Transport of biomolecules in asymmetric nanofilter arrays

We propose a theoretical model for describing the electric-field-driven migration of rod-like biomolecules in nanofilters comprising a periodic array of shallow passages connecting deep wells. The electrophoretic migration of the biomolecules is modeled as transport of point-sized Brownian particles, with the orientational degree of freedom captured by an entropy term. Using appropriate projections, the formulation dimensionality is reduced to one physical dimension, requiring minimal computation and making it ideal for device design and optimization. Our formulation is used to assess the effect of slanted well walls on the energy landscape and resulting molecule mobility. Using this approach, we show that asymmetry in the well shape, such as a well with one slanted and one vertical wall, may be used for separation using low-frequency alternating-current fields because the mobility of a biomolecule is different in the two directions of travel. Our results show that, compared to methods using direct-current fields, the proposed method remains effective at higher field strengths and can achieve comparable separation using a significantly shorter device.     

On the Growth and Fixed Points of Solutions of Second Order Differential Equations with Meromorphic Coefficients

In this paper, we investigate the growth and fixed points of solutions and their 1st, 2nd derivatives, differential polynomial of second order linear differential equations with meromorphic coefficients, and obtain that the exponents of convergence of these fixed points are all equal to the order of growth.     

Chemiluminescence immunoassay for cardiac troponin T by using silver nanoparticles functionalized with hemin/G-quadruplex DNAzyme on a glass chip array

The authors describe an array for chemiluminescence (CL) based determination of cardiac troponin T (cTnT), an important cardiovascular disease marker. The tracing tag consists of silver nanoparticles (AgNPs) loaded with guanine-rich DNA sequences and detection antibody in a high numerical ratio. The loaded AgNPs were then reacted with hemin to form a hemin/G-quadruplex DNAzyme. A disposable immunosensor array was fabricated by immobilizing capture antibody on corresponding sensing sites on a glass chip. Once a sandwich immunocomplex is formed on the array, the tracing tag catalyzes the CL reaction of the luminol-p-iodophenol and H₂O₂ system to produce a CL signal, which is collected by a CCD camera. An intuitive CL image is obtained containing all of the spots on the array. Under optimal conditions, the method shows a wide linear range over 4 orders of magnitude (from 0.003 to 270 ng·L^?1), a detection limit down to 84 fg·L^?1, and a throughput as high as 44 tests·h^?1. The results obtained with serum samples are in acceptable agreement with reference values. The AgNP-based tracing tag as well as the immunoassay method shows a promising potential for point-of-care testing for the early clinical diagnosis of cardiovascular disease.

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Graphical abstract Schematic presentation of silver nanoparticles (AgNPs) functionalized with hemin/G-quadruplex DNAzyme for highly sensitive chemiluminescence (CL) immunoassay of cardiac troponin T (cTnT) on a glass chip array.

     

Structure Characterization and Lead Detoxification Effect of Carboxymethylated Melanin Derived from <Emphasis Type="Italic">Lachnum</Emphasis> Sp.

In the present study, an intracellular melanin, named LIM205, was separated from Lachnum YM205 mycelia and was purified on a Sephadex G-15 column. The molecular weight of LIM205 was determined as 522 Da, and its molecular formula was speculated as C₂₈H₁₄N₂O₇S. The possible chemical structure of LIM205 was determined according to the results of Fourier transform infrared (FT-IR), ¹H NMR, ¹³C NMR, and pyrolysis/GC-MS analysis. With the aim to increase its water solubility, its carboxymethylated derivative, named CLIM205, was formed by the substitution of hydrogen atoms in LIM205 with one, two, and three carboxymethylate groups. FT-IR, UV, and ESI-MS analysis demonstrated that the carboxymethylate groups were conjugated onto LIM205. The lead detoxification activities of LIM205 and CLIM205 had also been investigated. In vivo test showed that both LIM205 and CLIM205 reduced the tissue lead concentration, enhanced lead excretion, and reversed lead-induced alterations in superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) concentrations in mice, with CLIM205 showed better efficacy. The study indicates that LIM205 and CLIM205 have significant lead detoxification effect which will contribute to solve related problems.     

Two new eudesmane derivatives from Verbesina virginica

<正>Two new eudesmane derivatives were isolated from the leaves and flowers of Verbesina virginica,along with the known 6-O-β-E -p-coumaroyl-4α-hydroxyeudesmane(1).Their structures were determined as 6-O-β-Z-p-coumaroyl-4α-hydroxyeudesmane(2) and 6-O-α-E-p-coumaroyl-1β-4α-dihydroxyeudesmane(3) by spectroscopic methods.     

