Versatile Enantioselective Synthesis of Functionalized Lactones via Copper-Catalyzed Radical Oxyfunctionalization of Alkenes

A versatile method for the rapid synthesis of diverse enantiomerically enriched lactones has been developed based on Cu-catalyzed enantioselective radical oxyfunctionalization of alkenes. The scope of this strategy encompasses a series of enantioselective difunctionalization reactions: oxyazidation, oxysulfonylation, oxyarylation, diacyloxylation, and oxyalkylation. These reactions provide straightforward access to a wide range of useful chiral lactone building blocks containing tetrasubstituted stereogenic centers, which are hard to access traditionally

Electroporation-Assisted Surface-Enhanced Raman Detection for Long-Term, Label-Free, and Noninvasive Molecular Profiling of Live Single Cells

Molecule characterization of live single cells is greatly important in disease diagnoses and personalized treatments. Conventional molecule detection methods, such as mass spectrography, gene sequencing, or immunofluorescence, are usually destructive or labeled and unable to monitor the dynamic change of live cellular molecules. Herein, we propose an electroporation-assisted surface-enhanced Raman scattering (EP-SERS) method using a microchip to implement label-free, noninvasive, and continuous detections of the molecules of live single cells. The microchip containing microelectrodes with nanostructured EP-SERS probes has a multifunction of cell positioning, electroporation, and SERS detection. The EP-SERS method capably detects both the intracellular and extracellular molecules of live single cells without losing cell viability so as to enable long-term monitoring of the molecular pathological process in situ. We detect the molecules of single cells for two breast cancer cell lines with different malignancies (MCF-7 and MDA-MB-231), one liver cancer cell line (Huh-7), and one normal cell line (293T) using the EP-SERS method and classify these cell types to achieve high accuracies of 91.4–98.3% using their SERS spectra. Furthermore, 24 h continuous monitoring of the heterogeneous molecular responses of different cancer cell lines under doxorubicin treatment is successfully implemented using the EP-SERS method. This work provides a long-term, label-free, and biocompatible approach to simultaneously detect intracellular and extracellular molecules of live single cells on a chip, which would facilitate research and applications of cancer diagnoses and personalized treatments

Polymer Valence Isomerism: Poly(Dewar‑<i>o</i>‑xylylene)s

Poly­(<i>o</i>-xylylene) (POX) has long been a challenging synthetic target despite its simple structure and potentially useful physical properties. In this report, we demonstrate a valence isomer strategy that leads to the formation of high molecular weight POX via an intermediate polymer of a unique structure, namely poly­(Dewar-<i>o</i>-xylylene) (PDOX). We show that the free radical polymerization of highly strained Dewar-<i>o</i>-xylylene (DOX) monomer afforded PDOX, a material with a high density of Dewar benzene units in the backbone through ring-retaining propagation. The thermal- and photoinduced isomerizations of PDOX to produce POX were investigated. This chemistry yields POXs that are difficult to obtain using traditional methods. Moreover, it also provides a potential entry into new reconfigurable materials featuring highly efficient postpolymerization main chain structural transformations

Computer-Vision-Based Dielectrophoresis Mobility Tracking for Characterization of Single-Cell Biophysical Properties

Fast and precise measurements of live single-cell biophysical properties is significant in disease diagnosis, cytopathologic analysis, etc. Existing methods still suffer from unsatisfied measurement accuracy and low efficiency. We propose a computer vision method to track cell dielectrophoretic movements on a microchip, enabling efficient and accurate measurement of biophysical parameters of live single cells, including cell radius, cytoplasm conductivity, and cell-specific membrane capacitance, and in situ extraction of cell texture features. We propose a prediction-iteration method to optimize the cell parameter measurement, achieving high accuracy (less than 0.79% error) and high efficiency (less than 30 s). We further propose a hierarchical classifier based on a support vector machine and implement cell classification using acquired cell physical parameters and texture features, achieving high classification accuracies for identifying cell lines from different tissues, tumor and normal cells, different tumor cells, different leukemia cells, and tumor cells with different malignancies. The method is label-free and biocompatible, allowing further live cell studies on a chip, e.g., cell therapy, cell differentiation, etc

A Mallows-type Model Averaging Estimator for the Varying-Coefficient Partially Linear Model

