Supramolecular Dye Aggregate Assembly Enables Ratiometric Detection and Discrimination of Lysine and Arginine in Aqueous Solution

Near-infrared fluorescent probe with large Stokes shift for specific detection of lysine

A new near-infrared (NIR) fluorescent probe CL based on coumarin- dicyanoisophorone was synthesized. Addition of Lys to probe CL solution in DMF/H2O (9:1, v/v) medium resulted in noticeable enhancement in the intensity of the fluorescence emission at 702 nm, accompanying distinct color change from yellow to pink. While addition of other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about substantial changes in both fluorescence emission and color. The detection limit was calculated to be 0.51 μM. Job's plot test revealed that probe CL and Lys formed a complex of 1:1 stoichiometry. Probe CL showed high stability and could be used to recognize Lys in a wide pH range of 4.0-10.0. The sensing mechanism was proposed and verified by 1H NMR spectral measurement. The dual-modal fluorescence turn-on and colorimetric NIR probe with an extremely large Stokes shift of 280 nm may be utilized for highly specific and practical sensing of Lys.

A Simple Selective Probe for Lysine Detection in Tablets, Food Samples and Cells

A novel probe ITQ (9-(((E)-1 H-inden-1-ylidene)methyl)-8-(3-(((E)-1 H-inden-1-ylidene)methyl)phenoxy)-2,3,6,7-tetrahydro-1 H,5 H-pyrido[3,2,1ij]quinolone) was successfully designed and synthesized to detect amino acid lysine (Lys). The selective sensing behavior of the probe ITQ was observed using absorption and emission spectral results. Further, the probe ITQ exhibits a strong binding affinity for Lys [1.4 × 104 M- 1] and detects and quantifies Lys even in its nanomolar concentration. Moreover, the probe ITQ detects Lys at 1:2 binding stoichiometry with suitable biological pH [4-11]. Furthermore, the probe ITQ was also successfully utilized to detect Lys in tablets, real samples (avocado, soyabean and pork) and in live HeLa cells.

Guest Binding with Sulfated Cyclodextrins: Does the Size of Cavity Matter?

Sulfated cyclodextrins have recently emerged as potential candidates for producing host-induced guest aggregation with properties better than p-sulfonatocalixarenes that have previously shown numerous applications involving the phenomena of host-induced guest aggregation. In the class of sulfated cyclodextrins (SCD), sulfated β-cyclodextrin (β-SCD) remains the most extensively investigated host molecule. Although it is assumed that the host-induced guest aggregation is predominantly an outcome of interaction of the guest molecule with the charges on the exterior of SCD cavity, it has not been deciphered whether the variation in the cavity size will make a difference in the efficiency of host-induced guest-aggregation process. In this investigation, we present a systematic study of host-induced guest aggregation of a cationic molecular rotor dye, Thioflavin T (ThT) with three different sulfated cyclodextrin molecules, α-SCD, β-SCD and γ-SCD, which differ in their cavity size, using steady-state emission, ground-state absorption and time-resolved emission measurements. The obtained photophysical properties of ThT, upon interaction with different SCD molecules, indicate that the binding strength of ThT with different SCD molecules correlate with the cavity size of the host molecule, giving rise to the strongest complexation of ThT with the largest host molecule (γ-SCD). The binding affinity of ThT towards different host molecules has been supported by molecular docking calculations. The results obtained are further supported with the temperature and ionic strength dependent studies performed on the host-guest complex. Our results indicate that for host-induced guest aggregation, involving oppositely charged molecules, the size of the cavity also plays a crucial role beside the charge density on the exterior of host cavity.

A cationic AIEgen and hexametaphosphate based simple and convenient fluorometric assay for alkaline phosphatase and its inhibitor

Alkaline phosphatase (ALP) is an important biomarker to diagnose a number of diseases, such as anaemia, hepatobiliary diseases, chronic nephritis, and hypothyroidism. Therefore, the development of simple and convenient assays to monitor levels of ALP is highly desirable. In the present study, an aggregation-induced emission based simple, real-time, and direct fluorescence detection platform has been developed, by using a tetracationic pyridinium derivative of tetraphenylethylene (TPy-TPE) and anionic sodium hexametaphosphate (HMP) as component units. The sensing system, based on the TPy-TPE-HMP assembly, is highly responsive to the ALP dependent disintegration of the TPy-TPE-HMP aggregation complex, owing to HMP digestion by ALP. The sensing platform has an ALP detection limit of 16 mU mL^-1 and linear range of 0-742 mU mL^-1, respectively. The enzyme kinetic parameters, K_m and V_max, have been evaluated. In addition, the potential applicability of the TPy-TPE-HMP sensing system has also been shown with diluted human serum samples. Moreover, the TPy-TPE-HMP probe system is also useful for screening inhibitors of ALP.

