Multiple ligand detection and affinity measurement by ultrafiltration and mass spectrometry analysis applied to fragment mixture screening

Binding affinity of a small molecule drug candidate to a therapeutically relevant biomolecular target is regarded the first determinant of the candidate's efficacy. Although the ultrafiltration-LC/MS (UF-LC/MS) assay enables efficient ligand discovery for a specific target from a mixed pool of compounds, most previous analysis allowed for relative affinity ranking of different ligands. Moreover, the reliability of affinity measurement for multiple ligands with UF-LC/MS has hardly been strictly evaluated. In this study, we examined the accuracy of K_d determination through UF-LC/MS by comparison with classical ITC measurement. A single-point K_d calculation method was found to be suitable for affinity measurement of multiple ligands bound to the same target when binding competition is minimized. A second workflow based on analysis of the unbound fraction of compounds was then developed, which simplified sample preparation as well as warranted reliable ligand discovery. The new workflow implemented in a fragment mixture screen afforded rapid and sensitive detection of low-affinity ligands selectively bound to the RNA polymerase NS5B of hepatitis C virus. More importantly, ligand identification and affinity measurement for mixture-based fragment screens by UF-LC/MS were in good accordance with single ligand evaluation by conventional SPR analysis. This new approach is expected to become a valuable addition to the arsenal of high-throughput screening techniques for fragment-based drug discovery.     

定碳定硫分析仪检定规程的探讨和修订建议

JJG 395–1997《定碳定硫分析仪检定规程》中的部分技术要求和检定项目已不能满足现代碳硫分析仪器检定/校准的要求。对规程的适用性、称量稳定性、示值误差、标准物质、重复性、分析时间等进行了探讨,并给出了修订建议。探讨了评定仪器检测空白的可能性,提出了依据碳硫测定基准国标方法的仪器检定/校准方法,以评定不同用途的测试仪器,并扩展了仪器检定/校准的范围。为计量部门修订规程提供参考,同时也为实验室合理评价,验收碳硫分析仪,及时掌握仪器的运行状况,保证分析数据的准确性、一致性和溯源性提供借鉴。     

Silver‐Catalyzed Cross‐Coupling of Isocyanides and Active Methylene Compounds by a Radical Process

Isocyanides are versatile building blocks, and have been extensively exploited in C? H functionalization reactions. However, transition‐metal‐catalyzed direct C? H functionalization reactions with isocyanides suffer from over‐insertion of isocyanides. Reported herein is a radical coupling/isomerization strategy for the cross‐coupling of isocyanides with active methylene compounds through silver‐catalysis. The method solves the over‐insertion issue and affords a variety of otherwise difficult to synthesize β‐aminoenones and tricarbonylmethanes under base‐ and ligand‐free conditions. This report presents a new fundamental C? C bond‐forming reaction of two basic chemicals.     

溴代二噁英的分析方法研究进展

溴代二噁英（PBDD/Fs）属于潜在的持久性有机污染物,是一种平面三环芳香化合物,具有致畸、致癌、致突变等特性。目前,对PBDD/Fs的分析检测的研究是一大热点,但国内研究较少。因此,探究PBDD/Fs的分析检测方法,对进一步控制PBDD/Fs污染具有重要科学意义。本文介绍了PBDD/Fs的特性及其分析方法,着重探讨了PBDD/Fs的提取、净化、仪器分析以及质量控制,以便了解当前溴代二噁英的分析检测水平,为后续开展溴代二噁英的分析检测提供方法参考。     

比较教学法在仪器分析实验教学中的应用

仪器分析实验是化学及相关专业的重要实验课程。结合课程特点和培养目标,提出了将比较教学法融入课堂的教学方法,指出了意义和作用,介绍了教学中开展比较教学的实践与应用。该方法加强了学生对仪器功能特点的掌握,激发其实验兴趣和创新精神,学生的认知能力在比较过程中不断建构、丰富、提高和发展,取得了较好的效果。     

Halide-directed Assembly of Mercury(II) Coordination Polymers for Electrochemical Biosensing Toward Penicillin

Three 1D/2D Hg^II coordination polymers (CPs), namely {[Hg₃(L)₂Cl₆](H₂O)}_n ( 1 ), [Hg(L)Br₂]_n ( 2 ), and [Hg(L)I₂]_n ( 3 ) were prepared by assembly of 3,4-bis(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L) with different inorganic Hg^II salts (i.e. HgCl₂, HgBr₂ or HgI₂). Single-crystal X-ray diffraction analysis reveals two types of bimetallic subunits [(Hg)₂C₆N₄] and [(Hg)₂C₁₂N₆] in CP 1 , which are further extended to a 2D coordination network. Both of CPs 2 and 3 show 1D zigzag arrays bridged by L ligands. Notably, the L ligands take the (η⁴, μ₄) coordination fashion in 1 but (η², μ₂) binding mode in 2 and 3 . The structural differences of CPs 1 – 3 indicate that the L ligand can adjust its coordination fashions to meet the requirements of Hg^II centers, relying on the presence of distinct halide anions. In addition, 1 can be applied to fabricate an electrochemical biosensor for the detection of penicillin.     

