Highly Sensitive Chemiluminescence Detection for PDMS/GIass Micro-chip Electrophoresis

This paper described a highly sensitive chemiluminescence detection system for micro-chip electrophoresis (MCE) based on luminol-hydrogen peroxide reaction catalyzed by the metal ions. The micro-chip was composed of poly(dimethylsiloxane) (PDMS) and glass, and was fabricated by micro-machining technology. The surface of channels was dynamically modified by polydimethylacrylamide (PDMA) in order to eliminate unhomogeneous electroosmotic flow (EOF) of the PDMS/glass chip, adsorption of molecules, and improve hydrophobicity on PDMS surface. The detection modes, reagent mix procedures and reaction conditions were optimized and the detection limit of 5×10 mol/L for cobalt (II) was achieved by MCE with chemiluminescence detection, which was about four orders of magnitude more sensitive than that reported in the reference.     

Three-Component Synthesis of Dioxaphosphorane-Fused Diphosphacycles Exhibiting Unique Dynamic Fluorescence “On/Off” Properties

Rigidly planar polycyclic phosphacycles featuring an internal dioxaphosphorane are promising photofunctional materials. However, the lack of efficient synthetic methods resulted in limited structural diversities which significantly hampered extensive study. Herein, we report a straightforward three-component synthesis of novel dioxaphosphorane-fused diphosphacycles with distinctive photophysical properties. Control experiments and theory calculations were performed to account for a plausible reaction mechanism. We also systematically investigated the structure-property relationships of these unprecedented platforms by combining experiments (X-ray analysis, optical and redox properties) and theoretical computations. Based on their unique structure and properties, a novel fluorescent switch for pH sensing was revealed by a dynamic ring-opening/ring-closing process.     

Glyphosate–Exonuclease Interactions: Reduced Enzymatic Activity as a Route to Glyphosate Biosensing

N-phosphonomethyle-glycine (glyphosate) is the most widely used pesticide worldwide due to its effectiveness in killing weeds at a moderate cost, bringing significant economic benefits. However, owing to its massive use, glyphosate and its residues contaminate surface waters. On site, fast monitoring of contamination is therefore urgently needed to alert local authorities and raise population awareness. Here the hindrance of the activity of two enzymes, the exonuclease I (Exo I) and the T5 exonuclease (T5 Exo) by glyphosate, is reported. These two enzymes digest oligonucleotides into shorter sequences, down to single nucleotides. The presence of glyphosate in the reaction medium hampers the activity of both enzymes, slowing down enzymatic digestion. It is shown by fluorescence spectroscopy that the inhibition of ExoI enzymatic activity is specific to glyphosate, paving the way for the development of a biosensor to detect this pollutant in drinking water at suitable detection limits, i.e., 0.6 nm .     

Tantalum Electrodes Modified With Well-Aligned Carbon Nanotube–Au Nanoparticles: Application to the Highly Sensitive Electrochemical Determination of Cefazolin

Carbon nanotube/nanoparticle hybrid materials have been proven to exhibit high electrocatalytic activity suggesting broad potential applications in the field of electroanalysis. For the first time, modification of Ta electrode with aligned multi-walled carbon nanotubes/Au nanoparticles introduced for the sensitive determination of the antibiotic drug, cefazolin (CFZ). The electrochemical response characteristics of the modified electrode toward CFZ were investigated by means of cyclic and linear sweep voltammetry. The modified electrode showed an efficient catalytic activity for the reduction of CFZ, leading to a remarkable decrease in reduction overpotential and a significant increase of peak current. Under optimum conditions, the highly sensitive modified electrode showed a wide linear range from 50 pM to 50 μM with a sufficiently low detection limit of 1?±?0.01 pM (S/N?=?3). The results indicated that the prepared electrode presents suitable characteristics in terms of sensitivity (458.2?±?2.6 μAcm^?2/μM), accuracy, repeatability (RSD of 1.8 %), reproducibility (RSD of 2.9 %), stability (14 days), and good catalytic activity in physiological conditions. The method was successfully applied for accurate determination of trace amounts of CFZ in pharmaceutical and clinical preparations without the necessity for samples pretreatment or any time-consuming extraction or evaporation steps prior to the analysis.     

A Light-Responsive Metal–Organic Framework Hybrid Membrane with High On/Off Photoswitchable Proton Conductivity

Mimicking biological proton pumps to achieve stimuli-responsive protonic solids has long been of great interest for their diverse applications in fuel cells, chemical sensors, and bio-electronic devices. Now, dynamic light-responsive metal–organic framework hybrid membranes can be obtained by in situ encapsulation of photoactive molecules (sulfonated spiropyran, SSP), as the molecular valve, into the cavities of the host ZIF-8. The configuration of SSP can be changed and switched reversibly in response to light, generating different mobile acidic protons and thus high on/off photoswitchable proton conductivity in the hybrid membranes and device. This device exhibits a high proton conductivity, fast response time, and extremely large on/off ratio upon visible-light irradiation. This approach might provide a platform for creating emerging smart protonic solids with potential applications in the remote-controllable chemical sensors or proton-conducting field-effect transistors.     

