Oxidative Nickel-Catalyzed <i>ortho</i>-C–H Amination of (Iso)quinolines with Alicyclic Amines Directed by a Sacrificial <i>N</i>‑Oxide Group

Transition metal (TM)-catalyzed direct amination of C–H bonds on free or fused pyridine (Py) rings with free amines still remains scarce because amines and the Py ring tend to adopt a nonproductive N-bound coordination with many TMs, leading to a significant decrease of catalytic reactivity. We herein disclose a nickel-catalyzed and a sacrificial N-oxide group directed oxidative coupling of (iso)quinolyl C–H bonds and alicyclic amines, which furnishes bioimportant amino(iso)quinolines efficiently and selectively in a single step. Noteworthy, this protocol avoids the use of aggressive reactants and very strong bases usually required when aminating on nonoxidized Py rings

Multi-objective optimisation of process parameters for laser-based directed energy deposition of a mixture of H13 and M2 steel powders on 4Cr5Mo2SiV1 steel

In present paper, a universal method for multi-objective parameter optimisation of additive manufacturing processes was proposed and successfully applied to laser-based directed energy deposition (DED) experiments with mixtures of H13 and M2 steel powders that were deposited on 4Cr5Mo2SiV1 hot work die steel. The DED experiments were designed and completed based on the response surface method with 13 groups of laser parameters. The microstructure of the deposited alloy steel was observed and its mechanical properties were tested. The deposited steel alloy achieved an ultimate tensile strength (UTS) of 1821 ± 30 MPa with a reasonable elongation of approximately 4.5%, and the bond strength specimens achieved a bond toughness of ∼10.66% with a moderate UTS (1329 ± 28 MPa). A multi-objective optimisation method was proposed based on response surfaces which were established according to microstructural characteristics and mechanical properties data. It provided a basis for achieving high strength or high toughness DED-fabricated steel alloys.</p

Oxidative Nickel-Catalyzed <i>ortho</i>-C–H Amination of (Iso)quinolines with Alicyclic Amines Directed by a Sacrificial <i>N</i>‑Oxide Group

Transition metal (TM)-catalyzed direct amination of C–H bonds on free or fused pyridine (Py) rings with free amines still remains scarce because amines and the Py ring tend to adopt a nonproductive N-bound coordination with many TMs, leading to a significant decrease of catalytic reactivity. We herein disclose a nickel-catalyzed and a sacrificial N-oxide group directed oxidative coupling of (iso)quinolyl C–H bonds and alicyclic amines, which furnishes bioimportant amino(iso)quinolines efficiently and selectively in a single step. Noteworthy, this protocol avoids the use of aggressive reactants and very strong bases usually required when aminating on nonoxidized Py rings

Copper Nanoparticle/N-Doped Ti₃C₂T_<i>x</i> MXene Hybrids with Enhanced Peroxidase-like Activity for Colorimetric Glucose Sensing

As a low-cost support, MXenes have attracted more and more attention in developing nanoenzymes with enhanced peroxidase- or oxidase-like activity. In this paper, we report a simple way to synthesize a N-doped Ti3C2Tx MXene, which provides a support platform for developing MXene-based nanozymes with an attractive structure and performance. By anchoring copper nanoparticles on N-doped Ti3C2Tx Cu nanoparticles, Cu nanoparticles (NPs)/N-doped Ti3C2Tx with satisfactory structural stability was prepared, displaying a synergistic effect and enhanced peroxidase-like activity. The superior peroxidase-like activity was confirmed by the oxidation kinetics of 3,3′,5,5′-tetramethylbenzidine (TMB) and density functional theory calculations. The characteristics of peroxidase-like nanozymes have promoted the development of colorimetric biosensors to evaluate the performance of Cu NPs/N-doped Ti3C2Tx. As expected, the nanozyme exhibits gratifying sensitivity, high selectivity, a low detection limit of 5 μM, and practicability in the detection of serum samples. Remarkably, the Cu NPs/N-doped Ti3C2Tx has remarkable stability and maintains its peroxidase-like activity after 1 month of storage. This work has laid a solid foundation for guiding the design of metal NPs/nonmetal-doped MXenes with outstanding peroxidase-like activity and expanding their application in biosensors

Colorimetric Signal Amplification Assay for Mercury Ions Based on the Catalysis of Gold Amalgam

