Latest ArticlesUnnatural amino acids (UAAs) have broad applications in pharmaceutical sciences and biological studies. Current synthetic methods for UAAs mainly rely on asymmetric catalysis and often require several steps. There is a lack of direct and simple methods. To address this challenge, we designed the LADA (labeling-activation-desulfurization-addition) strategy: selective labeling and activation of cysteine residues, the photocatalytic desulfurization and the subsequent radical addition to alkenes. Although composed of two steps, it is one-pot synthesis and has advantages such as high functional group tolerance, biocompatible reaction condition, and retained stereochemistry. This highly efficient strategy was successfully applied in the direct synthesis of unnatural amino acids and modifications of peptides with more than 50 examples.
DNA circuits are powerful tools in various applications such as logical computation, molecular diagnosis and synthetic biology. Leakage is a major problem in constructing complex DNA circuits. It directly affects the output signal and harms the circuit's performance significantly. In the traditional DNA circuits, the gate complex is a duplex structure. There are insufficient energy barriers to prevent spontaneous detachment of strands, resulting in a leak prone. Herein, we have developed triplex-structure based DNA circuit with ultra-low leakage and high signal-to-noise ratio (SNR). The triplex structure improves the stability in the absence of input. At the same time, the driving force of the strand displacement cascades reduces the influence of the triplex structure on the desired reaction. The SNR of the DNA circuit was increased to 695, while the desired reaction rate remained 90% of the conventional translator circuit. The triplex-structure mediated leakage prevention strategy was further tested at different temperatures and in DNA translator and seesaw circuits. We also constructed modular basic logic gates with a high efficiency and low leakage. On this basis, we further constructed triplex-structure based tertiary DNA logic circuits, and the SNR reached 295, which, to the best of our knowledge, was among the highest of the field. We believe that our scheme provides a novel, valid, and general tool for reducing leakages, and we anticipate that it will be widely adopted in DNA nanotechnology.
Implantable system maximizes drug concentration and continuously releases drugs near the tumor, which is an effective tool to solve the difficult retention of chemotherapy drugs in bladder cancer. In this work, a novel polysaccharide supramolecular injectable hydrogel (CCA hydrogels for short) is rapidly constructed by simply mixing cationic chitosan, anionic sulfobutyl ether β-cyclodextrin (SBE-β-CD) and a trace amount of silver ions. The injected hydrogel reconstituted and regained its shape in less than 1 h, and it can still maintain the elasticity suitable for the human body. By packaging the drug directly, the gel achieves a high concentration of doxorubicin, an anticancer drug. Using MB49-luc cells as the model of bladder tumor for anti-tumor in vivo, the CCA-DOX gel has obvious inhibitory effect on bladder tumor, and its inhibitory effect is much greater than that of free DOX. Therefore, this self-healing injectable hydrogel has great potential for in situ treatment of bladder cancer.
A new strategy to induce vesicle fusion has been developed by employing pillar[5]arene derivatives that were channel-like and were prepared by appending side chains onto pillar[5]arenes backbones. The channels feature with hydrophilic negatively and positively charged groups at both ends and hydrophobic Trp residues at the outer surface, which endows the channels with amphiphilicity. The zwitterionic amphiphilic channels could spontaneously incorporate into the bilayer membranes of lipid vesicles to induce vesicle fusion driven by the electrostatic interactions between negatively charged and positively charged groups.
Fast Fe(Ⅲ)/Fe(Ⅱ) circulation in heterogeneous peroxymonosulfate (PMS) activation remains as a bottleneck issue that restricts the development of PMS based advanced oxidation processes. Herein, we proposed a facile ammonia reduction strategy and synthesized a novel FeVO3-x catalysts to activate PMS for the degradation of a typical pharmaceutical, carbamazepine (CBZ). Rapid CBZ removal could be achieved within 10 min, which outperforms most of the other iron or vanadium-based catalysts. Electron paramagnetic resonance analysis and chemical probe experiments revealed SO4•−, •OH, O2•− and high valent iron (Fe(Ⅳ)) were all generated in this system, but SO4•− and Fe(Ⅳ) primarily contributed to the degradation of CBZ. Besides, X-ray photoelectron spectroscopy and X-ray adsorption spectroscopy indicated that both the generated low-valent V provides and oxygen vacancy acted as superior electron donors and accelerated internal electron transfer via the unsaturated V−O−Fe bond. Finally, the proposed system also exhibited satisfactory performance in practical applications. This work provides a promising platform in heterogeneous PMS activation.
