Residues Of Bovine Serum Albumin Research Articles

Heterocyclic (pyrazine)carboxamide Ru(ii) complexes: structural, experimental and theoretical studies of interactions with biomolecules and cytotoxicity.

Treatments of N-(1H-benzo[d]imidazol-2-yl)pyrazine-2-carboxamide (HL1) and N-(benzo[d]thiazol-2-yl)pyrazine-2-carboxamide carboxamide ligands (HL2) with [Ru(p-cymene)Cl2]2 and [Ru(PPh3)3Cl2] precursors afforded the respective Ru(ii) complexes [Ru(L1)(p-cymene)Cl] (Ru1), [Ru(L2)(p-cymene)Cl] (Ru2), [Ru(L1)(PPh3)2Cl] (Ru3), and [Ru(L2)(PPh3)2Cl] (Ru4). These complexes were characterized by NMR, FT-IR spectroscopies, mass spectrometry, elemental analyses, and crystal X-ray crystallography for Ru2. The molecular structure of complex Ru2 contains one mono-anionic bidentate bound ligand and display pseudo-octahedral piano stool geometry around the Ru(ii) atom. The interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated by spectroscopic techniques. The experimental binding studies suggest that complexes Ru1-Ru4 interact with DNA, primarily through minor groove binding, as supported by molecular docking results. Additionally, these complexes exhibit strong quenching of the fluorescence of tryptophan residues in BSA, displaying static quenching. The in vitro cytotoxicity studies of compounds Ru1-Ru4 were assessed in cancer cell lines (A549, PC-3, HT-29, Caco-2, and HeLa), as well as a non-cancer line (KMST-6). Compounds Ru1 and Ru2 exhibited superior cytotoxicity compared to Ru3 and Ru4. The in vitro cytotoxicity and selectivity of compounds Ru1 and Ru2 against A549, PC-3, and Caco-2 cell lines surpassed that of cisplatin.

Gold Nanomaterial System That Enables Dual Photothermal and Chemotherapy for Breast Cancer.

This study involves the fabrication and characterization of a multifunctional therapeutic nanocomposite system, as well as an assessment of its in vitro efficacy for breast cancer treatment. The nanocomposite system combines gold nanorods (GNRs) and gold nanoclusters (GNCs) to enable a combination of photothermal therapy and doxorubicin-based chemotherapy. GNRs of various sizes but exhibiting similar absorbance spectra were synthesized and screened for photothermal efficiency. GNRs exhibiting the highest photothermal efficiency were selected for further experiments. GNCs were synthesized in bovine serum albumin (BSA) and integrated into citrate-capped GNRs using layer-by-layer assembly. Glutaraldehyde crosslinking with the lysine residues in BSA was employed to immobilize the GNCs onto the GNRs, forming a stable "soft gel-like" structure. This structure provided binding sites for doxorubicin through electrostatic interactions and enhanced the overall structural stability of the nanocomposite. Additionally, the presence of GNCs allowed the nanocomposite system to emit robust fluorescence in the range of ~520 nm to 700 nm for self-detection. Hyaluronic acid was functionalized on the exterior surface of the nanocomposite as a targeting moiety for CD44 to improve the cellular internalization and specificity for breast cancer cells. The developed nanocomposite system demonstrated good stability in vitro and exhibited a pH- and near-infrared-responsive drug release behavior. In vitro studies showed the efficient internalization of the nanocomposite system and reduced cellular viability following NIR irradiation in MDA-MB-231 breast cancer cells. Together, these results highlight the potential of this nanocomposite system for targeted breast cancer therapy.

