C−N bonds are widely found in natural products, medicinal molecules and multifunctional materials. In recent years, the construction of C−N bonds through a radical coupling reaction between ...carbon‐centered radicals with nitrogen‐centered radicals has emerged as a frontier area in organic chemistry. This review summarizes the recent advances (especially those after 2012) in radical coupling reactions that facilitate the formation of C−N bonds. The main achievements on this area are presented according to the pattern of the nitrogen‐centered radicals generated. Selected examples of substrates are listed and special attention is paid to the reaction mechanisms. Moreover, a personal outlook is described at the end.
We study the evolution of galaxies and the circumgalactic medium (CGM) through cosmic time by correlating ∼50,000 Mg ii absorbers, tracers of cool gas (∼104 K), detected in the Sloan Digital Sky ...Survey quasar spectra with galaxies detected in the DESI Legacy Imaging Surveys. By doing so, we extract the properties of galaxies associated with absorbers from redshift 0.4 to 1.3 with effectively ∼15,000 pairs and explore the covering fraction of Mg ii absorbers as a function of galaxy type, stellar mass, impact parameter, and redshift. We find that the gas covering fraction increases with stellar mass of galaxies by . However, after we normalize the impact parameter by the virial radius of dark matter halos, the gas profiles around galaxies with masses ranging from 109 to become weakly dependent on stellar mass. In addition, the gas distribution depends on galaxy type: the covering fraction within around star-forming galaxies is 2-4 times higher than that around passive galaxies at all redshifts. We find that the covering fraction of strong absorbers ( ) around both types of galaxies evolves significantly with redshift, similarly to the evolution of star formation rate (SFR) of galaxies, while such an evolution is not detected for weak absorbers ( ). We quantify the H i mass traced by strong absorbers and find that the gas mass around galaxies evolves consistently with the SFR of galaxies. This result suggests that the properties of galaxies and their CGM coevolve through cosmic time. Finally, we discuss the origins of strong absorbers around passive galaxies and argue that its redshift evolution may trace the star formation activity of satellite galaxies.
We study the distribution and kinematics of the cool circumgalactic medium (CGM) of emission line galaxies (ELGs) traced by metal absorption lines. Using about 200,000 ELGs from SDSS-IV eBOSS and ...half a million background quasars from SDSS, we measure the median absorption strength of Mg ii and Fe ii lines in quasar spectra for impact parameters ranging from 10 kpc to 1 Mpc. For comparison, we measure the same quantity around luminous red galaxies (LRGs). On scales greater than 100 kpc both ELGs and LRGs exhibit similar absorption profiles. However, metal absorption is 5-10 times stronger around ELGs on smaller scales. The metal absorption strength is anisotropic, with an excess along the minor axis of the galaxies, indicating an outflow origin of the absorbing gas. The ratio between the velocity dispersion of the cool CGM and that of its host dark matter halo is about one for ELGs but about half for LRGs. These results show that the dichotomy of galaxy types is reflected in both the density distribution and kinematics of the CGM traced by metal absorption lines. Our results provide strong evidence that the CGM of ELGs is enriched by gas outflows generated by star formation.
Metal abundance and its evolution are studied for Mg ii quasar absorption line systems from their weak, unsaturated spectral lines using stacked spectra from the archived data of the Sloan Digital ...Sky Survey. They show an abundance pattern that resembles that of the Galactic halo or Small Magellanic Cloud, with metallicity Z/H showing an evolution from redshift z = 2 to 0.5: metallicity becomes approximately solar or even larger at . We show that the evolution of the metal abundance traces the cumulative amount of the hydrogen fuel consumed in star formation in galaxies. With the aid of a spectroscopic simulation code, we infer the median gas density of the cloud to be roughly 0.3 , with which the elemental abundance in various ionization stages, in particular C i, is consistently explained. This gas density implies that the size of the Mg ii clouds is of the order of 0.03 kpc, which suggests that individual Mg ii clouds around a galaxy are of a baryonic mass typically . This means that Mg ii clouds are numerous and "foamy," rather than a large entity that covers a sizable fraction of galaxies with a single cloud.
