Colorimetric and fluorometric discrimination of geometrical isomers (maleic acid vs fumaric acid) with real-time detection of maleic acid in solution and food additives.

Heterobis imine Schiff base probe L is able to discriminate geometrical isomers (maleic acid vs fumaric acid) through sharp colorimetric as well as fluorogenic responses even conspicuous with the naked eye. Colorimetric as well as fluorogenic sensing of maleic acid among various carboxylic acids was also demonstrated in ethanol-buffer medium. Sensing behavior of L was corroborated by (1)H NMR spectra, mass spectrometry, and theoretical calculations. Subsequently sensing behavior of L was used to probe maleic acid in starch rich food samples.

The first insight into the metabolite profiling of grapes from three Vitis vinifera L. cultivars of two controlled appellation (DOC) regions.

The characterization of the metabolites accumulated in the grapes of specific cultivars grown in different climates is of particular importance for viticulturists and enologists. In the present study, the metabolite profiling of grapes from the cultivars, Alvarinho, Arinto and Padeiro de Basto, of two Portuguese Controlled Denomination of Origin (DOC) regions (Vinho Verde and Lisboa) was investigated by gas chromatography-coupled time-of-flight mass spectrometry (GC-TOF-MS) and an amino acid analyzer. Primary metabolites, including sugars, organic acids and amino acids, and some secondary metabolites were identified. Tartaric and malic acids and free amino acids accumulated more in grapes from vines of the DOC region of Vinho Verde than DOC Lisboa, but a principal component analysis (PCA) plot showed that besides the DOC region, the grape cultivar also accounted for the variance in the relative abundance of metabolites. Grapes from the cultivar, Alvarinho, were particularly rich in malic acid and tartaric acids in both DOC regions, but sucrose accumulated more in the DOC region of Vinho Verde.

Study on tissue distribution, metabolite profiling, and excretion of [14C]-labeled flonoltinib maleate in rats.

Flonoltinib Maleate (FM) is a dual-target inhibitor that selectively suppresses Janus kinase 2/FMS-like tyrosine kinase 3 (JAK2/FLT3), which is currently in phase I/IIa clinical trial in China for the treatment of myeloproliferative neoplasms (MPNs). In this research, we used [14C]-labeled FM (14C-FM) to investigate the distribution, metabolism, and excretion of FM in rats using High-Performance Liquid Chromatography coupled with High-Resolution Mass Spectrometry/Radioactivity Monitoring (HPLC-HRMS/RAM) and liquid scintillation counter. The results revealed that FM displayed widespread distribution in rats. Furthermore, FM demonstrated rapid clearance without any observed risk of organ toxicity attributed to accumulation. Profiling of FM metabolites in rat plasma, feces, urine, and bile identified a total of 17 distinct metabolites, comprising 7 phase I metabolites and 10 phase II metabolites. The major metabolic reactions involved oxygenation, dealkylation, methylation, sulfation, glucuronidation and glutathione conjugation. Based on these findings, a putative metabolic pathway of FM in rats was proposed. The overall recovery rate in the excretion experiment ranged from 93.04 % to 94.74 %. The results indicated that FM undergoes extensive hepatic metabolism in SD rats, with the majority being excreted through bile as metabolites and ultimately eliminated via feces. A minor fraction of FM (<10 %) was excreted through renal excretion in the form of urine. Integration of the current results with previous pharmacokinetic investigations of FM in rats and dogs enables a comprehensive elucidation of the in vivo ADME processes and characteristics of FM, thereby establishing a solid foundation for subsequent clinical investigations of FM.

Composition of raft-like cell membrane microdomains resistant to styrene-maleic acid copolymer (SMA) solubilization.

