A versatile route to fabricate single atom catalysts with high chemoselectivity

Preparation of single atom catalysts (SACs) is of broad interest to materials scientists and chemists but remains a formidable challenge. Herein, we develop an efficient approach to synthesize SACs via a precursor-dilution strategy, in which metalloporphyrin (MTPP) with target metals are co-polymerized with diluents (tetraphenylporphyrin, TPP), followed by pyrolysis to N-doped porous carbon supported SACs (M1/N-C). Twenty-four different SACs, including noble metals and non-noble metals, are successfully prepared. In addition, the synthesis of a series of catalysts with different surface atom densities, bi-metallic sites, and metal aggregation states are achieved. This approach shows remarkable adjustability and generality, providing sufficient freedom to design catalysts at atomic-scale and explore the unique catalytic properties of SACs. As an example, we show that the prepared Pt1/N-C exhibits superior chemoselectivity and regioselectivity in hydrogenation. It only converts terminal alkynes to alkenes while keeping other reducible functional groups such as alkenyl, nitro group, and even internal alkyne intact

TLR3 Ligand PolyI:C Prevents Acute Pancreatitis Through the Interferon-β/Interferon-α/β Receptor Signaling Pathway in a Caerulein-Induced Pancreatitis Mouse Model

Acute pancreatitis (AP) is a common and devastating inflammatory disorder of the pancreas. However, there are still no effective treatments available for the disease. Therefore, it is important to discover new therapeutic targets and strategies for better treatment and prognosis of AP patients. Toll-like receptor 3 (TLR3) ligand polyI:C is a double-stranded RNA mimic that can be used as an immune stimulant. Our current study indicates that polyI:C exerted excellent anti-inflammatory effects in a caerulein-induced AP mouse model and taurocholate-induced pancreatic acinar cell line injury model. We found that polyI:C triggers type I interferon (IFN) production and downstream IFN-α/β receptor (IFNAR)-dependent signaling, which play key roles in protecting the pancreas from inflammatory injury. Knockout of IFN-β and IFNAR in mice abolished the preventive effects of polyI:C on caerulein-induced AP symptoms, which include pancreatic edema, neutrophil infiltration, the accumulation of reactive oxygen species (ROS), and inflammatory gene expression. Treating pancreatic acinar 266-6 cells with an IFNAR inhibitor, which blocks the interaction between type I IFN and IFNAR, diminishes the downregulation of oxidative stress by polyI:C. Additionally, a subsequent transcriptome analysis on the role of polyI:C in treating pancreatitis suggested that chemotaxis of neutrophils and the production of ROS were inhibited by polyI:C in the pancreases damaged by caerulein injection. Thus, polyI:C may act as a type I IFN inducer to alleviate AP, and it has the potential to be a promising therapeutic agent used at the early stages of AP

WT1 Recruits TET2 to Regulate Its Target Gene Expression and Suppress Leukemia Cell Proliferation

The TET2 DNA dioxygenase regulates cell identity and suppresses tumorigenesis by modulating DNA methylation and expression of a large number of genes. How TET2, like most other chromatin modifying enzymes, is recruited to specific genomic sites is unknown. Here we report that WT1, a sequence-specific transcription factor, is mutated in a mutually exclusive manner with TET2, IDH1 and IDH2 in acute myeloid leukemia (AML). WT1 physically interacts with and recruits TET2 to its target genes to activate their expression. The interaction between WT1 and TET2 is disrupted by multiple AML-derived TET2 mutations. TET2 suppresses leukemia cell proliferation and colony formation in a manner dependent on WT1. These results provide a mechanism for targeting TET2 to specific DNA sequence in the genome. Our results also provide an explanation for the mutual exclusivity of WT1 and TET2 mutations in AML and suggest an IDH1/2-TET2-WT1 pathway in suppressing AML

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Charge and energy transfer in binaphthalene molecule with two spiropyran units used for chiral molecular switches and logic gates

