同位素稀释高效液相色谱-串联质谱法测定水体、底泥、鱼及虾中氯硝柳胺残留量

建立了水体、底泥、鱼体自然比例带皮肌肉和虾肌肉中氯硝柳胺(NIC)残留量测定的同位素稀释高效液相色谱-串联质谱(HPLC-MS/MS)法。水样经碱化后以乙酸乙酯提取,其他样品采用0.1%氨水乙腈提取,C_(18)粉进行样品净化。以乙腈-水为流动相,流速为0.3 mL/min,采用Thermo Hypersil Gold C_(18)(150 mm×2.1 mm,5μm)色谱柱进行分离,氯硝柳胺稳定同位素标记物(氯硝柳胺-~(13)C_6)为内标,选择反应监测(SRM)模式扫描,内标法定量。结果表明氯硝柳胺在0.2～200μg/L范围内呈良好线性关系,相关系数(r~2)不小于0.999 5。空白水样在2.5、25、250 ng/L加标水平下的平均回收率为90.5%～109%,相对标准偏差(RSD)为3.2%～11%,检出限(LOD)为1.0 ng/L,定量下限(LOQ)为2.5 ng/L;空白底泥、黄颡鱼自然比例带皮肌肉和克氏原螯虾肌肉在0.5、5.0、50μg/kg加标水平下的平均回收率分别为89.4%～113%、92.8%～110%和94.1%～107%,RSD分别为4.6%～12%、2.8%～11%和3.2%～9.3%,LOD均为0.2μg/kg,LOQ均为0.5μg/kg。该方法的灵敏度、准确度和选择性高,适用于实际水产养殖环境水体、底泥、鱼和虾中氯硝柳胺的残留分析。     

Deciphering an Abnormal Layered‐Tunnel Heterostructure Induced by Chemical Substitution for the Sodium Oxide Cathode

Demands for large‐scale energy storage systems have driven the development of layered transition‐metal oxide cathodes for room‐temperature rechargeable sodium ion batteries (SIBs). Now, an abnormal layered‐tunnel heterostructure Na_0.44Co_0.1Mn_0.9O₂ cathode material induced by chemical element substitution is reported. By virtue of beneficial synergistic effects, this layered‐tunnel electrode shows outstanding electrochemical performance in sodium half‐cell system and excellent compatibility with hard carbon anode in sodium full‐cell system. The underlying formation process, charge compensation mechanism, phase transition, and sodium‐ion storage electrochemistry are clearly articulated and confirmed through combined analyses of in situ high‐energy X‐ray diffraction and ex situ X‐ray absorption spectroscopy as well as operando X‐ray diffraction. This crystal structure engineering regulation strategy offers a future outlook into advanced cathode materials for SIBs.     

Tuning Internal Strain in Metal–Organic Frameworks via Vapor Phase Infiltration for CO2 Reduction

A gas‐phase approach to form Zn coordination sites on metal–organic frameworks (MOFs) by vapor‐phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution‐phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO₂ to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200–300 mV. Using element‐specific X‐ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square‐pyramidal geometry with four Zn?N bonds in the equatorial plane and one Zn‐OH₂ bond in the axial plane. The fine‐tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials.     

Visible‐Light Photocatalysis of Asymmetric [2+2] Cycloaddition in Cage‐Confined Nanospace Merging Chirality with Triplet‐State Photosensitization

Although the photodimerization of acenaphthylene (ACE) has been known for 100 years, the asymmetric cycloaddition of its 1‐substituted derivatives is unknown. Herein, we report a supramolecular photochirogenic approach in which a homochiral and photoactive Δ/Λ‐[Pd₆(RuL₃)₈]²⁸⁺ metal–organic cage (Δ/Λ‐MOC‐16) is used as a supramolecular reactor for the enantioselective exited‐state photocatalysis of 1‐Br‐ACE. Owing to preorganization of the substrates by the supramolecular cage, stereochemical control of the triplet state, and nanospace transfer of energy and chirality, the cycloaddition of ACE proceeded with high selectivity for the formation of anti over syn stereoisomers, whereas the regio‐, stereo‐, and enantioselective cycloaddition of unsymmetrical 1‐Br‐ACE showed effective enantiodifferentiation of a pair of anti head‐to‐head stereoisomers. The enzyme‐mimicking photocatalysis was verified by catalytic turnover, rate enhancement, and competing‐guest inhibition experiments.     

