Cell‐ and Tissue‐Based Proteome Profiling and Dual Imaging of Apoptosis Markers with Probes Derived from Venetoclax and Idasanutlin

Venetoclax (ABT‐199) and idasanutlin (RG7388) are efficient anticancer drugs targeting two essential apoptosis markers, Bcl‐2 and MDM2, respectively. Recent studies have shown that the combination of these two drugs leads to remarkable enhancement of anticancer efficacy, both in vitro and in vivo. In an attempt to disclose the relationships of their protein targets, competitive affinity‐based proteome profiling coupled with bioimaging was employed to characterize their protein targets in the same cancer cell line and tumor tissue. A series of protein hits, including ITPR1, GSR, RER1, PDIA3, Apoa1, and Tnfrsf17 were simultaneously identified by pull‐down/LC–MS/MS with the two sets of affinity‐based probes. Dual imaging was successfully carried out, with the simultaneous detection of Bcl‐2 and MDM2 expression in various cancer cells. This could facilitate the novel diagnostic and therapeutic strategies of dual targeting of Bcl‐2/MDM2.     

Synthesis and Biological Evaluation of the Antimicrobial Natural Product Lipoxazolidinone A

Natural products have historically been a major source of antibiotics and therefore novel scaffolds are constantly of interest. The lipoxazolidinone family of marine natural products, with an unusual 4‐oxazolidinone heterocycle at their core, represents a new scaffold for antimicrobial discovery; however, questions regarding their mechanism of action and high lipophilicity have likely slowed follow‐up studies. Herein, we report the first synthesis of lipoxazolidinone A, 15 structural analogues to explore its active pharmacophore, and initial resistance and mechanism of action studies. These results suggest that 4‐oxazolidinones are valuable scaffolds for antimicrobial development and reveal simplified lead compounds for further optimization.     

Toblerols: Cyclopropanol‐Containing Polyketide Modulators of Antibiosis in Methylobacteria

Trans‐AT polyketide synthases (PKSs) are a family of biosynthetically versatile modular type I PKSs that generate bioactive polyketides of impressive structural diversity. In this study, we detected, in the genome of several bacteria a cryptic, architecturally unusual trans‐AT PKS gene cluster which eluded automated PKS prediction. Genomic mining of one of these strains, the model methylotroph Methylobacterium extorquens AM1, revealed unique epoxide‐ and cyclopropanol‐containing polyketides named toblerols. Relative and absolute stereochemistry were determined by NMR experiments, chemical derivatization, and the comparison of CD data between the derivatized natural product and a synthesized model compound. Biosynthetic data suggest that the cyclopropanol moiety is generated by carbon–carbon shortening of a more extended precursor. Surprisingly, a knock‐out strain impaired in polyketide production showed strong inhibitory activity against other methylobacteria in contrast to the wild‐type producer. The activity was inhibited by complementation with toblerols, thus suggesting that these compounds modulate an as‐yet unknown methylobacterial antibiotic.     

An Antibacterial β‐Lactone Kills Mycobacterium tuberculosis by Disrupting Mycolic Acid Biosynthesis

The spread of antibiotic resistance is a major challenge for the treatment of Mycobacterium tuberculosis infections. In addition, the efficacy of drugs is often limited by the restricted permeability of the mycomembrane. Frontline antibiotics inhibit mycomembrane biosynthesis, leading to rapid cell death. Inspired by this mechanism, we exploited β‐lactones as putative mycolic acid mimics to block serine hydrolases involved in their biosynthesis. Among a collection of β‐lactones, we found one hit with potent anti‐mycobacterial and bactericidal activity. Chemical proteomics using an alkynylated probe identified Pks13 and Ag85 serine hydrolases as major targets. Validation through enzyme assays and customized ¹³C metabolite profiling showed that both targets are functionally impaired by the β‐lactone. Co‐administration with front‐line antibiotics enhanced the potency against M. tuberculosis by more than 100‐fold, thus demonstrating the therapeutic potential of targeting mycomembrane biosynthesis serine hydrolases.     

A Redox‐Activated G‐Quadruplex DNA Binder Based on a Platinum(IV)–Salphen Complex

There has been increasing interest in the development of small molecules that can selectively bind to G‐quadruplex DNA structures. The latter have been associated with a number of key biological processes and therefore are proposed to be potential targets for drug development. Herein, we report the first example of a reduction‐activated G‐quadruplex DNA binder. We show that a new octahedral platinum(IV)–salphen complex does not interact with DNA in aqueous media at pH 7.4; however, upon addition of bioreductants such as ascorbic acid or glutathione, the compound is readily reduced to the corresponding square planar platinum(II) complex. In contrast to the parent platinum(IV) complex, the in situ generated platinum(II) complex has good affinity for G‐quadruplex DNA.     