An advantageous alternative to the use of detergents in biochemical studies on membrane proteins are the recently developed styrene-maleic acid (SMA) amphipathic copolymers. In our recent study [1] we demonstrated that using this approach, most T cell membrane proteins were fully solubilized (presumably in small nanodiscs), while two types of raft proteins, GPI-anchored proteins and Src family kinases, were mostly present in much larger (>250 nm) membrane fragments markedly enriched in typical raft lipids, cholesterol and lipids containing saturated fatty acid residues. In the present study we demonstrate that disintegration of membranes of several other cell types by means of SMA copolymer follows a similar pattern and we provide a detailed proteomic and lipidomic characterization of these SMA-resistant membrane fragments (SRMs).

Immunochemical characterisation of styrene maleic acid lipid particles prepared from Mycobacterium tuberculosis plasma membrane.

Membrane proteins of Mycobacterium tuberculosis (Mtb) can be targeted for the development of therapeutic and prophylactic interventions against tuberculosis. We have utilized the unique membrane-solubilising properties of the styrene maleic acid copolymer (SMA) to prepare and characterise 'styrene maleic acid lipid particles' from the native membrane of Mtb (MtM-SMALPs). When resolved by SDS-PAGE and visualised with coomassie blue, the molecular weights of Mtb membrane (MtM) proteins solubilised by SMA were mostly in the range of 40-70 kDa. When visualised by transmission electron microscopy, MtM-SMALPs appeared as nanoparticles of discrete shapes and sizes. The discoid nanoparticles exhibited a range of diameters of ~10-90 nm, with largest portion (~61%) ranging from 20-40 nm. MtM proteins of a molecular weight-range overlapping with that of MtM-SMALPs were also amenable to chemical cross-linking, revealing protein complex formation. Characterisation using monoclonal antibodies against seven MtM-associated antigens confirmed the incorporation of the inner membrane protein PRA, membrane-associated proteins PstS1, LpqH and Ag85, and the lipoglycan LAM into MtM-SMALPs. Conversely, the peripheral membrane proteins Acr and PspA were nearly completely excluded. Furthermore, although MtM showed an abundance of Con A-binding glycoproteins, MtM-SMALPs appeared devoid of these species. Immune responses of healthcare workers harbouring 'latent TB infection' provided additional insights. While MtM-SMALPs and MtM induced comparable levels of the cytokine IFN-γ, only MtM-SMALPs could induce the production of TNF-α. Antibodies present in the donor sera showed significantly higher binding to MtM than to MtM-SMALPs. These results have implications for the development of MtM-based immunoprophylaxis against tuberculosis.

Design and synthesis of malonohydrazide based colorimetric receptors for discrimination of maleate over fumarate and detection of F-, AcO- and AsO2- ions.

In this study, we have designed and synthesized two new organic receptors R1 and R2 based on malonohydrazide for the recognition of biologically important anions. The receptor R1 capable of colorimetric discrimination of maleate over fumarate ion, exhibit significant color change from pale yellow to wine red due to intermolecular hydrogen bond between the R1 and maleate ion, supported by 1HNMR titration, where the peak at δ12.0 ppm attributed to the NH proton experiences a downfield shift upon binding with maleate ion. Receptor R1, equipped with two electron-withdrawing NO2 moieties as the chromogenic signaling unit enhance the hydrogen bonding tendency and acidity, and thus when comparing with receptor R2, R1 displayed substantial higher redshift (∆λmax) of 148 nm, 143 nm, and 140 nm towards F-, AcO-, and maleate anion in the DMSO. In addition, the synthesized receptors R1 and R2 are able to detect F-, AcO-, and AsO2- ions as their sodium salts in an aqueous solution with visual color change. Receptor R1 exhibit electrochemical response towards F- and AcO- ions. The receptors R1 and R2 are successfully applied for quantitative detection of F- ion in the toothpaste solution in an aqueous medium. Additionally, R1 and R2 exhibit fluorescence enhancement towards F- and AcO- ions in the DMSO. As well, R1 and R2 demonstrate to be potentially useful colorimetric chemosensor for sensing maleate ion using the test strip. The theoretical calculation based on TD-DFT corroborates well with the experimental results of the receptors R1 and R2 with fluoride, acetate and maleate.

