The transformation of a large‐volume industrial by‐product and stable greenhouse gas fluoroform (HCF3) to useful products has recently received significant attention. Now, a simple and scalable ...preparation of AgCF3 by treatment of HCF3 with t‐BuOK and AgOAc is disclosed. The reactivity of the HCF3‐derived AgCF3 has been demonstrated by hydrotrifluoromethylation of alkenes and C−H trifluoromethylation of (hetero)arenes. This work not only provides a new avenue for the utilization of HCF3, but also presents a reliable and easy‐to‐execute synthesis of the relatively stable AgCF3 solution.
Don't cry for me: The direct argentination of fluoroform with t‐BuOK and AgOAc in DMF provided a practical approach to AgCF3. The HCF3‐derived AgCF3 solution exhibited unique stability and diverse reactivities, such as the hydrotrifluoromethylation of alkenes and C−H trifluoromethylation of arenes.
Neural stem cells (NSCs), capable of ischemia‐homing, regeneration, and differentiation, exert strong therapeutic potentials in treating ischemic stroke, but the curative effect is limited in the ...harsh microenvironment of ischemic regions rich in reactive oxygen species (ROS). Gene transfection to make NSCs overexpress brain‐derived neurotrophic factor (BDNF) can enhance their therapeutic efficacy; however, viral vectors must be used because current nonviral vectors are unable to efficiently transfect NSCs. The first polymeric vector, ROS‐responsive charge‐reversal poly(2‐acryloyl)ethyl(p‐boronic acid benzyl)diethylammonium bromide (B‐PDEA), is shown here, that mediates efficient gene transfection of NSCs and greatly enhances their therapeutics in ischemic stroke treatment. The cationic B‐PDEA/DNA polyplexes can effectively transfect NSCs; in the cytosol, the B‐PDEA is oxidized by intracellular ROS into negatively charged polyacrylic acid, quickly releasing the BDNF plasmids for efficient transcription and secreting a high level of BDNF. After i.v. injection in ischemic stroke mice, the transfected NSCs (BDNF‐NSCs) can home to ischemic regions as efficiently as the pristine NSCs but more efficiently produce BDNF, leading to significantly augmented BDNF levels, which in turn enhances the mouse survival rate to 60%, from 0% (nontreated mice) or ≈20% (NSC‐treated mice), and enables more rapid and superior functional reconstruction.
The first nonviral gene carrier, reactive‐oxygen‐species‐responsive charge‐reversal poly(2‐acryloyl)‐ethyl(p‐boronic acid benzyl)diethylammonium bromide (B‐PDEA), is shown to mediate efficient gene transfection to neural stem cells (NSCs). When BDNF gene plasmids are used, the transfected NSCs homing to the ischemic regions increase animal survival and reconstruct functions.
The development of concise, sustainable, and cost‐effective synthesis of aryltetralin lignans, bearing either a fused lactone or cyclic ether, is of significant medicinal importance. Reported is that ...in the presence of Fukuzumi's acridinium salt under blue LED irradiation, functionalized dicinnamyl ether derivatives are converted into aryltetralin cyclic ether lignans with concurrent generation of three stereocenters in good to high yields with up to 20:1 diastereoselectivity. Oxidation of an alkene to the radical cation is key to the success of this formal Diels–Alder reaction of electronically mismatched diene and dienophile. Applying this methodology, six natural products, aglacin B, aglacin C, sulabiroin A, sulabiroin B, gaultherin C, and isoshonanin, are synthesized in only two to three steps from readily available biomass‐derived monolignols. A revised structure is proposed for gaultherin C.
Under blue LED irradiation, dicinnamyl ether derivatives undergo double cyclization to afford tricyclic lignans. Six natural products are synthesized from the corresponding monolignols in two or three steps.
Natural killer (NK) cells are innate cytotoxic lymphocytes that contribute to immune responses against stressed, transformed, or infected cells. NK cell effector functions are regulated by ...microenvironmental factors, including cytokines, metabolites, and nutrients. Vitamin A is an essential micronutrient that plays an indispensable role in embryogenesis and development, but was also reported to regulate immune responses. However, the role of vitamin A in regulating NK cell functions remains poorly understood. Here, we show that the most prevalent vitamin A metabolite, all‐trans retinoic acid (atRA), induces transcriptional and functional changes in NK cells leading to altered metabolism and reduced IFN‐γ production in response to a wide range of stimuli. atRA‐exposed NK cells display a reduced ability to support dendritic cell (DC) maturation and to eliminate immature DCs. Moreover, they support the polarization and proliferation of regulatory T cells. These results imply that in vitamin A‐enriched environments, NK cells can acquire functions that might promote tolerogenic immunity and/or immunosuppression.
When exposed to Vitamin A, NK cells change their transcriptome, phenotype, and metabolism. Vitamin A curtails NK‐cell IFN‐γ production via IL‐18R‐mTOR‐cMyc‐IKbζ pathway. Furthermore, vitamin A‐treated NK cells support the differentiation and proliferation of FoxP3‐expressing regulatory T and Th17 cells.
