-3 exhibited the strong antiglycation activity, effectively suppressed the non-fluorescent AGE (CML), and the fructosamine level. Moreover, it decreased carbonyl compounds while also preventing the loss of thiol groups. Our results would be beneficial in the application of the food industry as a potential antiglycation agent for several chronic diseases.

Detection of acid protease using the fluorescent probe 3,3′-dipentylthiacarbocyanine iodide-BSA

In this work, an ‘on-off’ fluorescent probe was developed for detection of acid protease (ACP) based on bovine serum albumin (BSA) as the substrate. 3,3′-Dipentylthiacarbocyanine iodide, DiSC5(3), exhibits very weak fluorescence emission in aqueous solution, but following the addition of BSA, due to hydrophobic interactions between them, DiSC5(3) forms an aggregate with BSA and emits strong red fluorescence. When ACP is added, the fluorescence emission of the DiSC5(3)-BSA system is quenched because BSA is hydrolysed into peptide fragments and amino acids by ACP, destroying the DiSC5(3)-BSA system. The degree of fluorescence quenching of the DiSC5(3)-BSA system is proportional to the concentration of ACP over a range of 10–40 μg/mL, with a linear equation y = −4.8270x + 509.7066, a correlation coefficient R2 = 0.9986, and a detection limit of 1.44 μg/mL. The method has advantages including simple operation, high sensitivity and good selectivity, and can be used for detection of ACP in real samples.

In vitro interactions of two pesticides, propazine and quinoxyfen with bovine serum albumin: Spectrofluorometric and molecular docking investigations

Binding mechanisms of two selected pesticides, propazine (PRO) and quinoxyfen (QUI) with bovine serum albumin (BSA) was examined using fluorescence, absorption and molecular docking methods. Intrinsic fluorescence of BSA was quenched in the presence of both PRO and QUI. The quenching was ascertained to be conversely linked to temperature, which suggested the contribution of static quenching process in the PRO–BSA and QUI–BSA complex formations. This results were validated by the enhancement in absorption spectrum of BSA upon binding with PRO and QUI. Binding constant values (Kf = 9.55–0.60 × 10–3 M−1 for PRO–BSA system; Kf = 7.08–5.01 × 102 M−1 for QUI–BSA system) and number of binding site (n) values for the PRO–BSA and QUI–BSA systems at different temperatures affirmed a weak binding strength with a set of equivalent binding sites on BSA. Thermodynamic data obtained for both the PRO–BSA and QUI–BSA interactions predicted that the association process was spontaneous and non-covalent contacts such as hydrophobic interactions, van der Waals forces and hydrogen bonds participated in the binding reactions. This result was further supported by the molecular docking assessments. Three-dimensional spectral results revealed the microenvironmental alterations near tryptophan (Trp) and tyrosine (Tyr) residues in BSA by the addition of PRO and QUI. The docking analysis demonstrated the binding pattern for the PRO–BSA and QUI–BSA systems and disclosed the preferred binding site of both PRO and QUI as site I (subdomain IIA) of BSA.

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.

Surfactant influences the interaction of copper sulfide nanoparticles with biomolecules

