Ultra-sensitive detection of uranyl ions with a specially designed high-efficiency SERS-based microfluidic device

The uranyl ion(UO_2~(2+)) poses high risks to human health and the environment, hence its detection and monitoring is of utmost significance. However, the development of an ultra-sensitive, high-efficiency and convenient approach for on-site detection of UO_2~(2+) remains a challenge. Herein, a reliable and reusable surface-enhanced Raman spectroscopy(SERS)-based microfluidic biosensor was developed for rapid detection of UO_2~(2+) in real samples. The detection protocol involved the reaction of 5′-Rhodamine B(RhB)-labeled double-stranded DNA for UO_2~(2+)-specific DNAzyme-cleavage reaction in a U-shaped microchannel. Then, the reaction products were delivered into three parallel samples for high-throughput tests by SERS biochips,where 3 D ZnO-Ag mesoporous nanosheet arrays(MNSs) were modified with a single-stranded DNA(ssDNA). The ssDNAwas sequence-complementary with the 5′-RhB-labeled cleaved-stranded DNA(csDNA) from the reaction products. By the hybridization of ssDNA and csDNA, the signal probe RhB was fixed close to the surface of the ZnO-Ag MNSs to enhance the Raman signal. The limit of detection for UO_2~(2+) with the microfluidic-SERS biosensor was 3.71×10~(-15) M. An over 20,000-fold selectivity towards UO_2~(2+) response was also achieved in the presence of 15 other metal ions. The high-throughput microfluidicSERS biosensor operated well for practical UO_2~(2+) detection, with excellent recoveries in contaminated river and tap water from95.2% to 106.3%(relative standard deviation(RSD) 6.0%, n=6). Although the SERS-based microfluidic biosensor developed in this study was deployed for the detection of UO_2~(2+), the reusable and high-efficiency system may be expanded to the detection of other analytes on-site.     

Highly efficient visible-light photocatalytic ethane oxidation into ethyl hydroperoxide as a radical reservoir

Photocatalytic ethane conversion into value-added chemicals is a great challenge especially under visible light irradiation. The production of ethyl hydroperoxide (CH₃CH₂OOH), which is a promising radical reservoir for regulating the oxidative stress in cells, is even more challenging due to its facile decomposition. Here, we demonstrated a design of a highly efficient visible-light-responsive photocatalyst, Au/WO₃, for ethane oxidation into CH₃CH₂OOH, achieving an impressive yield of 1887 μmol g_cat⁻¹ in two hours under visible light irradiation at room temperature for the first time. Furthermore, thermal energy was introduced into the photocatalytic system to increase the driving force for ethane oxidation, enhancing CH₃CH₂OOH production by six times to 11 233 μmol g_cat⁻¹ at 100 °C and achieving a significant apparent quantum efficiency of 17.9% at 450 nm. In addition, trapping active species and isotope-labeling reactants revealed the reaction pathway. These findings pave the way for scalable ethane conversion into CH₃CH₂OOH as a potential anticancer drug.

Highly efficient visible-light driven photocatalytic oxidation of ethane into ethyl hydroperoxide was realized for the first time over Au/WO₃.     

Highly efficient atom transfer radical addition reactions with a RuIII complex as a catalyst precursor

The combination of the air-stable RuIII complex [Cp*RuCl2(PPh3)] with AIBN can be used to catalyze the atom transfer radical addition reactions of polychlorinated compounds and of sulfonyl chlorides to olefins with unprecedented turnover numbers of up to 44 000.     

Highly efficient electrogenerated chemiluminescence of natural chlorophyll a

Highly efficient electrogenerated chemiluminescence (ECL) of natural chlorophyll a (Chl a) was observed in acetonitrile with 1-butyl-3-methylimidazolium hexafluorophosphate as electrolyte and tri-n-propylamine (TPrA) as a coreactant. The collected ECL spectrum displayed a maximum emission peak at ca. 670 nm, suggesting that the same excited states with the photo-excitation processes were generated. The possible ECL reaction mechanism of this Chl a–TPrA system was discussed and established. ECL intensity of Chl a was proportional to its concentration over the range of 0.1–11 μM, and a high ECL efficiency (Φ_ecl) of 0.86 was calculated using Ru(bpy)₃^2 + as the standard (Φ_ecl = 1). Herein, an important property of natural Chl a was expanded and a new kind of ECL luminophores was developed. Moreover, it is expected that this high ECL efficiency of natural porphyrin complex has great potential to expand its ECL sensing application.     

Highly sensitive cyanide anion detection with a coumarin-spiropyran conjugate as a fluorescent receptor

A coumarin-spiropyran conjugate (2) shows a CN(-)-selective fluorescence enhancement under UV irradiation. This enables accurate determination of very low levels of CN(-) (>0.5 μM).     