Graphene can be decorated with functional groups on either side of its basal plane, giving rise to a bifunctional nanoscale building block that can undergo face-to-face assembly. We demonstrate that ...benzoic acid-functionalized graphene (BFG) can act as a structure-directing template in influencing the crystal growth of metal−organic framework (MOF). BFG is also incorporated into MOF as framework linker. Because of the high density of carboxylic groups on benzoic acid-functionalized graphene, an unusual MOF nanowire that grows in the 220 direction was synthesized. The diameter of the nanowire correlates closely with the lateral dimensions of the BFG. The intercalation of graphene in MOF imparts new electrical properties such as photoelectric transport in the otherwise insulating MOF. The results point to the possibility of using functionalized graphene to synthesize a wide range of structural motifs in MOF with adjustable metrics and properties.
A freestanding membrane composed of a nanofiber network of a graphene–polymer nanocomposite is fabricated by electrospinning and applied as an optical element in fiber lasers. The functionalization ...of graphene with conjugated organic molecules provides a handle for improving mechanical and thermal properties as well as tuning the optical properties. A small loading (0.07 wt%) of functionalized graphene enhances the total optical absorption of poly(vinyl acetate) (PVAc) by 10 times. The electrospun graphene–polymer nanocomposites exhibit wideband saturable absorbance for laser pulse shaping, and attain a larger modulation depth and smaller nonsaturable loss than single‐walled carbon nanotubes. The results show that electrospun graphene nanocomposites are promising candidates as practical and efficient photonic materials for the generation of ultrashort pulses in fiber lasers.
A series of functionalized graphene–polymer nanocomposites fabricated by electrospinning is investigated for its mechanical, thermal, and optical properties. A small loading (0.07 wt%) of functionalized graphene enhanced the total optical absorption of poly(vinyl acetate) (PVAc) tenfold. The electrospun graphene–polymer nanocomposites exhibit wideband saturable absorbance for laser pulse shaping, and attain a larger modulation depth and smaller nonsaturable loss than single‐walled carbon nanotubes.
Cross dehydrogenative coupling reactions (CDCs) are considerably more step‐ and atom efficient compared to classical cross coupling methods. In this context, the photochemical CDCs of ...hydrochlorocarbons and hydrofluorocarbons with methylarenes are herein described. This unprecedented CDC reaction concept enables a new retrosynthetic cut for the selective construction of valuable chlorinated and fluorinated organic skeletons, from industrially important dichloromethane, dichloroethane, difluoromethane (HFC‐32), and 1,1,1,2‐tetrafluoroethane (HFC‐134a).
Couple up: The unprecedented cross dehydrogenative coupling (CDC) reaction of industrially important dichloromethane, 1,2‐dichloroethane, difluoromethane and 1,1,1,2‐tetrafluoroethane enables a new retrosynthetic cut for the selective construction of chlorinated and fluorinated organic skeletons.
In this work we demonstrate a facile means to generate fluorescent carbon nanoribbons, nanoparticles, and graphene from graphite electrode using ionic liquid-assisted electrochemical exfoliation. A ...time-dependence study of products exfoliated from the graphite anode allows the reconstruction of the exfoliation mechanism based on the interplay of anodic oxidation and anion intercalation. We have developed strategies to control the distribution of the exfoliated products. In addition, the fluorescence of these carbon nanomaterials can be tuned from the visible to ultraviolet region by controlling the water content in the ionic liquid electrolyte.
The ideal tensile strengths of Cr along 001, 110 and 111 directions were calculated based on the first-principles method. The results show that the ideal tensile strengths are 30.83, 37.2 and ...35.49 GPa for anti-ferromagnetic Cr, while they are 33.09, 47.15 and 38.11 GPa for non-magnetic Cr along 001, 110 and 111 directions, respectively. It is obvious that 001 is the weakest direction. When the loading is applied on the direction 001, the ideal tensile strength is reached before the shear instability for both the anti-ferromagnetic and non-magnetic Cr; thus, Cr fails by cleavage and it is deemed to be intrinsically brittle. Meanwhile, for the anti-ferromagnetic Cr, the correlation between the magnetic moment and volume was analyzed, and the result shows that the magnetic moment increases with the increase in volume and eventually disappears with the increase in strain. In addition, the density of states in the process of loading was also discussed.
Understanding the behaviors of a single active chain in complex environments is not only an interesting topic in non-equilibrium physics but also has applicative implications in biological/medical ...engineering. In this work, by using molecular simulations, we systematically study the dynamical and conformational behaviors of an active polymer in crowded environments,
i.e.
, a single active chain confined in 2D space with randomly arranged obstacles. We found that the competition between the chain's activity and rigidity in the presence of obstacles leads to many interesting dynamical and conformational states, such as the diffusive expanded state, the diffusive collapsed state, and the localized collapsed state. Importantly, we found a counter-intuitive phenomenon,
i.e.
, crowded environments facilitate the diffusion of the active polymer within a large parameter space. As the crowdedness (packing fraction of obstacles) increases, the parameter space in which crowding-enhanced diffusion occurs still remains. This abnormal dynamics is attributed to a structural reason that the obstacles prevent active chains from collapsing. Our findings capture some generic features of active polymers in complex environments and provide insights into the design of novel drug delivery systems.
Active polymers diffuse more rapidly in crowded environments than in free space because of the swollen of conformation.