This paper sheds light into numerous features of the interaction of copper sulfide nanoparticles (CuS NPs) with vital proteins viz., bovine serum albumin (BSA), human serum albumin (HSA) and collagen in the absence and presence of different surfactants. We used the wet chemical co-precipitation process for the synthesis of CuS NPs. The synthesized NPs were characterized through fourier transform infrared Spectroscopy (FTIR), UV–visible spectroscopy, X-ray diffraction (XRD), zeta potential, dynamic light scattering (DLS), scanning electron microscopy (SEM), elemental mapping and energy dispersive X-ray spectroscopy (EDAX). CuS NPs-protein interactions were analyzed by fluorescence spectroscopy, circular dichroism spectroscopy (CD), UV–visible spectroscopy, DLS technique, sodium dodecyl sulphate -polyacrylamide gel electrophoresis (SDS -PAGE). The esterase activity and cysteine reactivity of BSA was checked in association with CuS NPs and surfactants. Furthermore, the radical scavenging activity of synthesized NPs was also tested (DPPH assay). Interaction of CuS NPs with DNA alone and in presence of surfactants was studied by gel electrophoresis. CTAB, DTAB and Tween 80 enhanced CuS NPs-protein binding. Tween 80 was furthermore found to impart constant biocompatibility to CuS NPs. The esterase and cysteine activity of BSA was found to remain unaffected in presence of Tween 80 only. Moreover, the antioxidant activity studies by DPPH assay revealed maximum radical scavenging activity for Tween 80 based systems. Fluorescence studies at 298, 303, 313, 319 and 327 K showed enhanced strength and association between CuS NPs and BSA in presence of Tween 80. The obtained thermodynamic parameters for NPs-protein bindings at various temperatures suggest the dominance of hydrogen bonding and Vander Waals forces between CuS NPs/Tween 80 and BSA systems. The present study evaluates the effects of surfactant coated CuS NPs on the vital biomolecules. The study thus possess potential in designing stable and biocompatible CuS NPs for biomedical utilizations.

The interaction between citronellol and bovine serum albumin: Spectroscopic, computational and thermal imaging studies

Citronellol (Cit), a typical component of rose essential oil, has a variety of physiological activities and is widely used in physiotherapy with tourmaline powder (TP). But the reaction mechanism with biomolecules was not concerned. Therefore, the action mechanism of Cit/TP to bovine serum albumin (BSA) was studied through spectroscopic, docking, dynamic simulation and thermal imaging methods. The results suggested that Cit and BSA could bind at site I chiefly under the driving forces of hydrogen bonds and Van der Waals forces, and the endogenous fluorescence quenching mode of BSA was static. Synchronous, three-dimensional fluorescence spectra, UV–vis, FT-IR reflected Cit could affect the microenvironment near tryptophan and promote the aggregation of the protein structure to change the conformation of BSA. The molecular dynamics (MD) simulation confirmed the conformational change of BSA after ligand binding. Besides, the analysis showed that the existence of TP could improve the affinity of Cit-BSA binding. Infrared thermal images proved that Cit and/or TP could improve the radiation temperature of BSA system. In brief, Cit could spontaneously bind to BSA and change the protein conformation, and the presence of TP would affect the binding mode of Cit-BSA. These findings will be beneficial to further research of Cit and TP in physiotherapy.

Micellization, interaction and thermodynamics behavior of BSA + SDS mixture in aqua-organic mixed solvent: Influences of temperature and solvent composition

The interaction of bovine serum albumin (BSA) with sodium dodecyl sulphate (SDS) in aqueous medium as well as aqua-organic mixed media has been performed using the conductivity measurement technique at several temperatures. The experiments were performed in the temperature ranges of 298.15–313.15 K with a gap of 5 K. The critical micelle concentration (CMC) and the degree of micelle ionization (α) have been computed from the specific conductivity versus the surfactant concentration plot. The CMC values achieved in the present study are dependent on the concentration of BSA, composition of the mixed solvent, and a variation of experimental temperature. For SDS + BSA mixture, an increase of BSA concentration causes a decrease in the values of CMC. Also, the values of CMC of SDS + BSA system in water-organic solvents were found to follow the order: CMCwater-DMF > CMCwater-AN > CMCwater-DMSO > CMCwater. In every case examined, the association of SDS + BSA mixture was spontaneous (negative ΔG0m). On the basis of observed ΔH0m and ΔS0m values for the SDS + BSA mixed system, it is expected that an electrostatic, hydrophobic, and ion–dipole interactions are in effect between SDS and BSA species, whereas the hydrophobic interaction is believed to be the main driving force for the aggregation process. In each of the case thoroughly detected, a linear relationship between ΔH0m and ΔS0m values was viewed, which is a strong indication in favor of the presence of enthalpy–entropy compensation phenomenon in the overall interaction process.

