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Förster resonance energy transfer (FRET) serves as a tool for measuring protein–protein interactions using various sensor molecules. The tension sensor module relies on FRET technology. In our study, this module was inserted within the actinin molecule to measure the surface tension of the cells. Given that the decay curve of FRET efficiency correlates with surface tension increase, precise and accurate efficiency measurement becomes crucial. Among the methods of FRET measurements, FRET efficiency remains the most accurate if sample fixation is successful. However, when cells were fixed with 4% paraformaldehyde (PFA), the actinin-FRET sensor diffused across the cytoplasm; this prompted us to explore fixation method enhancements. Glyoxal fixative has been reported to improve cytoskeletal morphologies compared to PFA. However, it was not known whether glyoxal fits FRET measurements. Glyoxal necessitates an acetic acid solution for fixation; however, acidic conditions could compromise fluorescence stability. We observed that the pH working range of glyoxal fixative aligns closely with MES (methyl-ethylene sulfonic acid) Good's buffer. Initially, we switched the acidic solution for MES buffer and optimized the fixation procedure for in vitro and in vivo FRET imaging. By comparing FRET measurements on hydrogels with known stiffness to tumor nodules in mouse lung, we estimated in vivo stiffness. The estimated stiffness of cancerous tissue was harder than the reported stiffness of smooth muscle. This discovery shed lights on how cancer cells perceive environmental stiffness during metastasis. [ABSTRACT FROM AUTHOR]

Context: Carbonyl compounds, especially aldehydes, emitted to the atmosphere, may suffer hydration in aerosols or water droplets in clouds. At the same time, they can react with hydroxyl radicals which may add or abstract hydrogen atoms from these species. The interplay between hydration and hydrogen abstraction is studied using density functional and quantum composite theoretical methods, both in the gas phase and in simulated bulk water. The H-abstraction from the aldehydic and geminal diol forms of formaldehyde, acetaldehyde, glycolaldehyde, glyoxal, methylglyoxal, and acrolein is studied to determine whether the substituent has any noticeable effect in the preference for the abstraction of one form or another. It is found that abstraction of the H-atom adjacent to the carbonyl group gives a more stable radical than same abstraction from the geminal diol in the case of formaldehyde, acetaldehyde, and glycolaldehyde. The presence of a delocalizing group in the Cα (a carbonyl group in glyoxal and methylglyoxal, and a vinyl group in acrolein), reverts this trend, and now the abstraction of the H-atom from the geminal diol gives more stable radicals. A further study was conducted abstracting hydrogen atoms from the other different positions in the species considered, both in the aldehydic and geminal diol forms. Only in the case of glycolaldehyde, the radical formed by H-abstraction from the –CH2OH group is more stable than any of the other radical species. Abstraction of the hydrogen atom in one of the hydroxyl groups in the geminal diol is equivalent to the addition of the •OH radical to the aldehyde. It leads, in some cases, to decomposition into a smaller radical and a neutral molecule. In these cases, some interesting theoretical differences are observed between the results in gas phase and (simulated) bulk solvent, as well as with respect to the method of calculation chosen. Methods: DFT (M06-2X, B2PLYP, PW6B95), CCSD(T), and composite (CBS-QB3, jun-ChS, SCVECV-f12) methods using Dunning basis sets and extrapolation to the CBS limit were used to study the energetics of closed shell aldehydes in their keto and geminal-diol forms, as well as the radical derived from them by hydrogen abstraction. Both gas phase and simulated bulk solvent calculations were performed, in the last case using the Polarizable Continuum Model. [ABSTRACT FROM AUTHOR]

Obesity is a complex condition associated with disruptions in carbohydrate, protein, and fat metabolism, linked to increased insulin resistance and glucose intolerance. High levels of Advanced Glycation End-products (AGEs) are associated with a range of chronic diseases, including kidney diseases, diabetic complications, cardiovascular diseases, and neurodegenerative diseases. Our study aims to investigate the accumulation of AGEs in the liver, renal and adipose tissues of mice fed a high-fat diet, contributing to a deeper understanding of obesity and its related metabolic disorders. Our study consists of three different groups fed with diets containing 60% and 10% fat. The Experiment 1 group was maintained on their diet for 12 weeks, while the obese 2 and control groups continued their diets for 24 weeks. AGEs in the liver and kidney tissues obtained were measured using the High-performance liquid chromatography grade (HPLC) method. Higher accumulation of AGEs has been observed in kidney tissue compared to adipose and liver tissues (p < 0.05). Moreover, the GO levels were notably higher in liver tissue than in adipose tissue of the D1 and D2 groups (p < 0.0001). Our results suggest that particularly in kidney tissue, increased filtration burden, functional impairment, and receptor interaction due to obesity may be effective. The lower levels of AGEs detected, especially in the obese groups compared to the control, can be attributed to the inability to metabolize AGEs due to tissue damage caused by obesity. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective fluorescence method has been conducted for the detection of Hg2+ based on aminophenylboronic acid–modified carboxyl magnetic beads (CMB@APBA) and CRISPR/Cas12a system mediated by glyoxal caged nucleic acid (gcDNA). As a bi-functional DNA linker, gcDNA offers advantages of simultaneous recognition by boronic acid and complementary DNA/RNA. Under acidic condition, gcDNA can be immobilized on CMB@APBA through the formation of borate ester bond. The formed boric acid–esterified gcDNA can further bind with complementary CRISPR RNA through A-T base pairing to activate Cas12a with kcat/Km ratio of 3.4 × 107 s−1 M−1, allowing for amplified signal. Hg2+ can specifically combine with CMB@APBA, resulting in the release of gcDNA from CMB@APBA and the following inhibition on the activation of CRISPR/Cas12a system around magnetic bead. Under optimal conditions, the method exhibits a linear range from 20 to 250 nM, with a detection limit of 2.72 nM. The proposed method can detect Hg2+ in milk and tea beverages, providing a great significance for on-site monitoring of Hg2+ contamination in food. [ABSTRACT FROM AUTHOR]

