Structure–Activity Relationships of JMV4463, a Vectorized Cathepsin D Inhibitor with Antiproliferative Properties: The Unique Role of the AMPA‐Based Vector

Cathepsin D (CathD) is overexpressed and secreted by several solid tumors and stimulates their growth, the mechanism of which is still not understood. In this context, the pepstatin bioconjugate JMV4463 [Ac‐arg‐O₂Oc‐(Val)₃‐Sta‐Ala‐Sta‐(AMPA)₄‐NH₂; O₂Oc=8‐amino‐3,6‐dioxaoctanoyl, Sta=statine, AMPA=ortho‐aminomethylphenylacetyl], containing a new kind of cell‐penetrating vector, was previously shown to exhibit potent antiproliferative effects in vitro and to delay the onset of tumors in vivo. In this study, we performed a structure–activity relationship analysis to evaluate the significance of the inhibitor and vector moieties of JMV4463. By modifying both statine residues of pepstatin we found that the antiproliferative activity is correlated with CathD inhibition, supporting a major role of the catalytic activity of intracellular CathD in cancer cell proliferation. Replacing the vector composed of four AMPA units with other vectors was found to abolish cytotoxicity, although all of the conjugates enabled pepstatin transport into cells. In addition, the AMPA₄ vector must be localized at the C terminus of the bioconjugate. The unexpected importance of the vector structure and position for cytotoxic action suggests that AMPA₄ enables pepstatin to inhibit the proteolysis of critical CathD substrates involved in cell proliferation via a unique mechanism of action.     

Indoloazepinone‐Constrained Oligomers as Cell‐Penetrating and Blood–Brain‐Barrier‐Permeating Compounds

Non‐cationic and amphipathic indoloazepinone‐constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [l ‐Aia‐Xxx]_n oligomers were investigated by circular dichroism (CD) and NMR spectroscopy. Whereas Boc‐[l ‐Aia‐Gly]_2,4‐OBn oligomers 12 and 13 and Boc‐[l ‐Aia‐β³‐h‐l ‐Ala]_2,4‐OBn oligomers 16 and 17 were totally or partially disordered, Boc‐[l ‐Aia‐l ‐Ala]₂‐OBn ( 14 ) induced a typical turn stabilized by C₅‐ and C₇‐membered H‐bond pseudo‐cycles and aromatic interactions. Boc‐[l ‐Aia‐l ‐Ala]₄‐OBn ( 15 ) exhibited a unique structure with remarkable T‐shaped π‐stacking interactions involving the indole rings of the four l ‐Aia residues forming a dense hydrophobic cluster. All of the proposed FITC‐6‐Ahx‐[l ‐Aia‐Xxx]₄‐NH₂ oligomers 19 – 23 , with the exception of FITC‐6‐Ahx‐[l ‐Aia‐Gly]₄‐NH₂ ( 18 ), were internalized by MDA‐MB‐231 cells with higher efficiency than the positive references penetratin and Arg₈. In parallel, the compounds of this series were successfully explored in an in vitro blood–brain barrier (BBB) permeation assay. Although no passive diffusion permeability was observed for any of the tested Ac‐[l ‐Aia‐Xxx]₄‐NH₂ oligomers in the PAMPA model, Ac‐[l ‐Aia‐l ‐Arg]₄‐NH₂ ( 26 ) showed significant permeation in the in vitro cell‐based human model of the BBB, suggesting an active mechanism of cell penetration.     

Biological Evaluation and X‐ray Co‐crystal Structures of Cyclohexylpyrrolidine Ligands for Trypanothione Reductase,an Enzyme from the Redox Metabolism of Trypanosoma

The tropical diseases human African trypanosomiasis, Chagas disease, and the various forms of leishmaniasis are caused by parasites of the family of trypanosomatids. These protozoa possess a unique redox metabolism based on trypanothione and trypanothione reductase (TR), making TR a promising drug target. We report the optimization of properties and potency of cyclohexylpyrrolidine inhibitors of TR by structure‐based design. The best inhibitors were freely soluble and showed competitive inhibition constants (K_i) against Trypanosoma (T.) brucei TR and T. cruzi TR and in vitro activities (half‐maximal inhibitory concentration, IC₅₀) against these parasites in the low micromolar range, with high selectivity against human glutathione reductase. X‐ray co‐crystal structures confirmed the binding of the ligands to the hydrophobic wall of the “mepacrine binding site” with the new, solubility‐providing vectors oriented toward the surface of the large active site.     

Herbivore-Mediated Effects of Glucosinolates on Different Natural Enemies of a Specialist Aphid

The cabbage aphid Brevicoryne brassicae is a specialist herbivore that sequesters glucosinolates from its host plant as a defense against its predators. It is unknown to what extent parasitoids are affected by this sequestration. We investigated herbivore-mediated effects of glucosinolates on the parasitoid wasp Diaeretiella rapae and the predator Episyrphus balteatus. We reared B. brassicae on three ecotypes of Arabidopsis thaliana that differ in glucosinolate content and on one genetically transformed line with modified concentrations of aliphatic glucosinolates. We tested aphid performance and the performance and behavior of both natural enemies. We correlated this with phloem and aphid glucosinolate concentrations and emission of volatiles. Brevicoryne brassicae performance correlated positively with concentrations of both aliphatic and indole glucosinolates in the phloem. Aphids selectively sequestered glucosinolates. Glucosinolate concentration in B. brassicae correlated negatively with performance of the predator, but positively with performance of the parasitoid, possibly because the aphids with the highest glucosinolate concentrations had a higher body weight. Both natural enemies showed a positive performance-preference correlation. The predator preferred the ecotype with the lowest emission of volatile glucosinolate breakdown products in each test combination, whereas the parasitoid wasp preferred the A. thaliana ecotype with the highest emission of these volatiles. The study shows that there are differential herbivore-mediated effects of glucosinolates on a predator and a parasitoid of a specialist aphid that selectively sequesters glucosinolates from its host plant.     