The current strategies for nanoelectrode functionalization usually involve sophisticated modification procedures, uncontrollable and unstable modifier assembly, as well as a limited variety of ...modifiers. To address this issue, we propose a versatile strategy for large‐scale synthesis of biomimetic molecular catalysts (BMCs) modified nanowires (NWs) to construct functionalized electrochemical nanosensors. This design protocol employs an easy, controllable and stable assembly of diverse BMCs‐poly(3,4‐ethylenedioxythiophene) (PEDOT) composites on conductive NWs. The intrinsic catalytic activity of BMCs combined with outstanding electron transfer ability of conductive polymer enables the nanosensors to sensitively and selectively detect various biomolecules. Further application of sulfonated cobalt phthalocyanine functionalized nanosensors achieves real‐time electrochemical monitoring of intracellular glutathione levels and its redox homeostasis in single living cells for the first time.
Versatile and large‐scale synthesis of biomimetic molecular catalyst modified nanowires provides an innovative perspective for simple and stable construction of functionalized electrochemical nanosensors. Such nanosensors enable the sensitive and selective detection of diverse biomolecules, and for the first time achieve real‐time electrochemical monitoring of intracellular glutathione levels and its redox homeostasis in single living cells.
Previous animal studies have shown that perfluorinated compounds (PFCs) have adverse impacts on birth outcomes, but the results have been inconclusive in humans. We investigated associations between ...prenatal exposure to perfluorooctanoic acid (PFOA), perfluorooctyl sulfonate (PFOS), perfluorononanoic acid (PFNA), and perfluoroundecanoic acid (PFUA) and birth outcomes.
In total, 429 mother-infant pairs were recruited from the Taiwan Birth Panel Study (TBPS). Demographic data were obtained by interviewing mothers using a structured questionnaire and birth outcomes were extracted from medical records. Cord blood was collected for PFOA, PFOS, PFNA, and PFUA analysis by ultra-high-performance liquid chromatography/tandem mass spectrometry.
The geometric mean (standard deviation) levels of PFOA, PFOS, PFNA, and PFUA in cord blood plasma were 1.84 (2.23), 5.94 (1.95), 2.36(4.74), and 10.26 (3.07) ng/mL, respectively. Only PFOS levels were found to be inversely associated with gestational age, birth weight, and head circumference per ln unit: adjusted β (95% confidence interval, CI) = -0.37 (-0.60, -0.13) wks, -110.2 (-176.0, -44.5) gm and -0.25 (-0.46, -0.05) cm. Additionally, the odds ratio of preterm birth, low birth weight, and small for gestational age increased with PFOS exposure per ln unit: adjusted odds ratio (OR) (95%CI) = 2.45 (1.47, 4.08), 2.61(0.85, 8.03) and 2.27 (1.25, 4.15). When PFOS levels were divided into quartiles, a dose-response relation was observed. However, PFOA, PFNA, and PFUA were not observed to have any convincing impact on birth outcomes.
An adverse dose-dependent association was observed between prenatal PFOS exposure and birth outcomes. However, no associations were found for the other examined PFCs.
Phenols are widely used as starting materials in both industrial and academic society. Dearomatization reactions of phenols provide an efficient way to construct highly functionalized ...cyclohexadienones. The main challenge to make them asymmetric by catalytic methods is to control the selectivity while overcoming the loss of aromaticity. In this tutorial review, an up to date summary of recent progress in CADA reactions of phenol and aniline derivatives is presented.
