Number Of Active Binding Sites Research Articles

Nondestructively Assemble Cell Membrane-Coated Nanoparticles by Host-Guest Interactions for Efficient Capture of Bioactive Compounds.

Cell membrane-coated nanoparticles (CNPs) have emerged as an attractive nanomedical tool. The basic premise is that the surface properties of natural cells can be integrated with the physical and chemical properties of nanoparticles by coating them with cell membranes. However, the degree of preservation of membrane proteins on nanoparticles, a key indicator related to the biomedical function of these biomimetic systems, is largely affected by the coating process. Herein, we report a supramolecular cell membrane conjugation strategy mediated by host-guest interactions to assemble CNPs without compromising protein activities. β-cyclodextrin (β-CD) was rapidly and stably inserted into the cell membrane by a lipid anchor without affecting the function of membrane proteins, thus attaching host-guest sites to the membrane surface. By harnessing the excellent binding affinity between β-CD attached to the membrane surface and adamantane, a supramolecular cell membrane-magnetic nanoparticle conjugate (CDM@AMNPs) was synthesized. Thanks to the nondestructive assembly of this strategy, CDM@AMNPs were endowed with a greater number of active binding sites, exhibiting efficient adsorption performance. This supramolecular conjugation strategy mediated by nonreceptor site-based host-guest interactions proposes a scalable and cell-friendly strategy for the development of highly efficient CNPs.

High-performance novel ZIF-67 and ZIF-67@MWNTs composite adsorbents for efficient removal of pharmaceutical contaminant from water: Exceptional capacity and excellent reusability

The removal of pharmaceutical waste products like ibuprofen (IBP) from water is very important for the environment and the health of human and aquatic organisms. In the present work, the adsorption of IBP from aqueous solution was investigated by synthesizing novel ZIF-67 and ZIF-67@MWNTs hybrid composite material by incorporating ZIF-67 particles with carboxyl functionalized multiwalled carbon nanotubes (COOH-MWNT). The synthesized ZIF-67 and ZIF-67@MWNTs adsorbents were characterized by the XPS, XRD, SEM, TEM, BET, FTIR, and TGA analysis to examine their physio-chemical properties. The synthesized novel ZIF-67 has a 1743 m2/g BET surface and 0.692 cm3/g total pore volume. The IBP adsorption process including isotherm and kinetic studies as well as the effect of different parameters i.e. pH, initial concentration, time, adsorbents, and their dosage were examined. Among all the synthesized composite materials, the ZIF-67@MWNT-50 mg material showed the highest IBP adsorption capacity of 841 ± 5 mg/g, about 467 ± 5 mg/g more than the ZIF-67 following the Langmuir and pseudo-second-order model. The enhancement in the IBP adsorption is because of the incorporation of COOH-MWNT and the presence of a large number of active binding sites which showed the van der Waal interactions, host–guest interactions, π- π interactions, and H-bonding between the adsorbate and adsorbent. For the detailed study of the IBP adsorption mechanism of ZIF-67, molecular dynamic (MD) simulations were performed. Additionally, the reusability of ZIF-67@MWNT-50 mg material via a simple regeneration method up to five cycles while maintaining about 96 % adsorption capacity of the pristine non-used ZIF-67@MWNT-50 mg material revealed its importance as an effective adsorbent for the adsorptive elimination of different pharmaceutical hazardous materials from water.

Characterization of Lactoperoxidase (LPO) Enzyme Thin Films for Volatile Organic Compound (VOC) Sensing

Spin-coated thin films of lactoperoxidase enzyme (LPO) were used on conjunction with the bio-composite (chitosan–gelatin), glutaraldehyde and cysteine as first-layers to characterize the interactions on the sensing characteristics. The prospect of tuning these three under-layers is to investigate the change of active vapor binding sites of LPO film after inter-layer interactions. Initially, spin-coated thin film properties of three under-layers and LPO are investigated by reporting deposited mass and layer thickness using the quartz crystal microbalance (QCM) frequency change. LPO spin-coated films with different under-layers are exposed to formic acid, acetic acid, chloroform, acetone and ethyl acetate vapors. The response characteristics of LPO films are investigated via QCM using time dependence frequency recording. LPO films are sensitive to those five vapors and the chemical and the physical properties of the analytes affect the sensitivity and the response rate. The results showed that the structural changes in the thin film affect the number of active binding sites of sensitive layer and thus the sensor response can be enhanced.

