Anthracene-Based Cyclophanes with Selective Fluorescent Responses for TTP and GTP: Insights into Recognition and Sensing Mechanisms

Three anthracene-based cyclophanes were synthesized and their binding properties towards nucleoside triphosphates were studied. A new polycyclic amine derived from dearomatized anthracene was identified as a major side product in the cyclization reaction between 9,10-anthracenedicarboxaldehyde and diethylenetriamine. Its structure was determined by single-crystal X-ray analysis. The cyclophanes were found to form 1:1 complexes with all nucleoside triphosphates as well as with pyrophosphate in a buffered aqueous solution at pH 6.2. A turn-on fluorescence response was observed for all nucleotides except for GTP, which demonstrated strong fluorescence quenching. The strongest turn-on fluorescence was observed for the largest receptor 3 in the presence of thymidine triphosphate (TTP). Based on the NMR and fluorescence experiments, two major binding modes for nucleotide complexes were identified.     

Fluorescent Peptide Beacons for the Selective Ratiometric Detection of Heparin

Heparin is extensively used as an anticoagulant drug during surgery. Two fluorophore‐functionalized cationic oligopeptides HS 1 and HS 2 were developed to monitor heparin ratiometrically in aqueous media. Upon binding to heparin, HS 1 and HS 2 undergo a conformational change from an open form to a folded form, which leads to a distinct change in the fluorescence properties. HS 1 switches from pyrene monomer emission to an excimer emission. For HS 2 , a fluorescence resonance energy transfer (FRET) process is enabled between a naphthalene donor and a dansyl acceptor. This method is highly selective for heparin relative to other similar biological analytes such as hyaluronic acid or chondroitin sulfate. HS 1 and HS 2 could also detect heparin ratiometrically in diluted bovine serum. The strong ratiometric emission color change can also be observed by the naked eye. Addition of the polycationic protein protamine releases both HS 1 and HS 2 from their heparin complex, which simultaneously restores pyrene monomer emission for the first case and decreases the FRET process for the latter case, respectively. Dynamic light scattering (DLS) and AFM studies confirm aggregate formation of heparin with HS 1 and HS 2 .     

Molecular Receptors for Recognition and Sensing of Nucleotides

Nucleotides are constituents of nucleic acids and they have a variety of functions in cellular metabolism. Synthetic receptors and sensors are required to reveal the role of nucleotides in living organisms and mechanisms of signal transduction events. In recent years, a large number of nucleotide-selective synthetic receptors have been devised, which utilize different molecular designs and sensing mechanisms. This Minireview presents recent progress in the design of synthetic molecular receptors for selective recognition of nucleotides in aqueous solution. The binding properties of receptors and the origins of their selectivity for a particular nucleotide are discussed.     

Supramolecular Assemblies with Aggregation-Induced Emission Properties for Sensing and Detection

The fabrication of new supramolecular materials for real-time detection of analytes including ions, organic pollutants, gases, biomolecules, and drugs is of pivotal importance in industrial manufacture, clinical treatment, and environmental remediation. Incorporating fluorescent molecules with distinct aggregation-induced emission (AIE) effects into supramolecular assemblies has received much attention over the past two decades, owing to the remarkable performance of the AIE-active supramolecular materials in sensing and detection. In this minireview, we summarize the recent progress of superior detection systems on the basis of supramolecular assemblies accompanied with AIE features. We envision that this minireview will be helpful and timely for relevant researchers to stimulate new thinking for constructing new AIE-based supramolecular materials with advanced architectures for effective sensing and detection.     

A Luminescent Probe for Ratiometric Optical Detection of HgII and Turn‐On Fluorescent Sensing of CuII

Luminescent detection of heavy metals continues to be of growing importance considering their increasing inseparable roles in modern day lifestyle. To this end, we report a simple yet interesting thiourea derivative that results in detection of Cu^II in a turn‐on fashion via a chemodosimetric redox reaction leading to oxidative cyclization of the chemosensor molecule. Elaborate studies with regard to the sensing process have been performed along with the proposal of a plausible cyclization mechanism of the molecule. Furthermore, the probe optically detects Hg^II, yet another heavy metal of prime importance, discernable even to the naked eye. The occurrence of a coordination complex has been proved by UV/Visible spectroscopic experiments as well as ESI‐mass spectrometry.     

