A simple and efficient assay platform with high sensitivity, convenient implementation, and moderate cost in reagents and instrumentation is most appropriate for routine applications. On the basis of the gold nanoparticle (AuNP) enumeration signal readout mode established in our laboratory, we have developed a nonamplification sandwich assay for nucleic acid detection with the 3 fM limit of detection for a sequence related to Alzheimer's disease. This AuNP counting based method takes advantages of the distinctive and strong localized surface plasmon resonance light scattering with the dark-field microscope and magnetic separation. It is shown that the presence of 20 nM random DNA sequence or calf thymus DNA with a mass up to 10(6)-fold of the targets do not significantly interfere with the assay signal. The spike recoveries of Hela cell lysate sample at 109.3% for 20 pM target and 110.5% for 100 pM target indicate the potential of this proposed method in practical sample applications. This nonamplification sandwich assay platform in principle is applicable to other assays such as the immunoassay and thus would be expected to find a breadth of applications that can make the best use of the simplicity and sensitivity.

Difluoroboron β-diketonates (BF bdks) show both fluorescence (F) and room-temperature phosphorescence (RTP) when confined to a rigid matrix, such as poly(lactic acid). These materials have been utilized as optical oxygen sensors (e.g., in tumors, wounds, and cells). Spectral features include charge transfer (CT) from the major aromatic donor to the dioxaborine acceptor. A series of naphthyl-phenyl dyes (BF nbm) (1-6) were prepared to test heavy-atom placement effects. The BF nbm dye (1) was substituted with Br on naphthyl (2), phenyl (3), or both rings (4) to tailor the fluorescence/phosphorescence ratio and RTP lifetime-important features for designing O sensing dyes by means of the heavy atom effect. Computational studies identify the naphthyl ring as the major donor. Thus, Br substitution on the naphthyl ring produced greater effects on the optical properties, such as increased RTP intensity and decreased RTP lifetime compared to phenyl substitution. However, for electron-donating piperidyl-phenyl dyes (5), the phenyl aromatic is the major donor. As a result, Br substitution on the naphthyl ring (6) did not alter the optical properties significantly. Experimental data and computational modeling show the importance of Br position. The S and T states are described by two singly occupied MOs (SOMOs). When both of these SOMOs have substantial amplitude on the heavy atom, passage from S to T and emission from T to S are both favored. This shortens the excited-state lifetimes and enhances phosphorescence.

A small fluorescence ratiometric probe consisting of a single dye species, N-methyl-6-hydroxyquinolinium (MHQ), and coupled enzymatic substrates, exhibits a dramatic colour change (deep blue to red) and possesses a huge response ratio (over 2000 fold) upon specific recognition of target enzymes. Such dramatic responses are attributed to the excited-state proton transfer processes of MHQ molecules in water. Here the detection of β-galactosidase and porcine pancreatic lipase is successfully demonstrated and this class of molecules has the potential to be developed as a "naked-eye" probe in vitro.

In their study of surface water bodies (WBs) in China, Feng et al. (1) used the global surface water dataset (GSWD) by Pekel et al. (2) to report that the abundance of WBs (>1 km 2) and their total area were underestimated greatly by previous studies (3, 4). However, the incorrect definitions of WBs, data coverage, and the temporal windows in Feng et al. (1) could have resulted in large errors, and thus discrepancies for the number of WBs detected and their area changes. As Earth's surface water is driven by changing climate and anthropogenic factors, it is important that an epoch date be defined at which the WB calculations are referenced. Feng et al. (1) used the GSWD (2), excluding rivers and streams, to calculate the WB occurrences in China during 1984 to 2015 and found there is a total of 6,821 WBs (>1 km 2). They argued that previous studies (e.g., refs. 3 and 4) have underestimated the number and sizes of WBs in China. Indeed, a smaller number (5,535) of lakes and reservoirs has been derived from Landsat images during 2005 to 2008 (3), and 2,693 lakes were mapped during 2005 to 2006 (4). Zhang et al. (5) demonstrated that China had 2,554 lakes (>1 km 2) in 2015 and that lake number and area in China including Tibetan Plateau (TP) have been increasing between the 1970s and 2015 (Fig. 1). When compiling a lake inventory, reservoirs and dams should be excluded, and a relatively stable season for WBs should be chosen to avoid seasonal, interannual, or longer variability (6). This is the reason why ±2-y or longer data intervals should be employed (5). These considerations are not addressed by Feng et al. (1), leading to the feasibility that the maximum WBs number and area were estimated. For the TP, Feng et al. (1) Sciences (XDA20060201 and XDA19070302), the National Key Research and Development Program of China (2018YFB0505005 and 2017YFA0603103-3), and the Natural Science Foundation of China (41871056). Funding support for H.X. was partially from the US NASA Award (80NSSC19M0194).

