Antibody-recruiting protein-catalyzed capture agents to combat antibiotic-resistant bacteria

Antibiotic resistant infections are projected to cause over 10 million deaths by 2050, yet the development of new antibiotics has slowed. This points to an urgent need for methodologies for the rapid development of antibiotics against emerging drug resistant pathogens. We report on a generalizable combined computational and synthetic approach, called antibody-recruiting protein-catalyzed capture agents (AR-PCCs), to address this challenge. We applied the combinatorial protein catalyzed capture agent (PCC) technology to identify macrocyclic peptide ligands against highly conserved surface protein epitopes of carbapenem-resistant Klebsiella pneumoniae, an opportunistic Gram-negative pathogen with drug resistant strains. Multi-omic data combined with bioinformatic analyses identified epitopes of the highly expressed MrkA surface protein of K. pneumoniae for targeting in PCC screens. The top-performing ligand exhibited high-affinity (EC₅₀ ∼50 nM) to full-length MrkA, and selectively bound to MrkA-expressing K. pneumoniae, but not to other pathogenic bacterial species. AR-PCCs that bear a hapten moiety promoted antibody recruitment to K. pneumoniae, leading to enhanced phagocytosis and phagocytic killing by macrophages. The rapid development of this highly targeted antibiotic implies that the integrated computational and synthetic toolkit described here can be used for the accelerated production of antibiotics against drug resistant bacteria.

Antibody-recruiting protein-catalyzed capture agent (AR-PCCs) are a new class of all-synthetic and highly targeted antibiotics that recruit endogenous immune responses to eliminate drug-resistant microbes.     

Total synthesis of penta-Me amurensin H and diptoindonesin G featuring a Rh-catalyzed carboacylation/aromatization cascade enabled by CC activation

Oligostilbenoids represented a family of natural products, which contained one or several multifused benzofuran substructures and displayed promising biological activities towards cancer as well as immunological therapeutic targets. A convergent-divergent strategy featuring Rh-catalyzed carboacylation/aromatization cascade reaction based on CC activation of benzocyclbutenones had been conceived. penta-Methyl amurensin H and diptoindolnesin G were successfully synthesized without any protecting groups, constituting a new entry towards oligostilbenoids’ natural product synthesis. The synthesis completed within 10 steps for both natural products, suggesting conciseness and efficacy of the CC activation in complex natural product synthesis.     

Computational and experimental studies of the effect of substituents on the singlet-triplet energy gap in phenyl(carbomethoxy)carbene

The effect of aromatic substitution on the singlet-triplet energy gap in substituted phenyl(carbomethoxy)carbene (X-Ph-C-CO(2)CH(3), PCC) has been explored by time-resolved infrared (TRIR) spectroscopy and gas-phase computational methods. The ground state of para-substituted PCC is calculated to change from the triplet state in p-NO(2)-PCC (Delta G(ST) = 6.1 kcal/mol) to the singlet state in p-NH(2)-PCC (Delta G(ST) = -2.8 kcal/mol). The absence of solvent perturbation in the TRIR spectra of p-N(CH(3))(2)-PCC (which should have electronic properties similar to p-NH(2)-PCC) and parent PCC is consistent with their ground states lying > +/-2 kcal/mol from the next available electronic state, in line with the computational results. The observation of solvent perturbation in the TRIR spectra of p-OCH(3)-PCC and p-CH(3)-PCC implies that their ground states lie < +/-1 kcal/mol from their next available electronic state. This is in agreement with our computational results, which predict a gas-phase Delta G(ST) of -0.8 and 1.6 kcal/mol for p-OCH(3)-PCC and p-CH(3)-PCC as compared to Delta G(ST) values of -3.9 and -1.3 kcal/mol from polarizable continuum model (PCM) calculations with acetonitrile as a solvent. Gas-phase computational results for the meta- and ortho-substituted PCC species are also presented, along with selected linear free energy (LFE) relationships for the para and meta species.     