Binding and Sensing Properties of a Hybrid Naphthalimide–Pyrene Aza-Cyclophane towards Nucleotides in an Aqueous Solution

Selective recognition of nucleotides with synthetic receptors is an emerging direction to solve a series of nucleic acid-related challenges in biochemistry. Towards this goal, a new aza-cyclophane with two different dyes, naphthalimide and pyrene, connected through a triamine linker has been synthesized and studied for the ability to bind and detect nucleoside triphosphates in an aqueous solution. The receptor shows Foerster resonance energy transfer (FRET) in fluorescence spectra upon excitation in DMSO, which is diminished dramatically in the presence of water. According to binding studies, the receptor has a preference to bind ATP (adenosine triphosphate) and CTP (cytidine triphosphate) with a “turn-on” fluorescence response. Two separate emission bands of dyes allow one to detect nucleotides in a ratiometric manner in a broad concentration range of 10⁻⁵–10⁻³ M. Spectroscopic measurements and quantum chemical calculations suggest the formation of receptor–nucleotide complexes, which are stabilized by dispersion interactions between a nucleobase and dyes, while hydrogen bonding interactions of nucleobases with the amine linkers are responsible for selectivity.     

Preparation of macrocyclic and ‘C-clamp’ dicarboxylate compounds

Reductive amination of bis-1,3-(aminomethyl)-4,6-diisopropylbenzene with the 4,4″-dicarboxaldehyde of 1,1′:3′,1″-terphenyl-2′-carboxylic acid, sodium salt, afforded a novel macrocyclic dicarboxylate compound in 71% isolated yield. Purification was effected by filtration in a single step. The synthesis and characterization of two new ‘C-clamp’ compounds, which also contain two m-terphenyl carboxylates but exhibit much greater degree of flexibility, are also described. These compounds are of interest as potential ligands or for host-guest chemistry.     

基于香豆素的比率型次氯酸荧光探针

次氯酸(HCl O)是生物体内重要的活性氧(ROS)之一,在人类免疫功能系统中扮演着重要的角色,有助于对入侵细菌和病原体进行破坏。本文设计并合成了基于香豆素为母体单元的比率型次氯酸荧光探针。研究结果表明,该探针对次氯酸识别显示出较高的选择性,检测线低至12 mol/L,荧光响应可在5 s内迅速完成,并伴随着溶液颜色由无色转变为黄绿色。其它常见的阴离子及氧化型物质对次氯酸检测均无干扰。此外,高分辨率质谱、荧光光谱和紫外可见光谱变化共同证实了该探针对次氯酸的检测机制为次氯酸对探针氧化水解。     

Label-Free Fluorescent Kinase and Phosphatase Enzyme Assays with Supramolecular Host-Dye Pairs

The combination of the macrocyclic hosts p-sulfonatocalix[4]arene and cucurbit[7]uril with the fluorescent dyes lucigenin and berberine affords two label-free enzyme assays for the detection of kinase and phosphatase activity by fluorescence monitoring. In contrast to established assays, no substrate labeling is required. Since phosphorylation is one of the most important regulatory mechanisms in biological signal transduction, the assays should be useful for identification of inhibitors and activators in high-throughput screening (HTS) format for drug discovery.     

Sulfate‐Selective Binding and Sensing of a Fluorescent [3]Rotaxane Host System

The chloride‐templated synthesis of a novel [3]rotaxane, capable of binding anionic guests, and incorporating a naphthalene group for fluorescence sensing is reported. Extensive ¹H NMR titration studies were used to probe the anion binding selectivity of the system. The rotaxane selectively recognises sulfate, undergoing an induced conformational change upon sulfate binding to form a 1:1 stoichiometric sandwich‐type complex, concomitant with significant quenching of the fluorescence. Binding of mono‐anionic guests results in the formation of a 2:1 stoichiometric guest–host complex, and a modest enhancement of the emission. Addition of an excess of sulfate in non‐competitive solvent also results in a 2:1 emissive complex.     

镧系金属有机骨架比例荧光检测萘普生

该文构筑了双荧光发射的比例型荧光传感器,并将其用于萘普生检测。以Eu3+为金属节点,1,3,5-苯三甲酸为配体,通过超声法合成了比例型荧光传感材料Eu-MOF。探究了Eu-MOF的形貌特征、光学性质及对萘普生的检测机理。单一激发光照射下,Eu-MOF呈现源于配体和Eu3+的双荧光发射峰。萘普生的荧光发射峰与Eu-MOF在375 nm处的荧光发射峰重合,且两者之间具有内滤光效应。因此,随着萘普生的逐渐加入,Eu-MOF在375 nm处的荧光发射峰强度逐渐增强,而623 nm处则逐渐减弱,从而可实现对萘普生的比例荧光检测。Eu-MOF检测萘普生的线性范围为0.07~2.3μmol/L,检出限为0.039μmol/L。Eu-MOF在萘普生的检测中表现出良好的选择性和抗干扰能力,是实际样品中萘普生检测的优势材料。     

A Supramolecular Strategy for the Synthesis of Cyclic Oligomers and Polymers by Ring Expansion

Ring-opening metathesis polymerization (ROMP) of strained macrocycles is a key method to prepare diverse polymers. However, lack of ring strain in most macrocycles is an impediment to polymerization. In this paper, the polymerization/oligomerization of unstrained macrocycles was achieved using a supramolecular approach, leading selectively to cyclic products. Diphenyl thiourea and other guest molecules were used as additives to the ROMP reaction of unstrained macrocycles. An intermediate host-guest complex leads to the stabilization of the open form of the macrocycle after treatment with Grubbs catalysts, thereby favoring polymerization by inhibiting the ring-closing reaction back to the monomer. This proof-of-concept enables ring-expansion polymerization of unstrained macrocycles leading to cyclic polymers with molecular weights up to 6700 Da.     