Spectroscopic Analysis of the Binding of Paraquat and Diquat Herbicides to Biosubstrates.

The study of the interaction of persistent organic pollutants with biosubstrates helps to unravel the pathways for toxicity, however, few mechanistic data are present in the literature for these systems. We analyzed the binding of paraquat (PQ) and diquat (DQ) herbicides to natural calf thymus DNA and a DNA G-quadruplex by spectrophotometric titrations, ethidium bromide exchange tests, viscometry, and melting experiments. The interaction with bovine serum albumin (BSA) protein was studied spectrofluorimetrically at different temperatures. The retention of the targets on positive, negative, and neutral micellar aggregates and liposomes was analyzed by ultrafiltration experiments. Despite some favorable features, PQ and DQ only externally bind natural DNA and do not interact with DNA oligonucleotides. Both herbicides bind bovine serum albumin (BSA). PQ binds BSA mainly according to an electrostatics-driven process. However, ultrafiltration data also show that some hydrophobic contribution participates in the features of these systems. The practical problems related to unfavorable spectroscopic signals and inner filter effects are also discussed. Overall, both herbicides show a low affinity for nucleic acids and weak penetration into liposomes; in addition, the equilibrium constants values found for BSA system suggest optimal conditions for transport in the body.

Contrastive Study of the Foaming Properties of N-Acyl Amino Acid Surfactants with Bovine Serum Albumin and Gelatin.

A detailed study on the foamability, foam stability, foam liquid-carrying capacity, and foam morphology of two N-acyl amino acid surfactants with bovine serum albumin (BSA) and gelatin were performed by foam scanning. The results showed that the foamability of the mixed system increased gradually and then tended to be stable with increasing surfactant concentration. The foamability of the high-concentration BSA system was stronger than that of the low-concentration BSA system. The foamability and foam stability of sodium N-lauroyl phenylpropanoic acid (N-C12P)/BSA were better than those of sodium N-lauroyl propylamino acid (N-C12A)/BSA, and the foamability and foam stability of N-C12A/gelatin was better than those of N-C12P/gelatin. The liquid-carrying capacity of the foam initially increased and then decreased with increasing time, and the maximum liquid-carrying capacity increased with increasing surfactant concentration. When the concentration of the surfactant was 8 mM, the drainage rate of N-C12A/protein was higher than that of N-C12P/protein. The morphology of the bubble gradually changed from spherical to polyhedron and the number of bubbles gradually decreased with time increasing. Differences in surfactant structure and protein type had an important effect on the number and area of foam.

Interaction of tetradecyltrimethylammonium bromide with bovine serum albumin in different compositions: Effect of temperatures and electrolytes/urea

Herein, the interaction of a protein, bovine serum albumin (BSA), with tetradecyltrimethylammonium bromide (TTAB, a cationic surfactant), has been investigated using the conductivity measurement technique in pure water and some sodium salts (NaCl, Na2SO4, Na2CO3, and Na3PO4) solutions at temperature range of 295.15–320.15 K. Results reveal that, in the plot of specific conductivity versus the concentration of TTAB, only a single critical micelle concentration (cmc) was found for the TTAB + BSA mixed system in all solvents media studied. The addition of BSA in aqueous TTAB solution, the value of cmc undergoes a change from its pure form, which indicates the presence of strong interaction operating between the BSA and TTAB molecules. In aqueous system, the cmc values of the TTAB + BSA mixtures are obtained higher compared to the values found for single TTAB surfactant. However, the addition of salt decreases the cmc value of mixed TTAB + BSA system. The values of cmc of the BSA + TTAB mixed system at 310.15 K and 1.00 mmol·kg−1 ionic strength of salt followed the order: cmcNa2CO3 > cmcNa3PO4 > cmcNaCl > cmcNa2SO4. The cmc values of TTAB + BSA mixture were found to be lowered in urea solution within the concentrations studied. The values of degree of dissociation (α) and fraction of counter ion binding (β) were found to be dependent on additives and temperature. The free energy of micellization (∆ Gmo) is negative for all the systems, which manifests that the micellization phenomenon is energetically spontaneous. The enhancement of the negative value of ∆ Gmo in aqueous salt solutions reveals an increase of spontaneity of the TTAB + BSA micellization process. The values of ∆ Gmo also reveal that the spontaneity of micelle formation is enhanced at higher temperatures in all media studied. The values of free energy of transfer (∆ Gm, to) were also determined for numerous solvent media used in the present study and described with appropriate reasoning.