A capillary zone electrophoresis method was developed for the separation and determination of strychnine and brucine in Strychnos nux-vomica L. and its preparation. The factors that could affect the separation were studied, such as the types and concentrations of electrolytes, pH, ionic strength and organic modifier. The optimum running buffer was 20 mmol/L of ammonium acetate containing 0.2 mol/L of glacial acetic acid (pH 3.64). The applied voltage was 25 kV and the wavelength of the UV detector was set at 214 nm. The established method with dopamine hydrochloride as internal standard was linear in the range of 5-100 microg/mL for both strychnine and brucine. The recovery was 102.96% for strychnine and 98.56% for brucine. The extracts of Strychnos nux-vomica and its preparation could be directly injected for analysis.

Since the first report 1) in 1985, capillary electrophoresis (CE) enantioseparation has become a very important area during the last two decades. In CE enantioseparation, the chiral selector can be directly added to the running buffer to provide chiral environment. Thus the two enantiomers can be separated owing to the difference in the interactions between chiral selectors and enantiomers. The most widely used chiral selectors are cyclodextrins (CDs) and various derivatives.2-7) Many papers on CE enantiomeric separation focused on optimization of experimental methods, for example, the type and concentration of CDs, buffer pH, ionic strength, etc. [8][9][10][11][12][13][14] Vescina et al. reported the CE enantiomeric separation of 35 basic pharmaceutical compounds using a total of 26 different CD derivatives with different functional groups and degrees of substitution.15) The experimental conditions were chosen based on literature reports and their own experience and more than 1000 CE experiments were involved. Ren and Liu investigated the effects of pH, b-CD concentration, electrolyte concentration, and methanol concentration on the chiral separation of dioxypromethazine enantiomers using capillary electrophoresis.16) Wioleta reported the application of carboxymethyl-b-CD as a chiral selector in capillary electrophoresis for enantiomer separation of selected neurotransmitters.17) The experimental factors have been optimized, such as the type and concentration of chiral selector, concentration of borate buffer, content of methanol, pH of electrolyte, and method of sample introduction into the capillary.17) However, the literature studies on enantiomeric separation of pharmaceutical compounds were limited by the explanation of how the enantiomeric separation occurred. The current study used a molecular docking technique to gain insight into the selector-enantiomer interaction energy and provided useful supporting information for enantiomeric separations.In this report, b-CDs were used as the chiral selectors and adrenaline and its analogues as the objects. The course of host-guest inclusion was determined by means of a molecular docking technique and thus the interaction energy was calculated by molecular mechanics calculations. Based on the results, the mechanism of chiral recognition is discussed. ExperimentalChemicals Adrenaline, noradrenaline and isopropyladrenaline were purchased from Shanghai Hefeng Pharmaceuticals Co., Ltd. Terbutaline was obtained from Shanghai Institute for Drug Control. Tris reagent was obtained from Shanghai Shisheng Cell Biotechnique Co., Ltd. b-CD was purchased from Suzhou Flavorings Factory; 2,3,6-trimethyl-b-CD was synthesized in our laboratory based on references 18,19) and the product was identified based on IR, NMR, and MS, which provided the physiochemical data such as the melting point of 156 to 157°C and IR (cm Ϫ1) of 2985, 2930, 2830, 1466, 1365, 1320, 1160, 1140, 1110, 1070. The uncoated fused-silica capillary was purchased from Hebei Yongnian Optical Fiber Factory.Apparat...

