New fluorescent and colorimetric chemosensors based on the rhodamine and boronic acid groups for the detection of Hg

Novel rhodamine B (RB) derivatives bearing mono and bis-boronic acid groups were investigated as Hg²⁺ selective fluorescent and colorimetric sensors. These derivatives are first examples of reversible fluorescent chemosensors for Hg²⁺ which utilized boronic acid groups as binding sites. Two new RB-boronic acid derivatives displayed selective ‘Off-On’-type fluorescent enhancements and distinct color changes with Hg²⁺. Selective fluorescent enhancement of two rhodamine derivatives was attributed to ring opening from the spirolactam (nonfluorescent) to ring-opened amide (fluorescent).     

Searching for the main anti-bacterial components in artificial Calculus bovis using UPLC and microcalorimetry coupled with multi-linear regression analysis

The fingerprints of artificial Calculus bovis extracts from different solvents were established by ultra-performance liquid chromatography (UPLC) and the anti-bacterial activities of artificial C. bovis extracts on Staphylococcus aureus (S. aureus) growth were studied by microcalorimetry. The UPLC fingerprints were evaluated using hierarchical clustering analysis. Some quantitative parameters obtained from the thermogenic curves of S. aureus growth affected by artificial C. bovis extracts were analyzed using principal component analysis. The spectrum-effect relationships between UPLC fingerprints and anti-bacterial activities were investigated using multi-linear regression analysis. The results showed that peak 1 (taurocholate sodium), peak 3 (unknown compound), peak 4 (cholic acid), and peak 6 (chenodeoxycholic acid) are more significant than the other peaks with the standard parameter estimate 0.453, -0.166, 0.749, 0.025, respectively. So, compounds cholic acid, taurocholate sodium, and chenodeoxycholic acid might be the major anti-bacterial components in artificial C. bovis. Altogether, this work provides a general model of the combination of UPLC chromatography and anti-bacterial effect to study the spectrum-effect relationships of artificial C. bovis extracts, which can be used to discover the main anti-bacterial components in artificial C. bovis or other Chinese herbal medicines with anti-bacterial effects.     

Boronic acid-based fluorescent receptors for selective recognition of thymine glycol

Thymine glycol is the major oxidation product of thymine. The amount of thymine glycol present within cellular DNA is one marker of the extent of oxidative damage, and chemosensors for thymine glycol have therefore a number of potential applications. In continuation of our studies devoted to the detection of modified nucleosides, we report herein our results toward the fluorescence detection of thymine glycol at both the nucleoside and the oligonucleotide levels using boronic acid sensors. These receptors show significant fluorescence enhancements and high selectivities in aqueous conditions upon binding with thymine glycol.     

A dual role of phenylboronic acid as a receptor for carbohydrates as well as a quencher for neighboring pyrene fluorophore

A simple amino acid based compound (1) containing a phenyl boronic group and pyrene fluorophore showed an enhanced fluorescence in aqueous solutions at physiological pH through suppression of the photoinduced electron transfer from pyrene to boronic acid on carbohydrate binding. The compound exhibited an interesting fluorescence change depending on pH with decreased emission intensity at acidic pH but enhanced emission intensity at basic pH unlike the fluorescent carbohydrate chemosensors using a PET process with amine and aryl-boronic acid. We have characterized a dual role of phenylboronic acid as a receptor for carbohydrates as well as a quencher for the fluorescence of pyrene fluorophore.     

Isolation and quantification of oligomeric pyranoanthocyanin-flavanol pigments from red wines by combination of column chromatographic techniques

A combination of column chromatography on Toyopearl gel HW-40 (S) and polyamide resin has been developed for the preparative isolation and further determination of pyranoanthocyanins of oligomeric nature formed after reaction between anthocyanins and different flavanols in a complex wine matrix. Polyamide chromatography was found to be exceptionally useful to separate oligomeric pyanoanthocyanins from other classes of wine flavonoids and polymerized pigments into an advanced state of purity for further identification and quantification by HPLC-diode array detector coupled with electrospray ionization mass spectrometry (HPLC-DAD/ESI-MS). Fractionation on Toyopearl gel chromatography allowed the separation of pyranoanthocyanins bearing the same flavanols (catechin, epicatechin and procyanidin dimers) but with different anthocyanin moieties (either acylated or non-acylated in the glucose residue) in order to allow further isolation of individual oligomeric pigments on C18 chromatography. A quantitative procedure for analyzing the major pyranoanthocyanin-flavanol derivatives in different aged wines is proposed for the first time. Results obtained showed good reproducibility and recovery regarding sample pretreatment and quantitative method for all analyzed oligomeric pyranoanthocyanins. The combination of these two chromatographic separations is likely to be applicable to the preparative isolation of other anthocyanin-derived pigments.     