A new binaphthalene molecule with two spiropyran units used for chiral molecular switches and logic gates was synthesized and chaxacterized.(12) In this paper, charge and energy transfer in binaphthalene molecule with two spiropyran units are theoretically investigated with quantum chemistry method, as well as 2D and 3D real space analysis methods, since molecule construction with photoinduced electron transfer or charge transfer is one of the most frequently used pathways for building useful sensors and molecular machines. The orientation and strength of transition dipole moment in absorption spectra are obtained by 3D transition density. The orientation and results of intramolecular charge transfer on the excitation are obtained with 3D charge difference densities. The electron-hole coherence and excitation delocalization in absorption spectra are investigated with 2D contour plots of transition density matrix. Overall, the computed results remain in good agreement with the relevant experimental data, and the theoretical results reveal the relationship between the function of sensor and the excited state properties of the structure and transformation of the compound, upon addition of acid and base in absorption spectra

Nonlinear optical microscopies (NOMs) and plasmon-enhanced NOMs for biology and 2D materials

In this review, we focus on the summary of nonlinear optical microscopies (NOMs), which are stimulated Raman scattering (SRS), coherent anti-Stokes Raman scattering (CARS), second harmonic generation (SHG), and two-photon excited fluorescence (TPEF). The introduction is divided into two parts: the principle of SRS, CARS, TPEF, and SHG and their application to biology and two-dimensional materials. We also introduce the connections and differences between them. We also discuss the principle of plasmon-enhanced NOM and its application in the above two aspects. This paper not only summarizes the research progress in the frontier but also deepens the readers’ understanding of the physical principles of these NOMs

Intermolecular charge and energy transfer in neurosporene and chlorophyll a derivative complex

Dye-sensitized solar cells using a chlorophyll a derivative (PPB a der.) as the sensitizer and carotenoids having different conjugation lengths as redox spacers was studied experimentally. In this Letter, the excited state properties of the neurosporene & PPB a der. complex are investigated theoretically with quantum chemistry method. The 2D real space analysis with the transition density matrix reveals that some excited states are locally excited states, and some is the intermolecular charge transfer (ICT) state. The 3D real space analysis reveals: (1) that the orientation and the strength of the dipole moment from transition density, and (2) the orientation and result of ICT in Neurosporene & PPB a der. complex from charge difference density. (c) 2005 Elsevier B.V. All rights reserved

Excited state properties of acceptor-substitute carotenoids: 2D and 3D real-space analysis

Excited state properties of three (neutral, weak and strong) acceptor-substitute carotenoids (beta-carotene) are studied theoretically with the methods of two-dimensional (2D) and three-dimensional (3D) real-space analysis. The influences of different (neutral, weak and strong) function groups attached to the polyene chain to the excited state property of the carotenoids are discussed. By the 3D real-space analysis, the charge and energy transfer of the three acceptor-substitute carotenoids after vertical absorption are studied with the transition density and charge difference density. By the 2D real-space analysis, the electron-hole coherences and excitation delocalization of the three acceptor-substitute carotenoids are studied with the transition density matrix. (C) 2004 Elsevier B.V. All rights reserved

Intramolecular charge transfer and locally excited states of the fullerene-linked quarter-thiophenes dyad

The ground and the excited state properties of the fullerene-linked quarter-thiophenes dyad were studied theoretically with the quantum chemistry method. To reveal the excited state properties of them in the vertical absorption process, the energies and densities of the HOMO and LUMO, the intramolecular charge transfer (ICT), locally excited (LE) are studied with transition density matrix, charge difference density and the off-resonant and resonant non-linear polarizabilities. The conclusion is drawn that there are also some intramolecular charge transfer (ICT) excited states, which result from large data of off-resonant and the resonant nonlinear polarizabilities in the vertical absorption process. (c) 2005 Elsevier B.V. All rights reserved