Gas-phase solvent-free complexation of phenolic acids in cyclodextrins: A mass spectrometric study.

Phenolic acids are phytochemicals commonly existing in plants that are also beneficial to the human body after consumption. As additives in the food industry, phenolic acids typically need stabilization by encapsulation. We have been studying cyclodextrins as potential encapsulating agents, elucidating the structure and energetics of the complexes they form with phenolic acids.

The effect of outer-sphere anions on the spectroscopic response of metal-binding chemosensors.

Ion pair receptors typically contain two separate binding sites, for the metal and the anion respectively. Here we report a less synthetically demanding approach, whereby we prepared a family of ion pair sensors based on a rhodamine fluorescent scaffold containing a tunable cation binding motif. When exposed to ion pairs, a competition for the metal ion is established between these ligands and anions.

Beta-Lactam Antibiotic Discrimination Using a Macromolecular Sensor in Water at Neutral pH.

Penicillins and cephalosporins belong to the β-lactam antibiotic family, which accounts for more than half of the world market for antibiotics. Misuse of antibiotics harms human health and the environment. Here, we describe an easy, fast, and sensitive optical method for the sensing and discrimination of two penicillin and five cephalosporin antibiotics in buffered water at pH 7.

Structural Features of a Family of Coumarin-Enamine Fluorescent Chemodosimeters for Ion Pairs.

A family of coumarin-enamine chemodosimeters is evaluated for their potential use as fluorescent molecular probes for multiple analytes [cadmium(II), cobalt(II), copper(II), iron(II), nickel(II), lead(II), and zinc(II)], as their chloride and acetate salts. These fluorophores displayed excellent optical spectroscopic modulation when exposed to ion pairs with different Lewis acidic and basic properties in dimethyl sulfoxide (DMSO). The chemodosimeters were designed to undergo excited-state intramolecular proton transfer (ESIPT), which leads to significant Stokes shifts (ca.

Light-responsive and Protic Ruthenium Compounds Bearing Bathophenanthroline and Dihydroxybipyridine Ligands Achieve Nanomolar Toxicity towards Breast Cancer Cells.

We report new ruthenium complexes bearing the lipophilic bathophenanthroline (BPhen) ligand and dihydroxybipyridine (dhbp) ligands which differ in the placement of the OH groups ([(BPhen) Ru(n,n'-dhbp)]Cl with n = 6 and 4 in 1 and 2 , respectively). Full characterization data are reported for 1 and 2 and single crystal X-ray diffraction for 1 . Both 1 and 2 are diprotic acids.

Discrimination and Quantitation of Biologically Relevant Carboxylate Anions Using A [Dye•PAMAM] Complex.

Carboxylate anions are analytical targets with environmental and biological relevance, whose detection is often challenging in aqueous solutions. We describe a method for discrimination and quantitation of carboxylates in water buffered to pH 7.4 based on their differential interaction with a supramolecular fluorescent sensor, self-assembled from readily available building blocks.

Singlet Oxygen Formation vs Photodissociation for Light-Responsive Protic Ruthenium Anticancer Compounds: The Oxygenated Substituent Determines Which Pathway Dominates.

Ruthenium complexes bearing protic diimine ligands are cytotoxic to certain cancer cells upon irradiation with blue light. Previously reported complexes of the type [(,)Ru(6,6'-dhbp)]Cl with 6,6'-dhbp = 6,6'-dihydroxybipyridine and , = 2,2'-bipyridine (bipy) (), 1,10-phenanthroline (phen) (), and 2,3-dihydro-[1,4]dioxino[2,3-][1,10]phenanthroline (dop) () show EC values as low as 4 μM (for ) vs breast cancer cells upon blue light irradiation ( 2017, 56, 7519). Herein, subscript denotes the acidic form of the complex bearing OH groups, and denotes the basic form bearing O groups.

Pattern-Based Recognition Systems: Overcoming the Problem of Mixtures.

The transformative potential of pattern-based sensing techniques is often hampered by their difficulty in dealing with mixtures of analytes, a drawback that severely limits the applications of this sensing approach (the "problem of mixtures"). We show here that this is not an intrinsic limitation of the pattern sensing method. Indeed, we developed general guidelines for the design of the sensing, signal detection, and data interpretation methods to avoid this constraint, which resulted in chemical fingerprinting systems capable of recognizing unknown mixtures of analytes in a single experiment, without separation or pre-treatment before data acquisition.