Skeleton-selective fluorescent chemosensor based on cyclodextrin bearing a 4-amino-7-nitrobenz-2-oxa-1,3-diazole moiety

A new type of fluorescent chemosensor, based on modified cyclodextrins bearing the fluorophore unit NBD-amine, was prepared. One of these new chemosensors, NC0betaCD, is sensitive to adamantane and borneol derivatives, which have a comparatively spherical shape that fits the beta-CD cavity, but is not sensitive to bile acids, which are strongly bound by the native beta-CD. Even in the presence of a bile acid, NC0betaCD can detect 1-adamantanol. Another of this new type of chemosensors, NC0gammaCD, is sensitive to bile acids but not to adamantane derivatives. The response of the new type of chemosensors to a guest was an increase in the fluorescence intensity.     

Stereochemical and regiochemical trends in the selective detection of saccharides

Several discreet sugar-boronate complexes exist in solution. This is due to the complex equilibria between isomeric species of even the simplest monosaccharides. In the current investigation, we determine the regio- and stereochemical features of the various equilibrating sugar isomers that induce signal transduction in boronic acid chemosensors such as 1 as well as 2 and 3. We present a unique example of a chemosensor (1) that is selective for ribose, adenosine, nucleotides, nucleosides, and congeners. As a result of this study, we are able to predict and achieve selective fluorescence and colorimetric responses to specific disaccharides as a consequence of their terminal sugar residue linkage patterns and configurations. We also find that the combined use of chemosensors exhibiting complementary reactivities may be used cooperatively to obtain enhanced selectivity for ribose and rare saccharides.     

A voltammetric electronic tongue made of modified epoxy-graphite electrodes for the qualitative analysis of wine

First results are presented of a new voltammetric electronic tongue which employs modified epoxy-graphite electrodes. This analytical tool has been applied to qualitative wine analysis, performing the classification of wine varieties, as well as recognition of the oxygenation effect. In the same way, studies related to the detection of some defects in wine production were also assessed, such as its vinegary taste in open-air contact or the use of excess sulphite preservative. The electronic tongue was formed by five voltammetric electrodes, four of them being bulk-modified with different substances: copper and platinum nanoparticles on one side, and polyaniline and polypyrrole powder on the other. The responses were preprocessed employing Principal Component Analysis (PCA) to visualize and identify distinct episodes. The resulting PCA scores were modelled with an artificial neural network that accomplishes final prediction with the qualitative classification of wines and/or detection of defects.     

Determination of total polyphenol index in wines employing a voltammetric electronic tongue

This work reports the application of a voltammetric electronic tongue system (ET) made from an array of modified graphite-epoxy composites plus a gold microelectrode in the qualitative and quantitative analysis of polyphenols found in wine. Wine samples were analyzed using cyclic voltammetry without any sample pretreatment. The obtained responses were preprocessed employing discrete wavelet transform (DWT) in order to compress and extract significant features from the voltammetric signals, and the obtained approximation coefficients fed a multivariate calibration method (artificial neural network-ANN-or partial least squares-PLS-) which accomplished the quantification of total polyphenol content. External test subset samples results were compared with the ones obtained with the Folin–Ciocalteu (FC) method and UV absorbance polyphenol index (I₂₈₀) as reference values, with highly significant correlation coefficients of 0.979 and 0.963 in the range from 50 to 2400 mg L⁻¹ gallic acid equivalents, respectively. In a separate experiment, qualitative discrimination of different polyphenols found in wine was also assessed by principal component analysis (PCA).     