Physical properties and thermal behavior of reconstituted tobacco sheet with precipitated calcium carbonate added in the coating process

Addition of precipitated calcium carbonate (PCC) to cellulosic products can reduce production costs and modify their physical properties. This study investigated the effects of adding PCC on the properties of reconstituted tobacco sheet (RTS), a cellulosic product. Scanning electron microscopy (SEM) analysis showed that adding PCC to the coating could modify the surface microstructure of RTS. With increasing PCC addition, the strength and tar release per cigarette of RTS decreased. However, the filling capacity, bulk, and CO release content in the mainstream smoke reached optimal values when the proportion of PCC in the coating was 8%. Thermogravimetry (TG) and differential thermogravimetry (DTG) analysis indicated that the main thermal pyrolysis stage occurred in the range of 200–400 °C, similar to cellulosic components. The Coats–Redfern equation was used to analyze the thermal pyrolysis mechanism. The fitting results showed that, in the range of 200–280 °C, the best fit model for RTS with 4 or 8% PCC was diffusion-controlled reaction (D1) with fitting correlation coefficient (r ²) of 0.9630 and 0.9576, respectively. Meanwhile, in the range of 280–400 °C, the most reliable fitting model for RTS with 4% PCC was chemical reaction (F2) with r ² = 0.9681. One reaction model could not describe the thermal pyrolysis of RTS with 12% PCC in the main decomposition stage. The thermal kinetic parameters suggested that addition of PCC to RTS coatings could modify the thermal pyrolysis mechanism, but did not change the peak temperatures in the main thermal decomposition stage. This study demonstrates that addition of PCC to RTS coating is a promising method to improve its quality.     

Phenazines as model low-midpoint potential electron shuttles for photosynthetic bioelectrochemical systems

Bioelectrochemical approaches for energy conversion rely on efficient wiring of natural electron transport chains to electrodes. However, state-of-the-art exogenous electron mediators give rise to significant energy losses and, in the case of living systems, long-term cytotoxicity. Here, we explored new selection criteria for exogenous electron mediation by examining phenazines as novel low-midpoint potential molecules for wiring the photosynthetic electron transport chain of the cyanobacterium Synechocystis sp. PCC 6803 to electrodes. We identified pyocyanin (PYO) as an effective cell-permeable phenazine that can harvest electrons from highly reducing points of photosynthesis. PYO-mediated photocurrents were observed to be 4-fold higher than mediator-free systems with an energetic gain of 200 mV compared to the common high-midpoint potential mediator 2,6-dichloro-1,4-benzoquinone (DCBQ). The low-midpoint potential of PYO led to O₂ reduction side-reactions, which competed significantly against photocurrent generation; the tuning of mediator concentration was important for outcompeting the side-reactions whilst avoiding acute cytotoxicity. DCBQ-mediated photocurrents were generally much higher but also decayed rapidly and were non-recoverable with fresh mediator addition. This suggests that the cells can acquire DCBQ-resistance over time. In contrast, PYO gave rise to steadier current enhancement despite the co-generation of undesirable reactive oxygen species, and PYO-exposed cells did not develop acquired resistance. Moreover, we demonstrated that the cyanobacteria can be genetically engineered to produce PYO endogenously to improve long-term prospects. Overall, this study established that energetic gains can be achieved via the use of low-potential phenazines in photosynthetic bioelectrochemical systems, and quantifies the factors and trade-offs that determine efficacious mediation in living bioelectrochemical systems.

Phenazines were explored as novel low-midpoint potential molecules for wiring cyanobacteria to electrodes.     

Precipitation of different calcite crystal morphologies in the presence of sodium stearate

