PDMS微芯片吸附牛血清白蛋白的研究

材料表面的物理和化学性质对蛋白质的吸附具有很大的影响[1].对蛋白质吸附的研究是研制生物传感器、生物芯片和生物材料的基础.     

Configuration of bovine serum albumin adsorbed on polymer particles with grafted dextran corona

The configuration of BSA macromolecules adsorbed on the surfaces of poly(alkylcyanoacrylate) nanoparticles has been determined using small angle neutron scattering (SANS). The nanoparticles were made by anionic emulsion polymerization (AEP) and self-assembly of dextran–poly(isobutylcyanoacrylate) (PICBA) copolymers. They have a hydrophobic PICBA core and a hydrophilic dextran corona. In vivo, they are recognized by the macrophages of the mononuclear phagocyte system. The amount of BSA bound to the particles, at adsorption equilibrium, has been determined through immunodiffusion, immunoelectrophoresis, and SANS. For particles with a radius of 25.3 nm, the adsorption was found to saturate at 64 adsorbed BSA molecules per particle. The configuration of the adsorbed BSA molecules was determined from the SANS scattering curves, first at full contrast, and then at contrast match. Both experiments indicate that the BSA molecules are adsorbed on the PICBA core, in a flat configuration. This result may be important for understanding the in vivo opsonization mechanisms of nanoparticles and their resulting biodistribution.     

Binding of naproxen to bovine serum albumin and tryptophan-modified bovine serum albumin

Two classes of binding sites, a single high-affinity site with an association constant of 4·8×10⁶ M⁻¹ and two low-affinity sites with association constant of about 0·05×10⁶ M⁻¹ have been observed in the interaction of Naproxen with bovine serum albumin (BSA). Chemical modification of two tryptophan residues in BSA with 2-hydroxy-5-nitrobenzyl bromide has led to a reduction in the association constant of the high-affinity site by 89% and its number of binding sites by 66% suggesting the involvement of tryptophan residues in the high-affinity site. In contrast, the two low-affinity sites were not affected by the modification. Binding of Naproxen to the low-affinity sites of BSA induces microdisorganisation of the albumin structure leading to conformational changes as evident from fluorescence measurements with 1-anilino-8-naphthalenesulphonic acid as the probe.     

Viscoelastic study of the adsorption of bovine serum albumin on gold and its dependence on pH

Using a quartz crystal resonator system operating at 5 MHz the shear wave propagating properties of bovine serum albumin (BSA) have been monitored as it is adsorbed on a gold surface from a phosphate buffered saline (PBS) solution. Employing a 2-layer model for the combined BSA layer and PBS solution, the viscoelasticity of the BSA layer may be determined in real time as the adsorption on gold proceeds. The viscoelasticity is found to depend on the pH of the PBS solution and changes gradually over long times. It is suggested that at the low frequency of the measurement, large-scale molecular motions are being monitored which are a consequence of the structural changes in the protein molecules undergoing adsorption. Such low-frequency molecular motions are difficult to examine by any other technique. The results and their interpretation in viscoelastic terms demonstrate the considerable potential of the quartz crystal resonator system for assessing the stability of proteins on surfaces and their suitability as coatings for prosthetic materials.     

Buildup mechanism of carboxymethyl cellulose and chitosan self-assembled films

Films with different numbers of layers have been built by alternating the adsorption of carboxymethyl cellulose (CMC) and chitosan (CHI) at different pH levels. The adsorption process was recorded by quartz crystal microbalance (QCM). The results showed that under all pH conditions considered, the growth of the films is nonlinear. The film construction performed at pH 4.0 (preferred assembly pH) with different numbers of bilayers (CMC/CHI as one bilayer) was also observed step by step by atomic force microscopy (AFM). Comparing the growth process from QCM with the surface morphological changes from AFM shows the existence of an inhomogeneous structure for the first nine bilayers, and, after a coalescence of islands, an increase in the number of bilayers was demonstrated. The possible growth mechanism was also evaluated.     