The Development of Boronic Acids as Sensors and Separation Tools

Synthetic receptors for diols that incorporate boronic acid motifs have been developed as new sensors and separation tools. Utilizing the reversible interactions of diols with boronic acids to form boronic esters under new binding regimes has provided new hydrogel constructs that have found use as dye‐displacement sensors and electrophoretic separation tools; similarly, molecular boronic‐acid‐containing chemosensors were constructed that offer applications in the sensing of diols. This review provides a somewhat‐personal perspective of developments in boronic‐acid‐mediated sensing and separation, placed in the context of the seminal works of others in the area, as well as offering a concise summary of the contributions of the co‐authors in the area. DOI 10.1002/tcr.201200006     

Catechol Moiety Integrated Tri-Aryl Type AIEgen for Visual and Quantitative Boronic Acid Detection

Novel functional AIEgen based on three compact bound aryl skeletons is designed and synthesized. This tri-aryl type luminogen (TA-Catechol) embedded with catechol moiety responds rapidly to series of boronic acids. Real-time visual and quantitative dual-mode detection method is established for the first time with modest precision and low detection limit (8.0 μM). Detailed mechanistic discussion identifies tetra-coordinated boronic species as the key intermediate within sensing procedure. Wide range of organic boronic acids compatible with this strategy is displayed which is promising in high throughput screening technology. Furthermore, solid-state sensing capability of TA-Catechol is also demonstrated.     

A highly selective and sensitive fluorescence sensing system for distinction between diphosphate and nucleoside triphosphates

Among the numerous chemosensors available for diphosphate (P(2)O(7)(4-), PPi) and nucleoside triphosphates (NTPs), only a few can distinguish between PPi and NTPs. Hence, very few bioanalytical applications based on such selective chemosensors have been realized. We have developed a new fluorescence sensing system for distinction between PPi and NTPs based on the combination of two sensors, a binuclear Zn(II) complex (1·2Zn) and boronic acid (BA), in which one chemosensor (1·2Zn) shows signal changes depending on the PPi (or NTP) concentration, and the other (BA) blocks the signal change caused by NTPs; this system enables the distinction of PPi from NTPs and is sensitive to nanomolar concentrations of PPi. The new sensing system has been successfully used for the direct quantification of RNA polymerase activity.     

超分子体系强的分子识别研究 23: 多胺修饰β-环糊精及其铜 配合物与萘衍生 物的包结配位作用

用荧光光谱滴定法测定了单-[6-(二乙烯三胺)-6-脱氧]-β-环糊精(1)、单-[6-(三乙烯四胺)-6-脱氧]-β-环糊精(2)及其铜配合物(3,4)与一系列萘衍生物在磷酸缓冲溶液(pH7.2,0.1mol.dm^-^3)中,25℃时形成超分子体系的稳定常数,并与母体β-环糊精的配位能力进行了比较。化学计量法表明,四种化学修饰β-环糊精与萘衍生物形成了1:1的超分子配合物。从尺寸适合、几何互补及多点识别等方面讨论了主体化合物对模型底物的分子选择性键合能力。结果表明,疏水相互作用、范德华力、静电相互作用及氢键等多种非共价键弱相互作用协同贡献于超分子配合物的形成,主-客体间的结构匹配在分子受体选择性键合底物形成超分子配合物中起重要作用。     

HPLC coupled with fluorescence detection for the determination of procyanidins in white wines

Summary In this study a high-performance liquid chromatography method was developed for the determination of procyanidin dimers B1, B2, B3, B4 and procyanidin trimers C1 and T2 in white wine using fluorescence detection. This method allowed analysis of white wine with no prior treatment. Limits of quantification were form 12 μg.L⁻¹ to 16 μg.L⁻¹. Reproductibility data for replicate analysis was measured and the CV was less than 4.5%. This method was used for the determination of these compounds in six French white wines.     