A Transcription Factor-Based Biosensor for Detection of Itaconic Acid.

Itaconic acid is an important platform chemical that can easily be incorporated into polymers and has the potential to replace petrochemical-based acrylic or methacrylic acid. A number of microorganisms have been developed for the biosynthesis of itaconate including Aspergillus terreus, Escherichia coli, and Saccharomyces cerevisiae. However, the number of strains and conditions that can be tested for increased itaconate titers are currently limited because of the lack of high-throughput screening methods. Here we identified itaconate-inducible promoters and their corresponding LysR-type transcriptional regulators from Yersinia pseudotuberculosis and Pseudomonas aeruginosa. We show that the YpItcR/P ccl inducible system is highly inducible by itaconic acid in the model gammaproteobacterium E. coli and the betaproteobacterium Cupriavidus necator (215- and 105-fold, respectively). The kinetics and dynamics of the YpItcR/P ccl inducible system are investigated, and we demonstrate, that in addition to itaconate, the genetically encoded biosensor is capable of detecting mesaconate, cis-, and trans-aconitate in a dose-dependent manner. Moreover, the fluorescence-based biosensor is applied in E. coli to identify the optimum expression level of cadA, the product of which catalyzes the conversion of cis-aconitate into itaconate. The fluorescence output is shown to correlate well with itaconate concentrations quantified using high-performance liquid chromatography coupled with ultraviolet spectroscopy. This work highlights the potential of the YpItcR/P ccl inducible system to be applied as a biosensor for high-throughput microbial strain development to facilitate improved itaconate biosynthesis.

An HPLC with evaporative light scattering detection method for the quantification of PEGs and Gantrez in PEGylated nanoparticles.

A rapid and precise HPLC method with evaporative light scattering detection (ELSD) for the separation and quantification of polyethyleneglycol 2000 (PEG 2000), polyethyleneglycol 6000 (PEG 6000) and poly(methyl vinyl ether-co-maleic anhydride) (Gantrez) in a nanosized pharmaceutical formulation has been developed. Separation was carried out on a PL aquagel-OH 30,8 microm column (300 mm x 7.5 mm), in a gradient elution with methanol-water as mobile phase at a flow rate of 1 ml/min. Quantification was determined in supernatants of PEGylated nanoparticles and the quantification limits were found to be 0.075 mg/ml for polyethyleneglycols and 0.25 mg/ml for Gantrez. The precision did not exceed 8% and accuracy range for PEGs (-11.50 and 10.61%) and Gantrez (-12.18 and 14.81%) were always within the acceptable limits. The amount of polyethyleneglycol associated to nanoparticles was also calculated by a Nuclear Magnetic Resonance Method ((1)H NMR). Likely, for both PEGs, a good relationship between both techniques was found. In summary, the developed HPLC technique provides an alternative for the routine and rapid analysis of PEGs and Gantrez in nanoparticle formulations.

Detection of unexpected frauds: Screening and quantification of maleic acid in cassava starch by Fourier transform near-infrared spectroscopy.

Fourier transform near-infrared (FT-NIR) spectroscopy and chemometrics were adopted for the rapid analysis of a toxic additive, maleic acid (MA), which has emerged as a new extraneous adulterant in cassava starch (CS). After developing an untargeted screening method for MA detection in CS using one-class partial least squares (OCPLS), multivariate calibration models were subsequently developed using least squares support vector machine (LS-SVM) to quantitatively analyze MA. As a result, the OCPLS model using the second-order derivative (D2) spectra detected 0.6%(w/w) adulterated MA in CS, with a sensitivity of 0.954 and specificity of 0.956. The root mean squared error of prediction (RMSEP) was 0.192(w/w, %) by using the standard normal variate (SNV) transformation LS-SVM. In conclusion, the potential of FT-NIR spectroscopy and chemometrics was demonstrated for application in rapid screening and quantitative analysis of MA in CS, which also implies that they have other promising applications for untargeted analysis.