Spectroscopic studies on the interaction of a novel porphyrin derivative (PFP) and bovine serum albumin

A novel porphyrin derivative (PFP) interaction with bovine serum albumin (BSA) was investigated by fluorescence and ultraviolet spectrophotometer. The experimental result revealed that a combined quenching procedure exists in the PFP–BSA system. The Stern–Volmer quenching constant (Ksv), bimolecular quenching constant (Kq), effective binding constant (Ka) were obtained at three temperatures. The thermodynamic parameters (ΔH, ΔG, and ΔS) were determined, which indicated that the binding process is spontaneous and the hydrophobic forces is playing a major role in the interaction. According to Förster non-radioactive energy transfer theory, the efficiency of energy transfer (E) and binding distance (r) were calculated, which demonstrated that there was no-radiative energy transfer happened during the whole process from PFP to BSA.

Protein–polymer interaction: Transfer loading at interfacial region of PES‐based membrane and BSA

ABSTRACTThe adsorption of proteins onto polymeric surfaces is encountered in many natural and industrial processes and is a prerequisite to their efficient identification, separation, and purification by methods such as chromatography, and filtration. Nevertheless, the exact nature of the adsorption mechanisms and interfacial interactions is not easy to identify for a given protein–polymer system. Here, we aim to document the adsorption mechanism of a protein–polymer system by investigating the adsorption as well as desorption phenomenon of a protein [bovine serum albumin (BSA)] from the polymeric surface [polyethersulfone (PES)]. The analyses performed to document the adsorption mechanism of the BSA–PES system include scanning electron microscope (SEM), attenuated total reflection‐Fourier transform infrared (FTIR), contact angle, zeta potential, surface charge density measurement, and Derjaguin–Landau–Verwey–Overbeek (DLVO). Here, SEM and FTIR identified the physical and chemical properties of pure PES and PES–BSA membranes. The low water contact angle of the PES–BSA membrane confirms its applicability for tissue engineering applications. Further, the zeta potential, surface charge density measurement, and DLVO analyses were performed to document the adsorption mechanism. The adsorption of BSA particles on the PES surface was carried out for pH values that ranged from 4 to 10 for contact times that ranged from 1 to 3 days. A monotonic increase in the zeta potential of the PES–BSA system indicated considerable adsorption of BSA particles on the PES surface. Further, BSA adsorption was very strong for pH values greater than 4.7 which confirms to strong electrostatic interactions between BSA and PES. The strong electrostatic interaction is also collaborated by low desorption rate, which was only ∼22% for pH 10 after 3 days of contact. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47931.

Rationalising drug delivery using nanoparticles: a combined simulation and immunology study of GnRH adsorbed to silica nanoparticles

Silica nanoparticles (SiNPs) have been shown to have significant potential for drug delivery and as adjuvants for vaccines. We have simulated the adsorption of GnRH-I (gonadotrophin releasing hormone I) and a cysteine-tagged modification (cys-GnRH-I) to model silica surfaces, as well as its conjugation to the widely-used carrier protein bovine serum albumin (BSA). Our subsequent immunological studies revealed no significant antibody production was caused by the peptide-SiNP systems, indicating that the treatment was not effective. However, the testosterone response with the native peptide-SiNPs indicated a drug effect not found with cys-GnRH-I-SiNPs; this behaviour is explained by the specific orientation of the peptides at the silica surface found in the simulations. With the BSA systems, we found significant testosterone reduction, particularly for the BSA-native conjugates, and an antibody response that was notably higher with the SiNPs acting as an adjuvant; this behaviour again correlates well with the epitope presentation predicted by the simulations. The range of immunological and hormone response can therefore be interpreted and understood by the simulation results and the presentation of the peptides to solution, paving the way for the future rational design of drug delivery and vaccine systems guided by biomolecular simulation.

