Biosynthesis of Diverse Ephedra-Type Alkaloids via a Newly Identified Enzymatic Cascade.

Ephedra-type alkaloids represent a large class of natural and synthetic phenylpropanolamine molecules with great pharmaceutical values. However, the existing methods typically rely on chemical approaches to diversify the N-group modification of Ephedra-type alkaloids. Herein, we report a 2-step enzymatic assembly line for creating structurally diverse Ephedra-type alkaloids to replace the conventional chemical modification steps. We first identified a new carboligase from Bacillus subtilis (BsAlsS, acetolactate synthase) as a robust catalyst to yield different phenylacetylcarbinol (PAC) analogs from diverse aromatic aldehydes with near 100% conversions. Subsequently, we screened imine reductases (IREDs) for the reductive amination of PAC analogs. It was found that IRG02 from Streptomyces albidoflavus had good activities with conversions ranging from 37% to 84% for the reductive alkylamination with diverse amine partners such as allylamine, propargylamine, and cyclopropylamine. Overall, 3 new bio-modifications at the N-group of Ephedra-type alkaloids were established. Taken together, our work lays a foundation for the future implementation of biocatalysis for synthesizing structurally diverse Ephedra-type alkaloids with potential new pharmaceutical applications.

Algicidal bacteria-derived membrane vesicles as shuttles mediating cross-kingdom interactions between bacteria and algae.

Bacterial membrane vesicles (BMVs) are crucial biological vehicles for facilitating interspecies and interkingdom interactions. However, the extent and mechanisms of BMV involvement in bacterial-algal communication remain elusive. This study provides evidence of BMVs delivering cargos to targeted microalgae. Membrane vesicles (MVs) from Chitinimonas prasina LY03 demonstrated an algicidal profile similar to strain LY03. Further investigation revealed Tambjamine LY2, an effective algicidal compound, selectively packaged into LY03-MVs. Microscopic imaging demonstrated efficient delivery of Tambjamine LY2 to microalgae Heterosigma akashiwo and Thalassiosira pseudonana through membrane fusion. In addition, the study demonstrated the versatile cargo delivery capabilities of BMVs to algae, including the transfer of MV-carried nucleic acids into algal cells and the revival of growth in iron-depleted microalgae by MVs. Collectively, our findings reveal a previously unknown mechanism by which algicidal bacteria store hydrophobic algicidal compounds in MVs to trigger target microalgae death and highlight BMV potency in understanding and engineering bacterial-algae cross-talk.

Deaggregation of mutant Plasmodium yoelii de-ubiquitinase UBP1 alters MDR1 localization to confer multidrug resistance.

Mutations in a Plasmodium de-ubiquitinase UBP1 have been linked to antimalarial drug resistance. However, the UBP1-mediated drug-resistant mechanism remains unknown. Through drug selection, genetic mapping, allelic exchange, and functional characterization, here we show that simultaneous mutations of two amino acids (I1560N and P2874T) in the Plasmodium yoelii UBP1 can mediate high-level resistance to mefloquine, lumefantrine, and piperaquine. Mechanistically, the double mutations are shown to impair UBP1 cytoplasmic aggregation and de-ubiquitinating activity, leading to increased ubiquitination levels and altered protein localization, from the parasite digestive vacuole to the plasma membrane, of the P. yoelii multidrug resistance transporter 1 (MDR1). The MDR1 on the plasma membrane enhances the efflux of substrates/drugs out of the parasite cytoplasm to confer multidrug resistance, which can be reversed by inhibition of MDR1 transport. This study reveals a previously unknown drug-resistant mechanism mediated by UBP1 through altered MDR1 localization and substrate transport direction in a mouse model, providing a new malaria treatment strategy.

Exploring Diversity through Dimerization in Natural Products by a Rational Tandem Mass-Based Molecular Network Strategy.

The step- and atom-efficient dimerization strategy is frequently used in nature to build structural complexity and diversity. We propose the rationale and structural features of the versatile monomers that are responsible for "diversity through dimerization". Using 5-FAM-maleimide combined with a UHPLC-MS/MS-FBMN workflow, we successfully identified a diverse set of dimeric natural products from fungus Panus rudis F01315, in which all four complex 4'5-ring scaffolds are derived from one monomeric epoxyquinol and endowed with functional diversity.

