Octahedral non-heme non-oxo Fe(IV) species stabilized by a redox-innocent N-methylated cyclam-acetate ligand

The ligand 1,4,8-tri-N-methyl-1,4,8,11-tetraazacyclotetradecane-11-acetic acid (Me3cyclam-acetic acid) has been synthesized by Eschweiler-Clarke methylation of cyclam-acetic acid, and the iron(III) complex [(Me3cyclam-acetate)FeN3]PF6, 1, has been synthesized, which has been found to have significantly different properties than its unmethylated analogue, [(cyclam-acetate)FeN3]PF6, 2. Whereas the iron ion in 2 is low spin with S = 1/2, 1 is found to be high spin at temperatures above 100 K, though low-spin species are observed at lower temperatures, indicating a spin crossover phenomenon. The iron(II) species 1red is electrochemically more accessible than 2red since the Fe2+/3+ redox wave in 1 appears approximately 350 mV more positive than the corresponding wave in 2. Also, 1 displays a reversible Fe3+/4+ redox wave, which is irreversible in 2, denoting that the Fe(IV) species 1ox is kinetically stable. 1red and 1ox have been generated electrochemically in solution and studied spectroscopically. M?ssbauer spectroscopy has confirmed that, in both reduction and oxidation, iron is the redox center, that 1red is high spin (S = 2), and that 1ox is low spin (S = 1), in contrast to 2red which is low spin and 2ox which could not be isolated.     

Ultra‐fast liquid chromatography coupled with electrospray ionization time‐of‐flight mass spectrometry for the rapid phenolic profiling of red maple (Acer rubrum) leaves

The red maple (Acer rubrum) species is economically important to North America because of its sap, which is used to produce maple syrup. In addition, various other red maple plant parts, including leaves, were used as a traditional medicine by the Native Americans. Currently, red maple leaves are being used for nutraceutical and cosmetic applications but there are no published analytical methods for comprehensive phytochemical characterization of this material. Herein, a rapid and sensitive method using liquid chromatography with electrospray ionization time‐of‐flight tandem mass spectrometry was developed to characterize the phenolics in a methanol extract of red maple leaves and a proprietary phenolic‐enriched red maple leaves extract (Maplifa™). Time‐of‐flight mass spectrometry and tandem mass spectrometry experiments led to the identification of 106 phenolic compounds in red maples leaves with the vast majority of these compounds also detected in Maplifa™. The compounds included 68 gallotannins, 25 flavonoids, gallic acid, quinic acid, catechin, epicatechin, and nine other gallic acid derivatives among which 11 are potentially new and 75 are being reported from red maple for the first time. The developed method to characterize red maple leaves phenolics is rapid and highly sensitive and could aid in future standardization and quality control of this botanical ingredient.     

Direct Observation of Unstable Reaction Intermediates by Acid‐Base Complex Formation

The structures of several unstable or metastable reaction intermediates that were photoproduced in crystals were analyzed by using X‐ray techniques. The presence of enough void space around the reactive group(s) is an essential factor for the reaction to occur with retention of the single‐crystal form. To expand the void space, an acid group (COOH) was substituted onto the reactant molecule and acid‐base complex crystals were prepared with several amines, such as dibenzylamine and dicyclohexylamine. Following the formation of such acid‐base complexes in crystals, the metastable structures of nitrenes and red species of photochromic salicylideneanilines have been successfully analyzed by using X‐ray techniques. Moreover, the structure of a Pt complex anion in the excited state has been analyzed, which formed acid‐base complex crystals with various alkylammonium cations. The formation of acid‐base complexes will be a powerful tool for directly observing the structure of unstable or metastable reaction intermediates by using X‐ray techniques.     