Photochemical Studies and Photoinduced Antibacterial Properties of Silver Nanoparticle-Encapsulated Biomacromolecule Bovine Serum Albumin Functionalised with Photoresponsive Chromophoric System 2-[(E)-(3-Hydroxynaphthalen-2-yl) diazenyl] Benzoic Acid

This study establishes the synthesis of silver nanoparticles (AgNPs), synthesis of a photoresponsive system 2-[(E)-(3-hydroxynaphthalen-2-yl) diazenyl] benzoic acid, and encapsulation of AgNPs into the biomacromolecular system, bovine serum albumin (BSA) functionally modified with the photoactive system by means of DCC coupling. The optical properties, structural properties, morphology, and size distribution were confirmed by various characterisation techniques such as ultraviolet (UV)/visible, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction analysis (XRD). The photo responsive behaviour of the functionally modified BSA and nanoparticle dispersed system were investigated. The antibacterial effects of AgNPs and photo induced antimicrobial properties of the functionally modified BSA-AgNP conjugates were evaluated against some selected bacterial strains such as Corynebacterium diphtheriae (gram +ve), Bacillus cereus (gram +ve), Raoultella ornithinolytica (gram -ve), and Salmonella typhimurium (gram -ve) using disc diffusion. We found that silver nanoparticles encapsulating functionally modified BSA seem to be an effective photoactive antimicrobial agent against the multidrug resistant strains of bacteria with better photo responsive properties and with wide applications in antimicrobial photodynamic therapy (APDT).

Moracin derivatives from Morus Radix as dual BACE1 and cholinesterase inhibitors with antioxidant and anti-glycation capacities

AimsMorus, a member of the family Moraceae and commonly known as the mulberry, comprises a pharmaceutically important plant group whose major constituents are the moracins. Moracin derivatives have received great attention because they exhibit a diverse range of biological functionalities. However, no studies have considered the anti-Alzheimer's disease (AD) and anti-glycation potential of moracin derivatives. Main methodsWe designed the current study to explore the anti-AD activity of moracin derivatives via in vitro inhibition of BACE1 and cholinesterase, their antioxidant activity via scavenging ONOO− and ABTS+ radicals, and their anti-diabetic activity through inhibition of advanced glycation end-products (AGEs) formation. Moreover, to define the mechanism of action of moracin derivatives in depth, we performed in silico molecular modeling using a computer-assisted drug design and modeling program. Key findingsAmong the four Morus-derived moracins tested, moracin S, which has a prenyl moiety in the 2-aryl benzofuran scaffold, possessed the highest BACE1 inhibitory activity. It also, in a dose-dependent fashion, decreased ONOO−-mediated bovine serum albumin (BSA) nitration and formation of AGEs and amyloid cross-β structures in the glycated BSA system, and it showed notable radical scavenging activity. In addition, enzyme kinetic and molecular docking studies demonstrated that moracin S is a potent, competitive BACE1 inhibitor that could interact with key catalytic aspartyl residues. SignificanceThe prenyl moiety in the 2-aryl benzofuran structure plays a crucial role in inhibition of BACE1. These in vitro and in silico results provide valuable information for the design of anti-AD drugs.