A strategy for one‐pot and large‐scale synthesis of functionalized core–shell nanowires (NWs) to high‐efficiently construct single nanowire electrodes is proposed. Based on the polymerization ...reaction between 3,4‐ethylenedioxythiophene (EDOT) and noble metal cations, manifold noble metal nanoparticles‐polyEDOT (PEDOT) nanocomposites can be uniformly modified on the surface of any nonconductive NWs. This provides a facile and versatile approach to produce massive number of core–shell NWs with excellent conductivity, adjustable size, and well‐designed properties. Nanoelectrodes manufactured with such core–shell NWs exhibit excellent electrochemical performance and mechanical stability as well as favorable antifouling properties, which are demonstrated by in situ intracellular monitoring of biological molecules (nitric oxide) and unraveling its relevant unclear signaling pathway inside single living cells.
Versatile one‐pot synthesis of functionalized core–shell nanowires breaks through the limitation of nanoelectrode materials to facilely construct high‐performance single nanowire electrodes. Concurrently with excellent electrochemical, mechanical, and antifouling properties, the nanowire electrodes show great superiority in real‐time monitoring of biological molecules and unraveling the relevant signaling pathway inside single living cells.
Extracellular vesicles (EVs) are emerging as a potential diagnostic test for cancer. Owing to the recent advances in microfluidics, on‐chip EV isolation is showing promise with respect to improved ...recovery rates, smaller necessary sample volumes, and shorter processing times than ultracentrifugation. Immunoaffinity‐based microfluidic EV isolation using anti‐CD63 is widely used; however, anti‐CD63 is not specific to cancer‐EVs, and some cancers secrete EVs with low expression of CD63. Alternatively, phosphatidylserine (PS), usually expressed in the inner leaflet of the lipid bilayer of the cells, is shown to be expressed on the outer surface of cancer‐associated EVs. A new exosome isolation microfluidic device (newExoChip), conjugated with a PS‐specific protein, to isolate cancer‐associated exosomes from plasma, is presented. The device achieves 90% capture efficiency for cancer cell exosomes compared to 38% for healthy exosomes and isolates 35% more A549‐derived exosomes than an anti‐CD63‐conjugated device. Immobilized exosomes are then easily released using Ca2+ chelation. The recovered exosomes from clinical samples are characterized by electron microscopy and western‐blot analysis, revealing exosomal shapes and exosomal protein expressions. The newExoChip facilitates the isolation of a specific subset of exosomes, allowing the exploration of the undiscovered roles of exosomes in cancer progression and metastasis.
On‐chip exosome isolation using immunoaffinity capture improves recovery from small sample volumes compared to ultracentrifugation. However, tetraspanins are not specific to cancer exosomes and some cancers secrete exosomes with low expression of tetraspanins. Here, a microfluidic‐device conjugated with proteins against phosphatidylserine (PS), shown to be expressed on the outer surface of cancer‐associated exosome, is used to isolate cancer‐associated exosomes.
Biologic function of the majority of microRNAs (miRNAs) is still unknown. Uncovering the function of miRNAs is hurdled by redundancy among different miRNAs. The deletion of
Dgcr8
leads to the ...deficiency in producing all canonical miRNAs, therefore, overcoming the redundancy issue.
Dgcr8
knockout strategy has been instrumental in understanding the function of miRNAs in a variety of cells in vitro and in vivo. In this review, we will first give a brief introduction about miRNAs, miRNA biogenesis pathway and the role of
Dgcr8
in miRNA biogenesis. We will then summarize studies performed with
Dgcr8
knockout cell models with a focus on embryonic stem cells. After that, we will summarize results from various in vivo
Dgcr8
knockout models. Given significant phenotypic differences in various tissues between
Dgcr8
and
Dicer
knockout, we will also briefly review current progresses on understanding miRNA-independent functions of miRNA biogenesis factors. Finally, we will discuss the potential use of a new strategy to stably express miRNAs in
Dgcr8
knockout cells. In future,
Dgcr8
knockout approaches coupled with innovations in miRNA rescue strategy may provide further insights into miRNA functions in vitro and in vivo.
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