Controlled Carboxylic Acid-Functionalized Silicon Nitride Surfaces through Supersonic Molecular Beam Deposition.

The functionalization of inorganic surfaces by organic functional molecules is a viable and promising method towards the realization of novel classes of biosensing devices. The proper comprehension of the chemical properties of the interface, as well as of the number of active binding sites for bioreceptor molecules are characteristics that will determine the interaction of the sensor with the analyte, and thus its final efficiency. We present a new and reliable surface functionalization route based on supersonic molecular beam deposition (SuMBD) using 2,6-naphthalene dicarboxylic acid as a bi-functional molecular linker on the chemically inert silicon nitride surface to further allow for stable and homogeneous attachment of biomolecules. The kinetically activated binding of the molecular layer to silicon nitride and the growth as a function of deposition time was studied by X-ray photoelectron spectroscopy, and the properties of films with different thicknesses were investigated by optical and vibrational spectroscopies. After subsequent attachment of a biological probe, fluorescence analysis was used to estimate the molecular layer's surface density. The successful functionalization of silicon nitride surface via SuMBD and the detailed growth and interface analysis paves the way for reliably attaching bioreceptor molecules onto the silicon nitride surface.

3D printing calcium alginate adsorbents for highly efficient recovery of U(VI) in acidic conditions

In this study, a three-dimensional (3D) porous calcium alginate (3D CA) scaffold was successfully constructed using a direct-ink-writing-based 3D printing method combined with an in-situ calcium ion cross-linking procedure. The 3D CA contained orderly aligned microstructures with excellent structural robustness and an abundant number of active binding sites. The adsorption experiments verified that 3D CA had a considerably wide pH value (3−10) serving range, but also delivered a significantly higher adsorption capacity for U(VI) (117.3 mg/g at pH = 2.5) under acidic conditions, compared to other previously reported alginate-based porous adsorbents. The adsorption mechanisms originated from the synergistic effect of electrostatic interactions and ion exchange. The 3D CA eluted the adsorbed U(VI) in a strong acid solution through protonation mechanism, facilitating the continued enrichment and recycling of U(VI). In addition, the 3D CA demonstrated good microstructure stability and absorption capacity stability when it was immersed in hydrochloric acid solutions at different concentrations (3.6 × 10–3 to 2 mol/L) for 24 h. Therefore, the 3D CA could be used for the removal and recycling of U(VI) from acidic solutions beyond its wide pH working range, due to its stronger acid stability and higher U(VI) adsorption capacity.

Microwave assisted ultrafast synthesis of graphene oxide based magnetic nano composite for environmental remediation

We have successfully synthesized multi-layer graphene oxide and graphene oxide based magnetic nanocomposite (M/GO) by microwave-assisted modified Hummers’ method for removal of toxic lead (Pb 2+ ) and cadmium (Cd 2+ ) ions from aqueous solution. The X-ray diffraction spectra of synthesized graphene oxide and M/GO confirm increased interlayer spacing along c-axis. Raman spectra revealed the good quality of synthesized GO and M/GO. The wrinkles were seen in the SEM images of synthesized graphene oxide. The presence of conjugated double bond (C C) and carbonyl (C O) were confirmed by using the UV–Vis spectroscopic spectra. Brunauer–Emmett–Teller (BET) analysis showed high (126 m 2 /g) surface area M/GO composite which accounts for large number of active binding sites for the adsorption of heavy metal ions. The adsorption studies revealed that Pb 2+ ions were efficiently adsorbed on GO sheets. Interestingly, M/GO showed better adsorption for cadmium ions. Addition of stock solution of Pb 2+ and Cd 2+ ions to M/GO solution, removal of M/GO containing Pb 2+ , and Cd 2+ ions using Neodymium magnet.