Investigating adsorption of bovine serum albumin on cellulosic substrates using magnetic resonance imaging

Cellulosic biomass is recalcitrant to enzymatic hydrolysis which greatly reduces the efficiency of biofuels production. Specifically, the lignin component of biomass is thought to provide non-productive binding sites for glycosyl hydrolases, effectively disabling the enzymes from completing further digestion. A thorough understanding of the adsorption rates of protein molecules on celluloses—especially lignocelluloses—is crucial to improving the cyclic steps of adsorption, diffusion, and reaction. We use magnetic resonance imaging (MRI) to detect concentrations of bovine serum albumin (BSA) in equilibrium with various cellulose substrates, including delignified and acid-treated lignocellulosic substrates. BSA is believed to be an effective adsorption blocker during enzymatic hydrolysis of lignocellulosics, and has been correlated with an increase in reaction yield. We found BSA to have little adsorption onto the chosen cellulose substrates in the low concentration range studied. Ultraviolet (UV) absorption measurements of reaction supernatants at 280 nm were used to confirm the MRI results for each of the substrate types. The advantages of the MRI technique are compared with that of the traditional UV measurement.     

Comparative study of the thermodynamics and extrathermodynamics on the conformational transformation and adsorption of bovine serum albumin

The adsorption and conformation transformation of bovine serum albumin (BSA) on a reversed-phase octadecylsilyl group based on silica reversed-phase chromatographic column were studied in the temperature of 12–50°C. The thermodynamic and extrathermodynamic data were determined and compared to each other. The results showed that when temperature was below 20°C, BSA existed only in its native conformation state A; whereas when temperature was over 20°C, parts of the conformation state A changed to state B. In transformation process, endothermal and nonspontaneous reaction occurred and the entropy change was favorable for the transformation; while in adsorption process, the reaction was exothermal and spontaneous and driven simultaneously by enthalpy and entropy change. The compensation temperature in the conformation transformation of BSA was significantly less than that in the adsorption of the two conformation states. This phenomenon demonstrated the big difference during the two processes.     

Effect of phosphorylated organic compound on the adsorption of bovine serum albumin by hydroxyapatite.

The amount of adsorption of bovine serum albumin (BSA) by hydroxyapatite (HAP) increased with a concentration of CaCl2 due to the bridging effect of Ca2+ between adsorbate BSA and adsorbent HAP. On the other hand, it decreased remarkably with a concentration of K2HPO4. This was explained in terms of the effects of ionic strength and competitive adsorption between inorganic phosphate anion (Pi) and BSA, because BSA is in negatively charged over the examined pHs. A similar effect was observed in the presence of phosphorylated compounds such as phosphoserine, phytate, and phosphorylated polyvinylalcohol. The inhibiting effect of these compounds was stronger than that of their mother compounds (serine, inositol, and polyvinylalcohol). This result shows that phosphate groups bound to the mother compounds interfere with the adsorption of BSA by HAP in the same manner that Pi does. Although the adsorption of BSA was almost irreversible with respect to dilution with water, desorption was performed when these organic phosphorylated compounds were added after the accomplishment of the adsorption of BSA. However, the effective concentration of the phosphorylated compounds for the desorption of BSA was fairly higher than that for the competitive inhibition against the BSA adsorption.     

Electrically polarized biphasic calcium phosphates: adsorption and release of bovine serum albumin

In this study, we applied electrical polarization technique to increase adsorption and control protein release from biphasic calcium phosphate (BCP). Three different biphasic calcium phosphate (BCP) composites, with hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP), were processed and electrically polarized. Our study showed that stored charge was increased in the composites with the increase in HAp percentage. Adsorption of bovine serum albumin (BSA), as a model protein, on the poled as well as unpoled surfaces of the composites was studied. The highest amount of BSA adsorption was obtained on positively poled surfaces of each composite. Adsorption isotherm study suggested a multilayer adsorption of BSA on the BCP composites. The effect of electrical polarization on BSA release kinetics from positively charged BCP surfaces was studied. A gradual increase in percent BSA release from positively charged BCP surfaces with decreasing stored charge was observed. Our study showed that the BCP based composites have the potential to be used as a drug or growth factor delivery vehicle.     