The influence of sodium stearate (NaSt) on the precipitation of calcium carbonate during the semicontinuous process of slaked lime carbonation was studied in the systems in which process parameters, like concentration of total dissolved calcium, temperature, CO(2) flow rate and initial addition rate of slaked lime, were controlled. It was found that calcite was the only calcium carbonate polymorph that appeared under the investigated experimental conditions, while FT-IR spectroscopy and thermogravimetric analysis of samples confirmed the presence of stearate on the surface of precipitated calcium carbonate (PCC). Specific surface area of PCC increased with increasing stearate content: the highest value, s = 52.8 m(2) g(-1), was obtained at t = 20 degrees C, c(tot) = 17.0 mmol dm(-3) and the stearate content of m(NaSt)/m(CaO) = 0.03. It was also found that hydrophobic calcite crystals in the form of rhombohedral and scalenohedral morphology can be produced at m(NaSt)/m(CaO) > 0.01. The exception is the case of nanosized PCC production, when much higher concentration of NaSt is needed, m(NaSt)/m(CaO) = 0.22. Minimal amount of stearate necessary to build up the monolayer and corresponding cross sectional area of one stearate molecule were estimated for the obtained calcite morphologies.     

Harpagide,a natural product,promotes synaptic vesicle release as measured by nanoelectrode amperometry

Parkinson''s disease (PD) is a neurodegenerative disorder characterized by progressive loss of dopaminergic (DAergic) neurons and low level of dopamine (DA) in the midbrain. Recent studies suggested that some natural products can protect neurons against injury, but their role on neurotransmitter release and the underlying mechanisms remained unknown. In this work, nanoelectrode electrochemistry was used for the first time to quantify DA release inside single DAergic synapses. Our results unambiguously demonstrated that harpagide, a natural product, effectively enhances synaptic DA release and restores DA release at normal levels from injured neurons in PD model. These important protective and curative effects are shown to result from the fact that harpagide efficiently inhibits the phosphorylation and aggregation of α-synuclein by alleviating the intracellular reactive oxygen level, being beneficial for vesicle loading and recycling. This establishes that harpagide offers promising avenues for preventive or therapeutic interventions against PD and other neurodegenerative disorders.

Nanoelectrode amperometry was used to monitor DA release inside single DAergic synapses, and demonstrated that harpagide effectively enhances synaptic DA release by reducing intracellular ROS generation and inhibiting α-Syn phosphorylation.     

Polyketides produced by Daldinia loculata cultured from Northern Manitoba

The fungus present in a soil sample collected from Northern Manitoba was cultured. The natural products produced by this organism were isolated and identified as the polyketides (1), (2), (3). A trace amount of the aromatic alcohol tyrosol (4) was also isolated. This organism was identified as Daldinia loculata by sequencing of the internally transcribed spacer region of the nuclear ribosomal DNA. The polyketides 1-3 were assayed against E. coli and it was observed that 1 displayed mild antibiotic activity.     

Ultra-fast sustainable synthesis,optimization and characterization of guava phenolic extract functionalized nanosilver with enhanced biomimetic attributes

There had been some reports demonstrating the green synthesis of silver nanoparticles using guava (Psidium guajava (L.) extract); however, detailed and in-depth interrogation of the vital synthesis parameters for rapid, facile, efficacious synthesis at room temperature, and robust characterization of the as-prepared nanoparticle is currently lacking. This study presents a comprehensive delineation of the sustainable phyto-fabrication of biogenic guava phenolic extract functionalized silver nanoparticles (GVE-SNP) based on guava phenolic extract as the sole reductant/stabilizer, as well as the synthesis optimization, thorough physicochemical characterization and potential biological applications of the as-prepared nanosilver. The results revealed that successful synthesis of GVE-SNP was instantaneous and maximum intensity of the plasmonic peak at 425 nm was achieved in less than 10 min. GVE-SNP was found to present stable, well-dispersed, round, uniform, and crystalline nanoparticles of about 5.88 nm. The FTIR and RAMAN spectra indicated that GVE-SNP surface was properly capped by bioactives from GVE. The nanoparticles displayed potent radical scavenging activity against ABTS⁺ and DPPH. Also, GVE-SNP exhibited a significant and dose–response inhibitory effect against tyrosinase. Furthermore, the nanoparticles displayed good cytotoxicity against L929 fibroblast and were found to possess strong antimicrobial properties, inhibiting the growth of S. aureus and S. epidermidis.     