Simple and sensitive fluorescence detection of trypsin with Cu2+-Bovine serum albumin complex as a peroxidase mimic

Trypsin is a serine protease playing a key role in regulating pancreatic exocrine function and can be applied as a marker for the diagnosis of pancreatitis. In this work, a convenient and sensitive fluorescent assay was developed toward trypsin. Hydrogen peroxide slowly oxidized a non-fluorescent o-phenylenediamine (OPD) into a fluorescent product 2,3-diaminophenothiazine (DAP) under the catalytic from copper ions. After the introduction of bovine serum albumin (BSA), the combination of BSA with copper ions formed a peroxidase mimic and significantly accelerated the reaction rate. As an efficient protease, trypsin cleaved the lysine and arginine residues in BSA. This destroyed the binding between Cu2+ and BSA, and brought in a reduction of the catalytic effect. The accompanying decrease in fluorescence provided a response to trypsin in the range of 0.01–600 ng/mL, with a detection limit of 0.007 ng/mL. The scheme had a good selectivity and was successfully applied to the detection of real samples.

CuCoO2 Nanoparticles as a Nanoprotease for Selective Proteolysis with High Efficiency at Room Temperature

AbstractMany nanoproteases contain tetravalent metal ions and catalyze peptide‐bond hydrolysis only at high temperature (60 °C). Here, we report a new and effective strategy to explore nanoproteases from nanoparticles containing low valent metal ions. We found that flower‐like CuCoO2 nanoparticles (CuCoO2 NPs) containing low valent Cu+ possessed excellent catalytic activity towards selective cleavage of peptide bonds with hydrophobic residues in bovine serum albumin (BSA) at room temperature. CuCoO2 NPs exhibited excellent stability and had great reusability. CuCoO2 NPs also hydrolyzed heat‐denatured and surfactant‐denatured BSA. Mechanism analysis revealed that the high Lewis acidity of Co3+ and the low valence of Cu+ were both essential for the high protease activity of CuCoO2 NPs. The flower‐like structure of CuCoO2 NPs and the strong nucleophilicity of Cu+‐bound hydroxyl endow them with excellent catalytic performance. The findings open a new way for the design and discovery of high‐efficiency nanoproteases.

CuCoO2 Nanoparticles as a Nanoprotease for Selective Proteolysis with High Efficiency at Room Temperature.

Many nanoproteases contain tetravalent metal ions and catalyze peptide-bond hydrolysis only at high temperature (60 °C). Here, we report a new and effective strategy to explore nanoproteases from the nanoparticles containing low valent metal ions. We found that flower-like CuCoO2 nanoparticles (CuCoO2 NPs) containing low valent Cu+ possessed excellent catalytic activity towards selective cleavage of peptide bonds with hydrophobic residues in bovine serum albumin (BSA) at room temperature. CuCoO2 NPs exhibited excellent stability and had great reuse performance. CuCoO2 NPs also hydrolyzed heat-denatured and surfactant-denatured BSA. Mechanism analysis revealed that the high Lewis acidity of Co3+ and the low valence of Cu+ were both essential for the high protease activity of CuCoO2 NPs. The flower-like structure of CuCoO2 NPs and the strong nucleophilicity of Cu+-bound hydroxyl endue them with excellent catalytic performance. The findings open a new way for design and discovery of high-efficiency nanoproteases.

Comprehending the intermolecular interaction of dacomitinib with bovine serum albumin: experimental and theoretical approaches

Dacomitinib (DAC), as a member of tyrosine kinase inhibitors is primarily used to treat non-small cell lung cancer. The intermolecular interaction between DAC and bovine serum albumin (BSA) was comprehended with the help of experiments and theoretical simulations. The outcomes indicated that DAC quenched the endogenous fluorescence of BSA through static quenching mode. In the binding process, DAC was preferentially inserted into the hydrophobic cavity of BSA subdomain IA (site III), and a fluorescence-free DAC-BSA complex with molar ratio of 1:1 was generated. The outcomes confirmed that DAC had a stronger affinity on BSA and the non-radiative energy transfer occurred in the combination process of two. And, it can be inferred from the outcomes of thermodynamic parameters and competition experiments with 8-aniline-1-naphthalenesulfonic acid (ANS) and D-(+)- sucrose that hydrogen bonds (H-bonds), van der Waals forces (vdW) and hydrophobic forces had a significant impact in inserting DAC into the hydrophobic cavity of BSA. The outcomes from multi-spectroscopic measurements that DAC could affect the secondary structure of BSA, that was, α-helix content decreased slightly from 51.0% to 49.7%. Moreover, the combination of DAC and BSA led to a reduction in the hydrophobicity of the microenvironment around tyrosine (Tyr) residues in BSA while had little influence on the microenvironment of around tryptophan (Trp) residues. The outcomes from molecular docking and molecular dynamics (MD) simulation further demonstrated the insertion of DAC into site III of BSA and hydrogen energy and van der Waals energy were the dominant energy of DAC-BSA stability. In addition, the influence of metal ions (Fe3+, Cu2+, Co2+, etc.) on the affinity of the system was explored. Communicated by Ramaswamy H. Sarma