Extraction chromatographic studies of Ti(IV) with cyanex 301 as impregnant—Recovery from red mud

Summary A silica gel column impregnated with bis-(2,4,4-trimethylpentyl)dithiophosphinic acid has been studied for the uptake of Ti(IV). Its chemical stability has been examined and its regeneration power checked. The stoichiometry of the extracted species is proposed and the loading capacity of the column material for Ti(IV) assessed. Some important binary separations of Ti(IV) from commonly associated metal ions have been achieved and the column has been used to recover high-purity titanium from red mud, a secondary sector material.     

Chemical Composition and Potential Practical Application of 15 Red Algal Species from the White Sea Coast (the Arctic Ocean)

Though numerous valuable compounds from red algae already experience high demand in medicine, nutrition, and different branches of industry, these organisms are still recognized as an underexploited resource. This study provides a comprehensive characterization of the chemical composition of 15 Arctic red algal species from the perspective of their practical relevance in medicine and the food industry. We show that several virtually unstudied species may be regarded as promising sources of different valuable metabolites and minerals. Thus, several filamentous ceramialean algae (Ceramium virgatum, Polysiphonia stricta, Savoiea arctica) had total protein content of 20–32% of dry weight, which is comparable to or higher than that of already commercially exploited species (Palmaria palmata, Porphyra sp.). Moreover, ceramialean algae contained high amounts of pigments, macronutrients, and ascorbic acid. Euthora cristata (Gigartinales) accumulated free essential amino acids, taurine, pantothenic acid, and floridoside. Thalli of P. palmata and C. virgatum contained the highest amounts of the nonproteinogenic amino acid β-alanine (9.1 and 3.2 μM g⁻¹ DW, respectively). Several red algae tend to accumulate heavy metals; although this may limit their application in the food industry, it makes them promising candidates for phytoremediation or the use as bioindicators.     

Spectrophotometric determination of osmium with 2R-acid in the presence of other platinum metals

Osmium(VIII) produces two coloured species with lambda(max) 680 nm (green) and 530 nm (red) with excess of 2-amino-8-naphthol-3,6-disulphonic acid in aqueous solution. The green complex is stable between pH 2.5 and 8.0 and the red complex between pH 11.0 and 12.0. The effects of temperature and time, reagent concentration, optimum conditions for the spectrophotometric determination of trace amounts of osmium, and other variables, have been studied at pH 11.5. At this pH, other platinum metals do not interfere. The sensitivity of the colour reaction is 0.2 microg/cm(2) and the system conforms to Beer's law over a concentration range of 1.5-10 microg of osmium.     

Spectroscopic study on sorption of hydrogen sulfide by means of red soil

This paper reports the results of the characterization of red soils in relation to the sorption of H2S from coal gas at 500 degrees C by spectroscopic techniques in order to provide more information on red soils' structural change both before and after reaction. In addition, by-products analysis has also been studied using Fourier transform infrared (FTIR) spectroscopy. Before and after the experiments the red soils were characterized with X-ray powder diffraction (XRPD), energy dispersion spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and FTIR spectroscopy. XRPD results indicate that iron oxide species disappear from the original to reacted red soil. EDS analysis shows that a significant amount of sulfur is present in the reacted red soil, which is in agreement with the results of the elemental analysis and the calculated value based on breakthrough curve. XPS regression fitting results further indicate that sulfur retention may be associated with the iron oxides. S 2p XPS fittings point out that the major sulfur species present in the reacted red soil are composed of S(-2), elemental sulfur, polysulfide, sulfite and sulfate. Additionally, the binding energy of iron shifts to a lower position for the reacted red soil, which indicates that iron oxides in the original red soil have been converted into iron sulfide. Appreciable amounts of the by-products CO2, SO2 and COS are detected by on-line FTIR spectroscopy during the initial and later stages of the sorption process. The formation of CO2 is related to the water-shift reaction, and SO2 is probably attributable to the reaction of organic matters and H2S. The concentration of COS is quantified by GC/FPD and found it to be about 350 ppm, which is close to the equilibrium concentration of the reaction of inlet CO and H2S at a temperature of 500 degrees C.     

