Toxic ligand conjugates as tools in the study of receptor-ligand interactions

We have constructed hybrid proteins in which the toxic A chains of ricin or diptheria toxin have been linked to either asialofetuin, fetuin, or epidermal growth factor (EGF). Both ASF-RTA and ASF-DTA are potent toxins on cultured rat hepatocytes, cells that display the asialoglycoprotein receptor. Toxicity of these two compounds is restricted to hepatocytes and can be blocked by asialoglycoproteins but not the native glycoproteins or asialoagalactoglycoprotein derivatives, indicating that the toxicity of the conjugates is mediated by the hepatic asialoglycoprotein receptor. The EGF-RTA conjugate is an extremely potent toxin on cells that can bind the hormone, but is only poorly effective on cells that are unable to bind EGF. The EGF-DTA conjugate, in contrast, is unable to kill 3T3 cells and is at least two orders of magnitude less effective than EGF-RTA on A431 cells, a cell line with 1-2 X 10(6) EGF receptors per cell. However, when EGF-RTA and EGF-DTA were tested on primary liver hepatocyte cultures, which were susceptible to both ASF-RTA and ASF-DTA, both EGF conjugates were potent toxins. Sensitivity of the hepatocyte cultures to ricin toxicity increases slightly during a 52-hr culture period. In contrast, sensitivity to EGF-RTA and ASF-RTA decline dramatically during this period. Receptors for both ligands remain plentiful on the cell surface during this time.     

Dermorphins, Opioid Peptides from Amphibian Skin, Act on Opioid Receptors of Mouse Neuroblastoma x Rat Glioma Hybrid Cells

Dermorphin and its Hyp6 analogue are opiate-like heptapeptides originally discovered in frog skin and characterized by the presence of a D-Ala2 residue in their sequence. They were assayed for their capacity to compete with [3H]Leu-enkephalin for binding to opioid receptors in membranes of neuroblastoma x glioma hybrid cells. In the presence of 7 nM-[3H]Leu-enkephalin, the concentrations at which they caused 50% inhibition of [3H]enkephalin binding (IC50 values) are 0.1 micro M and 0.3 micro M, respectively. In contrast, the synthetic L-Ala2-dermorphin shows very low affinity for the opioid receptors. In addition, like other opioid peptides, dermorphin and hyp6-dermorphin inhibit the elevation by prostaglandin E1 (PGE1) of the level of adenosine 3':5'-cyclic monophosphate (cyclic AMP) (IC50 values 0.2 micro M and 0.4 micro M, respectively). The inhibition is prevented by the opiate antagonist naloxone, L-Ala2-dermorphin is at least three orders of magnitude less potent in inhibiting the PGE1-evoked increase in the level of cyclic AMP. The results show that peptides with an amino acid sequence quite different from that of the enkephalins can bind to opioid receptors of the hybrid cells.     

Hybridization between tetraploid species of Alopecurus L. (Poaceae): chromosome behaviour of natural and artificial hybrids

The meiotic behaviour of plants from mixed populations of Alopecurus pratensis × A. geniculatus and of A. pratensis × A. arundinaceus ( 2n = 4×(= 28) is reported together with observations on some artificially produced hybrids. This meiotic behaviour is correlated with the degree of hybridity as shown by the hybrid index values of the plant. In A. pratensis × A. geniculatus hybrids there are marked differences between populations in the degree of meiotic disturbance and in one population there was an almost complete breakdown of meiosis. Alopecurus pratensis × A. arundinaceus hybrids show fairly regular meiotic pairing but in most plants there are a few univalent chromosomes at metaphase I. Artificially produced hybrids of A. pratensis × A. aequalis gave meiotic configurations that suggest that the genomes of the parent species are very similar. Taken together with the results from artificially produced hybrids of A. pratensis × A. geniculatus , it is suggested that bivalent-promoting mechanisms reduce multivalent formation both in the species and the hybrids. The interaction of different genotypes involved in the control of meiosis may account for the variation in meiotic behaviour in the different populations of hybrids. Pollen fertility is reduced in most populations of hybrids and likely to be an important factor permitting introgressive hybridization.     