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.

Binding characteristics of Bruton’s tyrosine kinase inhibitor ibrutinib with bovine serum albumin: multi-spectroscopic combined with molecular simulation

Ibrutinib, as an oral Bruton’s tyrosine kinase inhibitor, has highly potent, covalent irreversible, and other characteristics. In this work, the binding characteristics of ibrutinib with bovine serum albumin were investigated using multi-spectroscopic techniques and molecular simulations. The findings demonstrated that ibrutinib could quench the endogenous fluorescence of bovine serum albumin by static quenching mode, meanwhile bovine serum albumin could also quench the fluorescence of ibrutinib. In the binding process of ibrutinib with bovine serum albumin, ibrutinib caused a bathochromic shift in the absorption band of bovine serum albumin, further indicating that ibrutinib and bovine serum albumin formed a ground state ibrutinib and bovine serum albumin complex. It is confirmed that ibrutinib has a strong affinity to bovine serum albumin due to the binding constant of more 104 M−1. Experimental findings showed that ibrutinib resulted in the decrease in the hydrophobicity or the enhancement in the polarity of the surroundings around Tyr and Trp residues of bovine serum albumin and diminishing in α-helix and β-sheet content of bovine serum albumin. The findings from site-competition experiments confirmed that the binding site of ibrutinib onto bovine serum albumin was the same as that of ibuprofen, that is, ibrutinib bound to the site II' site of bovine serum albumin, which was verified by molecular docking. The findings from thermodynamic analysis revealed that ibrutinib spontaneously bound onto bovine serum albumin through an enthalpy-driven and the driving forces included hydrogen bonding and van der Waals forces being the dominating forces. The findings from molecular dynamics simulation confirmed that some residues such as ARG-208, ALA-209, ALA-212, LEU-326, and LYS-350 made major contributions in ibrutinib and bovine serum albumin complexation.

Investigation of the interaction between the functionalized mesoporous silica nanocarriers and bovine serum albumin via multi-spectroscopy

It is well known that the physicochemical properties of nanocarriers, which are closely related to the surface modification of nanoparticles, have crucial impacts on their biological effects. Herein, the interaction between functionalized degradable dendritic mesoporous silica nanoparticles (DDMSNs) and bovine serum albumin (BSA) was investigated for probing into the nanocarriers’ potential toxicity using multi-spectroscopy such as ultraviolet/visible (UV/Vis), synchronous fluorescence, Raman and circular dichroism (CD) spectroscopy. BSA, owing to its structural homology and high sequence similarity with HSA, was employed as the model protein to study the interactions with DDMSNs, amino-modified DDMSNs (DDMSNs-NH2) and hyaluronic acid (HA) coated nanoparticles (DDMSNs-NH2-HA). It was found that the static quenching behavior of DDMSNs-NH2-HA to BSA was accompanied by an endothermic and hydrophobic force-driven thermodynamic process, which was confirmed by fluorescence quenching spectroscopic studies and thermodynamic analysis. Furthermore, the conformational variations of BSA upon interaction with nanocarriers were observed by combination of UV/Vis, synchronous fluorescence, Raman and CD spectroscopy. The microstructure of amino residues in BSA changed due to the existence of nanoparticles, for example, the amino residues and hydrophobic groups exposed to microenvironment and the alpha helix (α-helix) content of BSA decreased. Specially, through thermodynamic analysis, the diverse binding modes and driving forces between nanoparticles and BSA were discovered because of different surface modifications on DDMSNs, DDMSNs-NH2 and DDMSNs-NH2-HA. We believe that this work can promote the interpretation of mutual impact between nanoparticles and biomolecules, which will be in favor of predicting the biological toxicity of nano-DDS and engineering functionalized nanocarriers.

