Mechanism of Abnormal Activation of MEK1 Induced by Dehydroalanine Modification.

Mitogen-activated protein kinase kinase 1 (MAPK kinase 1, MEK1) is a key kinase in the mitogen-activated protein kinase (MAPK) signaling pathway. MEK1 mutations have been reported to lead to abnormal activation that is closely related to the malignant growth and spread of various tumors, making it an important target for cancer treatment. Targeting MEK1, four small-molecular drugs have been approved by the FDA, including Trametinib, Cobimetinib, Binimetinib, and Selumetinib. Recently, a study showed that modification with dehydroalanine (Dha) can also lead to abnormal activation of MEK1, which has the potential to promote tumor development. In this study, we used molecular dynamics simulations and metadynamics to explore the mechanism of abnormal activation of MEK1 caused by the Dha modification and predicted the inhibitory effects of four FDA-approved MEK1 inhibitors on the Dha-modified MEK1. The results showed that the mechanism of abnormal activation of MEK1 caused by the Dha modification is due to the movement of the active segment, which opens the active pocket and exposes the catalytic site, leading to sustained abnormal activation of MEK1. Among four FDA-approved inhibitors, only Selumetinib clearly blocks the active site by changing the secondary structure of the active segment from α-helix to disordered loop. Our study will help to explain the mechanism of abnormal activation of MEK1 caused by the Dha modification and provide clues for the development of corresponding inhibitors.

Aryl Chloride-Directed Enantioselective C(sp2)-H Borylation Enabled by Iridium Catalysis.

We herein report the iridium-catalyzed enantioselective C-H borylation of aryl chlorides. A variety of prochiral biaryl compounds could be well-tolerated, affording a vast array of axially chiral biaryls with high enantioselectivities. The current method exhibits a high turnover number (TON) of 7000, which represents the highest in functional-group-directed asymmetric C-H activation. The high TON was attributed to a weak catalyst-substrate interaction that was caused by mismatched chirality between catalyst and substrate. We also demonstrated the synthetic application of the current method by C-B, ortho-C-H, and C-Cl bond functionalization, including programmed Suzuki-Miyaura coupling for the synthesis of axially chiral polyarenes.

Nickel(0)-Catalyzed Hydroalkenylation of Imines with Styrene and Its Derivatives.

A nickel(0)-catalyzed hydroalkenylation of imines with styrene and its derivatives is described. A wide range of aromatic and aliphatic imines directly coupled with styrene and its derivatives, thus providing various synthetically useful allylic amines with up to 95 % yield. The reaction offers a new atom- and step-economical approach to allylic amines by using alkenes instead of alkenyl-metallic reagents. Experiments and DFT calculations showed that TsNH2 promotes the proton transfer from the coordinated olefin to the imine, accompanied by a new C-C bond formation.

New cyclic C-geranylflavanones isolated from Paulownia fortunei fruits with their anti-proliferative effects on three cancer cell lines.

Seven new C-geranylated flavanones, fortunones F - L (1-7), were isolated from the fresh mature fruits of Paulownia fortunei (Seem.) Hemsl. Their structures were determined by extensive spectroscopic data interpretation (UV, IR, HRMS, NMR, and CD). These new isolated compounds were all with a cyclic side chain modified from the geranyl group. Among them, compounds 1-3 all possessed a dicyclic geranyl modification, which was described firstly for Paulownia C-geranylated flavonoids. All the isolated compounds were subjected to the cytotoxic assay on human lung cancer cell A549, mouse prostate cancer cell RM1 and human bladder cancer cell T24, respectively. Results indicated A549 cell line was more sensitive to C-geranylated flavanones than the other two cancer cell lines and compounds 1, 7 and 8 exhibited potential anti-tumor effects (IC50 ˂ 10 µM). Further research revealed the effective C-geranylated flavanones could exert their anti-proliferative activity on A549 cells by inducing apoptosis and blocking cells in G1 phase.

Fabrication of porous covalent organic frameworks as selective and advanced adsorbents for the on-line preconcentration of trace elements against the complex sample matrix.

Herein, for the first time, the typical porous Covalent Organic Frameworks (COFs) CTpBD with superior chemical stability and large surface area were applied as sorbents for solid phase extraction of trace ions via flow injection followed by inductively coupled plasma mass spectrometry (ICP-MS) detection. The well-prepared and fully-characterized CTpBD COFs were filled in solid phase extraction cartridge as novel and robust adsorbents for element analysis. Separation and enrichment of Cr (III), Mn (II), Co (II), Ni (II), Cd (II), V (V), Cu (II), As (III), Se (IV), and Mo (VI) was then carried out, and the contents were measured by ICP-MS. Owing to the large surface area and instinctive porous structure of CTpBD, preconcentration of the target trace elements via COF-filled on-line SPE column has achieved low detection limits of 2.1-21.6ngL-1 along with a wide linearity range at 0.05-25µgL-1 for all target ions. The relative standard deviations (RSD) of 1.2%-4.3% obtained via 11 parallel determinations at the sample concentration of 100ngL-1 revealed excellent repeatability of the developed methods Our proposed methods have been successfully utilized for trace element analysis in environmental and food samples.

A Rapid and Facile Detection for Specific Small-Sized Amino Acids Based on Target-Triggered Destruction of Metal Organic Frameworks.

Most of the reported metal organic frameworks (MOFs)-based DNA sensors were developed by utilizing the different adsorption capacities of MOFs to different structural DNAs (for example, single-stranded DNAs (ssDNAs) and double-stranded DNAs (dsDNAs)) or ssDNAs with different lengths. Herein, we introduced another strategy for the design of MOFs-based biosensing platforms. We found that specific small-sized amino acids (for example, glycine and serine) could lead to the destruction of the MOFs formed by [Cu(mal)(bpy)]·2H2O], thus recovering the fluorescence of a fluorophore-labeled ssDNA that had been quenched by MOFs. The corresponding working mechanism was discussed. On the basis of this finding, a mix-and-detect fluorescence method was designed for the turn-on detection of specific small-sized amino acids. The feasibility of its use in real serum samples was also demonstrated. Besides biosensing applications, the discovery of amino acids-triggered destruction of MOFs can also enrich the building blocks of molecular logic gate. As an example, a biomolecular logic gate that performs OR logic operation was constructed using glycine and a DNA strand as inputs.