Peripherally low symmetric substitution with electron-donating(EDG)and electron-withdrawing(EWG)substituents caused the rational modulation of geometric structure and even the electronic structure of triazasubporphyrin,the smallest 14πconjugated aza-porphyrinoids.Both structural characterization and spectroscopic investigation were discussed to provide an in-depth understanding of the relationship between peripheral push-pull substituents and SubPz core. 相似文献
A new polymorph of FeOF (up to now only known in its rutile type structure) was prepared by using a new synthesis approach formally based on anionic exchange using the well-known layered FeOCl as precursor. The synthesis was achieved using [CH3C(CH2O–)2(COO–)B] to vehicle fluorine through the formation of soluble (CH3)4N+ [CH3C(CH2O–)2(COO–)BF]− and using N,N-dimethylformamide (DMF) as the reacting medium. The XRD pattern of layered FeOF can be indexed with an orthorhombic cell which doubles along the b axis (which is the direction perpendicular to the layers) with respect to that of pristine FeOCl (a = 3.792(1) Å, b = 12.699(1) Å, c = 3.321(1) Å). Both thermal analysis and diffraction indicate similar stability for the layered and rutile polymorphs. Such findings are rationalized through Density Functional Theory calculations. It is found that the energy difference between the more stable rutile and layered polymorphs is practically nul. The origin of the similar stability lies in the fact that although the number of Fe–F and Fe–O bonds is different in the two structures, the strength of both the total number of Fe–O as well as Fe–F bonds are found to be almost identical. Even if the crystal and electronic structures are considerably different, the total bonding and thus, the stability of the two polymorphs, is comparable. The stability of different FeOF rutile type structures is also analyzed. 相似文献
Low extracellular electron transfer performance is often a bottleneck in developing high‐performance bioelectrochemical systems. Herein, we show that the self‐assembly of graphene oxide and Shewanella oneidensis MR‐1 formed an electroactive, reduced‐graphene‐oxide‐hybridized, three‐dimensional macroporous biofilm, which enabled highly efficient bidirectional electron transfers between Shewanella and electrodes owing to high biomass incorporation and enhanced direct contact‐based extracellular electron transfer. This 3D electroactive biofilm delivered a 25‐fold increase in the outward current (oxidation current, electron flux from bacteria to electrodes) and 74‐fold increase in the inward current (reduction current, electron flux from electrodes to bacteria) over that of the naturally occurring biofilms. 相似文献
The first neo‐confused hexaphyrin(1.1.1.1.1.0) was synthesized by oxidative ring closure of a hexapyrrane bearing two terminal “confused” pyrroles. The new compound displays a folded conformation with a short interpyrrolic C???N distance of 3.102 Å, and thus it readily underwent ring fusion to afford a neo‐fused hexaphyrin with an unprecedented 5,5,5,7‐tetracyclic ring structure. Furthermore, coordination of CuII triggered a ring opening/contracting reaction to afford a CuII complex of an N‐linked pentaphyrin derivative. The roles of reactive N? C bonds in the porphyrinoid macrocycles were demonstrated. 相似文献
For the first time, a novel biological affinity separating system called lipid raft stationary phase chromatography (LRSC) was developed. It was employed to screen bioactive components from Chinese gallnut, a traditional Chinese medicine (TCM). The LRSC was prepared by the addition of activated silica to Tris–HCl solution, which contains the isolated lipid rafts of U251 cells. This was followed by agitation, washing, centrifugation and then re-suspension of the residue in another Tris–HCl solution. The lipid rafts possess abundant receptor tyrosine kinase, specifically tropomyosin-related kinase A (TrkA), which is a widely researched anti-tumor drug target. Thus, TrkA provided the LRSC model with the ability to select fractions that specifically interact with it. Using a non-TrkA targeted anti-tumor drug (gemcitabine) and TrkA targeted anti-tumor drugs (lestaurtinib and gefitinib) as controls to evaluate the specific affinity of the LRSC column, the different fractions of Chinese gallnut were subjected to LRSC screening for the identification of anti-tumor components. As a result, the ether fraction of Chinese gallnut manifested desirable affinity properties. The methyl thiazolyl tetrazolium assay confirmed the anti-tumor effect of the screened ether fraction, and more importantly, the ether fraction failed woefully to exhibit its anti-proliferative activity in the presence of TrkA inhibitors (K252a and primary antibody). This further proves the selectivity of LRSC on TrkA-targeted drugs. The LRSC model has, therefore, shown to be of high efficiency and selectivity in screening bioactive components from the complex TCM extracts, thus offering an effective approach for the development of anticancer natural products. 相似文献
In this paper, we propose a coupled awareness—epidemic spreading model considering the heterogeneity of individual influences, which aims to explore the interaction between awareness diffusion and epidemic transmission. The considered heterogeneities of individual influences are threefold: the heterogeneity of individual influences in the information layer, the heterogeneity of individual influences in the epidemic layer and the heterogeneity of individual behavioral responses to epidemics. In addition, the individuals’ receptive preference for information and the impacts of individuals’ perceived local awareness ratio and individuals’ perceived epidemic severity on self-protective behavior are included. The epidemic threshold is theoretically established by the microscopic Markov chain approach and the mean-field approach. Results indicate that the critical local and global awareness ratios have two-stage effects on the epidemic threshold. Besides, either the heterogeneity of individual influences in the information layer or the strength of individuals’ responses to epidemics can influence the epidemic threshold with a nonlinear way. However, the heterogeneity of individual influences in the epidemic layer has few effect on the epidemic threshold, but can affects the magnitude of the final infected density.