Highly efficient continuous flow reactions using singlet oxygen as a "green" reagent

Described is a new method for the efficient in situ production of singlet oxygen in a simple continuous flow photochemical reactor. The extremely large interfacial area generated by running the biphasic mixture in a narrow channel at a high flow rate ensures high throughput as well as fast and efficient oxidation of various alkenes, 1,3-dienes, and thioethers on a preparative scale.     

Highly efficient quenching of nanoparticles for the detection of electron‐deficient nitroaromatics

Reported herein is the highly efficient quenching of fluorescent organic nanoparticles by 2,4‐dinitrotoluene and 2,4,6‐trinitrotoluene. These fluorescent nanoparticles are formed from the hydrophobic collapse of fluorescent polymer chains and display quenching efficiencies that are in line with the highest reported literature values. Moreover, the fluorescent quenching occurs only for the fluorescent nanoparticles, and not for the precursor polymer solutions, which display marked insensitivity to the presence of nitroaromatics. This aggregation‐dependent fluorescent quenching has numerous applications for the detection of small‐molecule electron‐deficient analytes. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4150–4155     

Highly efficient endoglycosidase-catalyzed synthesis of glycopeptides using oligosaccharide oxazolines as donor substrates

A highly efficient chemoenzymatic synthesis of N-glycopeptides was achieved. It was found that using synthetic oligosaccharide oxazolines, the mimics of the presumed oxazolinium ion intermediate formed in a retaining mechanism of substrate-assisted catalysis, as the donor substrates and GlcNAc-peptides as the acceptors, the endo-beta-N-acetylglucosaminidase (ENGase)-catalyzed transglycosylation gave a high yield (73-82%) of the corresponding glycopeptides in a regio- and stereospecific manner, regardless of the size of the peptide portions. The use of the oligosaccharide oxazolines as donor substrates not only expanded the substrate availability but also led to a substantial enhancement of the synthetic efficiency, compared to the use of natural N-glycans.     

Highly efficient asymmetric Michael addition of aldehyde to nitroolefin using perhydroindolic acid as a chiral organocatalyst

Perhydroindolic acids, the by-products obtained in the industrial production of a trandolapril intermediate, were used as chiral organocatalysts in asymmetric Michael addition reactions of aldehydes to nitroolefins. These proline-like catalysts are unique for their rigid bicyclic structure with two H atoms attached to the bridgehead C atoms lying on the opposite side of the ring. They therefore showed high efficiency in asymmetric Michael additions of aldehydes to nitroolefins. Under the optimal conditions, excellent diastereo- and enantioselectivities (up to 99/1 dr and 98% ee) were obtained with high chemical yields for a series of aldehydes and nitroolefins using only 5 mol% catalyst loading. The methodology features easily available catalysts, high catalytic efficiency and environmentally green procedures.     

Highly efficient esterification of carboxylic acids with alcohols by montmorillonite-enwrapped titanium as a heterogeneous acid catalyst

Montmorillonite-enwrapped titanium catalyst was found to efficiently promote the esterification of carboxylic acids with alcohols. In comparison to other catalysts reported to date, this heterogeneous catalyst offers a remarkably simple workup procedure, and is reusable without any appreciable loss in its activity and selectivity.     

Methyl benzoate as a marker for the detection of mold in indoor building materials

A convenient analytical method to quantify volatile organic compounds (VOCs) emitted from various building materials has not been addressed yet. This work presents a new and rapid automated method using SPME combined with GC/MS. Methyl benzoate - as a metabolic biomarker for mold growth-was used to indicate VOCs and to determine and assess mold growth on damp samples. Gypsum board and wall-board paper were used as examples of common indoor building materials. Optimized extraction conditions were carried out manually, using a GC/flame ionization detector. Moldy samples were analyzed using an automated SPME-GC/MS analysis under optimized conditions. The amount of methyl benzoate emitted from the studied samples ranged from 32 to 46 ppb, where the density of the fungal biomass was found to be 8 x 10(4) cells/mL. A relationship between the amount of fungal biomass and the emitted concentration of methyl benzoate was found and assessed based upon cultured mold samples taken from indoor building sites. The analytical method shows promise for the compound methyl benzoate, which can easily be identified at low detection limits (LOD = 3 ppb) and good linearity (>0.988), and its extraction and detection can be accomplished cleanly by current extraction techniques. Results suggest that this method with easy sample preparation can be used for quantitation and, of importance, minimal matrix effects are observed.     