Effects of selected two noble metal ions in medicine on the structure and activity of bovine serum albumin: A multi-spectral studies

In the present study, the toxic influence of two metallic ions on serum albumin was studied by using fluorescence, UV/vis, circular dichroism spectroscopy, and molecular docking, with the aim of delineating the effects of Pt(II) and Au(III) ions on the secondary and tertiary structure, the transportation function, the thermal stability, and the esterase-like activity of bovine serum albumin (BSA). The conformational change occurring in protein structure was monitored by CD and fluorescence spectroscopy. Pt(II) and Au(III) could react with some functional groups of BSA, making the secondary structure change and increasing the microenvironment around Tyr residues of BSA. The content of α-helix decreased remarkably and the contents of β-sheet, and random coil increased with increasing concentration of Pt(II) or Au(III) ion. Compared with Pt(II) ion, Au(III) ion is more likely to damage the tertiary structure of BSA and a higher number of Tyr residues are affected in Au(III)-BSA system. The fluorescence and UV/vis spectral results indicated the formation of Pt(II)-BSA and Au(III)-BSA complexes. In addition, metal ion binding decreased the ANS binding ability, the reversibility of the thermal unfolding process and the esterase-like activity of BSA. Therefore, this paper is expected to improve the toxicity evaluation mechanism of platinum and gold ions.

A BSA-squaraine hybrid system for selectively detecting Ag+ in absolute PBS and sequential construction of logic functions

A novel near infrared (NIR) fluorescent hybrid system (PD-SQ⊂BSA) assembled from squaraine dye PD-SQ and bovine serum albumin (BSA) was developed for selective detection of Ag+ over other metal ions in absolute PBS. The detection limit of PD-SQ⊂BSA for Ag+ is calculated to be about 8.99×10−8M, which is lower than the guidelines for drinking water set by the WHO. PD-SQ alone shows very weak fluorescence due to aggregation-caused quenching (ACQ) property. BSA can cause PD-SQ to partially disaggregate through electrostatic and hydrophobic interactions, but various metal ions including Ag+ cannot do. Interestingly, the presence of both BSA and Ag+ can trigger PD-SQ to almost completely disaggregate through synergic binding of multiple S-Ag linkings derived from the biothiol moieties in BSA and PD-SQ with Ag+, resulting in obvious turn-on fluorescence change. Absorption and field emission scanning electron microscope (FESEM) spectra have been used to prove the conversion of PD-SQ from aggregates to monomers. In addition, based on the fluorescence spectra changes of PD-SQ⊂BSA system upon addition of Hg2+ and ethylenediaminetetraacetic acid (EDTA), logic circuits including AND and INHIBIT logic gates with reset function were successfully constructed. This type of fluorescent system shows great potential for disease diagnosis, environmental protection, and information protection at the molecular scale.

Systematic Evaluation of Amide Proton Chemical Exchange Saturation Transfer at 3 T: Effects of Protein Concentration, pH, and Acquisition Parameters.