Application of amorphous zirconium (hydr)oxide/MgFe layered double hydroxides composite in fixed-bed column for phosphate removal from water

BACKGROUND AND OBJECTIVES: Fixed-bed column has been considered an industrially feasible technique for phosphate removal from water. Besides the adsorption capacity, the effectiveness of an adsorbent is also determined by its reusability efficiency. In this study, phosphate removal by a synthesized amorphous zirconium (hydr)oxide/MgFe layered double hydroxides composite in a fixed-bed column system was examined. METHODS: The effects of flow rate, bed height, phosphate concentration, solution pH, and adsorbent particle size on the phosphate adsorption ability were examined through a series of continuous adsorption experiments. The appropriate breakthrough curve models, phosphate adsorption from real anaerobic sludge and synthetic seawater, column regeneration and reusability, and adsorption mechanism were also investigated for practical application feasibility. FINDINGS: The results showed that the increased bed height and phosphate concentration, and reduced flow rate, pH, and adsorbent particle size were found to increase the column adsorption capacity. The optimum adsorption capacity of 25.15 mg-P/g was obtained at pH 4. The coexistence of seawater ions had a positive effect on the phosphate adsorption capacity of the composite. Nearly complete phosphate desorption, with a desorption efficiency of 91.7%, could be effectively achieved by 0.1 N NaOH for an hour. Moreover, the initial adsorption capacity was maintained at approximately 83% even after eight adsorption-desorption cycles, indicating that the composite is economically feasible. The high phosphate adsorption capacity of the composite involves three main adsorption mechanisms, which are electrostatic attraction, inner-sphere complexation, and anion exchange, where the amorphous zirconium hydr(oxide) on the surface of the layered double hydroxides likely increased the number of active binding sites and surface area for adsorption. CONCLUSION: The amorphous zirconium (hydr)oxide/MgFe layered double hydroxides composite, with its high adsorption capacity and superior reusability, has the potential to be utilized as an adsorbent for phosphorus removal in practical wastewater treatment. This study provides insights into the design of amorphous zirconium (hydr)oxide/MgFe layered double hydroxides composite for phosphorus removal and recovery in a practical system.

Mussel-inspired polydopamine functionalized recyclable coconut shell derived carbon nanocomposites for efficient adsorption of methylene blue

Relatively cheap or at no cost, easily available, renewable agricultural waste has been given a new purpose. Using coconut shells as the raw material, and being obtained from agricultural, industry by-products, or even waste materials were used as carbon resource. Acid etching coconut shells carbon (AC) rendered micro/nanoscale hierarchical structures and made the surface available for further modification. Then, the surface of acidified coconut shell carbon was engineered via mussel inspired chemistry. The polydopamine functionalized AC composites (AC-PDA) were applied for efficient removal of methylene blue (MB) dye. Further, the surface morphology, and chemical structure were evaluated by means of scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). Through the combination of acid etching and mussel inspired chemistry, organic functional groups can be successfully introduced onto the surface of the coconut shells carbon. The improvement of adsorption capacity of AC-PDA compared with AC is probably due to the increased number of active binding sites resulting from surface modification and formation of new functional groups.

Photocatalytic Activity of Nonprecious Metal WSe2/g-C3N4 Composite Under Visible Light Irradiation

The WSe2/g-C3N4 (graphite carbon nitride) composite with photocatalytic properties was synthesized using a hydrothermal method. This synthesis pathway can be characterized by being simple, inexpensive and nonpolluting, integrating the concept of green chemistry. The WSe2/g-C3N4 composite could effectively degrade methyl orange solution under visible light irradiation. The decolorization experiment of methyl orange solution shows that the degradation rate of the 30[Formula: see text]wt.% WSe2/g-C3N4 composite can reach 98.7% after 100[Formula: see text]min of illumination, while the degradation rate of pure g-C3N4 was only 87.6% under the same conditions. This can be attributed to the fact that the combination of WSe2 and g-C3N4 nanosheets can increase the number of active binding sites, increasing the rate of charge separation and transport ability, decreasing the recombination rate of the photogenerated electron–hole pairs. Therefore, the WSe2/g-C3N4 composite will have potential development as a new material with low cost, easy synthesis and excellent performance in photocatalytic degradation of water pollution.