Multicharged cyclodextrin supramolecular assemblies

Multicharged cyclodextrin (CD) supramolecular assemblies, including those based on positively/negatively charged modified mono-6-deoxy-CDs, per-6-deoxy-CDs, and random 2,3,6-deoxy-CDs, as well as parent CDs binding positively/negatively charged guests, have been extensively applied in chemistry, materials science, medicine, biological science, catalysis, and other fields. In this review, we primarily focus on summarizing the recent advances in positively/negatively charged CDs and parent CDs encapsulating positively/negatively charged guests, especially the construction process of supramolecular assemblies and their applications. Compared with uncharged CDs, multicharged CDs display remarkably high antiviral and antibacterial activity as well as efficient protein fibrosis inhibition. Meanwhile, charged CDs can interact with oppositely charged dyes, drugs, polymers, and biomacromolecules to achieve effective encapsulation and aggregation. Consequently, multicharged CD supramolecular assemblies show great advantages in improving drug-delivery efficiency, the luminescence properties of materials, molecular recognition and imaging, and the toughness of supramolecular hydrogels, in addition to enabling the construction of multistimuli-responsive assemblies. These features are anticipated to not only promote the development of CD-based supramolecular chemistry but also contribute to the rapid exploitation of these assemblies in diverse interdisciplinary applications.

A cyclodextrin-based macrocyclic oligosaccharide cavitand with a dual functionality limits the collagen fibrillogenesis: A possible carbohydrate-based therapeutic molecule for fibrotic diseases

β-Cyclodextrin (β-CD), a macrocyclic oligosaccharide cavitand, is a well-known candidate for drug delivery and formulation. In this study, we extended the application of β-CD using a β-cyclodextrin sulfate (β-CDS) as a possible therapeutic for fibrotic diseases caused by excess deposition of collagen fibrils. We have strategically chosen β-CDS, which mimics the natural existence of dermatan sulfate in the extracellular matrix, for limiting collagen fibrillation. The hydrophobic nature of the inner core β-CDS is expected to form an inclusion complex with hydrophobic side chain amino acids with the simultaneous action of forming an ionic bond through a negative charge on sulfate group with positively charged amino acids side chain in collagen. Various results suggested that such dual action not only limited the collagen fibrillation but also reduced the fibril size formed in the presence of β-CDS. The contemporary results thus indicate that β-CDS can be explored as a therapeutic molecule in fibrotic diseases.

Polyanionic Cyclodextrin-Induced Supramolecular Assembly of a Cationic Tetraphenylethylene Derivative with Aggregation-Induced Emission

The combination of supramolecular chemistry and aggregation-induced emission-based luminogens (AIEgens) has recently attracted tremendous attention because of its ability to offer large emission enhancement even in substantially dilute solutions. In this work, a new aggregation-induced emission (AIE)-based supramolecular assembly has been reported, which consists of a polyanionic cyclodextrin derivative and a tetracationic tetraphenylethylene (TPE) derivative. Ionic cyclodextrins have attracted significant attention in host-guest supramolecular chemistry and pharmaceutical industry. However, ionic derivatives of β-cyclodextrins have not been explored to establish noncovalent interactions-based aggregation assembly of the most popular class of AIEgens, i.e., tetraphenylethylene derivatives. The current report demonstrates AIE of a tetracationic methyl pyridinium derivative of tetraphenylethylene (TPy-TPE) induced by a polyanionic sulfated β-cyclodextrin (S-βCD). The AIE-based supramolecular assembly has been thoroughly investigated using steady-state fluorescence, ground-state absorbance, and time-resolved fluorescence measurements. Further, the response of the supramolecular assembly towards external stimuli, such as, ionic strength, pH, and temperature, has been investigated. In addition, the complexation behavior of the TPE derivative has also been compared with the native neutral β-cyclodextrin derivative, which delineates the important role of the negatively charged portal of S-βCD in inducing aggregation of the TPy-TPE. The stoichiometry of the complex has been found to be 3:1 for TPy-TPE:S-βCD, using Job's plot analysis. Finally, to get insights into the underlying interactions between the supramolecular assembly components, molecular docking calculations have been performed.