Quantitative Nuclear Magnetic Resonance Spectroscopy Based on PULCON Methodology: Application to Quantification of Invaluable Marine Toxin, Okadaic Acid.

ERETIC2 (Electronic Reference To access In vivo Concentrations 2) based on PULCON (Pulse Length-based Concentration determination) methodology is a quantitative NMR (qNMR) using an external standard. The performance of the PULCON method was assessed using maleic acid (MA). Quantification of the diarrhetic shellfish toxin and okadaic acid by PULCON was successfully consistent with that obtained by a conventional internal standard method, demonstrating that the PULCON method is useful for the quantification of invaluable marine toxins without any contaminations by an internal standard.

Application of quantitative NMR for purity determination of standard ACE inhibitors.

This study investigated the accuracy of the quantitative NMR method for purity determination of ACE inhibitors reference standards and the discovery of two pairs of new diastereoisomers. Six types of ACE inhibitors, imidapril hydrochloride, benazepril hydrochloride, lisinopril, enalapril maleate, quinapril hydrochloride, and captopril were quantificated and validated for the qNMR method by discussing factors that affect parameters of the qNMR experiment, internal standards, integration, pH-effect, and uncertainty. The results were compared with data obtained by the mass balance method. The study found that maleic acid influenced the quantification of captopril in deuteroxide because of a chemical reaction. The mixtures of the reaction products were isolated by HPLC and structurally elucidated by NMR as two pairs of new diastereoisomers, 1-[(2S,4R)-thio-2-methylpropionyl-5-d-ethanedicarboxylicacid]-L-proline and 1-[(2S,4S)-thio-2-methylpropionyl-5-d-ethanedicarboxylicacid]-L-proline. The results showed that the accuracy and precision of quantitative (1)H NMR spectroscopy satisfied the requirements for quantitative analysis of chemical reference standards and provided a simple, rapid, and reliable method for purity determination of ACE inhibitors systematically.

Development of NMR and raman spectroscopic methods for the determination of the degree of substitution of maleate in modified starches.

In this paper we report the application of NMR spectroscopy and Raman spectroscopy to determine the degree of maleate substitution in maleinated starches. Five kinds of maleinated starches were investigated and calibration sets were constructed to derive linear regression equations that may be used to predict the degree of maleate substitution for starch samples with unknown amounts of chemical modification. The calibration sets reported have very high linearity (r > 0.99) for both the NMR and Raman methods. The NMR and Raman calibration sets allow fast and nondestructive measurement of the degree of maleate substitution for different starches with little need of sample preparation.

Simultaneous determination of oxalic, fumaric, maleic and succinic acids in tartaric and malic acids for pharmaceutical use by ion-suppression reversed-phase high performance liquid chromatography.

A reliable method for the simultaneous determination of oxalic, fumaric, maleic, and succinic acids in tartaric and malic acids for pharmaceutical use by reversed-phase ion-suppression high performance liquid chromatography is presented. HPLC was achieved on a Nova-Pak C18 column by isocratic elution using water adjusted to pH 2.10-2.15 with perchloric acid, and detection was by UV adsorption at a wavelength of 210 nm. This method was found to be superior to previous liquid chromatography as well as other classical assay, and to be an attractive choice for the analysis of these compounds.

High pressure liquid chromatography of dentin primers and bonding agents.

OBJECTIVE: The purpose of this study was to analyse the composition of representative dentin primers and bonding agents, and to investigate the relationship between chromatographic retention times and partition coefficient (log P) values. METHODS: Dentin bonding systems (DBS) were analysed with reversed phase high-performance liquid chromatography (HPLC). The log P values were obtained computationally with the advanced chemistry development software. RESULTS: The DBS were analysed and the monomers were identified. The log P values were calculated and the relationship between log P and retention times for the monomers was described by the equation: log P = 2.436R(t) - 3.636, with a correlation value (r) of r = 0.9095. SIGNIFICANCE: The components of the DBS were successfully resolved and identified, thus illustrating the analytical power of HPLC regarding those systems. Also the log P values correlated with the retention times of monomers. Thus, they can be used as a prediction tool in future analysis. These findings are important for a mechanistic understanding of Primer and Adhesive actions in the bonding to the dentin.

