Certification of New Selenium-Enriched Yeast and Supplement Reference Materials for Selenomethionine Using Two Independent Measurement Strategies.

Selenium-enriched yeast possesses the unique ability of transforming chemical selenium, such as sodium selenite, into a biologically active form, which mitigates its toxic effects on the human body. The transformation product of this process, selenomethionine, can be safely and effectively absorbed and utilized by the human body; hence, it has been spiked into a selenium-enriched supplement. This study employs two distinct measurement strategies to determine the selenomethionine content in two candidate reference materials, a selenium-enriched yeast powder and supplement, using both organic and inorganic mass spectrometry.

An improved calibrated mass spectrometry for absolute copper isotope-ratio measurement using two strategies for mass bias correction factor.

Modern advances in multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) have greatly promoted the investigation of copper isotopes in various research fields. To meet the demand, an improved calibrated mass spectrometry for the absolute determination of copper isotopic composition was developed in this study. The method has made progress in the investigation of instrumental mass bias correction factor for copper isotopic analysis using MC-ICPMS through employing two independent strategies.

Accurate Determination of Trace Molybdenum in Drinking Water by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry.

A method for accurate and precise determination of trace molybdenum in drinking water by isotope dilution inductively coupled plasma mass spectrometry was developed, given the concentrations of Mo in drinking-water samples from Chaoyang and Changping districts of Beijing (China) as 1.017 ± 0.008 and 1.

Investigation of the crucial factors affecting accurate measurement of strontium isotope ratios by total evaporation thermal ionization mass spectrometry.

Rationale: An absolute method that does not require calibration is very important in several areas of isotope analysis due to the shortage of suitable certified reference materials (CRMs). As total evaporation thermal ionization mass spectrometry (TE-TIMS) theoretically overcomes mass fractionation through integrating the ion currents till the sample on the filament is completely exhausted, it could be an absolute method that does not require the use of CRMs for calibration. However, the lack of reliable method verification and reasonable uncertainty evaluation restricts its extensive application, and these effects need to be quantitatively evaluated.

On-off-on luminescent pyrophosphate probe based on the use of Mn-doped ZnS quantum dots and using Eu(III) as a mediator.

A selective phosphorescent on-off-on probe with long decay lifetime has been designed for the detection of pyrophosphate ions (PPi). The detection scheme is based on the use of europium(III)-modulated Mn(II)-doped ZnS quantum dots capped with N-acetyl-L-cysteine. Both the aggregation of quantum dots and electron transfer induced by Eu(III) ions cause phosphorescence to be quenched ("off" state).

Dispersion-aggregation-dispersion colorimetric detection for mercury ions based on an assembly of gold nanoparticles and carbon nanodots.

Mercury is a common heavy metal element in natural systems and is highly toxic to the human body. Herein, a novel colorimetric detection of Hg ions is proposed based on the aggregation of gold nanoparticles (AuNPs) induced by carbon quantum dots (CDs) with the assistance of glutathione (GSH). In this sensing system, the AuNP/CDs composite forms through Au-N bonds.

Accurate Determination of the Absolute Isotopic Composition and Atomic Weight of Molybdenum by Multiple Collector Inductively Coupled Plasma Mass Spectrometry with a Fully Calibrated Strategy.

A fully calibrated strategy has been investigated for the first time for the accurate determination of absolute isotopic composition and atomic weight of molybdenum using multiple-collector inductively coupled plasma mass spectrometry. The correction for instrumental mass bias was performed using synthetic isotope mixtures, which were gravimetrically prepared with all of the seven high-purity and isotopically enriched molybdenum isotope materials together. Six natural molybdenum materials, including molybdenum standard solution NIST SRM 3134, were accurately measured and yielded the absolute isotopic composition (in atom %, k = 1) of Mo-14.

Aggregation-Induced Emission Luminogen-Embedded Silica Nanoparticles Containing DNA Aptamers for Targeted Cell Imaging.

Conventional fluorophores usually undergo aggregation-caused quenching (ACQ), which limits the loading amount of these fluorophores in nanoparticles for bright fluorescence imaging. On the contrary, fluorophores with aggregation-induced emission (AIE) characteristics are strongly fluorescent in their aggregate states and have been an ideal platform for developing highly fluorescent nanomaterials, such as fluorescent silica nanoparticles (FSNPs). In this work, AIE luminogens based on salicylaldehyde hydrazones were embedded in silica nanoparticles through a facile noncovalent approach, which afforded AIE-FSNPs emitting much brighter fluorescence than that of some commercial fluorescein-doped silica and polystyrene nanoparticles.

A label-free and sensitive fluorescent method for the detection of uracil-DNA glycosylase activity.

The activity of uracil-DNA glycosylase (UDG), an enzyme in the base excision repair, is detected at a high sensitivity by a DNA substrate containing only one uracil through a label-free fluorescent approach, which is also successfully applied for the measurement of UDG inhibitors.

A facile, sensitive and selective fluorescent probe for heparin based on aggregation-induced emission.

A facile, rapidly responsive fluorescence turn-on probe for heparin with high selectivity and sensitivity was reported in this paper. The probe could aggregate on the negatively charged heparin template through electrostatic interactions and then display intense fluorescence due to its aggregation-induced emission (AIE) characteristics. Under optimal condition, the probe showed high selectivity to heparin over chondroitin sulfate(ChS), hyaluronic acid (HA), dextran (DeX) and other substances, with a linear range of 0.

A ratiometric fluorescent probe for hydrophobic proteins in aqueous solution based on aggregation-induced emission.

A novel fluorescent probe 1 is reported here with ratiometric response to hydrophobic proteins (casein) or proteins with hydrophobic pockets (BSA, HSA) through hydrophobic interaction. Probe 1 underwent deprotonation in aqueous solution at pH 7.4 and emitted blue fluorescence at 436 nm.

Label-free catalytic and molecular beacon containing an abasic site for sensitive fluorescent detection of small inorganic and organic molecules.

In this work, two methods with complementary features, catalytic and molecular beacon (CAMB) and label-free fluorescent sensors using an abasic site, have been combined into new label-free CAMB sensors that possess advantages of each method. The label-free method using a dSpacer-containing molecular beacon makes CAMB more cost-effective and less interfering with the catalytic activity, while CAMB allows the label-free method to use true catalytic turnovers for signal amplifications, resulting in a new label-free CAMB sensor for Pb(2+) ion, with a detection limit of 3.8 nM while maintaining the same selectivity.

Fluorescence turn-on detection of protamine based on aggregation-induced emission enhancement characteristics of 4-(6'-carboxyl)hexyloxysalicylaldehyde azine.

A novel fluorescence turn-on method for sensitive and selective detection of protamine was developed based on aggregation-induced emission enhancement (AIEE) characteristics of 4-(6'-carboxyl)hexyloxysalicylaldehyde azine (CHSA) induced by electrostatic interaction between protamine and CHSA(-). Under optimal conditions described, a large Stokes shift of approximately 198 nm could be observed, and the fluorescence enhancement at 538 nm was linearly related to the concentration of protamine in the range of 0.6-18 microg mL(-1) with the relative correlation coefficient of R(2) = 0.