An AIRE-active far-red ratiometric fluorescent chemosensor for specifically sensing Zn2+ and resultant Zn2+ complex for subsequent pyrophosphate detection in almost pure aqueous media

A simple Schiff-base fluorescent chemosensor (1) was synthesized by the reaction of 3-amino-pyrazine-2-carbohydrazide and 7-diethylamino-3-formylcoumarin; the sensor 1 displayed a notable green emission at 524 nm in DMSO and an aggregation-induced ratiometric emission (AIRE) at 555 nm in an almost buffered aqueous media (0.5% DMSO content). The AIRE of 1 was quenched following binding to Zn²⁺ ions, while the fluorescence emission in the far-red region was evidently enhanced at 628 nm. Notably, the ratiometric signal output could be utilized to specifically distinguish Zn²⁺ among various metal ions. Moreover, the 1-Zn²⁺ complex was effectively employed as a fluorescent ratiometric chemosensor for pyrophosphate (PPi) detection. The detection limit was 3.52 μM and 2.45 μM for Zn²⁺ and PPi, respectively. The binding mechanism was evaluated by ¹H NMR, ESI-MS, single-crystal X-ray diffraction, TEM, time-resolved fluorescence spectrophotometry, and density functional theory studies. Overall, owing to its sensitive fluorescence behavior, cell imaging studies demonstrated that this sensor is capable of sensing Zn²⁺ and PPi in living cells.

Host-Assisted Aggregation-Induced Emission of a Tetraphenylethylene Derivative and Its Responses toward External Stimuli

Aggregation-induced emission (AIE) of fluorogenic dyes offers many opportunities as smart materials, fluorescence sensing of analytes, bioimaging, molecular electronics, and many others. AIE dyes (called AIEgens) produce emission through aggregation, which are more advantageous than conventional emission of monomeric fluorophores, as the latter is unduly susceptible toward various quenching processes. Here, we report AIE enhancement of a polyanionic sulfonato-tetraphenylethylene (SuTPE) derivative, achieved through supramolecularly assisted dye aggregation, as SuTPE interacts with a multicationic amino-β-cyclodextrin (AβCD) host. Aggregation of the dye is induced mainly because of strong electrostatic interaction of SuTPE with AβCD, causing a significant extent of charge neutralization for the polyanionic dyes, helping their assemblage at the multicationic host portal. Job's plot studies suggest preferential formation of 2:1 dye-to-host stoichiometric complexes in the present system. Ionic-strength-dependent studies nicely support the involvement of electrostatic interaction in the present system through salt-induced disintegration of the SuTPE-AβCD complexes. The AIE enhancement for the SuTPE-AβCD system is very sensitive to the external stimuli, such as pH and temperature, suggesting its prospects in various stimuli-responsive applications. Furthermore, the SuTPE-AβCD system can suitably quantify an important bioanalyte, ATP, following a competitive binding strategy, suggesting its potential application as a supramolecular biosensor.

A hydrazone-based spectroscopic off-on probe for sensing of basic arginine and lysine

A simple probe BHN based on naphthol and benzothiazole is reported for detecting of arginine (Arg) and lysine (Lys) with high selectivity and sensitivity. The BHN in aqueous solution upon reacting with Arg or Lys induced a visible color change from colorless to yellow. The probe BHN can also be employed for fluorescence turn-on sensing of Arg and Lys with the limits of detection (LOD) of 5.20 × 10^-2 μM and 3.69 × 10^-2 μM, respectively. The naked eye colorimetric and fluorimetric detecting is lack of sensitive to other common amino acids including Gly, Ala, Ser, Pro, Val, Thr, Cys, Leu, Ile, Asn, Asp, Glu, Gln, Met, His, and Phe. The sensing mechanism has been proposed by pH investigation and ¹H NMR spectra.