Deciphering the mechanism of interaction of an ester-functionalized cationic gemini surfactant with bovine serum albumin: A biophysical and molecular modeling study

Protein–surfactant interactions have relevance in the fields of pharmaceuticals, detergency formulation, pharmacology, personal hygiene products, etc. Accordingly, we have analyzed the biomolecular interaction between a recently synthesized C16-E2O2-C16 gemini surfactant with the transport protein, bovine serum albumin (BSA), utilizing surface tension, fluorescence (intrinsic/extrinsic, synchronous, 3-D and resonance Rayleigh scattering (RRS)), circular dichroism (CD), UV–visible, Fourier transform infrared (FT-IR) and computational methods. The critical micelle concentration (CMC) and surface parameters of the gemini surfactant get modified in the presence of BSA. The interaction of the concerned surfactant with BSA occurred via a static quenching mechanism forming a less stable complex at the higher temperature. Based on calculated thermodynamic parameters, the interaction process was found to be spontaneous (∆Gb0 is negative) and that hydrogen bond (HB) and van der Waals (VDW) forces were predominant forces in stabilizing the complex (both ∆Hb0 and ∆Sb0 are negative). FT-IR and CD measurements demonstrated that the secondary structure conformation of BSA was perturbed because of the BSA-C16-E2O2-C16 complexation. The 3-D and RRS fluorescence studies demonstrated that the BSA size enlarged in presence of the gemini and ensued in the increment of scattering effect and suggested some conformational and micro-environmental alterations of Trp/Tyr residues of BSA (the same results were obtained for pyrene extrinsic fluorescence). Molecular docking and site marker displacement investigations recognized that the surfactant C16-E2O2-C16 predominantly binds within BSA’s site I (sub-domain IIA).

Insights into the impacts of dissolved organic matter of different origins on bioaccumulation and translocation of per- and polyfluoroalkyl substances (PFASs) in wheat

Per- and polyfluoroalkyl substances (PFASs) have been found to be widely present in soil. Dissolved organic matter (DOM) in soil are supposed to greatly affect the bioavailability of PFASs in soil. Herein, hydroponic experiments were conducted to understand the impacts of two kinds of typical DOM, bovine serum albumin (BSA) and humic acid (HA), on the uptake and translocation of legacy PFASs and their emerging alternatives, perfluorooctane sulfonic acid (PFOS), perfluorooctane acid (PFOA), perfluorohexane sulfonic (PFHxS) and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) in wheat (Triticum aestivum L.). The results indicated that both HA and BSA significantly inhibited the bioaccumulation and translocation of PFASs in the roots and shoots of wheat, and the impacts of BSA were greater than HA. This difference was explained by the greater binding affinities of the four PFASs with BSA than with HA, as evidenced by the equilibrium dialysis and isothermal titration calorimetry (ITC) analyses. It was noting that inhibition impacts of the BSA-HA mixture (1:1) were lower than BSA alone. The results of Fourier transform infrared (FT-IR) spectroscopy and excitation-emission matrix (EEM) fluorescence spectroscopy suggested that HA could bind with the fluorescent tryptophan residues in BSA greatly, competing the binding sites with PFASs and forming a cover on the surface of BSA. As a result, the binding of PFASs with BSA-HA complex was much lower than that with BSA, but close to HA. The results of this study shed light on the impacts of DOM in soil on the bioaccumulation and translocation of PFASs in plants.