Active nano-CuPt3 electrocatalyst supported on graphene for enhancing reactions at the cathode in all-vanadium redox flow batteries

Graphene-supported monometallic (Pt) and bimetallic (CuPt₃) cubic nanocatalysts have been investigated as new positive electrode materials for improving the VO₂⁺/VO²⁺ redox process occurring in the vanadium redox flow batteries (VRB). High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) have been employed to characterize the electrodes. The presence of the CuPt₃ nanocubes on graphene conferred higher electrocatalytic activity due to the much higher electroactive area compared to that obtained with the Pt nanoparticles. The electrochemical surface area of the nano-(CuPt₃)-decorated graphene electrode was 105% higher compared to non-decorated graphene, being then a promising alternative for improving the VRB.     

Synthesis and nuclear magnetic resonance properties of all geometrical isomers of conjugated linoleic acids

Pure geometric isomers of conjugated linoleic acid were prepared from castor oil as the primary starting material. Methyl octadeca-9Z, 11E-dienoate (2) and methyl octadeca-9Z, 11Z-dienoate (4) were obtained by zinc reduction of methyl santalbate (1, methyl octadec-11E-en-9-ynoate) and methyl octadec-11 Z-en-9-ynoate (3), respectively, as the key intermediates. Methyl octadeca-9E, 11E-dienoate (8) and methyl octadeca-9E, 11Z-dienoate (9) were prepared by demesylation of the mesyloxy derivative of methyl ricinelaidate (6, methyl 12-hydroxy-octadec-9 E-enoate). A study of the nuclear magnetic resonance spectral properties was carried out and the shifts of the olefinic carbon atoms of 18:2(9Z, 11E) (2) and 18:2(9E, 11Z) (9) were readily identified by a combination of incredible natural abundance double quantum transfer experiment, heteronuclear multiple bond correlation, and ¹H−¹³C correlation spectroscopy correlation techniques. Doubts remain in the absolute identification of the individual olefinic carbon atoms of the 18:2(9Z, 11Z) (4) and 18:2(9E, 11E) (8), except the fact that the shifts of the “inner” (C-10 and C-11) and “outer” (C-9 and C-12) positioned olefinic carbon atoms of the conjugated diene system are distinguishable.     

Airborne and laboratory studies of an IAGOS instrumentation package containing a modified CAPS particle extinction monitor

An evaluation of the operation and performance of a Cavity Attenuated Phase-Shift Particle Extinction Monitor (CAPS PM_ex) was performed for use on board commercial aircraft as part of the research infrastructure IAGOS (In-service Aircraft for a Global Observing System, www.iagos.org). After extensive laboratory testing, a new flow system, using mass flow controllers, was installed to maintain constant purge and sample flows under low and varying pressure conditions. The instrument was then tested for pressures as low as 200 hPa and evaluated against particle-free compressed air and CO₂. Extinction coefficients for the studied gases were in close agreement with literature values with differences between 2.2% and 8%, proving that the CAPS technology works at low pressures. The instrument's limit of detection, with respect to 3 times the variability of the background signal for the full pressure range, was 0.2 Mm^?1 for 60s integration time. During its first research aircraft operations, the IAGOS instrument prototype, composed of one CAPS PMex and one OPC, showed excellent results regarding the stability of the instruments and the potential for characterizing different aerosol types and for estimating the contribution of sub- and super-μm sized particles to aerosol light extinction.

Copyright © 2017 American Association for Aerosol Research     

Pyrethrins Protect Pyrethrum Leaves Against Attack by Western Flower Thrips, <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis>

Pyrethrins are active ingredients extracted from pyrethrum flowers (Tanacetum cinerariifolium), and are the most widely used botanical insecticide. However, several thrips species are commonly found on pyrethrum flowers in the field, and are the dominant insects found inside the flowers. Up to 80 % of western flower thrips (WFT, Frankliniella occidentalis) adults died within 3 days of initiating feeding on leaves of pyrethrum, leading us to evaluate the role of pyrethrins in the defense of pyrethrum leaves against WFT. The effects of pyrethrins on WFT survival, feeding behavior, and reproduction were measured both in vitro and in planta (infiltrated leaves). The lethal concentration value (LC50) for pyrethrins against WFT adults was 12.9 mg/ml, and pyrethrins at 0.1 % (w/v) and 1 % (w/v) had significantly negative effects on feeding, embryo development, and oviposition. About 20-70 % of WFT were killed within 2 days when they were fed chrysanthemum leaves containing 0.01-1 % pyrethrins. Chrysanthemum leaves containing 0.1 % or 1 % pyrethrins were significantly deterrent to WFT. In a no-choice assay, the reproduction of WFT was reduced significantly when the insects were fed leaves containing 0.1 % pyrethrins, and no eggs were found in leaves containing 1 % pyrethrins. Our results suggest that the natural concentrations of pyrethrins in the leaves may be responsible for the observed high mortality of WFT on pyrethrum.     

Combination of nuclear magnetic resonance spectroscopy and nonlinear methods to analyze the copolymerization of phosphonic acid derivatives

We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The ¹H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of r_HEMA = 1.83; r_ECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256.