Supramolecular tuning of thioflavin-T aggregation hosted by polystyrene sulfonate

Tunable and controllable emission is an extremely desirable feature for advanced functional materials that finds usage in optoelectronic utilization, fluorescence probing/sensing, drug-delivery monitoring, etc. In the present contribution, we have employed a macrocyclic host molecule, sulfobutyl ether-β-cyclodextrin (SBE-β-CD), as a tuning agent for an intensely emissive aggregate assembly of a molecular rotor dye, thioflavin-T (ThT), in the presence of an anionic polyelectrolyte, polystyrene sulfonate (PSS). The macrocyclic host breaks the PSS templated ThT aggregates and leads to encapsulation of released ThT molecules, tailoring the emission response of the system in terms of intensity and wavelength. Utilizing the established selectivity of the cyclodextrin-adamantane system, reverse control of this tunable emission has been further achieved. The controllable fluorescence system has been extensively investigated using ground-state absorption, steady-state and time-resolved emission spectroscopy. This kind of supramolecular tailoring of self-assembled aggregate emission has enormous potential in the field of fluorescence sensors and probes, and imaging and tracking in biological systems.

Anionic Polyelectrolyte-Induced Aggregation of Basic Orange 21: A Clue toward Metachromasia

The change in the color of chromophore upon being embedded in a biological tissue is known as metachromasia. Basic Orange 21 (BO21) is a cationic polymethine dye that has been implied as a supravital dye, which produces metachromasia in leukocytes. An improved differential counting of leukocytes has been achieved in the clinical setup based on characteristic metachromatic expressions of BO21 for different types of leukocytes. Although BO21 has been utilized as a chromatic indicator for leukocyte counting, there are limited number of investigations that focus on the factors that may be responsible for the spectral shift in absorption and emission spectra of BO21, which leads to its metachromatic behavior. In this work, we have investigated the effect of a synthetic anionic polyelectrolyte, polystyrene sulfonate (PSS), on the photophysical properties of BO21, using steady-state emission, ground-state absorption, and time-resolved emission measurements, to get an understanding of the factors that may be responsible for the spectral shift of BO21 in the cellular environment. PSS induces aggregation of BO21 molecules with large changes in its photophysical properties; this appears to be most likely the mechanism of spectral shift for BO21 reported in the cellular environment. The employment of external stimulus reveals BO21 aggregates to be significantly responsive toward external stimuli, for example, temperature and presence of salt in the medium, which further strengthens the proposal of aggregate formation. Further, we have also employed fluorescence upconversion spectroscopy with subpicosecond time resolution to estimate the excited-state lifetime of BO21.

Supramolecular Control on the Optical Properties of a Dye-Polyelectrolyte Assembly

Control of fluorescent molecular assemblies is an exciting area of research with large potential for various important applications, such as, fluorescence sensing/probing, cell imaging and monitoring drug-delivery. In the present contribution, we have demonstrated control on the extent of aggregation of a dye-polyelectrolyte assembly using a macrocyclic host molecule, sulfobutylether-β-cyclodextrin (SBE-β-CD). Initially, a cationic molecular rotor based organic dye, Auramine-O (AuO), undergoes aggregation in the presence of an anionic polyelectrolyte, polystyrene sulfonate (PSS), and displays a broad intense new emission band along with large variation in its absorption features and excited-state lifetime. A manipulation of the monomer-aggregate equilibrium of the dye-polyelectrolyte assembly has been achieved by introducing a cyclodextrin based supramolecular host, SBE-β-CD, which leads to relocation of AuO molecules from polyelectrolyte (PSS) to supramolecular host cavity, owing to the formation of a host-guest complex between AuO and SBE-β-CD. A reversible control on this manipulation of monomer-aggregate equilibrium is further achieved by introducing a competitive guest for the host cavity i. e., 1-Adamantanol. Thus, we have demonstrated an interesting control on the dye-polyelectrolyte aggregate assembly using a supramolecular host molecule which open up exciting possibilities to construct responsive materials using a repertoire of various host-specific guest molecules.

Effect of counter-anions on the aggregation of Thioflavin-T

The aggregation of small molecules in aqueous solution is known to be influenced by the ionic strength of the medium; however, the role played by the identity of salt in the phenomenon of small molecule aggregation is rarely investigated. In the present contribution, we have investigated the effect of counter-anions on the aggregation of a popular cationic amyloid sensing probe, Thioflavin-T (ThT), by taking six different anions, viz. chloride, bromide, acetate, iodide, tetrafluoroborate, and perchlorate. Our results clearly indicate that it is not the ionic strength of the medium which solely controls aggregation of small molecules but distinct ions behave distinctly with regard to the organization. In fact, distinct ion effects play a major role in the salt induced organization of fluorophores. Using detailed steady-state emission, time-resolved emission, and ground-state absorption measurements, the optical properties of salt induced aggregates of ThT have been characterized. We have rationalized our observations on the basis of the theory of matching water affinity, which suggests that the matching free hydration energy is a critical aspect for the formation of contact ion pairs, which eventually results in aggregation. In brief, a larger sized anion, perchlorate, has a lower free energy of hydration and forms a suitable contact ion pair, with a larger organic cation, ThT, having weaker hydration. This contact ion-pair formation subsequently leads to the formation of an aggregate assembly which is found to be emissive in nature. Therefore, it is possible to induce aggregation of ThT by selecting the right counterion with the appropriate size, which may help us to evaluate the false positive signals when high ionic strength and specific counterions are present in the sensing matrix.