Structural characteristics of activated carbons and ibuprofen adsorption affected by bovine serum albumin

Structural characteristics of a series of MAST carbons were studied using scanning electron microscopy images and the nitrogen adsorption isotherms analyzed with several models of pores and different adsorption equations. A developed model of pores as a mixture of gaps between spherical nanoparticles and slitlike pores was found appropriate for MAST carbons. Adsorption of ibuprofen [2-(4-isobutylphenyl)propionic acid] on activated carbons possessing different pore size distributions in protein-free and bovine serum albumin (BSA)-containing aqueous solutions reveals the importance of the contribution of mesopores to the total porosity of adsorbents. The influence of the mesoporosity increases when considering the removal of the drug from the protein-containing solution. Cellulose-coated microporous carbon Norit RBX adsorbs significantly smaller amounts of ibuprofen than uncoated micro/mesoporous MAST carbons whose adsorption capability increases with increasing mesoporosity and specific surface area, burnoff dependent variable. A similar effect of broad pores is observed on adsorption of fibrinogen on the same carbons. Analysis of the ibuprofen adsorption data using Langmuir and D'Arcy-Watt equations as the kernel of the Fredholm integral equation shows that the nonuniformity of ibuprofen adsorption complexes diminishes with the presence of BSA. This effect may be explained by a partial adsorption of ibuprofen onto protein molecules immobilized on carbon particles and blocking of a portion of narrow pores.     

The effect of adsorbed carboxymethyl cellulose on the cotton fibre adsorption capacity for surfactant

The research reported in this paper demonstrates that the capacity of cotton fibres to adsorb cationic surfactants as well as the rate of the adsorption process can be increased by adsorbing carboxymethyl cellulose (CMC) onto the fibre surfaces; in addition, the adsorption can be restricted to the fibre surface. CMC was deposited by means of adsorption from an aqueous solution. The adsorption of N-cetylpyridinium chloride (CPC) from an aqueous solution onto the CMC-modified fibres was measured using UV-spectrometric determination of the surfactant concentration in the solution. Adsorption onto the cotton fibres was studied in a weakly basic environment (pH 8.5) where cotton fibres are negatively charged and the CPC ion is positively charged. Modification of the fibres by adsorption of CMC introduces new carboxyl groups onto the fibre surfaces, thereby increasing the adsorption capacity of the fibres for CPC. The initial rate of adsorption of CPC increased proportionally with the amount of charge; however, this rate slowed down at high degrees of coverage on fibres with a high charge. The adsorption of cationic surfactant to the anionic surface groups was stoichiometric, with no indication of multilayer or admicelle formation. It was evident that the acidic group content of the fibres was the primary factor determining cationic surfactant adsorption to these fibres.     

Structure and properties of biodegradable carboxymethyl cellulose films containing silver nanoparticles

Silver nanoparticles stabilized in a solution of sodium carboxymethyl cellulose with a degree of substitution of 0.85 and a degree of polymerization of 600 have been synthesized. The structuring; physical, chemical, and mechanical properties; and antimicrobial activities of films prepared from sodium carboxymethyl cellulose solutions containing silver nanoparticles have been studied. The shapes, quantities, and sizes of the silver nanoparticles occurring in the sodium carboxymethyl cellulose films were determined with the use of transmission electron microscopy, atomic force microscopy, and UV spectroscopy. It was found that an increase in the concentration of silver nitrate in sodium carboxymethyl cellulose solutions, as well as photoirradiation of the films, leads to the changes in the sizes and shapes of silver nanoparticles. The shapes, sizes, and quantities of silver nanoparticles determine their biological activity. An increase in the quantity of 5- to 25-nm silver nanoparticles was found to enhance the microbicidal activities of the carboxymethyl cellulose films.     