Neuroprotective terpenoids from the leaves of Viburnum odoratissimum

Abstract

As a part of our ongoing search for neuroprotective compounds from natural products, two new iridoid glycosides, vibsansuspenside A-B (1-2), along with five known terpenoids (3-7), were isolated from the dry leaves of Viburnum odoratissimum. Their chemical structures were well determined by means of NMR spectroscopic data as well as HRESIMS analysis. All compounds were detected for their neuroprotective effects against H₂O₂-induced damage in human dopaminergic neuroblastoma cells (SH-SY5Y). Among them, compound 3 displayed the most potent neuroprotective ability, and further investigation by Annexin V/PI and Western blot analysis demonstrated that compound 3 could protect SH-SY5Y cells from oxidative damage through inhibiting cell apoptosis.

     

Indolocarbazole natural products: occurrence, biosynthesis, and biological activity

The indolocarbazole family of natural products, including the biosynthetically related bisindolylmaleimides, is reviewed (with 316 references cited). The isolation of indolocarbazoles from natural sources and the biosynthesis of this class of compounds are thoroughly reviewed, including recent developments in molecular genetics, enzymology and metabolic engineering. The biological activities and underlying modes of action displayed by natural and synthetic indolocarbazoles is also presented, with an emphasis on the development of analogs that have entered clinical trials for its future use against cancer or other diseases.     

Antimalarial 20-membered macrolides from Streptomyces sp. BCC33756

Two new natural products, samroiyotmycins A (1) and B (2), along with two naturally new novclobiocin 101 (3) and 4-hydroxy-3-(3-methylbut-2-enyl)benzamide (5), and five known substances including neoantimycin, clorobiocin (4), 29-O-methylabierixin, daidzein, and 1-(3-indolyl)-2,3-dihydroxypropan-1-one have been isolated from Streptomyces sp. BCC33756. Their chemical structures were determined based on NMR spectral information and the relative stereochemistry of compound 1 was determined by X-ray crystallographic data. Both samroiyotmycins A and B exhibited antimalarial activity against Plasmodium falciparum K1—multi-drug resistant strain, with IC₅₀ values of 3.65 and 3.16 μg/mL, respectively. Compound 1 was inactive against both cancerous (MCF-7, KB) and non-cancerous (Vero) cells, while compound 2 displayed cytotoxicity against Vero cell with IC₅₀ value of 29.57 μg/mL.     

Ecionines A and B, two new cytotoxic pyridoacridine alkaloids from the Australian marine sponge, Ecionemia geodides

Chemical investigations of the Australian marine sponge Ecionemia geodides resulted in the isolation of two new pyridoacridine alkaloids, ecionines A (1) and B (2), along with the previously isolated marine natural products, biemnadin (3) and meridine (4). Compounds 1 and 2 both contain an imine moiety, which is rare for the pyridoacridine structure class. The chemical structures of 1 and 2 were determined by extensive 1D and 2D NMR and MS data analyses. All compounds were tested against a panel of human bladder cancer cell lines, the increasingly metastatic TSU-Pr1 series (TSU-Pr1, TSU-Pr1-B1 and TSU-Pr1-B2) and the superficial bladder cancer cell line 5637. Ecionine A (1) displayed cytotoxicity against all cell lines, with IC₅₀ values ranging from 3 to 7 μM. This is the first report of chemistry from the sponge genus Ecionemia.     

Synthesis of 3-substituted 4-piperidinones via a one-pot tandem oxidation-cyclization-oxidation process: stereodivergent reduction to 3,4-disubstituted piperidines

A novel approach to 3-substituted 4-piperidinones is described. The one-pot tandem oxidation-cyclization-oxidation of unsaturated alcohols 1a-e by PCC or PCC and trifluoromethanesulfonic acid affords piperidinones 2a-e in good yield. Reduction of 2a-e by L-Selectride gives the corresponding cis 3,4-disubstituted piperidines with diastereomeric ratios of >99:1. By contrast, reduction of 2a-e by Al-isopropoxydiisobutylalane gives the trans products with diastereomeric ratios of up to 99:1.     