A colorimetric and fluorometric based dual readout approach for effective heparin sensing

Devising fluorescence-based turn-on probes for the specific and sensitive detection of Heparin is of utmost clinical importance. In this contribution, we have identified a molecular rotor based asymmetric cyanine probe, thiazole orange (TO), which enables an efficient colorimetric and fluorimetric detection of Heparin. TO undergoes the formation of emissive H-aggregates upon interaction with Heparin that display an impressive emission enhancement of ~22 fold together with drastic changes in the absorption spectra that yields a prominent colour change in the solution from orange to yellow. These seldom reported emissive H-aggregates of TO, serve as an efficient platform for Heparin detection with a LOD of 19 nM, fluorometrically and 34 nM, colorimetrically. The TO-Heparin complex is also accompanied by a large change in the excited-state lifetime. The TO-Heparin complex has been further utilized for the detection of Protamine, which is the only medically affirmed antitoxin of Heparin. Overall, our sensing system offers several advantages, such as, simple, dual read-out, economic and specific detection of Heparin with longer excitation and emission wavelength, rapid naked eye detection and utilizes an in-expensive commercially available fluoprophore, TO. Most importantly, our sensing system also displays a good performance in the biologically complex human serum matrix.

A Heparin based dual ratiometric sensor for Thrombin

Thrombin is an important enzyme that plays a pivotal role in the blood clotting pathways. An imbalance in the activity of this enzyme is clinically known to be associated with various diseases, such as thrombosis, inflammation, atherosclerosis, and haemophilia, suggesting the need to devise sensors for Thrombin detection. However, the majority of the fluorescence-based Thrombin assays rely on fluorescence labelling assays or Thrombin specific recognition biomolecules, such as, aptamers or antibody which requires sophisticated techniques and makes it very expensive. Herein, we report a simple, selective, sensitive and label-free fluorescence detection scheme for Thrombin which is based on the interaction between Thrombin and a fluorescent complex of Heparin with a molecular rotor dye, Thioflavin-T. The detection scheme exploits selective interaction between cationic Thrombin and anionic Heparin to modulate the monomer-aggregate equilibrium of the Thioflavin-T-Heparin system. Importantly, the present system offers a ratiometric response that has the ability for robust quantification of Thrombin concentration even in complex medium. The involvement of all commercially available components is a crucial advantage of this detection scheme. Further, the detection scheme also shows reasonable response in diluted serum matrix.

An anionic polyelectrolyte induced aggregate assembly of Thioflavin-T: A prospective platform for Protamine sensing

Protamine, a polycation, is biologically and medically relevant protein. Protamine exhibits a wide array of functions in biological processes like gene transfer, tissue and organogenesis, cell reproduction, etc. Medically, Protamine is the only clinically approved antidote for Heparin and is routinely used in various surgical interventions, and hence controlling Protamine dosing in patients is very crucial. Taking into account the medical significance of Protamine, designing simple, reliable and sensitive fluorescence sensors is highly desirable. In this work, we propose one such sensitive and reliable fluorescent sensor which is based on a template of dye-polyelectrolyte assembly constituting a molecular rotor dye, Thioflavin-T and an anionic synthetic polyelectrolyte, polystyrene sulfonate. The addition of Protamine, prompts drastic modulations in spectral features of dye-polyelectrolyte assembly which enables sensitive detection of Protamine in aqueous solution. Apart from sensitive detection, our sensing platform aids in highly selective sensing of Protamine compared to other proteins. Moreover, our sensor system is constructed on label-free, inexpensive, commercially available molecules posing as an advantage over other sensor systems which involve laborious synthesis protocols. Most importantly, our sensor template is able to sense Protamine in diluted serum sample, indicating the potential practical utility of our sensor system.