A Sensor Array for the Nanomolar Detection of Azo Dyes in Water.

Azo dyes are ubiquitous pollutants that contaminate water supplies and threaten human, biota, and ecosystem health. Their detection and discrimination are a considerable challenge owing to the numerous structural, chemical, and optical similarities between dyes, complexity of the wastewater in which they are found, and low environmental concentrations. Here, we demonstrate that the inner filter effect (IFE), in combination with conjugated polymer array-based sensing, offers a rapid approach for the quantitative profiling of these pollutants.

Disposable paper strips for carboxylate discrimination.

We describe a method for the differentiation of carboxylate anions on disposable paper supports (common printer paper, filter paper, chromatography paper), based on differential patterns of interactions between carboxylates and a fluorescent sensing system. The sensor was built from commercially available components, namely a polycationic fifth generation amine-terminated poly(amidoamine) dendrimer (PAMAM G5) and a small organic fluorophore (calcein) through non-covalent interactions. The assay's physical dimensions were chosen to conform to the microwell plate standard so detection could be carried out on widely available plate reader instrumentation.

A sensor array for the discrimination of polycyclic aromatic hydrocarbons using conjugated polymers and the inner filter effect.

Natural and anthropogenic activities result in the production of polycyclic aromatic hydrocarbons (PAHs), persistent pollutants that negatively impact the environment and human health. Rapid and reliable methods for the detection and discrimination of these compounds remains a technological challenge owing to their relatively featureless properties, structural similarities, and existence as complex mixtures. Here, we demonstrate that the inner filter effect (IFE), in combination with conjugated polymer (CP) array-based sensing, offers a straightforward approach for the quantitative and qualitative profiling of PAHs.

Bimacrocyclic Effect in Anion Recognition by a Copper(II) Bicyclam Complex.

The dicopper(II) complex of the bimacrocyclic ligand α,α'-bis(5,7-dimethyl-1,4,8,11-tetraazacyclotetradecan-6-yl)--xylene, , interacts with selected anions in dimethyl sulfoxide solution according to two different modes: (i) halides (Cl, Br, and I) and N coordinate the two metal centers at the same time between the two macrocyclic subunits that face each other and (ii) anionic species that do not fit the bridging coordination mode (e.g., NCO, SCN, CHCOO, NO , and HPO ) interact with copper(II) ions only at the "external" positions or their interaction is too weak to be detected.

Anion Recognition in Water, Including Sulfate, by a Bicyclam Bimetallic Receptor: A Process Governed by the Enthalpy/Entropy Compensatory Relationship.

The dimetallic system [Cu (L)] contains two facing equivalent metallocyclam subunits and incorporates ambidentate anions, mono- (halides) and poly-atomic (sulfate), which bridge the two Cu centres. Isothermal titration calorimetry (ITC) experiments in water showed that the log K values of the inclusion equilibria for halides and sulfate varied over a restricted interval (3.6±0.

A supramolecular sensing array for qualitative and quantitative analysis of organophosphates in water.

The organophosphate class of compounds includes common herbicides as well as highly toxic nerve gases whose detection is important from an environmental and a public safety perspective. We describe here a fluorescence turn-on sensor array for the rapid detection and quantitation of relevant organophosphates in neutral water. The array elements self-assemble from commercially available dyes and PAMAM dendrimers, and sensing is based on an indicator displacement assay.

An off-the-shelf sensing system for physiological phosphates.

An off-the-shelf supramolecular sensing system was designed to discriminate biologically relevant phosphates in neutral water using multivariate data analysis. The system is based on an indicator displacement assay comprising only two unmodified commercially available components: a dendritic poly-electrolyte and a common fluorescent dye. Effective discrimination of nucleotide diphosphates and inorganic diphosphate was achieved through principal component analysis (PCA).

The role of protein characteristics in the formation and fluorescence of Au nanoclusters.