Redox interaction of sulfonated polyaniline with vanadium(IV) in water

The redox interaction between poly(2-methoxyaniline-5-sulfonic acid) (PMAS, emeraldine form) and V(IV) readily occurred to produce the PMAS(red) and V(V) species in an aqueous solution. Notably, molecular oxygen was able to reoxidize PMAS(red) to form the catalytic redox cycle. This redox interaction was effectively observed in basic conditions rather than in acidic ones.     

A spectrophotometric method for the determination of fenvalerate and cypermethrin in presence of each other

A simple spectrophotometric method has been proposed for the determination of widely used pyrethroid pesticides, cypermethrin and fenvalerate. The method is based on the hydrolysis of these pesticides, upon which they release cyanide. The cyanide is reacted with bromine and pyridine to form glutaconic aldehyde, which is then coupled with sulphanilic acid to give an orange red dye in acidic medium having maximum absorbance at 480 nm. Beer’s law is obeyed in the ranges of 0.18–1.12 and 0.08–0.64 μg/mL for fenvalerate and cypermethrin, respectively. The proposed method is sensitive and found to be free from interferences of a large number of foreign species and other pesticides. The proposed method could be applied to the determination of fenvalerate and cypermethrin in their formulations and environmental samples.     

Enzymatic digestion and chromatographic analysis of arsenic species released from proteins

A method combining gel filtration chromatography (GFC), protease digestion, and ion pair chromatography with inductively coupled plasma mass spectrometry detection was developed for the determination of arsenic species bound to proteins. The method was first established by examining the interactions of two model proteins, metallothionein (MT) and hemoglobin, with three reactive trivalent arsenic species. It was then successfully applied to the speciation of arsenic in red blood cells of rats. Inorganic arsenite (iAs^III), monomethylarsonous acid (MMA^III), and dimethylarsinous acid (DMA^III) were efficiently released from the proteins by protease digestion at pH 8.0, with the recovery ranging from 93% to 106%. There was no oxidation of iAs^III or MMA^III during the protease digestion process. Up to 61% DMA^III (the least stable arsenic species) was unchanged, and the rest was oxidized to the pentavalent dimethylarsinic acid (DMA^V). The arsenic species in the red blood cells of control rats was present as DMA^III complex with hemoglobin. The method enabling the determination of the specific arsenic species that bind to cellular proteins is potentially useful for studying arsenic distribution, metabolism, and toxicity.     

Polysaccharides of algae 69. Monosaccharide composition of polysaccharides of several Pacific red algae studied by reductive hydrolysis of biomass

Polysaccharide composition of 23 species of red algae collected from the coastal waters of Kamchatka and Commander Islands has been determined. Total acid hydrolysis of biomass was carried out in the presence of borane-4-methylmorpholine complex under the conditions where 3,6-anhydrogalactose liberating from sulfated galactans was protected from the acid degradation due to reduction into 3,6-anhydrogalactitol. Partial hydrolysis of biomass in the presence of the same reducing agent gave rise to diastereomeric agarobiitol or carrabiitol (3,6-anhydro-4-O-β-d-galactopyranosyl-l-or -d-galactitol, respectively). Identification of these fragments made it possible to attribute the algal galactans to agars or carrageenans. The data obtained was used to confirm the correlations between the taxonomic status and polysac-charide composition of the red algae.

     

Emission spectra of nitrous oxide supported acetylene flames at atmospheric pressure

The emission spectra of a premixed flame of acetylene supported by nitrous oxide have been recorded under different fuel-gas mixture conditions. The emission spectra in these flames of a series of metals, for which it is difficult to obtain a significant population of ground state atoms for atomic absorption spectroscopy in more conventional flames, have also been studied. The red secondary zone which is present in the fuel-rich flames shows emission attributable to long-lived CN and NH species which form a strongly reducing atmosphere to inhibit refractory oxide formation from elements such as molybdenum, titanium and aluminium introduced into the flame. An attempt has also been made to explain some of the reactions which may occur between the flame species above the primary reaction zone.     