Selective Detection of Fe3+, F-, and Cysteine by a Novel Triazole-Linked Decaamine Derivative of Pillar[5]arene and Its Metal Ion Complex in Water

Appropriately functionalized pillar[n]arenes are elegant supramolecular hosts for ion and molecule sensing. A water-soluble decaamine derivative of pillar[5]arene (APA) bearing triazole and amide moieties is synthesized. The ion and molecular recognition properties of APA are studied by fluorescence, UV-visible, and ¹H nuclear magnetic resonance (NMR) spectroscopy. The APA selectively detects Fe³⁺ among 11 studied ions, which are important in several biological processes. Moreover, the in situ prepared Fe³⁺ complex of APA (FeAPA) exhibits the highest responsiveness toward F^- (∼12-fold) among 11 anions and cysteine (∼120-fold) among the 20 naturally occurring amino acids by a fluorescence turn-on mechanism.

Quinoline appended pillar[5]arene (QPA) as Fe3+ sensor and complex of Fe3+ (FeQPA) as a selective sensor for F-, arginine and lysine in the aqueous medium

A quinoline functionalized pillar[5]arene, QPA has been prepared and its interaction with biologically relevant ions and molecules in aqueous solution has been demonstrated. The sensor molecule, QPA has shown selectivity towards Fe³⁺ among eleven metal ions studied. The Fe³⁺ complex of QPA (FeQPA) selectively interacts with F^- among halides by ∼4 fold fluorescence enhancement. Further, FeQPA has shown selectivity towards arginine and lysine among twenty naturally occurring amino acids. The binding of QPA with Fe³⁺ has been confirmed by MALDI-TOF and ¹H NMR titrations.

Does the degree of substitution on the cyclodextrin hosts impact their affinity towards guest binding?

The degree of substitution on βCD rims by sulfobutylether groups significantly modulates the binding affinity of the SBE_nβCD hosts for the studied cationic guest molecule.

Stimulus-Responsive Supramolecular Host-Guest Assembly of a Cationic Pyrene Derivative with Sulfated β-Cyclodextrin

In general, aggregation-prone organic molecules are prevented from self-aggregation in the presence of macrocyclic hosts like β-cyclodextrin because of their preference for the formation of inclusion complex with guest molecules. On the contrary, sulfate-laced β-cyclodextrin has been recently reported to induce the aggregation of some of the non-aggregation-prone organic dyes, which have been subsequently utilized for biosensing applications. In the present contribution, we report the interaction of a cationic organic probe molecule, 1-pyrene methyl amine (PMA), which belongs to one of the most useful families of organic fluorescent probes, that is, pyrene, with a sulfated β-cyclodextrin derivative (SCD). Interaction of a cationic probe with a β-cyclodextrin derivative was studied using a variety of photophysical methods such as ground-state absorption, steady-state emission, and time-resolved emission techniques. Detailed photophysical investigations have revealed that SCD induces the ground-state association of PMA molecules. This SCD-induced aggregation of PMA molecules has been attributed to the charge neutralization of the cationic probe by negatively charged sulfate groups, which subsequently lead to their association because of the close proximity on the rims of cyclodextrin. This monomer-dimer equilibrium of the PMA-SCD system is found to be extremely responsive to external chemical stimuli like temperature, pH, ionic strength of the medium, and organic solvent (dimethyl sulfoxide), which projects them as potential platforms for various sensing applications including bioanalytes. The supramolecular assembly has been demonstrated to sense arginine.

A styryl based fluorogenic probe with high affinity for a cyclodextrin derivative

A styryl-based fluorogenic near-IR probe registers a very high association constant with sulfobutylether substituted β-cyclodextrin host, having prospects as biological marker and improved pH and temperature sensor.

Chiral Receptors for Lysine Based on Covalently Linked Bis- and Tris-binaphthylphosphoric Acids

The synthesis and application of three chiral receptors based on the covalent linkage of 1,1'-binaphthylphosphoric acids is reported. The binding of the lysine enantiomers to the chiral receptors was investigated by DOSY-NMR and NMR titrations, revealing that the bisphosphoric acid 1d acts as a highly stereoselective receptor for binding of d-lysine.

A supramolecular assembly enables discrimination between metalloproteins and non-metalloproteins

A supramolecular assembly yields turn-on fluorescence response for non-metalloproteins and turn-off response for metalloproteins.