Photoluminescence Rainbow from Coelenteramide—A Theoretical Study

A wide variety of marine bioluminescent organisms emit light via the excited‐state coelenteramide, which is produced from the coelenterazine oxidation via a series of complicated chemical reactions in protein. Photoluminescence of coelenteramide is a simple way to produce light without experiencing the intricate reactions starting from coelenterazine. To extend the color range of light emission, many coelenterazine analogues were synthesized, but mostly only produce blue and cyan fluorescence. Based on the 42 synthesized coelenterazine analogues, we theoretically studied the absorption and fluorescence properties of the corresponding coelenteramide analogues. The electronic effect, steric effect, conjugated effect and solvated effect were considered. The results indicated that conjugated effect has great influence on the strength and wavelength of fluorescence and large electron transfer is beneficial to redshift. Based on the regularities, we theoretically designed six coelenteramide analogues, and together with the original coelenteramide, the seven‐ones emit the seven colors of rainbow via their photoluminescences. This study expands the coelenteramide fluorescence to the whole visible light region and could inspire new application.     

Fluorimetric reaction-rate methods of inorganic analysis: a review

A review is given of the utilization in analytical chemistry of the rate of fluorescence reactions of inorganic species. These methods are of recent development and suggest the possibility of further analytical procedures. Two main types of methods, enzymatic and non-enzymatic, are distinguished, and their applications to inorganic analysis are discussed.     

Kinetics in cold Laval nozzle expansions: from atmospheric chemistry to oxidation of biomolecules in the gas phase.

New developments and recent applications of pulsed and miniaturised Laval nozzle technology allowing many gas-phase molecular processes to be studied at very low temperatures are highlighted. In the present Minireview we focus on molecular energy transfer and reactions of molecular radicals (e.g. OH) with neutral molecules. We show that with the combination of pulsed laser photolysis and sensitive laser-induced fluorescence detection a large number of fast reactions of radicals with more or less complex neutral molecules can be measured in Laval nozzle expansions nowadays. It is also demonstrated that collisional energy transfer of neutral molecules can be measured via kinetically controlled selective fluorescence (KCSF) excitation down to 58 Kelvin. Finally, we show that even the primary steps in the oxidation of biomolecules or biomolecular building blocks initiated by OH radicals can be followed at low temperatures. The temperature dependence of the measured rate constants is the key for an understanding of the underlying molecular mechanisms and the Laval nozzle expansion provides a unique environment for these measurements. The experimental finding that many reactions between radicals and neutral species can be rapid at low temperatures are discussed in terms of pre-reactive complexes formed in the overall complex forming bimolecular reactions.     

An evaluation of GC-MS and HPLC-FD methods for analysis of protein binders in paintings

Two chromatographic methods have been compared for analysis of protein-binding media used in paintings, namely, HPLC with fluorescence detection and GC-MS. The proteins were hydrolyzed to the corresponding amino acids (AAs) by gaseous HCl and the AAs were derivatized with methyl chloroformate, followed by GC-MS or by HPLC after derivatization with the AccQ fluorescence reagent. The hydrolysis, derivatization reactions and the chromatographic procedures have been optimized and applied to standard binding media, model and real samples of paintings. The methods have been compared and critically evaluated.     

Design and use of fluorogenic aldehydes for monitoring the progress of aldehyde transformations

We describe the first examples of fluorogenic aldehydes useful for monitoring many types of reactions including aldol reactions, allylations, and reductions. The fluorogenic aldehydes were constructed by covalent combination of a fluorophore and an aldehyde moiety via a linker. In the resulting single molecule, the aldehyde functioned as a quencher of the fluorophore's fluorescence. The reaction product, modified at the aldehyde functionality, no longer served as an effective quencher. The reaction products showed up to approximately 80-fold higher fluorescence than the aldehyde reactants.     