Variations in the response of five strains of mice to Leishmania mexicana.

Five strains of mice were studied in their ability to support Leishmania mexicana infection. Four strains, AKR, C57BL/6, DBA/2 and NMRI, were relatively resistant to cutaneous leishmaniasis. These strains developed delayed type hypersensitivity responses to leishmanial antigens and produced agglutinating antibodies. On the other hand Balb/c mice, highly susceptible to infection, failed to develop delayed type hypersensitivity responses and showed an impaired production of antibodies. Hybrids produced by mating C57BL/6 males and Balb/c females were no more susceptible than C57BL/6 mice, suggesting that resistance is inherited as a dominant character.     

Nature of FeSe2/N‐C Anode for High Performance Potassium Ion Hybrid Capacitor

Potassium ion hybrid capacitors have great potential for large‐scale energy devices, because of the high power density and low cost. However, their practical applications are hindered by their low energy density, as well as electrolyte decomposition and collector corrosion at high potential in potassium bis(fluoro‐sulfonyl)imide‐based electrolyte. Therefore, anode materials with high capacity, a suitable voltage platform, and stability become a key factor. Here, N‐doping carbon‐coated FeSe₂ clusters are demonstrated as the anode material for a hybrid capacitor, delivering a reversible capacity of 295 mAh g^?1 at 100 mA g^?1 over 100 cycles and a high rate capability of 158 mAh g^?1 at 2000 mA g^?1 over 2000 cycles. Meanwhile, through density functional theory calculations, in situ X‐ray diffraction, and ex situ transmission electron microscopy, the evolution of FeSe₂ to Fe₃Se₄ for the electrochemical reaction mechanism is successfully revealed. The battery‐supercapacitor hybrid using commercial activated carbon as the cathode and FeSe₂/N‐C as the anode is obtained. It delivers a high energy density of 230 Wh kg^?1 and a power density of 920 W kg^?1 (the energy density and power density are calculated based on the total mass of active materials in the anode and cathode).     

Imaging Carrier Dynamics and Transport in Hybrid Perovskites with Transient Absorption Microscopy

In this review, the recent progress in using transient absorption microscopy to image charge transport and dynamics in semiconducting hybrid organic–inorganic perovskites is discussed. The basic principles, instrumentation, and resolution of transient absorption microscopy are outlined. With temporal resolution as high as 10 fs, sub‐diffraction‐limit spatial resolution, and excited‐state structural resolution, these experiments have provided crucial details on charge transport mechanisms that have been previously obscured in conventional ultrafast spectroscopy measurements. Morphology‐dependent mapping unveils spatial heterogeneity in carrier recombination and cooling dynamics. By spatially separating the pump and probe beams, carrier transport across grain boundaries has been directly visualized. Further, femtosecond temporal resolution allows for the examination of nonequilibrium transport directly, revealing extraordinarily long‐range hot carrier migration. The application of transient absorption microscopy is not limited to hybrid perovskites but can also be useful for other polycrystalline materials in which morphology plays an important role in carrier transport.     

不同寄主对草地贪夜蛾生长发育和繁殖的影响

草地贪夜蛾是入侵我国的重大农业害虫,严重威胁我国粮食安全。为明确该虫在不同寄主植物上的适合度,本文系统研究了草地贪夜蛾取食花生、荞麦和生姜3种寄主生长发育和繁殖情况,组建了实验种群生命表。结果表明:草地贪夜蛾在3种寄主植物上的繁殖力高低为花生(771.73粒)>荞麦(477.13粒)>生姜(209.22粒),卵的孵化率无显著差异,幼虫和蛹重均是花生>荞麦>生姜。草地贪夜蛾取食花生、荞麦和生姜后的净增殖率(R 0)分别为226.36、102.45和20.75,内禀增长率(r m)分别为0.16、0.13和0.06。研究发现,草地贪夜蛾在花生、荞麦和生姜3种寄主植物上均能实现种群繁殖,其中,花生是最适宜的寄主,荞麦次之,生姜相对较不适宜。