Mercury is a major threat to the environment and to human health. It is highly desirable to develop a user-friendly kit for on-site mercury detection. Such a method must be able to detect mercury below the threshold levels (10 nM) for drinking water defined by the U.S. Environmental Protection Agency. Herein, we for the first time reported catalytically active gold amalgam-based reaction between 4-nitrophenol and NaBH₄ with colorimetric sensing function. We take advantage of the correlation between the catalytic properties and the surface area of gold amalgam, which is proportional to the amount of the gold nanoparticle (AuNP)-bound Hg²⁺. As the concentration of Hg²⁺ increases until the saturation of Hg onto the AuNPs, the catalytic performance of the gold amalgam is much stronger due to the formation of gold amalgam and the increase of the nanoparticle surface area, leading to the decrease of the reduction time of 4-nitrophenol for the color change. This sensing system exhibits excellent selectivity and ultrahigh sensitivity up to the 1.45 nM detection limit. The practical use of this system for Hg²⁺ determination in tap water samples is also demonstrated successfully

Conformation Restriction of Nonplanar Di-2-pyrimidyl Sulfide with Intramolecular N···C Interaction and Its Supramolecular Silver(I) Complexes

A series of silver­(I) complexes with semirigid di-2-pyrimidyl sulfide (DprS), namely, {[Ag₂(DprS)₂(CF₃CO₂)]­(CF₃CO₂)·2H₂O}_∞ (<b>1</b>), {[Ag₆(DprS)₆(CF₃SO₃)₅]­(CF₃SO₃)·3.5H₂O}_∞ (<b>2</b>), {[Ag₂(DprS)­(C₂F₅CO₂)₂]}_∞ (<b>3</b>), [Ag­(DprS)­(NO₃)_∞ (<b>4</b>), and {[Ag₃(DprS)₃]­(ClO₄)₃}_∞ (<b>5</b>), have been synthesized and characterized by single-crystal X-ray analysis. The silver­(I) complexes <b>1</b>–<b>2</b> and <b>4</b>–<b>5</b> exhibit one-dimensional tape-like coordination polymers with different topological structures, while complex <b>3</b> has a two-dimensional coordination network. In these complexes, the two pyrimidyl rings of each DprS are almost in an orthogonal orientation, a rigid nonplanar conformation, and the multidentate ligand adopts an unvaried <i>N</i>,<i>N′</i>,<i>N″</i>-μ₃ ligation mode despite the different anions (CH₃COO^– in <b>1</b>, CF₃SO₃^– in <b>2</b>, C₂F₅COO^– in <b>3</b>, NO₃^– in <b>4</b>, and ClO₄^– in <b>5</b>). Attractive intramolecular N_pyrimidyl···C_pyrimidyl interaction between a 1-positional N atom of one pyrimidyl ring and an electrophilic 2-positional C atom of the other ring of DprS is a common dominant interaction, which drives and stabilizes the nonplanar ligand conformation in these crystalline structures. Calculation through the self-consistent field crystal orbital method based on density functional theory indicates the presence of the N···C contact, a nucleophile–electrophile affinity. Unconventional anion−π_pyrimidyl interactions engaged in the construction of the supramolecular architectures of <b>1</b>–<b>5</b> also are presented and discussed

Conformation Restriction of Nonplanar Di-2-pyrimidyl Sulfide with Intramolecular N···C Interaction and Its Supramolecular Silver(I) Complexes

A series of silver­(I) complexes with semirigid di-2-pyrimidyl sulfide (DprS), namely, {[Ag₂(DprS)₂(CF₃CO₂)]­(CF₃CO₂)·2H₂O}_∞ (<b>1</b>), {[Ag₆(DprS)₆(CF₃SO₃)₅]­(CF₃SO₃)·3.5H₂O}_∞ (<b>2</b>), {[Ag₂(DprS)­(C₂F₅CO₂)₂]}_∞ (<b>3</b>), [Ag­(DprS)­(NO₃)_∞ (<b>4</b>), and {[Ag₃(DprS)₃]­(ClO₄)₃}_∞ (<b>5</b>), have been synthesized and characterized by single-crystal X-ray analysis. The silver­(I) complexes <b>1</b>–<b>2</b> and <b>4</b>–<b>5</b> exhibit one-dimensional tape-like coordination polymers with different topological structures, while complex <b>3</b> has a two-dimensional coordination network. In these complexes, the two pyrimidyl rings of each DprS are almost in an orthogonal orientation, a rigid nonplanar conformation, and the multidentate ligand adopts an unvaried <i>N</i>,<i>N′</i>,<i>N″</i>-μ₃ ligation mode despite the different anions (CH₃COO^– in <b>1</b>, CF₃SO₃^– in <b>2</b>, C₂F₅COO^– in <b>3</b>, NO₃^– in <b>4</b>, and ClO₄^– in <b>5</b>). Attractive intramolecular N_pyrimidyl···C_pyrimidyl interaction between a 1-positional N atom of one pyrimidyl ring and an electrophilic 2-positional C atom of the other ring of DprS is a common dominant interaction, which drives and stabilizes the nonplanar ligand conformation in these crystalline structures. Calculation through the self-consistent field crystal orbital method based on density functional theory indicates the presence of the N···C contact, a nucleophile–electrophile affinity. Unconventional anion−π_pyrimidyl interactions engaged in the construction of the supramolecular architectures of <b>1</b>–<b>5</b> also are presented and discussed