Влияние металлов переменной валентности на окислительную модификацию аминокислотных остатков альбумина

BACKGROUND: The constancy of the protein composition of the body is one of the most important conditions for normal vital activity. Deviations in the content of the main bioelements, in particular, mixed valence metals, caused by environmental factors, improper nutrition and other factors, lead to various disorders. One of the properties of metals of mixed valence is the abil-ity to cause metal-catalyzed oxidation of proteins in joint action with active forms of oxygen. It seems interesting to study the oxidative modification of the amino acid residues of albumin and the change in its properties. AIM: To study the effect of reactive oxygen intermediates generated by the Fenton reaction in the presence of Fe2+ and Cu2+ on the oxidative modification of amino acid residues of bovine serum albumin. MATERIALS AND METHODS: The study was carried out on bovine serum albumin (BSA), which was incubated for 2 hours in a mixture of Fenton's reagents – FeSO4 + H2O2 and in a mixture of СuSO4 + H2O2. The quantitative protein content in the samples was determined with the bromcresol green reagent (Albumin-Olvex). The content of carbonyl derivatives of proteins was estimated by the method of R.L. Levine modified by E.E. Dubinina. The content of thiol groups in albumin samples from the control and experimental groups was determined by the Ellman method with DTNB (under non-denaturing conditions. RESULTS: The presented results demonstrate that under the action of Cu2+ ions, the formation of carbonyl derivatives of aliphatic amino acids of albumin is less than in the presence of Fe2+, which can be explained by the different degrees of albumin affinity to metals of variable valence. The rate of mobility of oxidatively modified albumin in polyacrylamide gel decreases, which is explained by protein aggregation due to bityrosine cross-links. CONCLUSION: Variable valence metals affect the modification of albumin. The change in the functional properties of the protein is of physiological significance, including the case of extracellular mobilization of iron and copper.

Preparation of SiO2/YPO4:Nd/SiO2 composite microspheres with near-infrared luminescence and surface functionalization

In this study, the core/shell/shell-structured SiO2/YPO4:Nd/SiO2 composite microspheres with near-infrared luminescence property were prepared by sol-gel method. The morphology and structure of the as-prepared microspheres were observed by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and infrared spectroscopy (IR). These tests show that the composite microspheres have a sandwich structure. The diameter of the core SiO2 microspheres is ~ 220 nm, the intermediate layer thickness of rare-earth phosphate is ~ 5 nm, and the outer SiO2 layer is ~ 20 nm thick. The core/shell/shell microspheres are emitted at 1063 nm in the near-infrared region, which attributes to optical transparent windows of biological tissues. Meanwhile, the interaction between the composite microspheres and bovine serum albumin (BSA) was investigated. The results showed that the composite microspheres could quench the emission intensity of BSA by binding the tryptophan residues in BSA. The synthesized core/shell/shell composite microspheres may be used as near-infrared luminescence probes in the field of biological tissue imaging.

Tyrosine residues of bovine serum albumin play an important role in protecting SH-SY5Y cells against heme/H2O2/NO2--induced damage.

Serum albumin (SA) has been shown to act as a heme scavenger in hemolysis and can protect cell against the toxic effect of heme. However, the mechanism of SA in heme detoxification is not well understood. Interestingly, increasing studies indicate that heme/H2O2-dependent reaction is unlikely to be the principal cause of heme toxicity in excessive intravascular hemolysis conditions. Moreover, high levels of NO2- and NO3- were also found in patients with severe hemolytic diseases, which seem to involve in heme toxic effect as well. Therefore, we proposed that studying the protection mechanism of SA against the heme/H2O2/NO2--induced cytotoxicity may be more consistent with free heme-associated disorder pathologies. In this study, we tested the hypotheses that tyrosine residues of bovine serum albumin (BSA) play a prominent role in detoxifying heme in SH-SY5Y cells. Both BSA and tyrosine modified BSA (BSA-T) were used to explore this protective mechanism. Most of cellular injury (oxidative and nitrative damage) induced by heme/H2O2/NO2- were prevented by pretreatment with an equimolar concentration of BSA or BSA-T, and BSA was found more efficient than BSA-T. Meanwhile, BSA or BSA-T binding to heme is not accompanied by a decrease of heme's peroxidase activity. Collectively, these data suggest that the protecting effect of BSA against heme-induced damage in the intravascular hemolysis diseases is not accomplished by preventing the primary reactivity of heme with H2O2, but by trapping radical through special residues such as tyrosine to render other important protein less damaged.

