Microansamycins J and K from <i>Micromonospora</i> sp. HK160111mas13OE

Microansamycins were novel pentaketide ansamycins isolated from Micromonospora sp. HK160111mas13OE with AHBA-C2-C2-C3-C3 skeleton and diverse post-PKS modifications. In this paper, two new congeners, namely microansamycins J (1) and K (2), were identified based on their NMR, HRESIMS data and compared with those of microansamycins F and E. Neither showed antibacterial activity against Staphy­lococcus aureus ATCC25923 and Escherichia coli at 40 µg/mL.</p

Pentaketide Ansamycin Microansamycins A–I from Micromonospora sp. Reveal Diverse Post-PKS Modifications

Overexpression of the pathway-specific positive regulator gene <i>mas13</i> activated the cryptic gene cluster <i>mas</i>, resulting in the isolation of nine novel pentaketide ansamycins, namely, microansamycins A–I (<b>1</b>–<b>9</b>). These results not only revealed a biosynthetic gene cluster of pentaketide ansamycins for the first time but also presented an unprecedented scenario of diverse post-PKS modifications in ansamycin biosynthesis

Facile Fabrication of Cuprous Oxide-based Adsorbents for Deep Desulfurization

Deep desulfurization via π-complexation adsorption is an effective approach for the selective capture of aromatic sulfur compounds. Among various π-complexation adsorbents, Cu­(I)-containing materials attract great attention due to their low cost and high efficiency. In the present study, a one-pot thermal treatment strategy was developed to fabricate Cu₂O-based adsorbents for the first time. As-synthesized mesoporous silica SBA-15 was directly used as the support and the precursor Cu­(NO₃)₂ was introduced to the confined space between silica walls and template. The subsequent one-pot thermal treatment plays a triple role by decomposing Cu­(NO₃)₂ to CuO, removing the template P123, and reducing CuO to Cu₂O. In contrast to the traditional approach, our strategy provides a more convenient method for the preparation of Cu₂O-based adsorbents. For a typical material CuAS-3 derived from as-synthesized SBA-15, the yield of Cu­(I) is 73.3%, which is obviously higher than its counterpart CuCS-3 prepared from template-free SBA-15 (53.3%). We also demonstrate that the resultant materials are active in adsorptive desulfurization, and the amount of thiophene captured can reach 0.35 mmol·g^–1 over CuAS-3, which is obviously better than that over CuCS-3 (0.27 mmol·g^–1). Furthermore, the activity in adsorptive desulfurization can be well recovered with no apparent loss. The convenient preparation, high activity, and good reusability make the present materials highly promising for utilization as adsorbents in deep desulfurization

Nocarbenzoxazoles A–G, Benzoxazoles Produced by Halophilic Nocardiopsis lucentensis DSM 44048

Seven new benzoxazole derivatives, nocarbenzoxazoles A–G (<b>1</b>–<b>7</b>), were isolated from the halophilic strain Nocardiopsis lucentensis DSM 44048. Their structures were elucidated on the basis of 1D and 2D NMR spectroscopic data, HRESIMS, and X-ray single-crystal diffraction. The isolated compounds were assayed for their cytotoxicity against a panel of human tumor cell lines (HepG2, MDA-MB-231, MDA-MB-435, HeLa, and PC3). Compounds <b>1</b>–<b>6</b> were found to have modest or no activity. Compound <b>7</b> showed selective activity against HepG2 and HeLa with IC₅₀ values of 3 and 1 μM, respectively

Different Upconversion Properties of β‑NaYF₄:Yb³⁺,Tm³⁺/Er³⁺ in Affecting the Near-Infrared-Driven Photocatalytic Activity of High-Reactive TiO₂

Double-shell-structured β-NaYF₄:Yb³⁺,Tm³⁺/Er³⁺@SiO₂@TiO₂ upconversion photocatalysts have been successfully synthesized by a simple hydrothermal method. It is found that the double-shell-structured photocatalyst consists of uniform β-NaYF₄:Yb³⁺,Tm³⁺/Er³⁺ nanocrystals, SiO₂ as the media shell, and anatase TiO₂ nanocrystals exposed with the high-reactive {001} facets as the outer shell. The TiO₂ shell is modified to absorb both the UV and visible light in order to make sufficient use of the upconverted light from β-NaYF₄:Yb³⁺,Tm³⁺/Er³⁺ for photocatalysis. Effective energy transfer from β-NaYF₄:Yb³⁺,Tm³⁺/Er³⁺ to TiO₂ and its importance are confirmed. The photocatalytic activity in the degradation of Rhodamine B (RhB) under the near-infrared (NIR) (980 nm laser) irradiation suggests that the NIR-driven photocatalytic activity of the double-shell-structured photocatalyst is significantly dependent on the properties of the upconversion materials and the irradiated NIR power density. Moreover, the NIR-driven photocatalyst shows stable photocatalytic degradation of RhB in the recycled tests. This study suggests a promising system and a new insight to understand the application of appropriate upconversion materials to effectively utilize the NIR for photocatalytic applications of TiO₂-based photocatalysts, which may advance the application of solar energy in the future

