A new rhodamine‐based fluorescent chemodosimeter for mercuric ions in water media

A new rhodamine–ethylenediamine–nitrothiourea conjugate (RT) was synthesized and its sensing property as a fluorescent chemodosimeter toward metal ions was explored in water media. Analytical results from absorption and fluorescence spectra revealed that the addition of Hg²⁺ ions to the aqueous solution of the chemodosimeter RT caused a distinct fluorescence OFF–ON response with a remarkable visual color change from colorless to pink; however, no clear spectral and color changes were observed from other metal ions including: Zn²⁺, Cu²⁺, Cd²⁺, Pb²⁺, Ag⁺, Fe²⁺, Cr³⁺, Co³⁺, Ni²⁺, Ca²⁺, Mg²⁺, K⁺ and Na⁺. The sensing results and the molecular structure suggested that a Hg²⁺‐induced a desulfurization reaction and cyclic guanylation of the thiourea moiety followed by ring‐opening of the rhodamine spirolactam in RT are responsible for a distinct fluorescence turn‐on signal, indicating that RT is a remarkably sensitive and selective chemodosimeter for Hg²⁺ ions in aqueous solution. Hg²⁺ within a concentration range from 0.1 to 25 μM can be determined using RT as a chemodosimeter and a detection limit of 0.04 μM is achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of ethanol using permanganate–CdS quantum dot chemiluminescence system

A novel and highly sensitive chemiluminescence (CL) method for the determination of ethanol was developed based on the CdS quantum dots (QDs)–permanganate system. It was found that KMnO₄ could directly oxidize CdS QDs in acidic media resulting in relatively high CL emission. A possible mechanism was proposed for this reaction based on UV/Vis absorption, fluorescence and the generated CL emission spectra. However, it was observed that ethanol had a remarkable inhibition effect on this system. This effect was exploited in the determination of ethanol within the concentration range 12–300 µg/L, with detection at 4.3 µg/L. In order to evaluate the capability of presented method, it was satisfactorily utilized in the determination of alcohol in real samples. Copyright © 2014 John Wiley & Sons, Ltd.     

A new spectrofluorimetric method for the determination of some tetracyclines based on their interfering effect on resonance fluorescence energy transfer

A rapid, simple, inexpensive and highly sensitive spectrofluorimetric method was developed for the determination of trace amounts of some tetracyclines (TCs), namely tetracycline hydrochloride (TCH), oxytetracycline hydrochloride (OTCH) and minocycline hydrochloride (MCH). Binding rhodamine B (RhB) to gold nanoparticles (Au NPs) resulted in quenching of the fluorescence of RhB by a resonance energy transfer (FRET) mechanism, with Au NPs as the energy acceptors. The presence of TCs caused the release of RhB molecules and recovered their fluorescence, and this was used as a basis for the quantitative determination of TCs. The reaction was monitored spectrofluorimetrically by measuring the increase in fluorescence of RhB at 572 nm starting 5 min after mixing the reagents in Tris buffer solution (pH 6.5). The effect of various experimental factors such as buffer type, pH, concentrations of the involved reagents and reaction time were studied to optimize the reaction conditions. Under optimum conditions, the calibration graphs were linear within the ranges 2.08 × 10^?9–1.04 × 10^?6 mol/L, 2.01 × 10^?9–1.00 × 10^?6 mol/L and 2.02 × 10^?9–1.01 × 10^?6 mol/L and detection limits (LODs) of 0.61 × 10^?9, 0.32 × 10^?9 and 0.66 × 10^?9 mol/L were calculated for TCH, OTCH and MCH, respectively, with corresponding percent relative standard deviations (%RSDs) of 1.18, 1.21 and 1.54 (n = 5). The method was successfully applied to the determination of TCs in drinking water, human urine, bovine milk and breast milk samples. Copyright © 2014 John Wiley & Sons, Ltd.     

Genome-Wide Assessment of Outer Membrane Vesicle Production in Escherichia coli

The production of outer membrane vesicles by Gram-negative bacteria has been well documented; however, the mechanism behind the biogenesis of these vesicles remains unclear. Here a high-throughput experimental method and systems-scale analysis was conducted to determine vesiculation values for the whole genome knockout library of Escherichia coli mutant strains (Keio collection). The resultant dataset quantitatively recapitulates previously observed phenotypes and implicates nearly 150 new genes in the process of vesiculation. Gene functional and biochemical pathway analyses suggest that mutations that truncate outer membrane structures such as lipopolysaccharide and enterobacterial common antigen lead to hypervesiculation, whereas mutants in oxidative stress response pathways result in lower levels. This study expands and refines the current knowledge regarding the cellular pathways required for outer membrane vesiculation in E. coli.     

Use of random forest in FTIR analysis of LDL cholesterol and tri‐glycerides for hyperlipidemia

A quantitative determination method for the diagnosis of hyperlipidemia was developed using Fourier transform infrared (FTIR) spectroscopy. Random forest (RF) was demonstrated as a potential multivariate algorithm for the FTIR analysis of low‐density lipoprotein cholesterol (LDL‐C) and tri‐glycerides (TG) in human serum samples. The informative wavebands for LDL‐C and TG were selected based on the Gini importance. The selected wavebands were mainly within the fingerprint region. The RF modeling results were better than those derived using PLS in validation process, because the chance for over‐fitting was possibly eliminated in RF algorithm. ARF also demonstrated favorable results in the test process. The prospective model exhibited a higher than 90% true prediction in negative/positive properties for male and female samples. These clinical statistical results indicated the optimization of RF algorithm performed accurately in the FTIR determination of LDL‐C and TG. RF is evaluated as a promising tool for diagnosing and controlling hyperlipidemia in populations. The parameter optimization methodology is useful in the improving model accuracy using FTIR spectroscopic technology. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1693–1702, 2015