Allosteric Indicator Displacement Enzyme Assay for a Cyanogenic Glycoside

Indicator displacement assays (IDAs) represent an elegant approach in supramolecular analytical chemistry. Herein, we report a chemical biosensor for the selective detection of the cyanogenic glycoside amygdalin in aqueous solution. The hybrid sensor consists of the enzyme β‐glucosidase and a boronic acid appended viologen together with a fluorescent reporter dye. β‐Glucosidase degrades the cyanogenic glycoside amygdalin into hydrogen cyanide, glucose, and benzaldehyde. Only the released cyanide binds at the allosteric site of the receptor (boronic acid) thereby inducing changes in the affinity of a formerly bound fluorescent indicator dye at the other side of the receptor. Thus, the sensing probe performs as allosteric indicator displacement assay (AIDA) for cyanide in water. Interference studies with inorganic anions and glucose revealed that cyanide is solely responsible for the change in the fluorescent signal. DFT calculations on a model compound revealed a 1:1 binding ratio of the boronic acid and cyanide ion. The fluorescent enzyme assay for β‐glucosidase uses amygdalin as natural substrate and allows measuring Michaelis–Menten kinetics in microtiter plates. The allosteric indicator displacement assay (AIDA) probe can also be used to detect cyanide traces in commercial amygdalin samples.     

A unique quinolineboronic acid-based supramolecular structure that relies on double intermolecular B-N bonds for self-assembly in solid state and in solution

The boronic acid functional group plays very important roles in sugar recognition, catalysis, organic synthesis, and supramolecular assembly. Therefore, understanding the unique properties of this functional group is very important. 8-Quinolineboronic acid (8-QBA) is found to be capable of self-assembling in solid state through a unique intermolecular B-N bond mechanism reinforced by intermolecular boronic anhydride formation, π-π stacking, and hydrogen bond formation. NMR NOE and diffusion studies indicate that intermolecular B-N interaction also exists in solution with 8-QBA. In contrast, a positional isomer of 8-QBA, 5-quinolineboronic acid (5-QBA) showed very different behaviors in crystal packing and in solution and therefore different supramolecular network. Understanding the structural features of this unique 8-QBA assembly could be very helpful for the future design of new sugar sensors, molecular catalysts, and supramolecular assemblies.     

Glucose recognition by a supramolecular complex of boronic acid fluorophore with boronic acid-modified cyclodextrin in water

A boronic acid fluorophore (C1-APB)/boronic acid-modified γ-cyclodextrin (3-PB-γ-CyD) complex as a supramolecular sensor has been designed for selective glucose recognition in water. The fluorescent response behavior of the C1-APB/3-PB-γ-CyD complex under various pH conditions revealed that a C1-APB/3-PB-γ-CyD complex solution containing glucose showed a large increase in the fluorescence intensity under alkaline pH conditions. In contrast, only small increases in the fluorescence intensity were noted for fructose and without sugar solutions. The observed response selectivity for the C1-APB/3-PB-γ-CyD complex was on the order of glucose > galactose, mannose > fructose. The evidence on a large value of the inclusion constant (K(L·CyD) = 6.5 × 10(3) M(-1)), a marked broadening of the (1)H NMR spectra, and an enhancement of induced circular dichloism (ICD) intensity for the C1-APB/3-PB-γ-CyD complex by glucose binding supported the multi-point interaction of the C1-APB/3-PB-γ-CyD complex with glucose. These results demonstrated that the C1-APB/3-PB-γ-CyD complex functioned as an efficient supramolecular sensor for selective glucose recognition in water.     

1,3,5,7-四甲基-8-丙酰肼-二氟化硼-二吡咯甲烷柱前衍生高效液相色谱测定白酒中的脂肪醛

以合成的1,3,5,7-四甲基-8-丙酰肼-二氟化硼-二吡咯甲烷(BODIPY-丙酰肼)作为柱前荧光衍生试剂,用于高效液相色谱分离荧光法检测甲醛、乙醛、丙醛、丁醛、戊醛、己醛、庚醛、辛醛、壬醛、癸醛、十一醛、十二醛等12种脂肪醛.通过对衍生条件和分离条件进行优化,建立了测定脂肪醛的HPLC/FD新方法.衍生反应以H3P...     

Highly efficient fluorescent sensing for α-hydroxy acids with C3-symmetric boronic acid-based receptors

Two boronic acid-based fluorescent chemosensors in C₃ symmetry have been prepared with a facial method. These compounds show remarkable ability to recognize α-hydroxycarboxy acids and sugar acids over most saccharides. The fluorescence intensity of the receptors decreased obviously upon adding the α-hydroxy acids in a pH 8.71 buffer of methanol-water, which can be explained with the internal charge-transfer (ICT) mechanism.