Toehold-aided DNA recycling amplification using hemin and G-quadruplex reporter DNA on magnetic beads as tags for chemiluminescent determination of riboflavin

A toehold-aided DNA recycling amplification technology was developed based on the combination of toehold-aided DNA recycling and the hemin/G-quadruplex label. The dsDNA formed between aptamer and DNA1 was first immobilized on magnetic beads. On addition of target analyte (exemplified here for riboflavin), the aptamer-riboflavin complex is formed and DNA1 is released by the beads. After magnetic separation, the supernatant containing the released DNA1 is added to a solution containing the hairpin capture DNA on magnetic beads. DNA1 will hybridize with the hairpin capture DNA via toehold binding and branch migration. This process will open the hairpin structure, and an external toehold is formed in the newly formed dsDNA. On addition of reporter DNA containing the G-quadruplex, it will interact with the formed dsDNA via toehold binding and branch migration, resulting in the releasing of DNA1 and capturing of reporter DNA on the magnetic beads. The released DNA1 will bind to another hairpin capture DNA which can start another round of DNA1 recycling. Chemiluminescence (CL) is generated by the G-quadruplex-hemin-luminol CL reaction system. Under optimal conditions, the calibration plot is linear in the 0.1 to 700 nM riboflavin concentration range, with a 30 pM detection limit (at a signal-to-noise ratio of 3). The method was successfully applied to the quantitation of riboflavin in spiked urine samples.

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Graphical abstract Toehold-aided DNA recycling coupled with hemin G-quadruplex for target detection.

     

Immobilization and catalytic activity of lipase on mesoporous silica prepared from biocompatible gelatin organic template

Mesoporous silica (MPS) with high surface area (518.8 m²/g), tunable pore size (3.6-13.7 nm) was synthesized using inexpensive sodium silicate as the source of silica and the biodegradable gelatin as the structure directing agent. The amorphous mesostructures of the materials were characterized by N₂ adsorption-desorption isotherms, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized MPS was then utilized as supports for immobilization of Porcine pancreatic lipase (PPL) by physical adsorption. The measurements of Fourier transform infrared spectroscopy (FT-IR), N₂ adsorption-desorption isotherms and energy-dispersive spectroscopy (EDS) demonstrated that PPL had been adsorbed into the channels of the MPS. The immobilized PPL was used for catalyzing hydrolysis reaction of triacetin, and its correlative catalytic activity was studied. Compared with free PPL, the immobilized PPL possessed superior adaptability in alkaline range (pH = 7.0-9.0), good thermal stability and excellent reusability in phosphate buffer solution in hydrolysis reactions of triacetin. The results also indicated that the immobilized PPL maintained 45% of its initial activity even after being reused six times.     

Co-registration method for photoacoustic imaging and laser speckle imaging

Combining photoacoustic (PA) imaging with laser speckle (LS) imaging (LSI) can simultaneously determine total hemoglobin concentration (HbT), hemoglobin oxygen saturation (SO2), and blood flow rates. Thus,the co-registration of PA and LS images is important in physiological studies and pathological diagnosis.This letter presents a co-registration algorithm combining mutual information with the maximum betweenclass variance segmentation method (Otsu method). The mutual information and Otsu method are used to provide the registration measure criterion and image feature recognition, respectively. The evaluation results show that the registration function possesses a single maximum peak and high smoothness across the global co-registration district, indicating a robust behavior. Moreover, this method has good registration accuracy, and the fusion result simultaneously visualizes the separate functional information of two kindsof images.     

ALMOST AUTOMORPHIC MILD SOLUTIONS TO SOME FRACTIONAL DELAY DIFFERENTIAL EQUATIONS

In this paper,a new and general existence and uniqueness theorem of almost automorphic mild solutions is obtained for some fractional delay differential equations,using sectorial operators and the Banach contraction principle.     

Extremal Eigenvalues of the Sturm-Liouville Problems with Discontinuous Coefficients

In this paper, an extremal eigenvalue problem to the Sturm-Liouville equations with discontinuous coefficients and volume constraint is investigated. Liouville transformation is applied to change the problem into an equivalent minimization problem. Finite element method is proposed and the convergence for the finite element solution is established. A monotonic decreasing algorithm is presented to solve the extremal eigenvalue problem. A global convergence for the algorithm in the continuous case is proved. A few numerical results are given to depict the efficiency of the method.     

生物铵转运蛋白对NH3/NH4+作用机理研究

铵转运蛋白广泛存在于细菌、真菌、植物以及动物等各种生命体中。生物铵转运蛋白对NH₃/NH₄⁺的传输作用已被广泛研究,然而,对于通过铵转运蛋白疏水性孔腔的物种是带电荷的NH₄⁺离子还是电中性的NH₃分子,仍存在很大争议。本文综述了近年来生物铵转运蛋白对NH₃/NH₄⁺作用机理的研究进展,主要包括NH₃或NH₄⁺的传输及NH₃和H⁺共传输等机理。     

原位接枝炭黑/天然橡胶复合材料的制备及性能

采用原位固相接枝方法,使在高温和强剪切作用下降解的天然橡胶接枝到炭黑表面.通过对接枝前后炭黑填充天然橡胶的性能对比发现,原位接枝炭黑不但能提高天然橡胶的硫化速度,还能提高拉伸强度,定伸应力和撕裂强度等;动态力学性能的测试结果表明接枝炭黑填充的天然橡胶中接枝炭黑网络化程度较低,这些结果主要归因于接枝炭黑在橡胶基体中分散性的改善及炭黑与橡胶之间作用力的增加.