Evaluation of 99mTc-ceftazidime as bacterial infection imaging agent

Although our understanding of microorganisms has advanced significantly and antimicrobial therapy has become increasingly available, infection remains a major cause of patient morbidity and mortality. The use of radiopharmaceuticals for diagnosis of infection is increasing due to their ability to distinguish between septic and aseptic inflammation. A wide range of radiopharmaceuticals have been proposed to visualize infection and inflammation scintigraphically. Ceftazidime a cephalosporin antibiotic used to treat bacterial infections was investigated to label with ^99mTc. Labeling was performed using sodium dithionite as reducing agent at 100 °C for 10 min and radiochemical analysis involved ITLC and HPLC methods. The stability of labeled antibiotic was checked in the presence of human serum at 37 °C up to 24 h. The maximum radiolabeling yield was 95.4 ± 2.0 % corresponding to a specific activity of 178 GBq/mmol. Bacterial binding assay was performed with S. aureus and the in vivo distribution was studied in mice. Images showed minimal accumulation in nontarget tissues, with an average target/nontarget ratio of % 1.4 ± 0.2.     

Determination of enterostatin in human cerebrospinal fluid by capillary electrophoresis with laser induced fluorescence detection

A capillary electrophoresis (CE) method with laser induced fluorescence (LIF) detection is described for quantification of enterostatin (Val-Pro-Asp-Pro-Arg), a pentapeptide involved in appetite regulation and insulin secretion. Enterostatin and two other pentapeptides belonging to the enterostatin family (i.e. Ala-Pro-Gly-Pro-Arg and Val-Pro-Gly-Pro-Arg) were well separated from each other. The peptides were fluorescently tagged with naphthalene-2,3- dicarboxaldehyde (NDA) and separated by micellar electrokinetic chromatography (MEKC) in the presence of methanol as an organic modifier. Coupled with LIF detection, the method had a detection limit of 4.8 x 10(-6) M for enterostatin. The relative standard deviation was to be 4.0% from five determinations of enterostatin at 37.2 microM in a human cerebrospinal fluid (CSF) sample. Twenty-three human CSF samples were analyzed. The level of enterostatin ranged from 24 microM to 51 microM with a mean (+/- SEM) value of 41.7 +/- 2.0 microM.     

Determination of enterostatin in human cerebrospinal fluid by capillary electrophoresis with laser induced fluorescence detection

A capillary electrophoresis (CE) method with laser induced fluorescence (LIF) detection is described for quantification of enterostatin (Val-Pro-Asp-Pro-Arg), a pentapeptide involved in appetite regulation and insulin secretion. Enterostatin and two other pentapeptides belonging to the enterostatin family (i.e. Ala-Pro-Gly-Pro-Arg and Val-Pro-Gly-Pro-Arg) were well separated from each other. The peptides were fluorescently tagged with naphthalene-2,3- dicarboxaldehyde (NDA) and separated by micellar electrokinetic chromatography (MEKC) in the presence of methanol as an organic modifier. Coupled with LIF detection, the method had a detection limit of 4.8 × 10^–6 M for enterostatin. The relative standard deviation was to be 4.0% from five determinations of enterostatin at 37.2 μM in a human cerebrospinal fluid (CSF) sample. Twenty-three human CSF samples were analyzed. The level of enterostatin ranged from 24 μM to 51 μM with a mean (± SEM) value of 41.7 ± 2.0 μM.     

Highly efficient synthesis of N-substituted isoindolinones and phthalazinones using Pt nanowires as catalysts

A series of N-substituted isoindolinones have been successfully synthesized through the reductive C-N coupling and intramolecular amidation of 2-carboxybenzaldehyde and amines. This one-pot synthesis gives excellent yields using ultrathin Pt nanowires as catalysts under 1 bar of hydrogen. These unsupported catalysts can also be used for the synthesis of phthalazinones in high yield when hydrazine or phenyl hydrazine is used instead of amines.     

Quencher as leaving group: efficient detection of DNA-joining reactions

We describe a new fluorescence reporting strategy in which dabsyl, a well-known quencher, activates a hydroxyl group in a probe to convert it to a leaving group. When a nucleophilic phosphorothioate probe binds adjacent to a dabsyl quenched probe, autoligation occurs, releasing the quencher, and lighting up the probes, This signal change can be used to detect single nucleotide differences in DNA without enzymes or reagents.     

Highly efficient racemisation of a key intermediate of the antibiotic moxifloxacin

N-Chlorination by sodium dichloroisocyanurate and dehydrochlorination by TEA, followed by hydrogenation, allowed (1R,6S)-8-benzyl-7,9-dioxo-2,8-diazabicyclo[4.3.0]nonane to be quantitatively racemised and the resulting trans-free cis racemate to be recycled into the resolution process to yield (1S,6R)-8-benzyl-7,9-dioxo-2,8-diazabicyclo[4.3.0]nonane, a key intermediate of moxifloxacin.