Label-free electrochemical impedance genosensor based on 1-aminopyrene/graphene hybrids
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In this work, we proposed a novel simple protocol for preparing 1-aminopyrene/graphene (ApG) hybrids for fabricating label-free electrochemical impedance genosensor. Graphene, with the structure of a single-atom-thick sheet of sp2-bonded carbon atoms, was anchored to 1-aminopyrene (1-Ap) with the pyrenyl group via π-stacking interaction. The morphology, conductivity, and interaction of ApG hybrids were characterized by transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), UV-visible (UV-vis) and fluorescence spectra. The amino-substituted oligonucleotide probe was conjugated to 1-Ap by the cross-linker glutaraldehyde. The DNA hybridization reaction of oligonucleotide probe with target DNA was monitored by EIS. Under optimum conditions, the proposed biosensor exhibited high sensitivity and a low detection limit for detecting the complementary oligonucleotide. The target oligonucleotide could be quantified in a wide range of 1.0 × 10−12 to 1.0 × 10−8 M with good linearity (R = 0.9900) and low detection limit of 4.5 × 10−13 M (S/N = 3).The principle,character and classification of enzyme biosensor are introduced.The ways to achieve electric signal of the first generation biosensor,the superiorities of the second generation biosensor with medium and the methods and materials to fixate enzyme of the third generation enzyme biosensor are expounded.The present conditions of the third generation enzyme biosensor are commented on.Finally,the progressive directions of biosensor have also been prospected.
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The opportunity of enhancing the sequencing efficiency by applying continuous stacking hybridization is considered. The approach is based on the increase of duplex length by continuous stacking hybridization of oligonucleotides added to solution (l-oligonucleotides) to oligonucleotides immobilized on matrix (L-oligonucleotides). An analysis of reconstruction efficiency for sequenced fragments up to length of 30000 nucleotides was made. Various combinations of L- and l-oligonucleotide length were considered. The results obtained enable one to evaluate the potentialities of the proposed method for various nucleotide matrices and the complexity of experiment. Use of continuous stacking hybridization permits a considerable increase of the length of sequenced DNA fragments. We offer the approach for resolving ambiguities in branching points, which occur because of long repeats. It is based on continuous stacking hybridization of several l-oligonucleotides which form a "chain" stabilized by mutual stacking interaction.
Duplex (building)
Sequencing by hybridization
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π-Conjugated molecules and polymers are expected to have a variety of applications in organic electronics. Control over how these π-conjugated systems stack in the solid state is crucial for utilization of their desirable photophysical and electrical properties. Some molecules need to be designed with enhanced π-stacking abilities, whereas others might display novel properties as a result of restricting their π-stacking abilities. Furthermore, π-conjugated molecules or polymers that display partial π-stacking are of interest for potential new applications because of the synergy of the contrasting properties of stacked and isolated π-conjugated systems. Here, we highlight recent progress in molecular design to control π-stacking, with a particularly focus on the redox properties of these unique molecular systems.
Organic Electronics
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The stacking of layers forming three-dimensional periodic structures is explored in the general case, where neither the layers nor the stacking need to be close-packed, and the connectivity number for the system may be either two or four. Procedures are described whereby all possible stacking variants can be systematically derived for a given number of layers, and for a given number of possible stacking positions. The latter depends on the structure of the layer and on the stacking vector.
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Love waves, a variety of surface acoustic waves (SAWs), can be used to detect very small biological surface interactions and so have a wide range of potential applications. To demonstrate the practicality of a Love wave SAW biosensor, we fabricated a 155-MHz Love wave SAW biosensor and compared it with a commercial surface Plasmon resonance (SPR) using glycerol-water solution with known densities and viscosities to calibrate the response signals of the biosensors. And the mass per unit area of anti-mouse IgG bound with protein G onto the sensitive layer of the biosensor was calculated on the basis of the calibration result. The sensitivity of the Love wave SAW biosensor was the same as or greater than that of the SPR biosensor. Furthermore, the Love wave SAW biosensor was capable of measuring a much wider range of viscosities than the SPR biosensor. Although the operating principle of the Love wave SAW biosensor is completely different from that of the SPR biosensor, the subtle changes in the viscoelastic properties of the biological layer that accompany biological binding reactions on the sensitive layer can be monitored and measured in the same ways as with the SPR biosensor.