A Pyrene‐functionalized Polynorbornene for Ratiometric Fluorescence Sensing of Pyrophosphate

A novel pyrene‐functionalized polynorbornene ( P1 ) bearing sulfonamide NH and triazolium donors has been synthesized for ratiometric fluorescence sensing of PPi in aqueous solution. In addition, P1 is also used to monitor intracellular PPi and to detect PPi released during polymerase chain reaction.     

Design of Dual‐Emission Chemosensors for Ratiometric Detection of ATP Derivatives

Nucleoside pyrophosphate (nucleoside PP) derivatives are widespread in living cells and play pivotal roles in various biological events. We report novel fluorescence chemosensors for nucleoside PPs that make use of coordination chemistry. The chemosensors, which contain two Zn^II–dipicolylamine units, bind strongly to nucleoside PPs (K_app>10⁶ M ^?1) in aqueous solution and sense them by a dual‐emission change. Detailed fluorescence and UV/Vis spectral studies revealed that the emission changes of the chemosensors upon binding to nucleoside PPs can be ascribed to the loss of coordination between Zn^II and the acridine fluorophore. This is a unique sensing system based on the anion‐induced rearrangement of the coordination. Furthermore, we demonstrated the utility of these chemosensors in real‐time monitoring of two important biological processes involving nucleoside PP conversion: the apyrase‐catalyzed hydrolysis of nucleoside PPs and the glycosyl transfer catalyzed by β‐1,4‐galactosyltransferase.     

A Fluorescence Sensor Array Based on Zinc(II)-Carboxyamidoquinolines: Toward Quantitative Detection of ATP**

The newly prepared fluorescent carboxyamidoquinolines ( 1 – 3 ) and their Zn(II) complexes ( Zn@1-Zn@3 ) were used to bind and sense various phosphate anions utilizing a relay mechanism, in which the Zn(II) ion migrates from the Zn@1-Zn@3 complexes to the phosphate, namely adenosine 5’-triphosphate (ATP) and pyrophosphate (PPi), a process accompanied by a dramatic change in fluorescence. Zn@1-Zn@3 assemblies interact with adenine nucleotide phosphates while displaying an analyte-specific response. This process was investigated using UV-vis, fluorescence, and NMR spectroscopy. It is shown that the different binding selectivity and the corresponding fluorescence response enable differentiation of adenosine 5’-triphosphate (ATP), adenosine 5’-diphosphate (ADP), pyrophosphate (PPi), and phosphate (Pi). The cross-reactive nature of the carboxyamidoquinolines-Zn(II) sensors in conjunction with linear discriminant analysis (LDA) was utilized in a simple fluorescence chemosensor array that allows for the identification of ATP, ADP, PPi, and Pi from 8 other anions including adenosine 5’-monophosphate (AMP) with 100 % correct classification. Furthermore, the support vector machine algorithm, a machine learning method, allowed for highly accurate quantitation of ATP in the range of 5–100 μM concentration in unknown samples with error <2.5 %.     

荧光传感方法检测爆炸物的研究进展

爆炸物检测是当前国际安全中迫切关注的问题之一。在过去的几十年中,大量的荧光传感材料用于荧光传感检测气态、液态和固态爆炸物见诸于报道。近年来,为了实现爆炸物的快速响应、高灵敏和高选择性的检测,研究工作者大力开发了各种新型荧光材料。这篇综述总结了近年来用于爆炸物检测的先进荧光材料,详尽、系统、重点地介绍了共轭聚合物、荧光小分子、超分子体系、具有聚集诱导发光效应的活性材料及静电纺丝纳米材料等各种荧光材料在爆炸物检测中的应用,展望了荧光传感方法在爆炸物检测领域的应用前景。     

Molecular Recognition of Zwitterions with Artificial Receptors

Many biomolecules exist as internal ion pairs or zwitterions within a biologically relevant pH range. Despite their importance, the molecular recognition of this type of systems is specially challenging due to their strong solvation in aqueous media, and their trend to form folded or self‐assembled structures by pairing of charges of different sign. In this Minireview, we will discuss the molecular recognition of zwitterions using non‐natural, synthetic receptors. This contribution does not intend to make a full in‐depth revision of the existing research in the field, but a personal overview with selected representative examples from the recent literature.