MOESM1 of Ligase IV inhibitor SCR7 enhances gene editing directed by CRISPR–Cas9 and ssODN in human cancer cells

Additional file 1: Figure S1. A schematic illustration for constructing a Cas9, eGFP and gRNA co-expression vector. Figure S2. Determination of insertion repair efficiency at AAVS1 locus by DNA sequencing. Panel A shows a representative DNA sequencing of a TA clone without a mutation induced by Cas9 and insertion repair at the AAVS1 locus. The Cas9 targeted site of the AAVS1 locus is underlined. Panel B shows a representative DNA sequencing that confirms the incorporation of an ssODN-harbored EcoRI site at the targeted position of the AAVS1 locus. The EcoRI site is underlined. Panel C shows a representative DNA sequencing of a TA clone with NHEJ, but without insertion repair at the AAVS1 locus. The mutation sequences induced by Cas9 are underlined. Figure S3. The generation and validation of a GFP-silent mutation lentivirus vector and MCF-7/GFP-Mut cells. Panel A shows part of the GFP ORF with a premature termination codon, tGA, through a replacement of two nucleotides by GA in the sequence (GFP-Mut). Panel B shows a representative fluorescence image of 293T cells used for the package of lentivirus by co-transfecting the pSIN-EF1-GFP-Mut-Puromycin (left) or GFP-Wild type control (right) lentivirus vector together with auxiliary plasmids pSPAX2 and pMD2.G. Forty-eight hours after transfection, the supernatants were collected and the transfected 293T cells were examined by fluorescence microscope (5×). Fluorescence signal is undetectable in 293T cells transfected with GFP-Mut vector (left). Panel C shows that the replacement of two nucleotides, ac, in the wild-type, by GA leads to a formation of a termination codon tGA and a change in the PAM sequence. Panel D shows a representative gel image of T7E1 cleavage assay of disruption efficiency in MCF-7/GFP-Mut cells transfected by Cas9 and GFP-Mut sgRNA. Figure S4. Schematic diagrams for DNA sequencing of single cell-derived clones. Single GFP+ cell-derived clones were used to analyze homology-directed repair (HDR) and to evaluate the mutation-corrected rate. Genomic DNA from cell clones was PCR amplified, and the PCR products were sequenced directly. Representative DNA sequencing of cell clones are: Panel A – control HCT-116 cells; Panel B – gene mutation corrected cells; Panel C – cells with HDR but without mutation correction; and Panel D – cells without HDR. Table S1. PCR primers and oligonucleotides used for cloning sgRNA expression vector, HDR-mediated repair and Cas9 target sites

Hydrogenation of Carbon Dioxide Using Half-Sandwich Cobalt, Rhodium, and Iridium Complexes: DFT Study on the Mechanism and Metal Effect

The hydrogenation of carbon dioxide catalyzed by half-sandwich transition metal complexes (M = Co, Rh, and Ir) was studied systematically through density functional theory calculations. All metal complexes are found to process a similar mechanism, which involves two main steps, the heterolytic cleavage of H₂ and the hydride transfer. The heterolytic cleavage of H₂ is the rate-determining step. The comparison of three catalytic systems suggests that the Ir catalyst has the lowest activation free energy (13.4 kcal/mol). In contrast, Rh (14.2 kcal/mol) and Co (18.3 kcal/mol) catalysts have to overcome relatively higher free energy barriers. The different catalytic efficiency of Co, Rh, and Ir is attributed to the back-donation ability of different metal centers, which significantly affects the H₂ heterolytic cleavage. The highest activity of an iridium catalyst is attributed to its strong back-donation ability, which is described quantitatively by the second order perturbation theory analysis. Our study indicates that the functional group of the catalyst plays versatile roles on the catalytic cycle to facilitate the reaction. It acts as a base (deprotonated) to assist the heterolytic cleavage of H₂. On the other hand, during the hydride transfer, it can also serve as Brønsted acid (protonated) to lower the LUMO of CO₂. This ligand assisted pathway is more favorable than the direct attack of hydride to CO₂. These finds highlight that the unique features of the metal center and the functional ligands are crucial for the catalyst design in the hydrogenation of carbon dioxide