The fractal dimensions of the level sets of the generalized iterated Brownian motion

Let{W1(t), t∈R+} and {W2(t), t∈R+} be two independent Brownian motions with W1(0) = W2(0) = 0. {H (t) = W1(|W2(t)|), t ∈R+} is called a generalized iterated Brownian motion. In this paper, the Hausdorff dimension and packing dimension of the level sets {t ∈[0, T ], H(t) = x} are established for any 0 < T ≤ 1.     

Molecule-binding dependent assembly of split aptamer and γ-cyclodextrin: A sensitive excimer signaling approach for aptamer biosensors

A highly sensitive and selective fluorescence aptamer biosensors for the determination of adenosine triphosphate (ATP) was developed. Binding of a target with splitting aptamers labeled with pyrene molecules form stable pyrene dimer in the γ-cyclodextrin (γ-CD) cavity, yielding a strong excimer emission. We have found that inclusion of pyrene dimer in γ-cyclodextrin cavity not only exhibits additive increases in quantum yield and emission lifetime of the excimer, but also facilitates target-induced fusion of the splitting aptamers to form the aptamer/target complex. As proof-of-principle, the approach was applied to fluorescence detection of adenosine triphosphate. With an anti-ATP aptamer, the approach exhibits excimer fluorescence response toward ATP with a maximum signal-to-background ratio of 32.1 and remarkably low detection limit of 80 nM ATP in buffer solution. Moreover, due to the additive fluorescence lifetime of excimer induced by γ-cyclodextrin, time-resolved measurements could be conveniently used to detect as low as 0.5 μM ATP in blood serum quantitatively.     

Determination of phenylenediamine isomers in hair dyes by coal cinders micro-column extraction and MEKC

A new micellar electrokinetic chromatography (MEKC) method using beta-cyclodextrins (β-CDs) and 1-butyl-3-methylimidazolium hexafluorophosphates (ionic liquids) as additives was successfully developed for determination of para-, meta-, and ortho-phenylenediamines isomers (p-P, m-P, and o-P) in hair dyes. To improve the sensitivity of the MEKC-UV, a simple and cheap flow injection (FI) technique using a micro-column packed with coal cinders (the by-products from combustion in a boiler) as solid-phase extractant was also investigated. In the presence of 20 mmol L(-1) phosphates at pH 5.5, addition of 12 mmol L(-1) ionic liquids and 8 mmol L(-1) β-CDs greatly improved the separation efficiency. The three analytes could be quantitatively adsorbed by coal cinders, and desorbed readily with 0.15 mL of 0.01 mol L(-1) NaOH. Under the optimum conditions, an enrichment factor (EF) of 33.3 was obtained, and determination limits of p-P, m-P, and o-P were 1.97?×?10(-7), 0.99?×?10(-7), and 0.61?×?10(-7) mol L(-1), respectively. The adsorption capacities of the coal cinders micro-column for p-P, m-P, and o-P were all 1.20 mg g(-1). The presented procedure was successfully applied to the determination of p-P, m-P, and o-P in hair dyes with satisfactory results.     

Observation of sodium gel-induced protein modifications in dodecylsulfate polyacrylamide gel electrophoresis and its implications for accurate molecular weight determination of gel-separated proteins by matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometry (TOFMS) can potentially provide accurate molecular weight information of proteins separated by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). Several issues related to resolution and accuracy of molecular weight measurement are investigated by using a time-lag focusing MALDI-TOF mass spectrometer. The effects of the gel components SDS, glycerol, and tris buffer on the mass spectral signals are studied systematically. Glycerol and tris buffer are shown to have little or no effect on resolution and mass accuracy, whereas SDS degrades sensitivity, resolution, and mass accuracy even at low concentrations. A simple and fast gel extraction technique is presented which is capable of detecting proteins loaded at the low-picomole level on the gel. The sample preparation procedure used in this work appears to remove most of SDS from the gel, thereby reducing the peak broadening effect caused by SDS and resulting in high resolution and accurate measurement of proteins. However, for proteins containing cysteines, the molecular ions are composed of a distribution of acrylamide-protein adducts likely formed by reaction with unpolymerized acrylamide in the gel during the gel separation process. The implications of gel-induced protein modifications on the accurate molecular weight measurement of gel-separated proteins are discussed.     

Imaging cellular distribution of fluorescent supramolecular nanofibers

In this study, we used the 4-nitro-2,1,3-benzoxadiazole (NBD) as an aromatic capping group for a peptide to construct the supramolecular nanofibers. Taking the advantage of the fluorescence property of NBD, we could directly observe the cellular distribution of the self-assembled nanofibers. We found that the distributions of the nanofibers of NBD-FFETIGGY are different in four mammalian cells and two plant cells. The nanofibers are mainly located at the surface of two mammalian cells and one plant cell, while in the intracellular space of other cells. Different distributions of nanofibers lead to different protein binding patterns of the nanofibers in two different cell lines. We believe that a useful and versatile platform has been offered to the image cellular distribution of nanofibers, which can provide useful information to the biological functions of the self-assembled nanostructures.     

In Situ Amplification‐Based Imaging of RNA in Living Cells

Owing to its important physiological functions, especially as molecular biomarkers of diseases, RNA is an important focus of biomedicine and biochemical sensing. Signal amplification detection has been put forward because of the need for accurate identification of RNA at low expression levels, which is significant for the early diagnosis and therapy of malignant diseases. However, conventional amplification methods for RNA analysis depend on the use of enzymes, fixation of cells, and thermal cycling, which confine their performance to cell lysates or dead cells, thus the imaging of RNA in living cells remained until recently little explored. In recent years, the advance of isothermal amplification of nucleic acids has opened paths for meeting this need in living cells. This minireview tracks the development of in situ amplification assays for RNAs in living cells, and highlights the potential challenges facing this field, aiming to improve the development of in vivo isothermal amplification as well as usher in new frontiers in this fertile research area.     

The Variation of Composition of Resols Under Different Reaction Conditions

The multi-hydroxymethyl structure of resol makes it suitable for connecting two or more polyacrylamide chains as a crosslinker in oil recovery applications, but control of the structure and composition of the resol, whether in practice or theory, is still a controversial problem. In the present research, a series of resol prepolymers synthesized with different amounts and types of catalysts, formaldehyde to phenol molar ratio, reaction temperature and charging steps were characterized by high-performance liquid chromatography. It is found that the compositions of the resols barely changed with almost all the varying conditions, but the contents of each component were greatly affected by the variation of reaction conditions. Finally, the best conditions for preparing resol crosslinker were obtained.