Low molecular weight dicarboxylic acids in PM10 in a city with intensive solid fuel burning.

In this work, PM(10) samples were collected in a winter and a summer in Christchurch, a New Zealand city having intensive wood and coal burning and a serious air pollution problem in winter. Oxalic, malonic, succinic, maleic, glutaric and adipic acids in the samples were analysed using ion chromatography. It was suggested that solid fuel burning had large influence on the occurrence of these low molecular weight dicarboxylic acids resulting in significantly higher wintertime concentrations of maleic acid, oxalic acid and glutaric or adipic acid. The most pronounced feature observed was that maleic acid was the second most abundant species of the detected DCAs in the winter (with a mean of 74 ngm(-3) and the highest concentration ever reported of 231 ngm(-3)). In contrast, malonic acid experienced a low abundance in both seasons. The observed seasonal patterns and molecular distribution were inconsistent with those in most other urban areas. On an average, the total detected dicarboxylic acids accounted for about 0.5% of PM(10) mass with a maximum of 1.4% in the winter. The relative importance of different sources to individual dicarboxylic acids varied with seasons and is discussed in detail.

Artificially formed carieslike lesions around restorative materials.

Secondary caries formation around restorations is a major cause for their replacement. This in vitro study assessed the capacity of various restorative materials to to resist caries attack. An acidified gel technique was used to produce carieslike lesions around the restored teeth. Assessment of the occurrence and extension of carious lesions was performed using polarized light microscopy. The results showed wide variations in the ability of the restorative materials to resist erosion.

Salivary and plaque triclosan levels after brushing with a 0.3% triclosan/copolymer/NaF dentifrice.

The concentration and elimination rate of triclosan in saliva was assessed as part of a six week clinical study which evaluated the antiplaque efficacy of a 0.3% triclosan/PVM/MA copolymer/NaF dentifrice. On day one of the study the concentration of triclosan in whole saliva was determined at various times after dentifrice use for both the triclosan/PVM/MA copolymer/NaF and placebo dentifrice groups. The results indicated that the salivary triclosan levels ranged from 19.7 micrograms/ml at 5 minutes to 1 microgram/ml at 2 hours after use of the 0.3% triclosan dentifrice. The triclosan elimination curve for saliva exhibited a mono-exponential decline with a half-life of 26 minutes. The plaque content of triclosan, one hour after dentifrice use, which was determined at the end of the study, was found to be relatively high (25 micrograms/g) compared to that seen in saliva at the same time (6.2 micrograms/ml). It was concluded that the 0.3% triclosan/PVM/MA copolymer/NaF test dentifrice provided effective delivery and bioavailability of the antiplaque agent, triclosan. This was based on the relatively high salivary and plaque triclosan levels observed and the concomitant reduction in plaque formation seen at the end of the study.

Determination of iron limiting values according to PH. EUR. using 1,3-dibromo-5,5-dimethylhydantoin (DBH) instead of elemental bromine. Analytical methods of pharmacopoeias with DBH in respect to environmental and economical concern. Part 8.

PH. EUR. 2002 uses elemental bromine performing iron limit tests for maleic acid (iron 5 ppm) and titanium dioxide (iron 200 ppm). 1,3-Dibromo-5,5-dimethylhydantoin (DBH) can replace bromine water. For the iron limit test of maleic acid bivalent iron is oxidized to trivalent iron by bromine resp. DBH, because the unsaturated, in high concentration existing acid reacts substantially slower. On the other hand maleic acid removes the excess of bromine. The bromine oxidation for the iron limiting values of titanium dioxide according to the pharmacopoeia is not required. Metallic iron as well as ferrous salts are converted to trivalent iron, when the titanium test solution is prepared by boiling with concentrated sulphuric acid in the presence of anhydrous sodium sulphate.