Love wave
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Modulating the Interlayer Stacking of Covalent Organic Frameworks for Efficient Acetylene Separation
Controllable modulation of the stacking modes of 2D (two-dimensional) materials can significantly influence their properties and functionalities but remains a formidable synthetic challenge. Here, an effective strategy is proposed to control the layer stacking of imide-linked 2D covalent organic frameworks (COFs) by altering the synthetic methods. Specifically, a modulator-assisted method can afford a COF with rare ABC stacking without the need for any additives, while solvothermal synthesis leads to AA stacking. The variation of interlayer stacking significantly influences their chemical and physical properties, including morphology, porosity, and gas adsorption performance. The resultant COF with ABC stacking shows much higher C2 H2 capacity and selectivity over CO2 and C2 H4 than the COF with AA stacking, which is not demonstrated in the COF field yet. Furthermore, the outstanding practical separation ability of ABC stacking COF is confirmed by breakthrough experiments of C2 H2 /CO2 (50/50, v/v) and C2 H2 /C2 H4 (1/99, v/v), which can selectively remove C2 H2 with good recyclability. This work provides a new direction to produce COFs with controllable interlayer stacking modes.
Acetylene
Covalent organic framework
Separation (statistics)
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<p>Predicting the strength of stacking interactions involving heterocycles is vital for several fields, including structure-based drug design. While quantum chemical computations can provide accurate stacking interaction energies, these come at a steep computational cost. To address this challenge, we recently developed quantitative predictive models of stacking interactions between drug-like heterocycles and the aromatic amino acids Phe, Tyr, and Trp (DOI: 10.26434/chemrxiv.7628939.v4). These models depend on heterocycle descriptors derived from electrostatic potentials (ESPs) computed using density functional theory and provide accurate stacking interactions without the need for expensive computations on stacked dimers. Herein, we show that these ESP-based descriptors can be reliably evaluated directly from the atom connectivity of the heterocycle, providing a means of predicting both the descriptors and the potential for a given heterocycle to engage in stacking interactions without resorting to any quantum chemical computations. This enables the conversion of simple molecular representations (<i>e.g</i>. SMILES) directly into accurate<i> </i>stacking interaction energies using a freely-available online tool, thereby providing a way to rapidly rank the stacking abilities of large sets of heterocycles.</p> <p> </p>
Quantum chemical
Rank (graph theory)
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As an extension of Table 7.1.5B of International Tables for X-ray Crystallography [(1967), Vol. II. Birmingham: Kynoch Press], the possible stacking variants up to ten layers are arranged according to the percentage of hexagonal stacking. A method is given which allows one to calculate the number of possible stacking variants for any number of layers.
Table (database)
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The efficiency of sequencing by hybridization to an oligonucleotide microchip grows with an increase in the number and in the length of the oligonucleotides; however, such increases raise enormously the complexity of the microchip and decrease the accuracy of hybridization. We have been developing the technique of contiguous stacking hybridization (CSH) to circumvent these shortcomings. Stacking interactions between adjacent bases of two oligonucleotides stabilize their contiguous duplex with DNA. The use of such stacking increases the effective length of microchip oligonucleotides, enhances sequencing accuracy and allows the sequencing of longer DNA. The effects of mismatches, base composition, length and other factors on the stacking are evaluated. Contiguous stacking hybridization of DNA with immobilized 8mers and one or two 5mers labeled with two different fluorescent dyes increases the effective length of sequencing oligonucleotides from 8 to 13 and 18 bases, respectively. The incorporation of all four bases or 5-nitroindole as a universal base into different positions of the 5mers permitted a decrease in the number of additional rounds of hybridization. Contiguous stacking hybridization appears to be a promising approach to significantly increasing the efficiency of sequencing by hybridization.
Sequencing by hybridization
DNA–DNA hybridization
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