Discovery of urea-based pleuromutilin derivatives as potent gram-positive antibacterial agents.

There is an urgent need to discover new antibacterial drugs and provide new treatment options for clinical antimicrobial resistance (AMR) pathogen infections. Inspired by the structural insights from analyzing the co-crystal structure of lefamulin with the ribosomes of S. aureus, a series of novel pleuromutilin derivatives of phenylene sulfide incorporated with urea moiety were designed and synthesized. The structure-activity relationship (SAR) study revealed that derivatives with urea in the meta position of phenylene sulfide had optimal antibacterial activities in vitro. Among them, 21h was the most potent one against Methicillin-resistant Staphylococcus aureus (MRSA) and clinical AMR Gram-positive bacteria with minimum inhibitory concentrations (MICs) in the range of 0.00195-0.250 µg/mL. And it possessed low resistance frequency, prolonged Post-Antibiotic Effect and the capability to overcome lefamulin-induced resistance. Furthermore, 21h exhibited potent antibacterial activity in vivo in both the thigh infection model and trauma infection model, representing a promising lead for the development of new antibiotics against Gram-positive pathogens, especially for AMR bacteria.

Pharmacological Targeting of Vacuolar H+-ATPase via Subunit V1G Combats Multidrug-Resistant Cancer.

Multidrug resistance (MDR) in cancer remains a major challenge for the success of chemotherapy. Natural products have been a rich source for the discovery of drugs against MDR cancers. Here, we applied high-throughput cytotoxicity screening of an in-house natural product library against MDR SGC7901/VCR cells and identified that the cyclodepsipeptide verucopeptin demonstrated notable antitumor potency. Cytological profiling combined with click chemistry-based proteomics revealed that ATP6V1G directly interacted with verucopeptin. ATP6V1G, a subunit of the vacuolar H+-ATPase (v-ATPase) that has not been previously targeted, was essential for SGC7901/VCR cell growth. Verucopeptin exhibited strong inhibition of both v-ATPase activity and mTORC1 signaling, leading to substantial pharmacological efficacy against SGC7901/VCR cell proliferation and tumor growth in vivo. Our results demonstrate that targeting v-ATPase via its V1G subunit constitutes a unique approach for modulating v-ATPase and mTORC1 signaling with great potential for the development of therapeutics against MDR cancers.

Biosynthesis and Chemical Diversification of Verucopeptin Leads to Structural and Functional Versatility.

A synthesis program for structurally complex macrocycles is very challenging. Herein, we propose a biosynthesis pathway of the pyranylated cyclodepsipeptide verucopeptin to make enough supply and to diversify verucopeptin by genetic manipulation and one-step semisynthesis. The synthesis relies on the intrinsic reactivity of the interchangeable hemiketal pyrane and opened keto along with adjacent alkene. Biological evaluation of verucopeptin-oriented analogs delivers a potent AMP-activated protein kinase (AMPK) agonist, antibacterial agent, and selective NFκB modulator.

New 12,8-Eudesmanolides from Eutypella sp. 1-15.

Four new 12,8-Eudesmanolides (1-4) and one known compound 5 named 13-Hydroxy-3,7(11)-eudesmadien-12,8-olide, were isolated from a mangrove rhizosphere-derived fungus Eutypella sp. 1-15. Their structures with absolute stereochemistry were determined by the comprehensive spectroscopic data, experimental and calculated ECD analysis. Compound 1 exhibited potent anticancer activity against JEKO-1 and HepG2 with IC50 values of 8.4 and 28.5 µM, respectively. Additionally, compound 1 also showed moderate antimicrobial activity.

Enhancing the Elasticity of Ultrathin Single-Wall Carbon Nanotube Films with Colloidal Nanocrystals.