<p>In the last decade, significant theoretical advances have been made in the area of frequentist model averaging (FMA); however, the majority of this work has emphasised parametric model setups. This paper considers FMA for the semiparametric varying-coefficient partially linear model (VCPLM), which has gained prominence to become an extensively used modeling tool in recent years. Within this context, we develop a Mallows-type criterion for assigning model weights and prove its asymptotic optimality. A simulation study and a real data analysis demonstrate that the FMA estimator that arises from this criterion is vastly preferred to information criterion score-based model selection and averaging estimators. Our analysis is complicated by the fact that the VCPLM is subject to uncertainty arising not only from the choice of covariates, but also whether the covariate should enter the parametric or nonparametric parts of the model.</p

Wireless Oxygen Sensors Enabled by Fe(II)-Polymer Wrapped Carbon Nanotubes

Oxygen causes food spoilage and drug degradation, which is addressed commercially by modified atmosphere packaging. We report herein a wireless oxygen sensor, O₂-<i>p</i>-CARD, from solution processed Fe^II-poly­(4-vinylpyridine)-single-walled carbon nanotube composites on commercial passive near-field communication tags. A large irreversible attenuation in the reflection signal of an O₂-<i>p</i>-CARD was observed in response to oxygen at relevant concentrations, enabling non-line-of-sight monitoring of modified atmosphere packaging. These devices allow for cumulative oxygen exposure inside a package to be read with a conventional smartphone. We have demonstrated that an O₂-<i>p</i>-CARD can detect air ingress into a nitrogen-filled vegetable package at ambient conditions. This technology provides an inexpensive, heavy-metal-free, and smartphone-readable method for <i>in situ</i> non-line-of-sight quality monitoring of oxygen-sensitive packaged products

Asymmetric Total Syntheses of Ansamacrolactams (+)-Q-1047H-A‑A and (+)-Q-1047H-R‑A

The total syntheses of ansamacrolactams (+)-Q-1047H-A-A (<b>16</b>) and (+)-Q-1047H-R-A (<b>17</b>) have been achieved for the first time in 17 steps, leading to the reassignment of the relative stereochemistries and absolute configurations of their natural counterparts. The key steps in the synthetic work included an asymmetric chelation-controlled vinylogous Mukaiyama aldol reaction for the stereoselective synthesis of the <i>syn</i>-aldol adduct <b>7b</b> and an intramolecular SmI₂-mediated Reformatsky reaction for the formation of the macrocyclic lactam <b>14</b>

Quantitative analysis of <i>53R</i> mRNA levels in cells co-transfected with different plasmids.

<p>GCO cells co-transfected with pSM155-amiR-53R-1/pEGFP-N3-53R, pSM155-amiR-53R-2/pEGFP-N3-53R and pSM155-amiR- 53R-3/pEGFP-N3-53R, respectively. <i>53R</i> mRNA level from each group was measured by real-time PCR analysis 72 h post transfection. Group co-transfected with pSM155-amiR-PB2/pEGFP-N3-53R was used as negative control. The value of negative control was designated as 1.0 (n = 3). The values represent averages of three independent experiments, with the range indicated (±S.D). *P<0.05 versus control.</p

Oligonucleotides sequence encoding 53R-specific pre-miRNAs.

<p>Bold letters represent sense sequences of engineered amiRNAs derived from the target gene.</p

Premixed MILD Combustion of Propane in a Cylindrical Furnace with a Single Jet Burner: Combustion and Emission Characteristics

This paper reports the combustion and emission characteristics of the premixed MILD combustion of propane established by a single jet burner in a laboratory-scale cylindrical furnace. Measurements are made of spatial distributions of the furnace temperature and species concentrations (O₂, CO₂, CO, and NO) and also exhaust emissions of CO and NO. Experiments are conducted for different values of thermal input, injection diameter, and global equivalence ratio (Φ). Results are analyzed with the aids of computational fluid dynamics (CFD) simulations and chemical kinetic calculations, which use a simplified perfectly stirred reactor (PSR) system with exhaust gas recirculation (EGR). It is observed that the premixed MILD combustion of propane in the present furnace can be established once the injection momentum rate is sufficiently high to enable the flue gas recirculation rate <i>K</i>_<i>v</i> > 2.5 (critical value) for Φ = 1.0. The critical <i>K</i>_<i>v</i> increases as Φ falls. Inlet conditions of the transition regime should be avoided to prevent the occurrence of instability and flashback for this regime. The present premixed MILD combustion of propane generates low CO and NO emissions. At a sufficient residence time, an increased speed injection reduces NO emission mainly by growing <i>K</i>_<i>v</i> and thus reducing the local peak temperature. In the present premixed MILD combustion, the prompt and reburning routes of NO formation are important. The effects of temperature, equivalence ratio, recirculation rate, and residence time should be systematically considered when optimizing the combustion system for ultralow NO emission