Metastable molybdenum carbide (α-MoC), as a catalyst and an excellent support for metal catalysts, has been widely used in thermo/electro-catalytic reactions. However, the selective synthesis of α-MoC remains a great challenge. Herein, a simple one-pot synthetic strategy for the selective preparation of metastable α-MoC is proposed by electrochemical co-reduction of CO2 and MoO3 in a low-temperature eutectic molten carbonate. The synthesized α-MoC shows a reed flower-like morphology. By controlling the electrolysis time and monitoring the phase and morphology of the obtained products, the growth process of α-MoC is revealed, where the carbon matrix is deposited first followed by the growth of α-MoC from the carbon matrix. Moreover, by analyzing the composition of the electrolytic products, the formation mechanism for α-MoC is proposed. In addition, through this one-pot synthetic strategy, S-doped α-MoC is successfully synthesized. Density functional theory (DFT) calculations reveal that S doping enhanced the HER performance of α-MoC by facilitating water absorption and dissociation and weakening the bond energy of Mo-H to accelerate H desorption. The present work not only highlights the valuable utilization of CO2 but also offers a new perspective on the design and controllable synthesis of metal carbides and their derivatives.
Early diagnosis and treatment of cancer requires the development of tools that are both sensitive and selective in detecting spermine. In this study, we presented a "supramolecular cyclization-induced emission enhancement" strategy for the sensitive and selective detection of spermine. A new pillar[5]arene probe (P1) demonstrated excellent solution/solid dual-state emission properties, and the addition of certain spermine (Spm) resulted in fluorescence enhancement due to the synergy of multiple weak interactions that restricted the free motion of P1 in the P1⊃Spm complex. This mechanism was further confirmed by time-resolved spectroscopy, DFT calculations, and IGM analysis. With its low limit of detection and high selectivity, P1 is a promising tool for measuring spermine in artificial urine samples.
Photocatalytic and photoinduced silyl radicals cascade cyclization procedures for the green and simple preparation of fused tetracyclic skeleton silylated indolo[2,1-a]isoquinoline-6(5H)-ones from 2-aryl-N-acryloyl indoles with hydrosilanes are developed. The photocatalytic reaction is carried out with 9,10-dicyanoanthracene (DCA) as an organophotocatalyst and 3-acetoxyquinuclidine as hydrogen atom transfer (HAT) catalyst at room temperature under metal- and oxidant-free conditions. The keys to the success of photoredox-catalytic conversion include (1) the reductive quenching of DCA* [E1/2(*P/P–) = +1.97 V vs. SCE in MeCN] by 3-acetoxyquinuclidine (Ep = +1.22 V vs. SCE in MeCN), and (2) the thermodynamic feasibility of hydrogen atom abstraction from hydridic Si–H bond by electrophilic N+•. Particularly, the simple photoinduced cascade cyclization using (TMS)3SiH with 2-aryl-N-acryloyl indoles was exploited via an electron−donor−acceptor (EDA) complex under visible light irradiation.
N-formylation of amines, a class of synthetically important reactions, is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency. Here, an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine, which achieved a reaction yield of 82.97% and a selectivity of > 99% at 12 min using cheap organic dye photocatalyst under mild reaction conditions. The influence of essential parameters, including light intensity, temperature and equivalents of the gas, additive and photocatalyst, on the reaction yield was systematically studied. Furthermore, kinetic investigations were conducted, exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity, temperature and photocatalyst equivalent. The microflow photocatalytic approach established in this work, which realized a markedly higher space-time yield than the conventional batch method (37.9 vs. 0.212 mmol h−1 L−1), paves the way for the continuous, green and efficient synthesis of N-formamides.
Herein, two antimony sulfates, named RbSb(SO4)2 (1) and CsSb(SO4)2 (2), have been successfully synthesized with the introduction of Sb3+ cation with stereochemically active lone pairs (SCALP) into sulfates by the conventional hydrothermal method. Both two compounds endow short ultraviolet (UV) absorption edges (281 nm and 278 nm, respectively) and large birefringence (0.171@546 nm and 0.174@546 nm, respectively), which means that they are promising short-wave UV optical materials. Interestingly, though both of the two compounds exhibit similar 1D chained structures, and possess the same functional moieties including SbO4 seesaws and SO4 tetrahedral groups, they exhibit significantly opposite macroscopic symmetries, i.e., compound 1 crystallizes in a centrosymmetric (CS) manner (P21/n) and compound 2 in a noncentrosymmetric (NCS) manner (P212121), due to the size of cations [r(Rb+) = 1.56 Å, r(Cs+) = 1.67 Å] affects the orientation of SCALP of the adjacent Sb3+.
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