Enzymatic self-assembly/disassembly turns “ON”/“OFF” the mimetic hydrolytic activity of histidine nanofibers

Mimetic enzymes are devised as alternates or supplements of natural enzymes in broad fields but regulating their activities in a switchable manner remains challenging.Herein,we proposed an enzymatic self-assembly/disassembly strategy to address this issue.A peptide molecule Nap FFEYIH(YH) was rationally designed which,after self-assembling into nanofibers,lined up the histidine moieties to form active hydrolysis centers for mimicking hydrolase activity.Enzymatic dephosphorylation of Nap FFEYp IH...     

Highly enantioselective copper-catalyzed alkylation of β-ketoesters and subsequent cyclization to spirolactones/bi-spirolactones

Cu-catalyzed enantioselective alkylation of β-ketoesters using alcohols for in situ preparation of alkylating reagents is reported. A number of functionalized β-ketoesters containing a quaternary carbon stereocenter are obtained with up to 99% ee. The alkylation products derived from 2-substituted allylic alcohols or their corresponding iodides can then be converted to spirolactones, bi-spirolactones, and related chiral target products.     

Microwave Effect On Partial Oxidation of Methane to Syngasover Ni/ZrO_2

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An international intercomparison on “self-calibrated” alanine EPR dosimeters

The results, obtained by six independent electron paramagnetic resonance (EPR) laboratories, of the dose response coefficients (K_dr) of “self-calibrated” solid-state EPR dosimeters containing alanine as a radiation-sensitive material and Mn²⁺/MgO as an internal reference material, are reported. The intercomparison trial was divided into three steps. It started with the distribution of dosimeters among the participating EPR laboratories with the purpose of irradiating them with known doses of γ-rays and to estimate the K_dr. The percentage standard deviation (PSD) of the K_dr obtained at individual labs was in the range of 1.4–4.6%. The interlaboratory PSD of the K_dr was 8%, primarily pointing to variations in irradiation procedures and EPR spectrometer settings. Further investigations showed that the main source of the interlaboratory PSD is differences in the calibrations of irradiators and settings of EPR acquisition parameters. In order to provide reproducible estimates of the K_dr, low microwave power and modulation amplitude using a combination of sweep time and time constant that gives a distortion-free EPR spectrum should be utilized. In the third step following such a procedure, measuring the same irradiated alanine dosimeter at the respective laboratories, spectrometers (12 instruments of 6 different models and 3 producers) and 10 operators gave an interlaboratory PSD of 3.1%. In conclusion, EPR dosimetry using “self-calibrated” alanine dosimeters may be used as a secondary standard, although a careful calibration of the EPR spectrometer must be performed in order to further reduce the uncertainty.     

Highly reactive “RIKEN click” probe for glycoconjugation on lysines

One pot double click strategy containing strain-promoted click-reaction followed by 6π-azaelectrocyclization (RIKEN click reaction) has worked well in the synthesis of multivalent homogeneous and heterogeneous N-glycoalbumins. We have slightly changed the structure of linker unsaturated aldehyde used in this method. As a result it can be easily synthesized from commercially available material and furthermore, the enhancement of its reactivity towards both click-reactions was observed. The data described in this Communications facilitate the usage of the double click strategy as a general method for the synthesis of a variety of neo-N-glycoproteins.     

Sensitive and selective DNA probe based on “turn-on” photoluminescence of C-dots@RGO

In this study, highly hydrophilic and photoluminescent sheets of reduced graphene oxide decorated with carbon dots (C-dots@RGO), methylene blue (MB), and a probe DNA have been used for the detection of DNA. The photoluminescence of C-dots@RGO is quenched by MB, which is restored in the presence of a target DNA. The combination of the C-dots@RGO, MB, and a DNA probe is selective for perfectly matched DNA over mismatched DNA, mainly because relative to single-stranded DNA, double-stranded DNA intercalates more strongly with MB, but interacts more weakly with RGO. In the presence of a target DNA, MB intercalates with the as-formed double-stranded DNA and is released from the surface of C-dots@RGO, leading to “turn-on” photoluminescence. The practicality of this assay has been validated by the determination of tumor suppressor gene BRCA1, with linearity over the concentration range from 25 to 250 nM and a limit of detection (LOD, at a signal-to-noise ratio of 3) of 14.6 nM. The C-dots@RGO probe provides higher specificity towards target DNA than towards common salts, carbohydrates, amino acids, and proteins found in real samples. Having the advantages of simplicity, cost-effectiveness, selectivity, and sensitivity, the DNA-P/C-dots@RGO–MB probe on microwells has been successfully employed for the detection of DNA, suggesting its potential for multiple analyses of DNA targets when various DNA probes are employed.     