Effects of acetonitrile on adsorption behavior of bovine serum albumin onto synthetic calcium hydroxyapatite particles

The objective of this study was to examine the effects of acetonitrile (AN) on the adsorption behavior of bovine serum albumin (BSA) onto calcium hydroxyapatite [Ca10(PO4)6(OH)2 Ca10, Hap] materials by combining the ultraviolet (UV) and circular dichroism (CD) measurements of BSA solution. The structural change of BSA molecules with addition of AN was investigated by UV and CD spectroscopy measurements prior to studying adsorption behavior of BSA onto Hap. The CD spectra revealed that the fraction of alpha-helical content of BSA is remarkably decreased at AN concentrations above 30 vol.%, while beta-sheet content is increased. On the other hand, the percentages of random coil and turn contents were decreased only slightly. In addition to this secondary structural change of BSA, the UV spectra suggested that the tertiary structure of protein molecules was also changed by the addition of large amounts of AN; BSA molecules associate to form molecular aggregates at [AN]> or =40 vol.%. From the adsorption of BSA onto Hap particles (ca. 30 nm in the particle length) from a water-AN mixed solution, it was revealed that the adsorption behavior of BSA strongly depends on the change of secondary and tertiary structures of BSA by addition of AN. The contraction of BSA molecules at low AN concentrations (10-20 vol.%) gave their small cross-sectional area, providing a large amount of adsorption (n(BSA)), although n(BSA) was decreased above 30 vol.% AN by enlargement of BSA molecules with solvation and unfolding some alpha-helix domains. The n(BSA) values of the systems with AN exhibited a maximum; n(BSA) was increased at a lower BSA concentration region, although it was decreased at a higher BSA concentration due to self-association. Accompanying the change of n(BSA) with AN addition, the maxima of electrophoretic mobility (em) of the Hap particles were observed for the systems with AN, although the em of Hap particles was normally increased and saturated with increase in protein coverage for the native structure on the system without AN. On the other hand, because the aggregated BSA molecules could be cooperatively bound, the adsorption of BSA onto the Hap particles with large size (108 nm in the particle length) was enhanced in the presence of AN.     

A novel dual-impedance-analysis EQCM system--investigation of bovine serum albumin adsorption on gold and platinum electrode surfaces

Both quartz crystal micro-balance (QCM) impedance and electrochemical impedance spectroscopy (EIS) methods are widely used in interface studies. This paper presents details about a new strategy for simultaneous, mutual-interference-free and accurate measurements of QCM impedance and EI, through connecting a suitable capacitance in series with the piezoelectric quartz crystal (PQC) between QCM impedance and EIS measurement instruments. Combined and individual measurements of QCM impedance and EIS during silver deposition gave results comparable with each other, demonstrating the reliability of the proposed method. Bovine serum albumin (BSA) adsorption on gold and platinum electrodes in Britton-Robinson (B-R) buffers was investigated, and the Fe(CN)6(3-)/Fe(CN)6(4-) couple was used as an electrochemical probe to characterize BSA adsorption. While the reversibility of Fe(CN)6(3-)/Fe(CN)6(4-) couple on bare Au and Pt electrodes changed very slightly with decreasing solution pH from pH approximately 7 to pH approximately 2, the standard rate constant (ks) of this couple increased abruptly with solution pH below pH approximately 4.5 at a BSA-modified Au electrode, but decreased with solution pH at a BSA-modified Pt electrode. By analyzing the QCM impedance data with a modified BVD equivalent circuit and the EI data with a modified Randle's equivalent circuit, inflexion changes at pH approximately 4.5 were all found at pH-dependent responses of the resonant frequency, the double-layer capacitance, the capacitance of the adsorbed BSA layer, the peak-absorbance values of BSA solutions at 277.5 and 224.5 nm, and so on. It was also found that a BSA adsorption layer can effectively inhibit gold corrosion during ferrocyanide oxidation in a ferrocyanide-containing BR solution. Some preliminary explanations of these findings have been given. The proposed method is highly recommended for wider applications in surface science.     