A boronic acid based intramolecular charge transfer probe for colorimetric detection of hydrogen peroxide

Many oxidative stress related diseases and adverse health conditions have been associated with the negative effects of hydrogen peroxide and other similar reactive oxygen species in human body. Therefore, increasing attention has been attracted to the detection and monitoring of hydrogen peroxide in living organisms and food items. In this work, a simple, inexpensive colorimetric method for the quantitative determination of hydrogen peroxide in aqueous sample is described. This method utilizes the de-protection of aryl boronic acid to yield a strongly colored water-soluble dye, which is capable of absorbing and emitting in the red region of the spectrum. The mechanism is faster in alkaline condition and utilizes the intramolecular charge transfer between strong phenolate donor and TCF acceptor, thus allowing a naked eye detection of hydrogen peroxide within seconds. The method is unaffected by the presence of various salts, metal ions, and other interfering species, and it can provide a limit of detection as low as ~1 ppm in aqueous samples. This unique way of generating a fluorogenic donor-acceptor pair holds a potential of this dye and other related derivatives for understanding the role of hydrogen peroxide in physiology and pathology.     

Analysis of oak tannins by liquid chromatography-electrospray ionisation mass spectrometry

Extractable tannins were analysed by liquid chromatography-electrospray ionisation mass spectrometry in two oak species, North American white oak (Quercus alba) and European red oak (Quercus robur). They mainly included various glucose gallic and ellagic acid esters. The structures were partially determined, and they included grandinin/roburin E, castalagin/vescalagin, gallic acid, valoneic acid bilactone, monogalloyl glucose, digalloyl glucose, trigalloyl glucose, ellagic acid rhamnose, quercitrin and ellagic acid.     

Raman spectroelectrochemical study of electrode processes at Neutral red- and poly(Neutral red) modified electrodes

The redox dye Neutral red (NR), adsorbed and electropolymerized at a roughened gold electrode, has been studied by Raman spectroscopy at λ_ex of 676.4 nm in an electrochemical cell. Spectral bands have been assigned based on density functional theory (DFT) calculations. The number and position of the bands, as well as their intensity depend on electrode potential, allowing one to discern different redox forms of NR or its polymer. The observed changes in band positions and intensities have been analyzed. Electrooxidation of hydroquinone and ascorbic acid at a gold electrode modified with adsorbed or electropolymerized layer of NR has been studied with in situ Raman spectroelectrochemical technique. During electrooxidation of solution species, NR layer contains both oxidized and reduced forms of this modifier. It has been shown that the relative content of a reduced form of NR at electrode surface increases with increasing concentration of any of oxidizable species used. It has been concluded that anodic oxidation of ascorbic acid or hydroquinone at NR or polyNR modified electrode proceeds within the modifier layer rather than at a modifier/electrolyte interface. In this respect, electrooxidation follows a redox mechanism.     

Raman spectroelectrochemical study of electrode processes at Neutral red- and poly(Neutral red) modified electrodes

The redox dye Neutral red (NR), adsorbed and electropolymerized at a roughened gold electrode, has been studied by Raman spectroscopy at λ_ex of 676.4 nm in an electrochemical cell. Spectral bands have been assigned based on density functional theory (DFT) calculations. The number and position of the bands, as well as their intensity depend on electrode potential, allowing one to discern different redox forms of NR or its polymer. The observed changes in band positions and intensities have been analyzed. Electrooxidation of hydroquinone and ascorbic acid at a gold electrode modified with adsorbed or electropolymerized layer of NR has been studied with in situ Raman spectroelectrochemical technique. During electrooxidation of solution species, NR layer contains both oxidized and reduced forms of this modifier. It has been shown that the relative content of a reduced form of NR at electrode surface increases with increasing concentration of any of oxidizable species used. It has been concluded that anodic oxidation of ascorbic acid or hydroquinone at NR or polyNR modified electrode proceeds within the modifier layer rather than at a modifier/electrolyte interface. In this respect, electrooxidation follows a redox mechanism.     

