Terahertz Selective Emission Enhancement from a Metasurface-Coupled Photoconductive Emitter in Quasi-Near-Field Zone

We present a THz emission enhancement of 41 times at 0.92 THz from a metasurface made of T-shaped resonators excited in a quasi-near-field zone. Such a metasurface has an intrinsic transmission minimum with Q factor of 4 at 1.25 THz under far-field excitation. When this metasurface is coupled onto the backside of a 625-μm-thick photoconductive emitter, the metasurface is below the Fraunhofer distance to the excitation source. As such, one broad enhancement around 0.47 THz and another extremely narrow enhancement at 0.92 THz in the emission spectrum are observed owing to a quasi-near-field excitation. Theoretically, the Q factor of the latter is up to 307, which is limited by the spectral resolution in experiment. The numerical simulations indicate that the T-shaped resonators serve as an array of plasmonic antennas resulting in the aforementioned emission enhancement of THz radiation.

     

Synthesized Zn(II)-Amino Acid and -Chitosan Chelates to Increase Zn Uptake by Bean (Phaseolus vulgaris) Plants

Journal of Plant Growth Regulation - Plants require optimum amounts of nutrients for suitable growth and yield production. Accordingly, the most efficient methods of fertilization, including the...     

Spermine as a possible endogenous allosteric activator of carboxypeptidase A: multispectroscopic and molecular simulation studies

Abstract

Carboxypeptidase A (EC.3.4.17.1) is a zinc-containing proteolytic enzyme that removes the C-terminal amino acid from a peptide chain with the free carboxylate-terminal. In this study, the effect of spermine interaction on the structure and thermal stability of Carboxypeptidase A was investigated by ultraviolet???visible spectroscopy, fluorescence spectroscopy, circular dichroism, Kinetic measurement, molecular docking and simulation studies have also been followed at the pH of 7.5. The transition temperature of Carboxypeptidase A, as a criterion of protein thermal stability, in the presence of spermine was enhanced by increasing the concentration of spermine. The results of fluorescence intensity changes, at two temperatures of 308 and 318?K, also suggested that spermine had a great ability to quench the fluorescence of Carboxypeptidase A through the static quenching procedure. The thermodynamic parameters changes, including standard Gibbs free-energy, entropy and enthalpy, showed that the binding of spermine to Carboxypeptidase A was spontaneous and the hydrogen bonding and van der Waals interactions played a major role in stabilizing the Carboxypeptidase A–spermine complex. The changes in the content of the α-helix and the β-sheet of the Carboxypeptidase A with binding to spermine were shown by the CD spectra method. Further, kinetic studies revealed that by increasing concentration of spermine, the activity of Carboxypeptidase A was enhanced. Also, the docking study revealed that the hydrogen bonding and van der Waals interactions played a major role in stabilizing the Carboxypeptidase A–spermine complex. As a result, spermine could be considered as an activator and a stabilizer for Carboxypeptidase A.

Communicated by Ramaswamy H. Sarma     

Antibody–drug conjugates (ADCs) for cancer therapy: Strategies,challenges, and successes

Targeted delivery of therapeutic molecules into cancer cells is considered as a promising strategy to tackle cancer. Antibody–drug conjugates (ADCs), in which a monoclonal antibody (mAb) is conjugated to biologically active drugs through chemical linkers, have emerged as a promising class of anticancer treatment agents, being one of the fastest growing fields in cancer therapy. The failure of early ADCs led researchers to explore strategies to develop more effective and improved ADCs with lower levels of unconjugated mAbs and more-stable linkers between the drug and the antibody, which show improved pharmacokinetic properties, therapeutic indexes, and safety profiles. Such improvements resulted in the US Food and Drug Administration approvals of brentuximab vedotin, trastuzumab emtansine, and, more recently, inotuzumab ozogamicin. In addition, recent clinical outcomes have sparked additional interest, which leads to the dramatically increased number of ADCs in clinical development. The present review explores ADCs, their main characteristics, and new research developments, as well as discusses strategies for the selection of the most appropriate target antigens, mAbs, cytotoxic drugs, linkers, and conjugation chemistries.     

Lactate damages primary hippocampal neurons in vitro

In the present study, rat primary cultures were used to study the effect of lactate on the survival of hippocampal neurons in the presence or absence of glucose. Our results showed no extensive cell damage under glucose‐free conditions compared with glucose‐rich conditions. Addition of 10 and 50 mM lactate to glucose‐free and glucose‐rich media increased the cell damage significantly, as observed by morphology and lactate dehydrogenase activity. The results of the present study suggest that primary neurons in vitro are not sensitive to glucose deficiency and the presence of lactate damages the neurons in a concentration‐dependent manner.     

Neuronal expression of a single‐subunit yeast NADH–ubiquinone oxidoreductase (Ndi1) extends Drosophila lifespan

The ‘rate of living’ theory predicts that longevity should be inversely correlated with the rate of mitochondrial respiration. However, recent studies in a number of model organisms, including mice, have reported that interventions that retard the aging process are, in fact, associated with an increase in mitochondrial activity. To better understand the relationship between energy metabolism and longevity, we supplemented the endogenous respiratory chain machinery of the fruit fly Drosophila melanogaster with the alternative single‐subunit NADH–ubiquinone oxidoreductase (Ndi1) of the baker’s yeast Saccharomyces cerevisiae. Here, we report that expression of Ndi1 in fly mitochondria leads to an increase in NADH–ubiquinone oxidoreductase activity, oxygen consumption, and ATP levels. In addition, exogenous Ndi1 expression results in increased CO₂ production in living flies. Using an inducible gene‐expression system, we expressed Ndi1 in different cells and tissues and examined the impact on longevity. In doing so, we discovered that targeted expression of Ndi1 in fly neurons significantly increases lifespan without compromising fertility or physical activity. These findings are consistent with the idea that enhanced respiratory chain activity in neuronal tissue can prolong fly lifespan.