Elucidation of interactions of BSA with [EPMpyr]+[Cl]− using spectroscopic techniques with reference to theoretical thermodynamic and molecular docking studies

On the premise that bovine serum albumin (BSA) is a suitable substitute for Human Serum Albumin (HSA) in experiments, its interactions with ionic liquid (IL), N‑2′,3′‑epoxypropyl‑N‑methyl‑2‑oxopyrrolidinium chloride, ([EPMPyr]{Cl}), was studied. This was done on the basis that the data would give information on the potential role of ionic liquids (ILs) in drug delivery, involved in the treatment of diseases. This was effected by eliciting data from the interactions using UV–visible absorption, emission spectroscopy, circular dichroism (CD), FTIR and molecular docking. The subsequent changes in microenvironment around the tryptophan (Trp) residues in BSA were observed using fluorescence spectroscopy techniques. Furthermore, UV and CD results indicated that the secondary structure of BSA was affected by interaction of IL at high concentrations and temperatures. In addition, the thermophysical and thermodynamic studies were used to evaluate the thermostability of BSA on interaction with IL at various concentrations. These thermophysical and thermodynamic values provided evidence that interactions such as H-bond, dipole, and non-covalent interactions occured in the BSA-IL system. This is attributed, mainly, to hydrophobic and electrostatic interactions resulting in the unfolding of polypeptides within BSA. Therefore, the hydrogen bonding interaction and cation-protein interactions are the driving processes for strong binding between BSA and the IL. Furthermore, molecular docking shows that the entry of IL into subdomains of protein is due to the cationic moiety of oxopyrrolidine interacting with the hydrophobic residues of the domains.

Investigation on the conformational changes of bovine serum albumin in a wide pH range from 2 to 12

The conformation of bovine serum albumin largely depends on its microenvironment pH and affects its physical functions and applications. In this study, we investigated the effects of pH (wide range 2–12) on the conformation of bovine serum albumin based on spectroscopic signals by various spectroscopic means including fluorescence, synchronous fluorescence, resonance light scattering, UV-visible absorption, and circular dichroism. The changes in spectroscopic signals, such as peak position and intensity, showed that the structure of bovine serum albumin varied significantly with pH. The conformation of bovine serum albumin was compact at pH 6–7, as indicated by the largest peak position values and peak intensities in the fluorescence, synchronous fluorescence, and RLS spectra. The structure of bovine serum albumin became loose in the acidic or alkaline environment, as indicated by the decreased peak position values and peak intensities. The microenvironment of the amino acid residues of bovine serum albumin also varied with pH, as indicated by the changing peak position values. At pH 7, the hydrophobicity of the tyrosine and tryptophan residues was the weakest, as indicated by the minimum synchronous fluorescence signals. In addition, the secondary structure of bovine serum albumin, especially α-helix, varied with pH. The content of α-helix reached the maximum value of 68% at pH 6–8, whereas it decreased in the acidic or alkaline environment. The study provides valuable details for studying the physiological function and applications of serum albumins.

INTERACTION OF COPPER OXIDE NANOPARTICLES WITH BOVINE SERUM ALBUMIN BY SPECTROSCOPIC STUDIES

Objective: Since structural changes of adsorbed protein are necessary for cellular uptake of nanoparticles (NPs) it is of prime importance to know about structural changes of bovine serum albumin (BSA) when it interacts with CuO NPs–a potential new antitumor drug.Methods: CuO NPs prepared by sol-gel technique were characterized by x-ray diffraction (XRD) and tunneling electron microscope (TEM) techniques. The conformational changes induced by CuO NPs on BSA were studied by various spectroscopic techniques such as steady state and time-resolved fluorescence measurements. The changes in fluorescence emission parameters such as fluorescence intensity, fluorescence emission maximum and lifetimes of fluorescent residues in BSA were studied.Results: XRD analysis showed the average particle size as 32 nm. The TEM micrograph showed particles of different size varying from 10 to 45 nm. Fluorescence quenching was confirmed due to a decrease in fluorescence intensity of CuO NPs–BSA complex. The analysis of lifetime measurements indicated BSA contained two tryptophan (trp) residues that fluoresced in different environments. Static quenching mechanism was confirmed by time-resolved measurements when BSA interacted with CuO NPs.Conclusion: Minor structural changes of BSA protein were observed during the interaction studies.