Baseline studies of the global pollution

Summary Fishes have been used to characterize pristine aquatic environments. In samples from a lake in the Tyrolian Alps (arctic char) and Northwest Ireland (pike), the Caspian Sea (sturgeon/Sevruga), the North Atlantic (salmon), the North Pacific (salmon) and the Antarctic Ocean at South Georgia (antarctic cod) hexachlorobenzene and polychlorinated camphene (PCC, Toxaphene) have been found.Samples are extracted by n-hexane/acetone (2+1), following a dimethylformamide/hexane clean-up of the lipid matrix. Adsorption chromatography on Florisil (1.25% water content) allows the elution of hexachlorobenzene, 4,4-DDE and the polychlorobiphenyls (PCB) with n-hexane, while the mixture nhexane/diethyl ether (90+10) will elute the polychlorocamphenes (PCC) together with the hexachlorocyclohexane isomers and the DDT group.Identification of the PCC has been done by matching their retention indices measured by high resolution ECD glass capillary gas chromatography using the nalkyl-trichloroacetates as references and technical Toxaphene together with a slightly dehydrochlorinated product as authentic samples. The PCC content of the samples from the lakes in the European Alps and Northwest-Ireland, the North Pacific and the Antarctic Ocean was 125, 240, 285 and 68 ng of PCC per g of extractable lipids, respectively. The samples from the Caspian Sea and the North Atlantic had 1,625 and 3,500 ng of PCC per g of extractable lipids, respectively. All samples but the one from the Antarctic Ocean (liver) were spawn.Besides hexachlorobenzene and the PCC all samples contained polychlorobiphenyls (PCB), the, and-isomers of hexachlorocyclohexane, the compounds of the DDT-group and many other ECD-dectable not yet identified compounds.The work has been supported by the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg, and has been partly presented at the Ninth Annual Symposium on the Analytical Chemistry of Pollutants, May 7–9, 1979, Jekyll Island, Georgia, U.S.A.     

Removal of Cd2+ from contaminated water by nano-sized aragonite mollusk shell and the competition of coexisting metal ions

The potential of using nano-sized aragonite mollusk shell (nano-Bio-ARA) to remove Cd(2+) from contaminated water was investigated by comparing the sorption kinetics and isotherms with the nano-sized calcite-type mollusk shell (nano-Bio-CAL) and nano-sized geological calcite (nano-Geo-CAL). Nano-Bio-ARA displayed extremely high sorption capacity to Cd(2+) (8.91mmol/g), much higher than nano-Bio/Geo-CAL, and many other natural or engineered materials. The results of thermodynamic experiments indicated that the sorption of Cd(2+) on the nano-ARA was a spontaneous and endothermic process. The coexisting metals in the solution displayed competition effect to the sorption of Cd(2+) on nano-Bio-ARA in the following order: Cu(2+)>Cr(3+)>Pb(2+)>Zn(2+)>Ca(2+). EDTA impeded the sorption of Cd(2+) on nano-Bio-ARA due to its strong chelating capacity to Cd(2+) in the solution. The results demonstrate that nano-Bio-ARA is a potential high-effective material to treat Cd(2+) contaminated water.     

Synthesis of novel 1,3,4-oxadiazole derivatives containing diamides as promising antibacterial and antiviral agents

In this paper, a variety of novel 1,3,4-oxadiazole derivatives possessing diamides were synthesized and tested for their antibacterial and antiviral activity. Preliminary antibacterial assays indicated that some intermediates and title compounds displayed excellent inhibition effects against plant pathogens Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac). Further studies revealed that compound H15 exhibited the strongest activities against Xoo and Xac with minimal EC₅₀ values of 0.7 and 5.9 μg/mL, respectively. Antiviral bioassays suggested that some of these structures displayed appreciable curative activities and moderate protective effects against tobacco mosaic virus (TMV) in vivo. Among them, compound H8 exerted the best chemotherapeutic effect against TMV with the curative rate of 60.0% at 500 µg/mL, which was comparable with those of commercial agricultural antiviral agent ningnanmycin (54.2%). Given their significant biological activities, this kind of compound could serve as new leading compounds in the study of antibacterial and antiviral chemotherapy.     