Protein-encapsulated gold nanoclusters have shown many advantages over other gold nanocluster systems, including green synthesis, biocompatibility, high water solubility, and the ease of further conjugation. In this article, we systematically investigated the effects of the protein size and amino acid content on the formation and fluorescent properties of gold nanoclusters using four model proteins (bovine serum albumin, lysozyme, trypsin, and pepsin). We discovered that the balance of amine and tyrosine/tryptophan containing residues was critical for the nanocluster formation.

Differentiation of Functional Groups and Biologically Relevant Anions Using AT-PAMAM Dendrimers.

Biological anions have often proven to be difficult analytes to differentiate in solution. Many of the anions bear similar structural characteristics and similar charge states. Using a commercially available indicator and AT-PAMAM dendrimers, a sensing ensemble for a number of biological anions was constructed.

Electronic structure and photophysics of (C=C)tetra-p-tolylporphyrin2+.

The electronic structure and photophysical properties of (C=C)TTP(2+) (TTP = tetra-p-tolylporphyrin) were scrutinized by using quantum mechanical calculations and transient absorption spectroscopic measurements. When compared to a metalloporphyrin, the presence of the C=C unit in (C=C)TTP(2+) causes a splitting of the degenerate LUMO and a large decrease in the HOMO-LUMO gap, while the 2+ charge and tolyl groups lead to additional charge-transfer-like transitions in the visible absorption spectrum. The small HOMO-LUMO gap and ruffled structure lead to a very short excited-state lifetime of 10 ± 0.

PAMAM dendrimer-induced aggregation of 5(6)-carboxyfluorescein.

The binding of the fluorescent polyanionic probe 5(6)-carboxyfluorescein (CF) to various generations of dendrimers (G3-G7) was studied in buffered aqueous media by absorbance and fluorescence spectroscopy and by isothermal titration calorimetry (ITC). Absorbance, fluorescence, and fluorescence anisotropy data were collected concurrently by using a multiwell plate format. Because ITC does not depend on the presence of a chromophore/fluorophore for measurement, it allowed the exploration of concentration ratios otherwise unattainable in the spectroscopy experiments.

The use of differential receptors to pattern peptide phosphorylation.

An array sensing scheme for the differentiation of small peptides and their phosphorylated analogues is introduced. The technique involves a series of receptors created by appending random peptides to a C(3v) symmetric scaffold that binds phosphomonoesters. Five specific peptide sequences were selected through a screening technique.

Homo- and hetero-dinuclear anion complexes.

The tripodal system 4, in which urea fragments are appended to the three terminal amine nitrogen atoms of a tris(2-aminoethyl)amine (tren) subunit, includes a Cu(II) ion and two anions X-, according to a cascade mechanism through three well defined stepwise equilibria in a DMSO solution. The first anion X- (halide, N3-, NCS-, NO2-, H2PO4-) seeks the Cu(II) centre coordinated by the tren moiety; the second anion X- interacts with the trisurea cavity, but this occurs only if the stronger H-bond acceptors, such as N3- and H2PO4-, are used. Binding of the second X- ion is favoured by the preorganising effect exerted by the metal and disfavoured by the steric and electrostatic repulsions between the anions.

The influence of the boat-to-chair conversion on the demetallation of the nickel(II) complex of an open-chain tetramine containing a piperazine fragment.

The nickel(II) complex with an open chain tetramine containing a piperazine fragment (1) displays an unusual resistance to demetallation in acidic solution and exhibits a lifetime of about five minutes in a solution 0.1 M in HClO4 and 7.0 M in NaClO4.

Does a reinforced kinetic macrocyclic effect exist? the demetallation in strong acid of copper(II) Complexes with open and cyclic tetramines containing a piperazine fragment.

The demetallation in acidic solution of the Cu(II) complexes with open-chain and cyclic tetramines containing a piperazine unit (2 and 3) has been investigated in terms of its kinetic aspects and compared with the behaviour of unsubstituted counterparts (tetramines 1 and 4). The presence of the piperazine fragment slows demetallation of the open-chain-ligand complex owing to the activation barrier associated with the conformational change from boat-to-half-boat; however, it does not affect the demetallation of the macrocyclic complex, which involves the spontaneous boat-to-twist conformational change. Thus, lateral reinforcement of a cyclam-like ligand does not add any further contribution to the typical inertness in demetallation of macrocyclic complexes.