Polymeric fluorescent dyes for labeling of proteins and nucleic acids

In order to increase the sensitivity of fluorescence labeling in biochemical reactions and diagnostic procedures a labeling technique with polymeric fluorescence dyes was established and tested for its applicability. The fluorescence dye is based on the fluorophor coumarine and was covalently linked to the model proteins strepavidine and IgG. The dye was synthesized by radical polymerization of three different types of functional monomers to ensure water solubility, covalent coupling to proteins, and fluorescence. The molecular weight range was between 20 and 200 kDa. Fractions of narrow molecular weight distribution were prepared by gel filtration on Superdex 200. The relationship between size and charge of the different fractions was analyzed by gel electrophoresis. Covalent conjugation to proteins was carried out by formation of a peptide bond between a carboxylic group of the functional monomers and an amino group of the protein mediated by 1-ethyl-3-(3-dimethylamino-propyl)-carbodiimide (EDC). A novel type of gel electrophoresis was developed in order to analyze and optimize the conjugation reaction; the results were in agreement with those from analytical ultracentrifugation with fluorescence detection. Hydrodynamic studies of the uncoupled dye and the protein-dye conjugates exhibited a drastic decrease of Stokes radius of the dye due to the coupling to the protein. Under optimum conditions the fluorescence intensity of a protein-polymeric dye conjugate was enhanced 40-fold compared to a monomeric dye. Biotin binding to the protein streptavidin was not affected significantly by the conjugation with the polymeric dye. At present, the applicability of the polymeric dye in biochemical and diagnostic reactions seems to be limited due to strong but unspecific hydrophobic interactions which might be overcome by using fluoresceine as monomeric dye.     

Raman spectrometry as a screening tool for solvent-extracted azo dyes from polyester-based textile fibres

Some types of textile fibres are considered to be the cause of allergic reactions and other adverse health effects on humans. The main compounds behind these health problems usually contain azo groups in their chemical structure, which are widely employed as azo dyes in the manufacture of textile and clothing products. In this respect, availability of simple analytical procedures for identifying azo groups in textiles is of concern, not only for toxicological studies, but also for clinical and forensic investigations. In this work, conventional Raman spectrometry was assessed as an analytical tool for identification of the azo function in the extracts of fibres obtained after applying a liquid-solvent extraction procedure to the polyester-based textile products. A medium-polarity solvent of ethanol-diethyl ether (1:1 mixture) was shown to be the most effective extraction medium. Two laser lines at 514.5 nm and 785 nm were compared, with the longer wavelength preferred as additional peaks were identified in the Raman spectrum, which had better signal-to-background and signal-to-noise ratios owing to decreased fluorescence in contrast to excitation at 514.5 nm. The method reported is a convenient procedure that can be applied in many instances when rapid screening of fibre dyes is required.     

Organomercury Compounds in Organic Synthesis

Organomercurials have been known since 1850 and many synthetic routes to these compounds presently exist. The ability of these compounds to accommodate a wide variety of functional groups and to tolerate quite diverse reaction conditions makes them attractive as synthetic intermediates. While the solvomercuration-demercuration and divalent carbon transfer reactions remain the most widely used of the organomercurial reactions, a number of new synthetic procedures employing organomercurials have been developed in recent years. Many of these involve transmetallation reactions with palladium salts.     

Reproducibility and scalability of solvent-free microwave-assisted reactions: from domestic ovens to controllable parallel applications

The heating of different parallel arrays in domestic ovens offers the possibility to perform multiple reactions in one irradiation experiment, blending the advantages of microwave heating technology and parallel chemistry. However, they are usually performed without an appropriate temperature control; thus, reproducibility becomes a major issue limiting the application of such reactions. This is exemplified when working at a different scales or using different instruments. For the first time a typical solvent-free reaction described in a domestic oven has been reproduced in monomode reactor, scaled up in a controlled multimode oven and reproduced in parallel, 24 reactions were carried out in a well plate. Parallel reactions were performed in a Weflon multiwell plate to assure identical conditions for each individual reaction. As many reactions under microwave irradiation have been performed in solvent-free conditions, this result opens new possibilities in reproducibility, scalability and combinatorial chemistry and permits to take advantage of many synthetic procedures described in domestic ovens.     