Synthesis of the fungal natural product (−)-xylariamide A

The first synthesis of the fungal natural product (−)-xylariamide A 1 is reported. N,O-Bis(trimethylsilyl)acetamide induced coupling of d-tyrosine with (E)-but-2-enedioic acid 2,5-dioxo-pyrrolidin-1-yl ester methyl ester 5 produced the dechloro natural product 6, which was subsequently monochlorinated using oxone and KCl to yield synthetic 1. (−)-Xylariamide A 1, (+)-xylariamide A 2 and (−)-dechloroxylariamide A 6 displayed no cytotoxic or antimicrobial activity.     

Synthetic studies of cystobactamids as antibiotics and bacterial imaging carriers lead to compounds with high in vivo efficacy

There is an alarming scarcity of novel chemical matter with bioactivity against multidrug-resistant Gram-negative bacterial pathogens. Cystobactamids, recently discovered natural products from myxobacteria, are an exception to this trend. Their unusual chemical structure, composed of oligomeric para-aminobenzoic acid moieties, is associated with a high antibiotic activity through the inhibition of gyrase. In this study, structural determinants of cystobactamid''s antibacterial potency were defined at five positions, which were varied using three different synthetic routes to the cystobactamid scaffold. The potency against Acinetobacter baumannii could be increased ten-fold to an MIC (minimum inhibitory concentration) of 0.06 μg mL⁻¹, and the previously identified spectrum gap of Klebsiella pneumoniae could be closed compared to the natural products (MIC of 0.5 μg mL⁻¹). Proteolytic degradation of cystobactamids by the resistance factor AlbD was prevented by an amide-triazole replacement. Conjugation of cystobactamid''s N-terminal tetrapeptide to a Bodipy moiety induced the selective localization of the fluorophore for bacterial imaging purposes. Finally, a first in vivo proof of concept was obtained in an E. coli infection mouse model, where derivative 22 led to the reduction of bacterial loads (cfu, colony-forming units) in muscle, lung and kidneys by five orders of magnitude compared to vehicle-treated mice. These findings qualify cystobactamids as highly promising lead structures against infections caused by Gram-positive and Gram-negative bacterial pathogens.

Structure–activity relationship studies of the natural product cystobactamid at four different positions led to novel imaging probes and analogs with superior antibacterial activities and in vivo efficacy.     

Evaluation of renal protective effects of the green-tea (EGCG) and red grape resveratrol: role of oxidative stress and inflammatory cytokines

Epigallocatechin-gallate (EGCG) and resveratrol (RSVL) are two of the most promising natural medicines. We verified their capacity to ameliorate cisplatin (CP)-induced disruption of renal glomerular filtration rate (GFR) in rats, and sought the mediatory involvement of lipid peroxidation (malondialdehyde [MDA]-level) and inflammatory cytokine (TNF-α) therein. CP (10 mg kg?1), a single i.p. dose, disrupted GFR (11-fold-rise in proteinuria, 2-5-fold rise in serum creatinine/urea levels) after 7 days, and killed all animals after 10 days. Kidney-homogenates from CP-treated rats displayed higher MDA and TNF-α, but lower reduced-glutathione (GSH) levels. Rats treated with EGCG (50 mg kg?1, but not 25 mg kg?1) had no fatalities and showed significantly-recovered GFR; while their kidney-homogenates had markedly reduced MDA, TNF-α and enhanced GSH levels at 7 days. Conversely, RSVL or quercetin (25, 50 mg kg?1) neither improved GFR nor reduced (MDA)/TNF-α levels after 7 days. Resuming treatment with 50 mg kg?1 for 10 days rescued only 25% of animals (p > 0.05). Correlation studies showed a significant association between creatinine level, and each of MDA (r = 0.91), GSH (r = -0.87), and TNF-α (0.91). The study showed for the first time that EGCG, unlike RSVL, can protect against CP-induced nephrotoxicity. At the molecular level, CP triggers a high level of oxidative stress and systemic inflammation, events that were all abrogated with EGCG; better than RSVL or quercetin.