A Self-Assembled Copper-Selenocysteine Nanoparticle for Enhanced Chemodynamic Therapy via Oxidative Stress Amplification

Chemodynamic therapy (CDT) as a catalytic anticancer strategy utilizes transition metal ions to initiate the Fenton reaction to produce high levels of cytotoxic hydroxyl radicals(·OH) in situ. Nevertheless, current existing CDTs are normally restricted by the high levels of existing antioxidant molecules and/or enzymes, such as glutathione (GSH) and thioredoxin reductase (TrxR), in a tumor internal environment, which could suppress CDT via ·OH depletion. Herein, to enhance ·OH-induced cellular damage by CDT, a self-assembled copper-selenocysteine nanoparticles (Cu-SeC NPs) was fabricated through a one-pot process. In our design, once Cu-SeC NPs were endocytosed by tumor cells, Cu2+ was reduced to Cu+ by cellular GSH, promoting in situ Fenton-like reactions to trigger ·OH rapid production in cells as well as the depletion of GSH. Furthermore, the gradually released selenocysteine can inhibit TrxR activity to weaken the protection of antioxidant systems and provide a favorable microenvironment for CDT. As a result, both paths synergistically resulted in massive reactive oxygen species (ROS) accumulation and amplified oxidative stress in tumor sites for enhanced CDT. As a new intelligent anticancer nanoplatform, Cu-SeC NPs exhibit synergistic antitumor effects with negligible systemic toxicity. Thus, the proposed strategy provides a new avenue for further development of progressive therapeutic systems

Spherical Nucleic Acid Probe Based on 2′-Fluorinated DNA Functionalization for High-Fidelity Intracellular Sensing

Traditional spherical nucleic acids (SNAs) based on gold nanoparticles (AuNPs) assembled through Au–S covalent bonds are widely used in DNA-programmable assembly, biosensing, imaging, and therapeutics. However, biological thiols and other chemical substances can break the Au–S bonds and cause response distortion during the application process, specifically in cell environments. Herein, we report a new type of SNAs based on 2′-fluorinated DNA-functionalized AuNPs with excellent colloidal stability under high salt conditions (up to 1 M NaCl) and over a broad pH range (1–14), as well as resistance to biothiols. The fluorinated spherical nucleic acid probe (Au/FDNA probe) could detect targeted cancer cells with high fidelity. Compared to the traditional thiolated DNA-functionalized AuNP probe (Au–SDNA probe), the Au/FDNA probe exhibited a higher sensitivity to the target and a lower signal-to-background ratio. Furthermore, the Au/FDNA probe could discriminate target cancer cells in a mixed culture system. Using the proposed FDNA functionalization method, previously developed SNAs based on AuNPs could be directly adapted, which might open a new avenue for the design and application of SNAs

Hygrocins C–G, Cytotoxic Naphthoquinone Ansamycins from <i>gdmAI</i>-Disrupted <i>Streptomyces</i> sp. LZ35

Six hygrocins, polyketides of ansamycin class, were isolated from the <i>gdmAI</i>-disrupted Streptomyces sp. LZ35. The planar structure of hygrocins C–E (<b>1</b>–<b>3</b>) was determined by one-dimensional and two-dimensional NMR spectroscopy and high-resolution mass spectrometry. They are derivatives of hygrocin A but differ in the configuration at C-2 and the orientation of the C-3,4 double bond. Hygrocin F­(<b>4</b>) and G­(<b>5</b>) were shown to be isomers of hygrocin C (<b>1</b>) and B (<b>6</b>), respectively, due to the different alkyl oxygen participating in the macrolide ester linkage. Hygrocins C, D, and F were found to be toxic to human breast cancer MDA-MB-431 cells (IC₅₀ = 0.5, 3.0, and 3.3 μM, respectively) and prostate cancer PC3 cells (IC₅₀ = 1.9, 5.0, and 4.5 μM, respectively), while hygrocins B, E, and G were inactive

Activating a Cryptic Ansamycin Biosynthetic Gene Cluster To Produce Three New Naphthalenic Octaketide Ansamycins with <i>n</i>‑Pentyl and <i>n</i>‑Butyl Side Chains

Genome mining is a rational approach to discovering new natural products. The genome sequence analysis of <i>Streptomyces</i> sp. LZ35 revealed the presence of a putative ansamycin gene cluster (<i>nam</i>). Constitutive overexpression of the pathway-specific transcriptional regulatory gene <i>nam1</i> successfully activated the <i>nam</i> gene cluster, and three novel naphthalenic octaketide ansamycins were discovered with unprecedented <i>n</i>-pentylmalonyl-CoA or <i>n</i>-butylmalonyl-CoA extender units. This study represents the first example of discovering novel ansamycin scaffolds via activation of a cryptic gene cluster