Wittig and Wittig-Horner reactions under phase transfer catalysis conditions

Wittig and Wittig-Horner reactions are favorite tools in preparative organic chemistry. These olefination methods enjoy widespread and recognition because of their simplicity, convenience, and effciency. Phase transfer catalysis (PTC) is a very important method in synthetic organic chemistry having many advantages over conventional, homogenous reaction procedures. In this paper, we attempt to summarize the aspects concerning Wittig and Wittig-Horner reactions that take place under phase transfer catalysis conditions.     

碳碳不饱和键氟化加成反应的研究进展

选择性地向有机物中引入氟原子越来越受到重视，近年来通过碳碳不饱和键的 氟化加成来引入氟原子发展迅速。综述了碳碳不饱和键氟化加成反应的研究进展。     

Removal of Ascorbic Acid Interference in Horseradish Peroxidase Estimations of Hydrogen Peroxide

Abstract

Ascorbic acid, which depresses the colour and interferes in reactions in colorimetric and fluorometric assay procedures for hydrogen peroxide involving horseradish peroxidase, has been removed from solutions by treatment with an iodine reagent. This reagent strongly interferes with procedures involving scopoletin, 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) and the reaction between 3-dimethylaminobenzoic acid and 3-methyl-2-benzothiazolinone hydrazone. The iodine reagent slightly depressed the fluorescence obtained using hydroxyphenylacetic acid but this was the most suitable electron donor for amounts of hydrogen peroxide between 6 and 60 nmol. Hydroxyphenylacetic acid spontaneously reduces residual iodine.     

Capillary gel electrophoresis of single-stranded DNA fragments with UV detection

Capillary gel electrophoresis has proven to be a powerful tool in biomedical research. We report our investigation of some of the critical parameters affecting separations of single-stranded DNA fragments as monitored by ultraviolet (UV) absorbance detection. Although not as sensitive as laser-induced fluorescence (LIF), UV absorbance detection allows one to calculate quite accurately, and inexpensively, the molarity of each separated DNA fragment and, moreover, the signal “fading” effect normally observed with LIF detection can be, in many cases, substituted for fluorescence to detect the many different single-stranded DNAs, as well as for detection of sequencing reactions.     

PHOTO-INDUCED INTERMOLECULAR AND INTRAMOLECULAR ELECTRON-TRANSFER REACTIONS BETWEEN XANTHENE DYES AND DONORS/ACCEPTORS

A number of electron donors, acceptors and diads containing xanthene dyes were sythesized. When the dyes were excited, the rate constants and the efficiencies of the intermolecular and intramolecular photo-induced electron transfer reactions were determined and calculated. It is found that the photo-induced electron transfer reactions occurred between xanthene dyes and many, including very weak donors or acceptors. The rate constants of intermolecular reactions were controlled by diffusion, and influenced by the reactant concentrations. The laser flash experiments showed that for low reactant concentrations, this kind of reactions took place mainly via the triplet excited state of the dyes. If different electric charges exist with dyes and donors/acceptors, there will be static quenching of the dyes' fluorescence. The intramolecular electron transfer reactions are independent of the solution concentrations, and they may directly proceed via the singlet excited state of the dyes effectively.     

Dual-color fluorescence cross-correlation spectroscopy on a planar optofluidic chip

Fluorescence cross-correlation spectroscopy (FCCS) is a highly sensitive fluorescence technique with distinct advantages in many bioanalytical applications involving interaction and binding of multiple components. Due to the use of multiple beams, bulk optical FCCS setups require delicate and complex alignment procedures. We demonstrate the first implementation of dual-color FCCS on a planar, integrated optofluidic chip based on liquid-core waveguides that can guide liquid and light simultaneously. In this configuration, the excitation beams are delivered in predefined locations and automatically aligned within the excitation waveguides. We implement two canonical applications of FCCS in the optofluidic lab-on-chip environment: particle colocalization and binding/dissociation dynamics. Colocalization is demonstrated in the detection and discrimination of single-color and double-color fluorescently labeled nanobeads. FCCS in combination with fluorescence resonance energy transfer (FRET) is used to detect the denaturation process of double-stranded DNA at nanomolar concentration.     