Comprehensive study of interaction between biocompatible PEG-InP/ZnS QDs and bovine serum albumin.

Polyethylene glycol (PEG) surface modified biocompatible InP/ZnS quantum dots (QDs) act as a potential alternative for conventional carcinogenic cadmium-based quantum dots for in vivo and in vitro studies. Comprehensively, we studied the interaction between a model protein bovine serum albumin (BSA) and PEGylated toxic free InP/ZnS QDs using various spectroscopic tools such as absorption, fluorescence quenching, time resolved and synchronous fluorescence spectroscopic measurements. These studies principally show that tryptophan (Trp) residues of BSA have preferable binding affinity towards PEG-InP/ZnS QDs surface and a blue shift in Trp fluorescence emission is a signature of conformational changes in its hydrophobic microenvironment. Photoluminescence (PL) intensity of Trp is quenched by ground state complex formation (static quenching) at room temperature. However, InP/ZnS@BSA conjugates become unstable with increasing temperature and PL intensity of Trp is quenched via dynamic quenching by PEG-InP/ZnS QDs. Experimentally determined thermodynamic parameters for these conjugates have shown spontaneity, entropy driven and exothermic nature of bio-conjugation. The calculated binding affinity (n ≅ 1, Hill coefficient) suggest that the affinity of InP/ZnS QDs for a BSA protein is not dependent on whether or not other BSA proteins are already bound to the QD surface. Energy transfer efficiency (E), Trp residue to InP/ZnS QDs distances and energy transfer rate (kT ) were all obtained from FÖrster resonance energy.

Interaction of zearalenone with bovine serum albumin as determined by fluorescence quenching.

The major aim of this study was to examine the binding of zearalenone (ZEN) to bovine serum albumin (BSA) by measuring the quenching of the intrinsic fluorescence of the protein under aqueous conditions. The results suggest that ZEN has a strong ability to quench the intrinsic fluorescence of BSA through a static mechanism. The hydrophobicity of the microenvironment around the tyrosine (Tyr) residues in BSA was increased in the presence of ZEN. The quenching constants, ratio of protein with ZEN, and thermodynamic parameters were determined. The collaborative action of hydrophobic and electrostatic interactions was involved in the binding process and the formation of the complex was mainly enthalpy-driven. The average binding distance between ZEN and BSA was calculated to be 2.20nm. This is much closer in magnitude than the distance reported for the binding of most toxins to HSA and most pharmaceuticals to BSA, indicating a strong affinity.

Multivalent neuraminidase hydrolysis resistant triazole-sialoside protein conjugates as influenza-adsorbents

We report the synthesis of pseudo triazole-sialoside protein conjugates of various valency that are resistant to neuraminidase for the adsorption of influenza viruses. The glycotriazole monomer bearing an amine-functionalized linker was synthesized by click chemistry and grafted to the lysine residues of bovine serum albumin (BSA) or human serum albumin (HSA) via diethyl squarate and adipate-based strategy. The binding of hemagglutinin (HA) and neuraminidase (NA) on the virion surface by the synthetic neoglycoproteins were evaluated by hemagglutination and neuraminidase inhibition assay, respectively. The results demonstrated that these synthetic glycoproteins have significantly higher affinity with NA than HA. The interactions between these neoglycoproteins and intact influenza viruses were further investigated by Dynamic Light Scattering (DLS) technique. The pronounced agglutination indicated that these glycoconjugates can be used as adsorbents to prevent virus from invading host cells as well as the release of newly synthesized viral particles, which are crucial in the life cycle of the influenza virus. With the high binding affinity to intact influenza viruses, these neoglycoproteins can also be used as probe to elucidate the molecular mechanism of the sialic acid-influenza recognition and biosensors for influenza detection.