“Head‐to‐Middle” and “Head‐to‐Tail” cis‐Prenyl Transferases: Structure of Isosesquilavandulyl Diphosphate Synthase

We report the first X‐ray crystallographic structure of the “head‐to‐middle” prenyltransferase, isosesquilavandulyl diphosphate synthase, involved in biosynthesis of the merochlorin class of antibiotics. The protein adopts the ζ or cis‐prenyl transferase fold but remarkably, unlike tuberculosinol adenosine synthase and other cis‐prenyl transferases (e.g. cis‐farnesyl, decaprenyl, undecaprenyl diphosphate synthases), the large, hydrophobic side chain does not occupy a central hydrophobic tunnel. Instead, it occupies a surface pocket oriented at 90° to the hydrophobic tunnel. Product chain‐length control is achieved by squeezing out the ligand from the conventional allylic S1 binding site, with proton abstraction being achieved using a diphosphate‐Asn‐Ser relay. The structures revise and unify our thinking as to the mechanism of action of many other prenyl transferases and may also be of use in engineering new merochlorin‐class antibiotics.     

Identification of Tumor Initiating Cells with a Small‐Molecule Fluorescent Probe by Using Vimentin as a Biomarker

Tumor initiating cells (TICs) have been implicated in clinical relapse and metastasis of a variety of epithelial cancers, including lung cancer. While efforts toward the development of specific probes for TIC detection and targeting are ongoing, a universal TIC probe has yet to be developed. We report the first TIC‐specific fluorescent chemical probe, TiY, with identification of the molecular target as vimentin, a marker for epithelial‐to‐mesenchymal transition (EMT). TiY selectively stains TICs over differentiated tumor cells or normal cells, and facilitates the visualization and enrichment of functionally active TICs from patient tumors. At high concentration, TiY also shows anti‐TIC activity with low toxicity to non‐TICs. With the unexplored target vimentin, TiY shows potential as a first universal probe for TIC detection in different cancers.     

"烯-二炔"模型化合物前体--6-硫杂-13-氧杂双环[9.3.0]-3,8-十四二炔的合成(Ⅱ)

以顺-1,2,3,6-四氢邻苯二甲酸酐为原料,经还原、环化、臭氧化、Wittig羰基烯化、酯化、二醇化和硫化等8步反应,合成了新型抗癌抗菌素"烯-二炔"的双环前体:6-硫杂-13-氧杂双环[9.3.0]-3,8-十四二炔.该合成路线步骤少,收率高,反应条件温和.6个新化合物4-9的结构均经元素分析、核磁共振、红外光谱和质谱确证.     

超高效液相色谱-四极杆飞行时间质谱快速筛查与确证生鲜牛乳中80种抗生素和激素

采用超高效液相色谱-四极杆飞行时间高分辨质谱(UHPLC-QTOF MS)技术建立了生鲜牛乳中80种抗生素和激素的快速筛查方法。牛乳样品经含1%乙酸的乙腈溶液提取,采用QuEChERS(Quick,Easy,Cheap,Effective,Rugged and Safe)方法净化。目标药物经Agilent ZORBAX SB C_(18)色谱柱(3. 0 mm×100 mm,1. 8μm)分离,以乙腈-0. 1%甲酸水溶液为流动相进行梯度洗脱,使用Dual AJS ESI源,在正离子模式下进行数据采集,基质匹配标准曲线法定量。结果表明,80种抗生素和激素类药物在各自的浓度范围内线性关系良好(r~2≥0. 990 0),其定量下限(LOQ,S/N=10)为5～100μg/kg。LOQ加标水平下,80种兽药中23种兽药的回收率为50. 2%～59. 7%,相对标准偏差为1. 1%～13. 0%;其余57种兽药的回收率为61. 7%～119%,相对标准偏差为0. 3%～19. 0%。结合精确分子质量数、保留时间、同位素丰度和二级特征碎片离子对目标化合物进行快速筛查与确证。该方法快速简便、准确、灵敏,适用于牛乳中抗生素和激素类药物残留的高通量筛查与定性鉴定。     

Self‐Delivery Nanoparticles of Amphiphilic Acyclic Enediynes for Efficient Tumor Cell Suppression

Four acyclic maleimide‐based enediyne compounds with different hydrophilicity were synthesized through Sonogashira reaction to reveal a self‐delivery antitumor drug platform. As proved by ESR analysis, the enediyne compounds undergo Bergman‐like cyclization and generate diradical intermediates at physiological temperature, which are able to induce DNA‐cleavage through the abstraction of H atoms from the sugar‐phosphate backbones. When the critical aggregation concentration is reached in water, the amphiphilic enediyne compounds self‐assemble into nanoparticles and possess the self‐delivery ability to be facilely admitted by tumor cells, resulting in greatly improved cytotoxicity (IC₅₀ down to 10 μmol·L^–1) and much higher tumor cell apoptosis rate (up to 86.6%) in comparison with either the hydrophilic or the lipophilic enediyne compound. The enhanced endocytosis of the amphiphilic enediyne compounds was further confirmed through confocal laser scanning microscopy analysis. The unveiled relationship between the hydrophilicity of enediyne drugs and their therapeutic efficacy will provide a guideline for the design of new self‐delivery drugs employed in medicinal applications.