A simple method for urine estrogen determination of nonpregnant women

Summary A new method for quantitating urinary estrogen by gasliquid chromatography is described. A minimum of 50 cm³ of urine sample is required for the preliminary enzyme hydrolysis. The hydrolysate is extracted with a mixture of ether and ethyl acetate followed by multiple washes or rotary evaporation to eliminate interfering emulsions. The estrogen fractions are silylated, concentrated and chromatographed on a 3% OV-225 column. This method combines the advantages of several procedures while eliminating many of the adverse reactions previously encountered. The method is sufficiently sensitive to quantitate estrogens in the nanogram range.     

Chemistry in microstructured reactors

The application of microstructured reactors in the chemical process industry has gained significant importance in recent years. Companies that offer not only microstructured reactors, but also entire chemical process plants and services relating to them, are already in existence. In addition, many institutes and universities are active within this field, and process-engineering-oriented reviews and a specialized book are available. Microstructured systems can be applied with particular success in the investigation of highly exothermic and fast reactions. Often the presence of temperature-induced side reactions can be significantly reduced through isothermal operations. Although microstructured reaction techniques have been shown to optimize many synthetic procedures, they have not yet received the attention they deserve in organic chemistry. For this reason, this Review aims to address this by providing an overview of the chemistry in microstructured reactors, grouped into liquid-phase, gas-phase, and gas-liquid reactions.     

Photoinduced electron-transfer reactions in two room-temperature ionic liquids: 1-butyl-3-methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium hexafluorophosphate

Photoinduced electron transfer in two room-temperature ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF(6)) and 1-octyl-3-methylimidazolium hexafluorophosphate (OMIM-PF(6)), has been investigated using steady-state fluorescence quenching of 9,10-dicyanoanthracene with a series of single electron donors. From these fluorescence quenching rates, reorganization energy (lambda) values and k(diff) values can be derived from a Rehm-Weller analysis. In many cases, these fluorescence quenching reactions occur at rates larger than what would be expected based on the Smoluchowski equation. In addition, lambda values of 10.1 kcal/mol and 16.3 kcal/mol for BMIM-PF(6) and OMIM-PF(6), respectively, have been determined.     

On-chip processing of particles and cells via multilaminar flow streams

The processing of particles, cells, and droplets for reactions, analyses, labeling, and coating is an important aspect of many microfluidic workflows. However, performing multi-step processes is typically a laborious and time-consuming endeavor. By exploiting the laminar nature of flow within microchannels, such procedures can benefit in terms of both speed and simplicity. This can be achieved either by manipulating the flow streams around the objects of interest, particularly for the localized perfusion of cells, or by manipulating the objects themselves within the streams via a range of forces. Here, we review the variety of methods that have been employed for performing such “multilaminar flow” procedures on particles, cells, and droplets.     

Asymmetric organocatalytic Biginelli reactions: a new approach to quickly access optically active 3,4-dihydropyrimidin-2-(1H)-ones

The Biginelli reaction, known for over 100 years, is an important multicomponent reaction for accessing dihydropyrimidinones (DHPMs). The individual enantiomers of DHPMs exhibit different or even opposite pharmaceutical activities, which require synthetic methods to easily access the optically pure DHPMs. In recent decades, many efforts have focused on developing procedures for the preparation of optically active Biginelli products. In this article, we will summarize the developments in the synthetic methods to access optically active DHPMs with an emphasis on the recent advances in the asymmetric catalytic Biginelli reactions, along with concepts to design the organocatalytic asymmetric variants.