Photoactivated Fluorescence Enhancement in F,N-Doped Carbon Dots with Piezochromic Behavior

Photoactivation in CdSe/ZnS quantum dots (QDs) on UV/Vis light exposure improves photoluminescence (PL) and photostability. However, it was not observed in fluorescent carbon quantum dots (CDs). Now, photoactivated fluorescence enhancement in fluorine and nitrogen co-doped carbon dots (F,N-doped CDs) is presented. At 1.0 atm, the fluorescence intensity of F,N-doped CDs increases with UV light irradiation (5 s–30 min), accompanied with a blue-shift of the fluorescence emission from 586 nm to 550 nm. F,N-doped CDs exhibit photoactivated fluorescence enhancement when exposed to UV under high pressure (0.1 GPa). F,N-doped CDs show reversible piezochromic behavior while applying increasing pressure (1.0 atm to 9.98 GPa), showing a pressure-triggered aggregation-induced emission in the range 1.0 atm–0.65 GPa. The photoactivated CDs with piezochromic fluorescence enhancement broadens the versatility of CDs from ambient to high-pressure conditions and enhances their anti-photobleaching.     

Direct Observation of Dynamic Bond Evolution in Single-Atom Pt/C3N4 Catalysts

Single-atom catalysts are promising platforms for heterogeneous catalysis, especially for clean energy conversion, storage, and utilization. Although great efforts have been made to examine the bonding and oxidation state of single-atom catalysts before and/or after catalytic reactions, when information about dynamic evolution is not sufficient, the underlying mechanisms are often overlooked. Herein, we report the direct observation of the charge transfer and bond evolution of a single-atom Pt/C₃N₄ catalyst in photocatalytic water splitting by synchronous illumination X-ray photoelectron spectroscopy. Specifically, under light excitation, we observed Pt−N bond cleavage to form a Pt⁰ species and the corresponding C=N bond reconstruction; these features could not be detected on the metallic platinum-decorated C₃N₄ catalyst. As expected, H₂ production activity (14.7 mmol h⁻¹ g⁻¹) was enhanced significantly with the single-atom Pt/C₃N₄ catalyst as compared to metallic Pt-C₃N₄ (0.74 mmol h⁻¹ g⁻¹).     

Unveiling the Activity and Stability Origin of BiVO4 Photoanodes with FeNi Oxyhydroxides for Oxygen Evolution

Understanding the origin of formation and active sites of oxygen evolution reaction (OER) cocatalysts is highly required for solar photoelectrochemical (PEC) devices that generate hydrogen efficiently from water. Herein, we employed a simple pH-modulated method for in situ growth of FeNi oxyhydroxide ultrathin layers on BiVO₄ photoanodes, resulting in one of the highest currently known PEC activities of 5.8 mA cm⁻² (1.23 V_RHE, AM 1.5 G) accompanied with an excellent stability. More importantly, both comparative experiments and density functional theory (DFT) studies clearly reveal that the selective formation of Bi−O−Fe interfacial bonds mainly contributes the enhanced OER activities, while the construction of V−O−Ni interfacial bonds effectively restrains the dissolution of V⁵⁺ ions and promotes the OER stability. Thereby, the synergy between iron and nickel of FeNi oxyhydroxides significantly improved the PEC water oxidation properties of BiVO₄ photoanodes.     

Infrared-induced temperature distributions of solid D2 ices

A specific-wavelength infrared (IR) light (λ=3140 nm) was irradiated into a solid D₂ ice prepared in a cylinder target cell. The temperature in the solid D₂ ice oscillated periodically with a high amplitude when irradiated by the IR light. The temperature oscillation has been well explained based on the two-dimensional heat transfer theory plus the IR-irradiation effect. The transmission optical imaging reveals that such a temperature oscillation is favorable to recrystallize the solid D₂ ice from multicrystal to quasi single crystal. This suggests an efficient method to layer the solid hydrogen-isotope ice for the inertial-confinement-fusion (ICF) experiments.