Thin bilayers of contrasting nanomaterials are ubiquitous in solution-processed electronic devices and have potential relevance to a number of applications in flexible electronics. Motivated by recent mesoscopic simulations demonstrating synergistic mechanical interactions between thin films of single-wall carbon nanotubes (SWCNTs) and spherical nanocrystal (NC) inclusions, we use a thin-film wrinkling approach to query the compressive mechanics of hybrid nanotube/nanocrystal coatings adhered to soft polymer substrates. Our results show an almost 2-fold enhancement in the Young modulus of a sufficiently thin SWCNT film associated with the presence of a thin interpenetrating overlayer of semiconductor NCs. Mesoscopic distinct-element method simulations further support the experimental findings by showing that the additional noncovalent interfaces introduced by nanocrystals enhance the modulus of the SWCNT network and hinder network wrinkling.

Excluded Volume Approach for Ultrathin Carbon Nanotube Network Stabilization: A Mesoscopic Distinct Element Method Study.

Ultrathin carbon nanotube films have gathered attention for flexible electronics applications. Unfortunately, their network structure changes significantly even under small applied strains. We perform mesoscopic distinct element method simulations and develop an atomic-scale picture of the network stress relaxation. On this basis, we put forward the concept of mesoscale design by the addition of excluded-volume interactions. We integrate silicon nanoparticles into our model and show that the nanoparticle-filled networks present superior stability and mechanical response relative to those of pure films. The approach opens new possibilities for tuning the network microstructure in a manner that is compatible with flexible electronics applications.

Twisting Carbon Nanotube Ropes with the Mesoscopic Distinct Element Method: Geometry, Packing, and Nanomechanics.

The geometry and internal packing of twisted ropes composed of carbon nanotubes (CNTs) are considered, and a numerical solution in the context of the mesoscopic distinct element method (MDEM) is proposed. Compared to the state of the art, MDEM accounts in a computationally tractable manner for both the deformation of the fiber and the distributed van der Waals cohesive energy between fibers. These features enable us to investigate the torsional response in a new regime where the twisted rope develops packing rearrangements and aspect-ratio-dependent geometric nonlinearities. MDEM emerges as a robust simulation method for studying twisted agglomerates comprising semiflexible nanofibers.

Aspertetranones A-D, Putative Meroterpenoids from the Marine Algal-Associated Fungus Aspergillus sp. ZL0-1b14.

Aspertetranones A-D (1-4), four new highly oxygenated putative rearranged triketide-sesquiterpenoid meroterpenes, were isolated from the marine algal-associated fungus Aspergillus sp. ZL0-1b14. On the basis of a comprehensive spectroscopic analysis, the planar structures of aspertetranones were determined to possess an unusual skeleton in the terpenoid part. The relative and absolute configurations of the aspertetranones were assigned on the basis of NOESY analysis, X-ray crystallography, and circular dichroism spectroscopy. Compounds 1-4 were evaluated for anti-inflammatory activity in LPS-stimulated RAW264.7 macrophages. Aspertetranone D exhibited an inhibitory effect against IL-6 production with 69% inhibition at 40 µM.

Two new spirooxindole alkaloids from rhizosphere strain Streptomyces sp. xzqh-9.

Two new spirooxindole alkaloids spindomycins A (1) and B (2) were isolated from rhizosphere strain Streptomyces sp. xzqh-9. Their structures were elucidated by comprehensive spectroscopic analyses of NMR and MS data. The absolute configurations of 1 and 2 were determined by experimental and theoretical calculation of electronic circular dichroism (ECD). Antitumor, lactate dehydrogenase, and tyrosine kinase inhibitory activities of two compounds were evaluated, while only spindomycin B (2) exhibited weak inhibitory activity against tyrosine kinase Bcr-Abl.

Rings and rackets from single-wall carbon nanotubes: manifestations of mesoscale mechanics.

We combine experiments and distinct element method simulations to understand the stability of rings and rackets formed by single-walled carbon nanotubes assembled into ropes. Bending remains a soft deformation mode in ropes because intra-rope sliding of the constituent nanotubes occurs with ease. Our simulations indicate that the formation of these aggregates can be attributed to the mesoscopic mechanics of entangled nanotubes and to the sliding at the contacts. Starting from the single-walled carbon nanotubes, the sizes of the rings and rackets' heads increase with the rope diameter, indicating that the stability of the experimental aggregates can be largely explained by the competition between bending and van der Waals adhesion energies. Our results and simulation method should be useful for understanding nanoscale fibers in general.