Effect of bovine serum albumin on the structure and properties of Langmuir Blodgett films based phosphocholine and cholesterol

Mono- and bilayer Langmuir-Blodgett films based on phosphocholine and cholesterol and prepared by horizontal and vertical deposition are investigated by atomic force microscopy. It was found that bovine serum albumin (BSA) included at the stage of film formation. At the same time, isolation has a considerable effect on their structure. It was shown that the globular formation of nanostructures with heights of 4–7 nm occurs as a result of transferring lipids to a hydrophobic surface from a subphase containing BSA, indicating the reorganization of monolayers during protein isolation and inclusion in its composition.     

金丝桃苷与牛血清白蛋白相互作用的研究

采用荧光共振能量转移法研究了金丝桃苷与牛血清白蛋白的相互作用.金丝桃苷对牛血清白蛋白(BSA)的荧光猝灭类型是静态猝灭,25℃时的结合位点数为0.5451.并依据F(o)ster非辐射能量转移理论,研究了给体(牛血清白蛋白)--受体(金丝桃苷)间的结合距离R.和能量转移效率E分别为2.04nm和0.66.同时,采用同步...     

Influence of the mobile phase composition on the adsorption isotherms of an amino-acid derivative on immobilized bovine serum albumin

Summary The saturation capacity of columns packed with bovine serum albumin immobilized on silica has been determined for the N-benzoyl derivative of leucine at different compositions of a 1-propanol/water mobile phase. In all cases it has been found that the equilibrium adsorption data are well accounted for by a biLangmuir isotherm. The experimental data are consistent with the assumption that the column saturation capacity of the chiral selective sites as well as the saturation capacity of the non-selective sites are independent of the 1-propanol concentration in the range 0–10%.     

Fibronectin and bovine serum albumin adsorption and conformational dynamics on inherently conducting polymers: a QCM-D study

Quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to characterize the adsorption of the model proteins, bovine serum albumin (BSA) and fibronectin (FN), to polypyrrole doped with dextran sulfate (PPy-DS) as a function of DS loading and surface roughness. BSA adsorption was greater on surfaces of increased roughness and was above what could be explained by the increase in surface area alone. Furthermore, the additional mass adsorbed on the rough films was concomitant with an increase in the rigidity of the protein layer. Analysis of the dynamic viscoelastic properties of the protein adlayer reveal BSA adsorption on the rough films occurs in two phases: (1) arrival and initial adsorption of protein to the polymer surface and (2) postadsorption molecular rearrangement to a more dehydrated and compact conformation that facilitates further recruitment of protein to the polymer interface, likely forming a multilayer. In contrast, FN adsorption was independent of surface roughness. However, films prepared from solutions containing the highest concentration of DS (20 mg/mL) demonstrated both an increase in adsorbed mass and adlayer viscoelasticity. This is attributed to the higher DS loading in the conducting polymer film resulting in presentation of a more hydrated molecular structure indicative of a more unfolded and bioactive conformation. Modulating the redox state of the PPy-DS polymers was shown to modify both the adsorbed mass and viscoelastic nature of FN adlayers. An oxidizing potential increased both the total adsorbed mass and the adlayer viscoelasticity. Our findings demonstrate that modification of polymer physicochemical and redox condition alters the nature of protein-polymer interaction, a process that may be exploited to tailor the bioactivity of protein through which interactions with cells and tissues may be controlled.     

Effect of carboxymethyl cellulose concentration on physical properties of biodegradable cassava starch-based films

Background  

Cassava starch, the economically important agricultural commodity in Thailand, can readily be cast into films. However, the cassava starch film is brittle and weak, leading to inadequate mechanical properties. The properties of starch film can be improved by adding plasticizers and blending with the other biopolymers.