The goal of this work was to systematically evaluate the reproducibility of amide proton transfer chemical exchange saturation transfer (APT-CEST) at 3 T and its signal dependence on pH, protein concentration, and acquisition parameters. An in vitro system based on bovine serum albumin (BSA) was used, and its limitations were tested by comparing it to in vivo measurements. The contribution of small endogenous metabolites on the APT-CEST signal at 3 T was also investigated. In addition, the reliability of different z-spectrum interpolations as well as the use of only a few frequency offset data points instead of a whole z-spectrum were tested. We created both a BSA phantom at different concentrations and pH values and a metabolite phantom with different small molecules. Chemical exchange saturation transfer data were acquired using a 2-dimensional fast spoiled gradient-echo sequence with pulsed CEST preparation at different saturation durations and power levels. Healthy volunteer measurements were taken for comparison. Z-spectra were interpolated using a 24th-order polynomial (Poly), an eighth-order Fourier series (Fourier), and a smoothing Spline (sSpline) algorithm. To evaluate reduced data sets, only 6 to 14 frequency offsets of the z-spectrum were used and interpolated via a cubic Spline. Region of interest (ROI) evaluations were used to investigate the reproducibility of amide magnetization transfer ratio asymmetry [MTRasym(3.5 ppm)] and to analyze the MTRasym and z-spectra. Interscan standard deviations of MTRasym(3.5 ppm) were always below 0.3%. MTRasym(3.5 ppm) increased when the BSA concentrations increased and decreased when the pH increased. The amine MTRasym signal of small molecules was very small compared with BSA and was only detectable using short saturation times and higher power levels. The MTRasym(3.5 ppm) between BSA concentration steps and between nearly all pH steps was significantly different for all 3 fitting methods. The Fourier and sSpline methods showed no statistically significant differences; however, the results for the Poly method were significantly higher at some concentrations and pH values. Using only few frequency offsets resulted in less significant differences compared with fitting the complete z-spectrum. In general, MTRasym(3.5 ppm) of gray matter, white matter, and ventricle ROIs from volunteer scans increased with an increase in saturation power and partially decreased with an increase in saturation duration. Intra-ROI covariances of MTRasym(3.5 ppm) revealed the highest variations for Poly, whereas using reduced spectral data resulted in an increased signal variation. Amide proton transfer-CEST imaging is a highly reproducible method in which absolute signal differences of approximately 0.5% are detectable in principle. For in vivo applications, Fourier or sSpline interpolations of z-spectra are preferable. Using reduced data sets delivers similar results but with increased variation and therefore decreased (pH/concentration) differentiation capability. Differentiation capability increases with increases in the saturation duration and power level. The results from the in vitro BSA system cannot be directly transferred to the in vivo situation due to different chemical environments resulting in, for example, higher asymmetric macromolecular cMT effects in vivo. Amine signals from small molecules are unlikely to contribute to APT-CEST at 3 T (except for creatine); however, signals can be enhanced by using short saturation times and higher power levels.

Complexation of bovine serum albumin and gold nanorods revealed by plasmon-enhanced light scattering spectroscopy

ABSTRACTComplexation of bovine serum albumin (BSA) and gold nanorods has been investigated by plasmon-enhanced light scattering spectroscopy under external stimuli such as the changes in hydrogen ion concentration value and ionic strength, with addition of ethanol. The results indicated that the BSA chains tend to adopt a coil conformation by decreasing hydrogen ion concentration value. Scattering intensity of the gold nanorods–BSA system gradually decreases because BSA chains tend to adopt a coil conformation with addition of sodium chloride. This work will further extend the application range of this method due to its simplicity, rapidity, and sensitivity.

Binding nature and conformational alternations of bovine serum albumin upon interaction with synthesized LaF3:Ce,Tb luminescent nanocrystals using multi-spectroscopic approach

Water-soluble LaF3:Ce,Tb luminescent nanocrystals (RLNCs) were successfully fabricated according to previously reported literatures. The experimental results indicate that the as-prepared nanocrystals consist of well crystallized hexagonal phases, having a nearly spherical shape with an average diameter of 10nm. The interaction of RLNCs with bovine serum albumin (BSA) was studied mainly via fluorescence quenching in combination with circular dichroism (CD) and ultraviolet–visible (UV–vis) absorption spectroscopy under imitated physiological conditions. The fluorescence titration results reveal that RLNCs could efficiently quench the intrinsic fluorescence of BSA mainly through a dynamic quenching procedure. The binding constant and the number of binding site at 300K were estimated to be 4.606×103Lmol−1 and 0.98, respectively. Meanwhile, the thermodynamic parameters for RLNCs–BSA system were also determined, suggesting that the binding reaction between RLNCs and BSA took place spontaneously and was primarily driven by hydrophobic forces. Furthermore, it was found that the binding of RLNCs to BSA was mainly located in site I and the binding distance was estimated to be 3.0nm. Finally, the synchronous fluorescence, three dimensional (3D) fluorescence, and CD spectroscopy were used to explore the conformational alterations of protein induced by RLNCs.