The detection and analysis of α-dicarbonyl compounds (α-DCs) in food can guide the daily diet of patients with various chronic diseases. However, these compounds have poor stability, lack color-generating groups, and have low ionization efficiency. Therefore, it is difficult to monitor them. We established a new simple and sensitive method for the simultaneous determination of four α-DCs, including glyoxal (GO), methylglyoxal (MG), 2,3-butanedione (DMGO), and 3-deoxyglucosone (3-DG) in beer by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) with pre-column derivatization using 3-benzyl-2-oxo-4λ3-thiazolidine-4-carbohydrazide (BOTC), a novel MS probe for targeted identification of carbonyl compounds. α-DCs were derivatized with BOTC at 60 °C for 60 min, and the gradient analysis was carried out on a CSH C18 (2.1 mm × 50 mm; 1.7 μm) column for 5 min with a mobile phase A of 0.1% formic acid (FA) in water and mobile phase B of 0.1% FA in acetonitrile. The linearity range of this method was 0.39–500 μM (R2 ≥ 0.9995). The limits of detection (LOD) were in the range of 13–50 fmol. The average recoveries of α-DCs were 95.15–101.67%. This method was successfully applied to the detection of α-DCs in beer; the content of 3-DG was the highest, several hundred times higher than that of GO, MG, and DMGO, and the difference was significant. This new BOTC derivatization-based UHPLC-MS/MS method for the simultaneous detection of four α-DCs in beer is highly sensitive and can be used for the detection of α-DCs in alcoholic beverages. [ABSTRACT FROM AUTHOR]

The formation of the most widely used antithyroid drug in the world, 1-methyl-1H-imidazole-2(3H)-thione (methimazole or thiamazole), by the reduction of 4,5-dihydroxy-1-methylimidazolidine-2-thione (1-Me-DHIT) with 1-methylthiourea or by the reaction of 1-methylthiourea excess and glyoxal were studied. A new method for the synthesis of methimazole from available reagents, 1-Me-DHIT and 1-methylthiourea, was proposed. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) and the Møller–Plesset expansion (MP2) calculations were benchmarked to characterize the structure of novel derivatives of carbene hydroxymethylene. In this regard, eleven numbers of primary aldehydes including formaldehyde, acetaldehyde, formyl chloride, 2-chloroacetaldehyde, formyl fluoride, 2-fluoroacetaldehyde, formic acid, propionaldehyde, glyoxal, methyl formate, and formyl bromide (1H–11Br) were scrutinized, at the B3LYP/6-311++G(3d,3p) level of theory. Thereafter, the process of keto-enol tautomerism via a [1,2]-H-shift of 1H–11Br was monitored to reach their corresponding enol forms (1P–11P). For all species (except for one structure), the TS involves a triangle structure of C–O–H and yields cis or trans isomers of a singlet ground-state (S) carbene that contrasts the multiplicity of ordinary carbenes. The bond dissociation energy (BDE) calculations were carried out for the homolytic cleavage of C–H bonds of 1H–11Br. The AIM, as a promising analysis that definitely reveals the nature of the bond, was conducted to characterize the eigenvalues at the bond critical points (BCPs). In addition, the relation between the Hammett equation and thermodynamic parameters was obtained. Our investigation suggests new stable S derivatives of carbene hydroxymethylene that can be isolated. [ABSTRACT FROM AUTHOR]

