Search

β‐Branched chiral amines with contiguous stereocenters are valuable building blocks for preparing various biologically active molecules. However, their asymmetric synthesis remains challenging. Herein, we report a highly diastereo‐ and enantioselective biocatalytic approach for preparing a broad range of β‐branched chiral amines starting from their corresponding racemic ketones. This involves a dynamic kinetic resolution‐asymmetric reductive amination process catalyzed using only an imine reductase. Four rounds of protein engineering endowed wild‐type PocIRED with higher reactivity, better stereoselectivity, and a broader substrate scope. Using the engineered enzyme, various chiral amine products were synthesized with up to >99.9 % ee, >99 : 1 dr, and >99 % conversion. The practicability of the developed biocatalytic method was confirmed by producing a key intermediate of tofacitinib in 74 % yield, >99.9 % ee, and 98 : 2 dr at a challenging substrate loading of 110 g L−1. Our study provides a highly capable imine reductase and a protocol for developing an efficient biocatalytic dynamic kinetic resolution‐asymmetric reductive amination reaction system. [ABSTRACT FROM AUTHOR]

The composition of protection monolayer exerts great influence on the molecular and electronic structures of atomically precise monolayer protected metal nanoclusters. Four isostructural Ag/cyanurate/phosphine metallamacrocyclic monolayer protected Ag22 nanoclusters are synthesized by kinetically controlled in‐situ ligand formation‐driven strategy. These eight‐electron superatomic silver nanoclusters feature an unprecedented interfacial bonding structure with diverse E‐Ag (E=O/N/P/Ag) interactions between the Ag13 core and metallamacrocyclic monolayer, and displays thermally activated delayed fluorescence (TADF), benefiting from their distinct donor‐acceptor type electronic structures. This work not only unmasks a new core‐shell interface involving cyanurate ligand but also underlines the significance of high‐electron‐affinity N‐heterocyclic ligand in synthesizing TADF metal nanoclusters. This is the first mixed valence Ag0/I nanocluster with TADF characteristic. [ABSTRACT FROM AUTHOR]

Microglia are the primary immune cells in the central nervous system with functional plasticity. They can be activated into M1 and M2 phenotypes when neuroinflammation‐related diseases occur. M1 phenotype cells produce pro‐inflammatory mediators that cause neuroinflammation and the M2 phenotype can secrete anti‐inflammatory cytokines that protect neurons from damage. Therefore, inhibiting the M1 phenotype while stimulating the M2 phenotype has been suggested as a potential therapeutic approach for treating neuroinflammation‐related diseases. Puerarin has been demonstrated to exert anti‐inflammatory and neuroprotective effects. However, the role of puerarin in regulating microglia polarization and its reaction mechanism has not been fully elucidated. In this paper, a metabolomics approach with ultra‐performance liquid chromatography–mass spectrometry was performed to investigate the metabolic changes of BV‐2 cells in different phenotypes and test the effects of puerarin on polarization. Thirty‐nine metabolites were identified as the biomarkers related to the polarization of BV‐2 cells and puerarin intervention reverted the content of most of the biomarkers. Our study demonstrated that puerarin could play a key role in M1/M2 polarization of BV‐2 cells from a perspective of metabolomics, and it could regulate the balance between promotion and suppression of inflammation. [ABSTRACT FROM AUTHOR]

Abstract: Cadmium is considered one of the most harmful carcinogenic heavy metals in the human body. Although many scientists have performed research on cadmium toxicity mechanism, the toxicokinetic process of cadmium toxicity remains unclear. In the present study, the kinetic response of proteome in/and A549 cells to exposure of exogenous cadmium was profiled. A549 cells were treated with cadmium sulfate (CdSO4) for different periods and expressions of proteins in cells were detected by two‐dimensional gel electrophoresis. The kinetic expressions of proteins related to cadmium toxicity were further investigated by reverse transcription‐polymerase chain reaction and western blotting. Intracellular cadmium accumulation and content fluctuation of several essential metals were observed after 0–24 hours of exposure by inductively coupled plasma mass spectrometry. Fifty‐four protein spots showed significantly differential responses to CdSO4 exposure at both 4.5 and 24 hours. From these proteins, four expression patterns were concluded. Their expressions always exhibited a maximum abundance ratio after CdSO4 exposure for 24 hours. The expression of metallothionein‐1 and ZIP‐8, concentration of total protein, and contents of cadmium, zinc, copper, cobalt and manganese in cells also showed regular change. In synthesis, the replacement of the essential metals, the inhibition of the expression of metal storing protein and the activation of metal efflux system are involved in cadmium toxicity. [ABSTRACT FROM AUTHOR]

Accurate identification of the molecular targets of bioactive small molecules is a highly important yet challenging task in biomedical research. Previously, a method named DPAL (DNA-programmed affinity labeling) for labeling and identifying the cellular targets of small molecules and nucleic acids was developed. Herein, DPAL is applied for the target identification of Alisertib (MLN8237), which is a highly specific aurora kinase A (AKA) inhibitor and a drug candidate being tested in clinical trials for cancer treatment. Apart from the well-established target of AKA, several potential new targets of MLN8237 were identified. Among them, p38 mitogen-activated protein kinase (p38) and laminin receptor (LAMR) were validated to be implicated in the anticancer activities of MLN8237. Interestingly, these new targets were not identified with non-DNA-based affinity probes. This work may facilitate an understanding of the molecular basis of the efficacy and side effects of MLN8237 as a clinical drug candidate. On the other hand, this work has also demonstrated that the method of DPAL could be a useful tool for target identification of bioactive small molecules. [ABSTRACT FROM AUTHOR]

A reliable and rapid method based on rapid-resolution liquid chromatography-diode array detection (RRLC-DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF/MS) has been developed for the isolation and characterization of multiple constituents in the root of Stellera chamaejasme L., which was extracted by sonication with methanol in an optimized procedure. Separation of the multiple constituents was achieved on an Agilent Zorbax XDB-C18 (50 × 3.0 mm i.d.; 1.8 µm) column using a gradient elution at a flow rate of 0.4 mL/min. The detection wavelength was 210 nm. Mass spectra were acquired in both positive and negative modes. A formula database of the known chemical constituents in the root of Stellera chamaejasme L. was established by an Agilent software. Twenty-two obvious peaks appeared in the total ion chromatogram and nine of them were characterized by TOF/MS. The RRLC-DAD and ESI-TOF/MS method with ultrasonic extraction would be useful for rapid and effective characterization of chemical constituents in the root of Stellera chamaejasme L. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]