A versatile TOCN/CGG self-assembling hydrogel for integrated wastewater treatment

Water pollution caused by industrial discharges is a severe threat to our society. Thus, efficient and sustainable materials that can provide potential effective solutions are in high demand. The present work reports the development of a versatile strategy based on TEMPO-oxidized cellulose nanofibers (TOCN)/cationic guar gum (CGG) self-assembling hydrogels to remedy wastewater containing oil, heavy metal ions or organic dyes. The TOCN/CGG hydrogel-coated filter papers, prepared via a layer-by-layer deposition process, show a high oil/water separation efficiency (around 99%), with the coating amount of being as low as 0.032 g m−2 (dry mass). Through gravitational force only, the water flux can be as high as 443 L m−2 h−1. The as-prepared oil/water separation materials exhibited good recyclability. The monolithic TOCN/CGG hydrogel can also efficiently remove copper ions (Cu2+) and dyes (i.e. thioflavin T and methyl orange), based on an adsorption mechanism. The adsorption amount of Cu2+ can be as high as 498.5 mg g−1, while that of thioflavin T and methyl orange can be 430.2 mg g−1 and 134.3 mg g−1, respectively. The mass transfer driving force and the number of active binding sites are the two main factors affecting the adsorption process. This all-polysaccharide hydrogel system may be a promising potential for wastewater remedy, due to its facile/“green” preparation process and high performance, as well as the abundance and environmental-friendliness of its raw materials.

Development of a Highly Active Fluorescence-Based Detector for Yeast G Protein-Coupled Receptor Ste2p.

Twenty analogs of [Orn6,D-Ala9]α-factor were synthesized and assayed for their biological activities: seven analogs of [Orn6,X9]α-factor, seven analogs of [X6,D-Ala9]α-factor, five analogs of [X5,X6,D-Ala9]α-factor, and native α-factor (X = amino acids). Their biological activities (halo, gene induction, and affinity) were measured using S. cerevisiae Y7925 and LM102 and compared with those of native α-factor (100%). G protein-coupled receptor was expressed in strain LM102 containing pESC-LEU-STE2 vector. [Dap6,D-Ala9]α-factor with weak halo activity (10%) showed the highest receptor affinity (＞ 230%) and the highest gene induction activity (167%). [Arg6,D-Ala9]α-factor showed the highest halo activity (2,000%). The number of active binding sites per cell (about 20,000 for strain LM102) was determined using a newly-designed fluorescence-based detector, [Arg6,D-Ala9]α-factor-Edan, with high sensitivity (12,500-fold higher than the absorption-based detector [Orn6]α-factor-[Cys]3).

One-step direct immunoassay with horseradish peroxidase as antigen for studying the functionality of antibody surfaces

Antibody-coated surfaces (Ab surfaces) play a key role in bioanalytical tools developed for biosensors and diagnostics. Therefore, a high and well-defined functional activity of the Ab surface is required. The functional activity of the Ab surface depends on its available binding sites i.e. “the active sites” that are able to capture antigen (Ag). The number of active binding sites strongly depends on the immobilization strategy used to fix the Ab on the solid surface. Determination of layer thickness or surface topology are often used to characterize the Ab surfaces but there is no gold standard method for the study of the functionality of the Ab surfaces.For that purpose, we aim at developing an assay allowing to determine the performances of Ab surfaces. In the present study, anti-horseradish peroxidase antibody (anti-HRP Ab) is used as capture Ab covalently bound to the surface and enzyme HRP as Ag. This direct assay permits, in one-step, to generate a signal utilizing the catalytic properties of HRP. The signal is directly proportional to the amount of HRP bound on the Ab surface, and therefore to the active binding sites of immobilized Ab. The HRP/anti-HRP Ab interactions may be a useful indicator to construct accurate and reproducible active Ab surfaces and also to improve their performances in term of stability and sensitivity.Optimization of the assay parameters and quality of the results are presented. A good repeatability and an acceptable inter-day precision (RSD < 10%) are reported.