“Comment” on the Reply to the Paper “On the Elber–Karplus Reaction Path-Following Method and Related Procedures”

The flaws in the Reply [1] to our paper [2] have been pointed out. Elber and Karplus (EK) have not disproved our irrefutable global statement that the energy average cannot be minimized which rebuts the theoretical background of EK-type calculations. Another statement of ours has shown that even a curve for which the average energy is locally minimal for all directional perturbations in the sense of classical variational calculus cannot be identical with the reaction path (RP) defined as a steepest descent path (SDP). EK found an error in the early preprint of our theoretical paper [3] and because of this error they qualified our correct variational statement as false for all the SDPs consisting of a straight line each. Mixing global and variational arguments, EK refuted our criticism in a logically incorrect manner. In this Comment we prove that both of our earlier statements invariably remain in force and the criticism included in those has been as well-established and solid as was before.     

Narrow-disperse Highly Cross-linked “Living” Polymer Microspheres by Two-stage Precipitation Polymerization

Narrow-disperse, surface-functionalized "living" polymer microspheres with uniformly cross-linked structures were prepared by two-stage precipitation copolymerization of styrene and divinylbenzene. The two-stage precipitation polymerization is composed of an initial conventional precipitation polymerization for the nucleation followed by a reverse atom transfer radical polymerization(reverse ATRP) for the controlled polymerization process. The polymerization parameters(including reaction time for the first stage, AIBN amount and monomer loading) have been studied to show significant influences on the morphologies. Moreover, narrower size distribution and an ATRP initiator-functional surface of resulting particles can be obtained by applying reverse ATRP to conventional precipitation polymerization in the second stage. Furthermore, the "livingness" of the resulting polymer microspheres was testified by their surface modification of poly[2-(dimethylamino) ethyl methacrylate](PDMAEMA) brushes via surface-initiated ATRP(SI-ATRP).     

Highly regioselective ring-opening of aziridines with arenesulfinates on water: a facile access to β-amino/vinyl sulfones

We have developed a LiBr catalyzed efficient synthesis of β-amino sulfones from readily available aziridines and sodium sulfinates in good to excellent yields. The synthetic potential of β-amino sulfones has also been demonstrated by their facile conversion to the corresponding vinyl sulfones. The use of water as reaction media, atom-economy and isolation of products by simple filtration in the case of solid β-amino sulfones are certain green virtues of the synthetic protocol.     

“Ship-in-a-Bottle” Approach to Synthesize Ag@hm-SiO2 Yolk/Shell Nanospheres

An e ective protocol is presented for the synthesis of Ag@hm-SiO₂ yolk/shell nanostructures (YSNs) via a facile “ship-in-a-bottle” method. TEM observations show that the as-obtained Ag@hm-SiO₂ YSNs have a single silver core in the interior of hollow mesoporous silica (hm-SiO₂) nanospheres, in which the thickness of hm-SiO₂ outer shell is about 14 nm and the silver core has an average size of about 43 nm. And the content of silver in Ag@hm-SiO₂ YSNs is about 10.29% based on the inductively coupled plasma measurement. The as-synthesized Ag@hm-SiO₂ YSNs exhibited signi cantly enhanced catalytic performance compared with the pure Ag nanoparticles toward the reduction of 4-nitrophenol to 4-aminophenol in the presence of Na₄.     

An Upgraded “Two-in-One” Strategy toward Highly Crystalline Covalent Organic Frameworks

A highly crystalline bicarbazole-based covalent organic framework (BCzP-COF) was synthesized via an upgraded “two-in-one” strategy by the self-polycondensation of A₂B₂ monomer with two neopentyl acetal and two amine groups. Such a strategy is propitious to afford higher crystallinity, larger special surface areas and better morphology than that of using unprotected monomer with free aldehydes and amines. Additionally, the off-white powder of BCzP-COF could serve as acidichromism sensor with a significant color change. Intriguingly, the conductivity of the protonated BCzP-COF can improve by six orders of magnitude compared to that of the pristine samples. This work has the potential to lead to bicarbazole-functional materials for chemosensors and electronic devices.     

Report On ‘Action Research: Overcoming the Sports Mentality Approach to Assessment/Evaluation’

In this workshop, George Bodner contrasted evaluation with assessment, and presented Action Research as a method for evaluating curriculum changes. He emphasized that any major change in teaching will have some effect; if test scores or other analyses do not reflect this effect, then one must use other tools to uncover it. Bodner defined Action Research as qualitative information-gathering and analysis from all available sources, including reflective journals, comments from students, and personal interviews. In the past few decades, such qualitative research has given way to more quantitative studies, such as analysis of test scores. Bodner argued in his presentation that these quantitative measures are more precise, but less accurate, than Action Researchs subjective, informal methods of evaluation.     

Comments to EURACHEM/CITAC guide “Measurement uncertainty arising from sampling”

The EURACHEM/CITAC Guide “Measurement uncertainty arising from sampling” deals with the design and analysis of experiments for the evaluation of the sampling and analytical standard deviation when a defined sampling and analytical method is used for the determination of the concentration, expressed as mass fraction (mg/kg), of an analyte in a specified material. The Guide recommends reporting the relative expanded uncertainty and using it directly, i.e. it implicitly assumes that the standard deviation is proportional to the mass fraction even in case the experimental data do not support this assumption. Example A1 (and some of the other examples of the Guide) demonstrates that this can result in extreme levels of underestimation or overestimation of the uncertainty of measurement results. Hence, such recommendations should be avoided!