Coated tools are currently widely used tool technology in machining. The influence of tool coating on heat transfer has become an active field of research enjoying constantly increasing attention in the field of machining. This paper is devoted to the cutting temperature in machining H13 hardened steel with monolayer coated tools (TiN, TiAlN, and Al2O3) and multilayer coated tools (TiN/TiC/TiN and TiAlN/TiN). Equivalent composite thermal conductivity and thermal diffusivity of multilayer coated tools were calculated using the equivalent approach. The established heat transfer analytical models estimated coating temperature in turning. The effect of tool coating in steady and transient heat transfer was studied, as well as the cutting temperature distribution. It reveals that the tool coating material and coating thickness can influence the cutting temperature distribution of coated tool. Thermal conductivity of coating material affects the steady cutting temperature distribution, and thermal diffusivity of coating material affects the transient cutting temperature distribution of coating tools.

Fluorometrically reactive peptides of leucine-and methionine-enkephalins in rat brain tissues such as cortex, striatum and hypothalamus were simultaneously assayed by reversed-phase high performance liquid chromatography with fluorometric detection, based on precolumn derivatization specific for N-terminal tyrosine-containing peptides. The enkephalin peptides extracted from the tissues were converted into fluorescent derivatives by reaction with hydroxylamine, cobalt(II) ion and borate in a weakly alkaline aqueous solution (pH 8.5). The fluorescent derivatives of the peptides were separated on a reversed-phase column (TSKgel ODS-120T) by gradient elution of acetonitrile in the mobile phase containing borate buffer (pH 8.5) and tetrabutylammonium chloride, and then determined by fluorometry. The peaks of both the enkephalins in the tissue sample were not observed in the chromatogram after the enzymatic degradation with carboxypeptidase A. The determined concentrations of the leucine-and methionine-enkepalins in the tissues were 20-238 pmol and 80-75 pmol per g of the tissue, respectively. The method was sensitive enough to determine the endogenous enkephalins at concentrations as low as Ca. 6 pmol per g of the brain tissues. KeywordsEnkephalin, rat brain, fluorometry, high performance liquid chromatography, precolumn derivatizationEnkephalins, leucine-enkephalin (LE; Tyr-Gly-GlyPhe-Leu) and methionine-enkephalin (ME; Tyr-GlyGly-Phe-Met), have opiate-like activity in nervous systems.' Recently, opioid peptides have been found to act in vivo as neurotransmitters via interaction with opiate receptors.2Most of the opioid peptides involving LE and ME have a tyrosyl residue at the Nterminus in their molecules.During the studies on the physiological mechanism of the opioid peptides, many methods have been developed for the quantitative determination of the opioid peptides in biological samples. These methods include bioassay3, radioimmunoassay (RIA)4'5, enzyme-immunoassay6, radioreceptorassay' and mass spectrometry8, either alone or in combination with high performance liquid chromatography (HPLC).HPLC can simultaneously separate many synthetic and biological peptides9"0, and has the advantages of superior reproducibility, practicability and speed in the analysis. However, the quantification of the endogenous opioid peptides in brain tissues by the current HPLC methods with spectrophotometric'° and electrochemical" detections is hampered by problems of insufficient sensitivity and selectivity for the peptides.To resolve the problems in the HPLC, we previously developed a unique chemical reaction'2 for N-terminal Tyr-containing peptides, by which the peptides yields intense fluorescences under mild conditions in the presence of hydroxylamine, cobalt(II) ion and borate. This reaction provided a single fluorescent product for each of the synthetic peptides and did not permit the production of fluorescent derivatives for peptides having no N-terminal tyrosyl residue (e.g. Gly-Tyr, Phe-Arg-Gly and Arg-Val-Tyr-Ile-His-Pro-Phe...