New hybrid nanocomposite of copper terephthalate MOF-graphene oxide: synthesis, characterization and application as adsorbents for toxic metal ion removal from Sungun acid mine drainage

The application of a hybrid Cu(tpa).GO (Cu(tpa) copper terephthalate metal organic framework, GO graphene oxide) composite as a new adsorbent for the removal of toxic metal ions was reported. New hybrid nanocomposite with excellent dispersibility and stability was successfully fabricated by the simple and effective ultrasonication method. The synthesized composite was characterized by scanning electron microscopy (SEM), UV-Vis and Fourier-transform infrared (FT-IR) techniques. The characterization results concluded that the binding mechanism of the Cu(tpa) and GO was related to both π-π packing and hydrogen bonding. For scrutinizing the sorption activity, the prepared adsorbents were assessed for the removal of Mn2+, Cu2+, Zn2+, Cd2+, Pb2+ and Fe3+ metal ions from aqueous synthetic solution and also acid mine drainage (AMD) wastewater. The sorption experiments demonstrated that the removal efficiency was significantly improved by modified hybrid Cu(tpa).GO composite, owing to the significant number of active binding sites and unique structure formed based on π-conjugated networks. Also, it was shown that the adsorption reaction was mainly attributed to the chemical interactions between metal ions and the surface functional groups. Moreover, kinetic and adsorption studies clarified that the adsorption process onto the Cu(tpa).GO follows a pseudo-second-order kinetics and fits the Langmuir and Freundlich adsorption models. Holistically, the results of this research represent that applying Cu(tpa).GO can be remarked as an effective adsorbent with high possibility at conventional water treatment.

High-Throughput, Protein-Targeted Biomolecular Detection Using Frequency-Domain Faraday Rotation Spectroscopy.

A clinically relevant magneto-optical technique (fd-FRS, frequency-domain Faraday rotation spectroscopy) for characterizing proteins using antibody-functionalized magnetic nanoparticles (MNPs) is demonstrated. This technique distinguishes between the Faraday rotation of the solvent, iron oxide core, and functionalization layers of polyethylene glycol polymers (spacer) and model antibody-antigen complexes (anti-BSA/BSA, bovine serum albumin). A detection sensitivity of ≈10 pg mL-1 and broad detection range of 10 pg mL-1 ≲ cBSA ≲ 100 µg mL-1 are observed. Combining this technique with predictive analyte binding models quantifies (within an order of magnitude) the number of active binding sites on functionalized MNPs. Comparative enzyme-linked immunosorbent assay (ELISA) studies are conducted, reproducing the manufacturer advertised BSA ELISA detection limits from 1 ng mL-1 ≲ cBSA ≲ 500 ng mL-1 . In addition to the increased sensitivity, broader detection range, and similar specificity, fd-FRS can be conducted in less than ≈30 min, compared to ≈4 h with ELISA. Thus, fd-FRS is shown to be a sensitive optical technique with potential to become an efficient diagnostic in the chemical and biomolecular sciences.

A Fully Synthetic Transcriptional Platform for a Multicellular Eukaryote

Regions of genomic DNA called enhancers encode binding sites for transcription factor proteins. Binding of activators and repressors increase and reduce transcription, respectively, but it is not understood how combinations of activators and repressors generate precise patterns of transcription during development. Here, we explore this problem usinga fully synthetic transcriptional platform in Drosophila consisting of engineered transcription factor gradients and artificial enhancers. We found that binding sites for a transcription factor that makes DNA accessible are required together with binding sites for transcriptional activators to produce a functional enhancer. Only in this context can changes in the number of activator binding sites mediate quantitative control of transcription. Using an engineered transcriptional repressor gradient, we demonstrate that overlapping repressor and activator binding sites provide more robust repression and sharper expression boundaries than non-overlapping sites. This may explain why this common motif is observed in many developmental enhancers.

A Lattice Model of Cross-Linked Polymeric Materials: The Role of Frustration

The diversity of properties of cross-linked polymeric materials cannot be explained by the constituent polymer chains alone but is attributed in part to their cross-linking. We propose a three-dimensional lattice model of bulk, polymeric materials that consist of stiff, cross-linked chains. Each chain has a randomly distributed, fixed number of binding that are capable of forming cross-links, which we call active binding sites (ABSs). The number of ABSs per unit length of chain, their interaction strength, and their distribution are the key parameters by which variability is achieved in representative materials. Inevitably, systems with a random distribution of ABSs retain unsatisfied bonds. We refer to these as frustrated systems. Numerically, an interfacial crossover is observed from an ordered state at low temperature to a disordered state at high temperature; the crossover scale depends on ABS density. Randomness may therefore provide organisms with a method of varying materials properties while avoiding critical oscillations.