Sequence‐Dependent DNA Functionalization of Upconversion Nanoparticles and Their Programmable Assemblies

DNA‐modified lanthanide‐doped upconversion nanoparticles (DNA‐UCNPs) that combine the functions of DNA and the optical features of UCNPs have shown great promise in a wide range of fields. However, challenges remain in precisely tethering and orienting the DNA strands on the UCNP surface. Herein, we systematically investigate the sequence dependence of DNAs in their interactions with UCNPs, and reveal that poly‐cytosine (poly‐C) has high affinity for the UCNP surface. A general approach to synthesize monodispersed DNA‐UCNP conjugates is developed using poly‐C‐containing diblock DNA strands. The poly‐C segment of the DNA strand binds to the surfaces of UCNPs and the second segment is oriented perpendicularly on the UCNP surface, making the DNA‐UCNPs highly stable and monodispersed in aqueous solution. The dense layer of DNA on the UCNP surface enables the programmable assembly of UCNPs with other DNA‐functionalized nanoparticles or DNA origamis through hybridization, resulting in the formation of well‐organized complex structures.     

Three‐Pronged Attack by Homologous Far‐red/NIR AIEgens to Achieve 1+1+1>3 Synergistic Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has long been shown to be a powerful therapeutic modality for cancer. However, PDT is undiversified and has become stereotyped in recent years. Exploration of distinctive PDT methods is thus highly in demand but remains a severe challenge. Herein, an unprecedented 1+1+1>3 synergistic strategy is proposed and validated for the first time. Three homologous luminogens with aggregation‐induced emission (AIE) characteristics were rationally designed based on a simple backbone. Through slight structural tuning, these far‐red/near‐infrared AIE luminogens are capable of specifically anchoring to mitochondria, cell membrane, and lysosome, and effectively generating reactive oxygen species (ROS). Notably, biological studies demonstrated combined usage of three AIE photosensitizers gives multiple ROS sources simultaneously derived from several organelles, which gives superior therapeutic effect than that from a single organelle at the same photosensitizers concentration. This strategy is conceptually and operationally simple, providing an innovative approach and renewed awareness of improving therapeutic effect through three‐pronged PDT.     

Intracellular Entropy‐Driven Multi‐Bit DNA Computing for Tumor Progression Discrimination

Tumor progressions such as metastasis are complicated events that involve abnormal expression of different miRNAs and enzymes. Monitoring these biomolecules in live cells with computational DNA nanotechnology may enable discrimination of tumor progression via digital outputs. Herein, we report intracellular entropy‐driven multivalent DNA circuits to implement multi‐bit computing for simultaneous analysis of intracellular telomerase and microRNAs including miR‐21 and miR‐31. These three biomolecules can trigger respective DNA strand displacement recycling reactions for signal amplification. They are visualized by fluorescence imaging, and their signal outputs are encoded as multi‐bit binary codes for different cell types. The results can discriminate non‐tumorigenic, malignant and metastatic breast cells as well as respective tumors. This DNA computing circuit is further performed in a microfluidic chip to differentiate rare co‐cultured cells, which holds a potential for the analysis of clinical samples.     

3‐O‐Sulfation of Heparan Sulfate Enhances Tau Interaction and Cellular Uptake

Prion‐like transcellular spreading of tau in Alzheimer's Disease (AD) is mediated by tau binding to cell surface heparan sulfate (HS). However, the structural determinants for tau–HS interaction are not well understood. Microarray and SPR assays of structurally defined HS oligosaccharides show that a rare 3‐O‐sulfation (3‐O‐S) of HS significantly enhances tau binding. In Hs3st1^?/? (HS 3‐O‐sulfotransferase‐1 knockout) cells, reduced 3‐O‐S levels of HS diminished both cell surface binding and internalization of tau. In a cell culture, the addition of a 3‐O‐S HS 12‐mer reduced both tau cell surface binding and cellular uptake. NMR titrations mapped 3‐O‐S binding sites to the microtubule binding repeat 2 (R2) and proline‐rich region 2 (PRR2) of tau. Tau is only the seventh protein currently known to recognize HS 3‐O‐sulfation. Our work demonstrates that this rare 3‐O‐sulfation enhances tau–HS binding and likely the transcellular spread of tau, providing a novel target for disease‐modifying treatment of AD and other tauopathies.     

The Redox Coupling Effect in a Photocatalytic RuII‐PdII Cage with TTF Guest as Electron Relay Mediator for Visible‐Light Hydrogen‐Evolving Promotion

A nanocage coupling effect from a redox Ru^II‐Pd^II metal–organic cage (MOC‐16) is demonstrated for efficient photochemical H₂ production by virtue of redox–guest modulation of the photo‐induced electron transfer (PET) process. Through coupling with photoredox cycle of MOC‐16, tetrathiafulvalene (TTF) guests act as electron relay mediator to improve the overall electron transfer efficiency in the host–guest system in a long‐time scale, leading to significant promotion of visible‐light driven H₂ evolution. By contrast, the presence of larger TTF‐derivatives in bulk solution without host–guest interactions results in interference with PET process of MOC‐16, leading to inefficient H₂ evolution. Such interaction provides an example to understand the interplay between the redox‐active nanocage and guest for optimization of redox events and photocatalytic activities in a confined chemical nanoenvironment.