[Quantitative analysis of chlorpheniramine maleate in cough and cold drugs by ion-pair high-performance liquid chromatography for the simultaneous determination of chlorpheniramine and maleate].

A simple, rapid and convenient chromatographic method, which permits the simultaneous determination of chlorpheniramine (CP) and maleate (MA), recently developed by the authors was applied to the analysis of chlorpheniramine maleate (CPM) in cough and cold drugs. In this method, a Capcell Pak C8 column and an isocratic mobile phase containing 15% methanol, 50 mM KH2PO4 and 5mM tetra-n-butylammonium phosphate as an ion-pair reagent were used. By using the mobile phase adjusted to pH 3.0 with orthophosphoric acid, fumaric acid, MA, CP, acetaminophen (paracetamol), caffeine, and m- and p-hydroxybenzoic acid as candidates for an internal standard were eluted separately within 17 min. Detection was carried out with UV detector at 215 nm. Under the same conditions, five other antihistamines analogous to CPM were also separated. The calibration graphs for CP and MA showed good linearity in the range of 0.5-10 nmol (0.195-3.9 micrograms) per 20 microliters injection, respectively. The proposed method was successfully applied to the simultaneous determination of CP and MA, i.e., CPM analysis, in commercial cough and cold drugs which pharmaceutical forms were tablet, granule and syrups.

Adsorption and transport of polymaleic acid on Callovo-Oxfordian clay stone: batch and transport experiments.

Dissolved Organic Matter (DOM) can affect the mobility of radionuclides in pore water of clay-rich geological formations, such as those intended to be used for nuclear waste disposal. The present work studies the adsorption and transport properties of a polycarboxylic acid, polymaleic acid (PMA, Mw=1.9kDa), on Callovo-Oxfordian argillite samples (COx). Even though this molecule is rather different from the natural organic matter found in clay rock, the study of its retention properties on both dispersed and intact samples allows assessing to which extent organic acids may undergo sorption under natural conditions (pH7) and what could be the impact on their mobility. PMA sorption and desorption were investigated in dispersed systems. The degree of sorption was measured after 1, 8 and 21days and for a range of PMA initial concentrations from 4.5×10(-7) to 1.4×10(-3)mol.L(-1). The reversibility of the sorption process was estimated by desorption experiments performed after the sorption experiments. At the sorption steady state, the sorption was described by a two-site Langmuir model. A total sorption capacity of COx for PMA was found to be 1.01×10(-2) mol.kg(-1) distributed on two sorption sites, one weak and one strong. The desorption of PMA was incomplete, independently of the duration of the sorption phase. The amount of desorbable PMA even appeared to decrease for sorption phases from 1 to 21days. To describe the apparent desorption hysteresis, two conceptual models were applied. The two-box diffusion model accounted for intraparticle diffusion and more generally for nonequilibrium processes. The two-box first-order non-reversible model accounted for a first-order non-reversible sorption and more generally for kinetically-controlled irreversible sorption processes. The use of the two models revealed that desorption hysteresis was not the result of nonequilibrium processes but was due to irreversible sorption. Irreversible sorption on the strong site was completed after 1day and represented 96% of the total sorption on this site. On the weak site the irreversible uptake was slower and completed only after 16days but it also dominated the sorption. 85% of the PMA sorbed on the weak site was not desorbable after 21days of sorption. The migration of PMA was studied by applying a hydraulic gradient to a clay core inserted in a stainless steel cell. Breakthrough of polymaleic acid, simulated with a 1D transport model including the two-box first-order non-reversible model, revealed that the mobility of PMA was limited by the same set of reversible/irreversible interactions as observed in the dispersed system. However, to describe efficiently the transport, the total sorption capacity had to be reduced to 33% of the capacity estimated in batch experiments. The irreversible sorption on the weak site was also slower in the intact sample than in the crushed sample. Geometrical constraints would therefore affect both the accessibility to the sorption sites and the kinetics of the irreversible sorption process.