Ionic Liquid‐Hemoglobin‐Carbon Paste Composite Bioelectrode and Its Electrocatalytic Activity

A new carbon ionic liquid paste bioelectrode was fabricated by mixing hemoglobin (Hb) with graphite powder, ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF₄) and liquid paraffin homogeneously. Nafion film was cast on the electrode surface to improve the stability of bioelectrode. Direct electrochemistry of Hb in the bioelectrode was carefully investigated. Cyclic voltammetric results indicated that a pair of well‐defined and quasi‐reversible electrochemical responses appeared in pH 7.0 phosphate buffer solution (PBS), indicating that direct electron transfer of Hb was realized in the modified electrode. The formal potential (E^0′) was calculated as ?0.316 V (vs. SCE), which was the typical characteristic of the electrochemical reaction of heme Fe(III)/Fe(II) redox couple. Based on the cyclic voltammetric results the electrochemical parameters of the electrode reaction were calculated. This bioelectrode showed high electrocatalytic activity towards the reduction of trichloroacetic acid (TCA) with good stability and reproducibility.     

A new biomarker of protein oxidation degree and site using angiotensin as the target by MS

Hydroxyl radicals generated from Fenton reaction were used to damage the angiotensin. The oxidative damage degree and sites of peptides were measured by HPLC–MS and MS/MS. Experimental results proved that the oxidative damage degree increased with longer reaction time. The results also showed that the side chains of phenylalanine and tyrosine in angiotension can be attacked by hydroxyl radicals to form the oxidative products. A new strategy was established to monitor the oxidative degree and sites of peptides and laid the foundation for protein oxidation. This method can be used to investigate the mechanism of protein oxidative damage caused by oxidative stress which is induced by environmental pollutants and physiological activities. There will also be a wide application in the research of pathogenesis of some disease related to oxidative stress.     

A New Strategy to Identify and Eliminate the Inner Filter Effects by Outer Filter Technique

To identify and eliminate the inner filter effects (IFEs), prepositive and side cells containing absorbents are fixed beside the fluorescer contained cell. In this way, excitation and emission lights can be quenched by primary and secondary outer filter effects respectively, depending on absorbent concentration and cell length. Herein the quenching of emission fluorescence caused by IFEs can be equally reduced by outer filter effects (OFEs) and the interference of IFEs was eliminated. This approach was experimentally used for identifying the interaction mode and mechanism between BSA and nanoAg. Results showed that the quenching of BSA fluorescence and synchronous fluorescence mainly attributes to IFEs, instead of static/dynamic fluorescent quenching. In view of the above, the elimination of the interference of IFEs by the design of OFEs plays an important part in the precise application of fluorescence detector.     

Effects of doping on the surface energies of nanocrystals and evidence from studies at high pressure

Zn_1−XMn_XS (X=0.85% and 1.26%) nanoparticles have been synthesized using a specially designed equipment and we have studied the influence of doping Mn²⁺ on the surface energy of ZnS. The high pressure behaviors of ZnS nanocrystals with different dopant contents have been investigated using angle-dispersive synchrotron X-ray powder diffraction up to 45.1 GPa. Theoretical calculations show that doping with Mn²⁺ increases the surface energy of the nanocrystals. The theoretical result has been further corroborated by our experimental observation of an increase in the phase transition pressure of Mn²⁺ doped ZnS nanocrystals in diamond-anvil-cell studies.     

Inclusion complexes of phosphorylated daidzein derivatives with β-cyclodextrin: Preparation and inclusion behavior study

In the present work the feasibility of β-cyclodextrin in complexation was explored, as a tool for improving the solubility and biological ability of daidzein derivatives. A series of phosphorylated daidzein derivatives featuring different chain lengths were synthesized through a modified Atherton-Todd reaction and their inclusion complexes with βCD were prepared by coprecipitation method. The inclusion complexation behavior was studied by fluorescence, UV, FT-IR, MS and (1)H NMR. The results showed that only phosphorylated daidzein derivative carrying small substituent group ((C(2)H(5)O)(2)PO) entered the cavity of βCD and formed 1:1 inclusion complex. The formation constant was 175(mol/L)(-1).