True Reference Nanosensor Realized with Silicon Nanowires

Conventional gate oxide layers (e.g., SiO(2), Al(2)O(3), or HfO(2)) in silicon field-effect transistors (FETs) provide highly active surfaces, which can be exploited for electronic pH sensing. Recently, great progress has been achieved in pH sensing using compact integrateable nanowire FETs. However, it has turned out to be much harder to realize a true reference electrode, which--while sensing the electrostatic potential--does not respond to the proton concentration. In this work, we demonstrate a highly effective reference sensor, a so-called reference FET, whose proton sensitivity is suppressed by as much as 2 orders of magnitude. To do so, the Al(2)O(3) surface of a nanowire FET was passivated with a self-assembled monolayer of silanes with a long alkyl chain. We have found that a full passivation can be achieved only after an extended period of self-assembling lasting several days at 80 °C. We use this slow process to measure the number of active proton binding sites as a function of time by a quantitative comparison of the measured nonlinear pH-sensitivities to a theoretical model (site-binding model). Furthermore, we have found that a partially passivated surface can sense small changes in the number of active binding sites reaching a detection limit of δN(s) ≈ 170 μm(-2) Hz(-1/2) at 10 Hz and pH 3.

Ultrasensitive gene regulation by positive feedback loops in nucleosome modification

Eukaryotic transcription involves the synergistic interaction of many different proteins. However, the question remains how eukaryotic promoters achieve ultrasensitive or threshold responses to changes in the concentration or activity of a single transcription factor (TF). We show theoretically that by recruiting a histone-modifying enzyme, a TF binding non-cooperatively to a single site can change the balance between opposing positive feedback loops in histone modification to produce a large change in gene expression in response to a small change in concentration of the TF. This mechanism can also generate bistable promoter responses, allowing a gene to be on in some cells and off in others, despite the cells being in identical conditions. In addition, the system provides a simple means by which the activities of many TFs could be integrated at a promoter.

The synthesis and initial characterization of an immobilized purinergic receptor (P2Y 1) liquid chromatography stationary phase for online screening

The synthesis and initial characterization of an immobilized purinergic receptor (P2Y 1) liquid chromatography stationary phase for online screening

Number of active transcription factor binding sites is essential for the Hes7 oscillator

BackgroundIt is commonly accepted that embryonic segmentation of vertebrates is regulated by a segmentation clock, which is induced by the cycling genes Hes1 and Hes7. Their products form dimers that bind to the regulatory regions and thereby repress the transcription of their own encoding genes. An increase of the half-life of Hes7 protein causes irregular somite formation. This was shown in recent experiments by Hirata et al. In the same work, numerical simulations from a delay differential equations model, originally invented by Lewis, gave additional support. For a longer half-life of the Hes7 protein, these simulations exhibited strongly damped oscillations with, after few periods, severely attenuated the amplitudes. In these simulations, the Hill coefficient, a crucial model parameter, was set to 2 indicating that Hes7 has only one binding site in its promoter. On the other hand, Bessho et al. established three regulatory elements in the promoter region.ResultsWe show that – with the same half life – the delay system is highly sensitive to changes in the Hill coefficient. A small increase changes the qualitative behaviour of the solutions drastically. There is sustained oscillation and hence the model can no longer explain the disruption of the segmentation clock. On the other hand, the Hill coefficient is correlated with the number of active binding sites, and with the way in which dimers bind to them. In this paper, we adopt response functions in order to estimate Hill coefficients for a variable number of active binding sites. It turns out that three active transcription factor binding sites increase the Hill coefficient by at least 20% as compared to one single active site.ConclusionOur findings lead to the following crucial dichotomy: either Hirata's model is correct for the Hes7 oscillator, in which case at most two binding sites are active in its promoter region; or at least three binding sites are active, in which case Hirata's delay system does not explain the experimental results. Recent experiments by Chen et al. seem to support the former hypothesis, but the discussion is still open.