In situ Raman spectroelectrochemical study of electrocatalytic processes at polyaniline modified electrodes: Redox vs. metal-like catalysis

Two processes of electrocatalytic oxidation of solution species at conducting polymer modified electrodes have been studied for the first time with in situ Resonance Raman spectroelectrochemical technique at a red laser excitation (λ = 632.8 nm), namely electrooxidation of hydroquinone at a sulfonated polyaniline modified electrode in an acidic solution and electrooxidation of ascorbic acid at polyaniline modified electrode in a pH-neutral solution. In both cases, characteristic Raman features have been identified for different redox forms of conducting polymers and changes in the net redox state of a polymer layer during electrooxidation of solution species have been studied. It has been shown that an increase in the concentration of oxidizable species causes an increase of the net content of a reduced form of polyaniline in the modifying layer. From this, the redox (vs. metal-like) mechanism of electrocatalysis at conducting polymer modified electrodes has been deduced.     

Determination of sulfonated azo dyes in river water samples by capillary zone electrophoresis

A method based on capillary zone electrophoresis coupled with photodiode-array detection has been developed to determine several sulfonated dyes, including a sulfonated dye (acid yellow 1), and the sulfonated azo dyes acid orange 7, acid orange 12, acid orange 52, acid red 26, acid red 27 and acid red 88. A CElect-FS75 CE column is used. The electrophoresis buffer contains a 1:5 dilution of 10 mM phosphoric acid and tetrabutylammonium hydroxide buffer (pH 11.5), and 25 mM of triethylamine, the final pH being 11.55. The detection limits for the seven dyes ranged from 0.1 to 4.53 microg/ml. Spiked river water samples (100 ml), containing different concentration levels (0.025-0.150 microg/ml) of the dyes were analyzed after acidification (pH 3) and pre-concentration in disposable SPE Oasis HLB, 1 ml cartridges.     

A Portable Fill‐and‐Flow Channel Biosensor with an Electrode to Predict the Effect of Interferences

A portable fill‐and‐flow channel biosensor with a “predictor electrode” is described. The predictor electrode, on the opposite channel wall and upstream of the detector electrode, allows direct evaluation of the current due to interfering species at the detector electrode. A model is developed which shows that the reaction at the upstream predictor electrode has no significant effect on the concentration distribution of the interfering species at the detector electrode. This enables a straightforward correction of the current at the detector electrode and a determination of the analyte concentration. The effect of interference from ascorbic acid in the detection of glucose in samples was efficiently removed by using such a concept. The recovery of glucose from samples containing ascorbic acid was 103% (s=12%, n=3). The approach was also applied to a biosensor for the determination of glucose in red wine samples containing polyphenolic interferents.     

Photoconvertible fluorescent protein EosFP: biophysical properties and cell biology applications

EosFP is a fluorescent protein from the coral Lobophyllia hemprichii that changes its fluorescence emission from green to red upon irradiation with near-UV light. Here we present the spectroscopic properties of wild-type EosFP and a variety of monomeric and dimeric mutants and provide a structural interpretation of its oligomerization and photoconversion, which is based on X-ray structure analysis of the green and red species that we reported recently. Because functional expression of the monomeric EosFP variant is limited to temperatures of 30 degrees C, we have developed a tandem dimer. This construct, in which two EosFP subunits are connected by a flexible 12 amino acid linker, expresses well after fusion with the androgen and endothelin A receptors at 37 degrees C. A variety of applications in cellular imaging, developmental biology and automated high-content screening applications are presented, which demonstrate that EosFP is a powerful tool for in vivo monitoring of cellular processes.