The crosslinking mechanism of glyoxal and asparagine was analyzed, and the relationship between the mechanism and practical performances of soy protein-based adhesives was also discussed. It is shown that when pH=1 and 3, glyoxal reacted with asparagine in the form of major cyclic ether compounds. When pH =5, glyoxal reacted with asparagine in two structural forms of sodium glycollate and cyclic ether compounds. However, amidogens of asparagine were easy to develop protonation under acid conditions. Supplemented by the instability of cyclic ether compounds, the reaction activity and reaction degree between glyoxal and asparagine were relatively small. Under alkaline conditions, glyoxal mainly reacted with asparagine in the form of sodium glycollate. With the increase of pH, the polycondensation was more sufficient and the produced polycondensation products were more stable. The reaction mechanism between glyoxal and asparagine had strong correspondence to the practical performances of the adhesives. Glyoxal solution could develop crosslinking reactions with soy protein under both acid and alkaline conditions. Bonding strength and water resistance of the prepared soy protein-based adhesives were increased significantly. When pH>7, glyoxal had relatively high reaction activity and reaction intensity with soy protein, and the prepared adhesives had high crosslinking density and cohesion strength, showing relatively high bonding strength, water resistance and thermal stability. [ABSTRACT FROM AUTHOR]

A novel voltammetric platform based on pencil graphite electrode (PGE) modification has been proposed, containing bimetallic (NiFe) Prussian blue analogue nanopolygons decorated with electro-polymerized glyoxal polymer nanocomposites (p-DPG NCs@NiFe PBA Ns/PGE). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV) were utilized to investigate the electrochemical performance of the proposed sensor. The analytical response of p-DPG NCs@NiFe PBA Ns/PGE was evaluated through the quantity of amisulpride (AMS), one of the most common antipsychotic drugs. Under the optimized experimental and instrumental conditions, the method showed linearity over the range from 0.5 to 15 × 10−8 mol L−1 with a good correlation coefficient (R = 0.9995) and a low detection limit (LOD) reached, 1.5 nmol L−1, with excellent relative standard deviation for human plasma and urine samples. The interference effect of some potentially interfering substances was negligible, and the sensing platform demonstrated an outstanding reproducibility, stability, and reusability. As a first trial, the proposed electrode aimed to shed light on the AMS oxidation mechanism, where the oxidation mechanism was monitored and elucidated using the FTIR technique. It was also found that the prepared p-DPG NCs@NiFe PBA Ns/PGE platform had promising applications for the simultaneous determination of AMS in the presence of some co-administered COVID-19 drugs, which could be attributed to the large active surface area, and high conductivity of bimetallic nanopolygons. [ABSTRACT FROM AUTHOR]

Acid and alkali pretreatment are the most commonly employed strategy in a lignocellulosic biorefinery. The main objective of the study was to evaluate the chemical implications of acid and alkali on the lignin structure and subsequently on the adhesive performance. The study also aimed to investigate the effect of complete replacement of phenol and formaldehyde in the commercial wood adhesive with phenolic lignin and glyoxal, respectively. The phenolic lignin was derived from the two differentially pretreated sugarcane bagasse, i.e., acid and alkali. The isolated lignin was characterized and utilized for the synthesis of lignin-based glyoxal resin. The resins were comparatively evaluated for their mechanical properties as wood adhesives. Adhesives derived from acid pretreated sugarcane bagasse were found to be superior to lignin derived from alkali pretreated sugarcane bagasse in terms of mechanical properties and shear strength. [ABSTRACT FROM AUTHOR]

Background: In glycolysis, hydroxyl radicals emerge via the auto-oxidation pathway in a status of hyperglycemia, and by binding to proteins or lipids, form advanced glycation end-products (AGE). Glyoxal (GO) and methylglyoxal (MGO) are precursors of AGEs. The aim of this prospective, case-control study was to investigate the difference in levels of AGE precursors in patients with and without diabetes and to investigate the relationship between the change in rates of the AGE precursors and treatment in diabetic patients. Methods: The study included 21 treatment-naive patients diagnosed with type 2 diabetes and 21 age and gender-matched healthy control subjects. Throughout an observation period of 3 months, the diabetic patients were started on anti-diabetic treatment and used no additional treatment or supplementary products. The GO and MGO levels were examined with the HPLC method. Results: The GO and MGO levels were determined to be 1.74 and 0.024μg/mL respectively in the diabetic patients and 1.14 and 0.002 μg/mL in the control group. After 3 months of treatment, a statistically significant decrease compared to pre-treatment values was determined of 0.684 μg/mL in GO and 0.01989 μg/mL in MGO (p=0.001, p<0.01). No statistically significant relationship was determined between the change in HbA1c at 3 months compared to pre-treatment and the changes in GO and MGO (p>0.05). Conclusion: The level of AGE precursors was found to be significantly higher in diabetic patients than in the healthy control group. Although there was a significant decrease in AGE precursors when the HbA1c level fell in patients who followed anti-diabetic treatment and diabetes-appropriate diet recommendations, this decrease was at different rates in each patient, which demonstrated that the HbA1c level is not the only determinant of AGE level in plasma. It can be concluded that with appropriate diet and antidiabetic treatment, significant reductions can be obtained in several risk factors which increase the level of AGE precursors. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the amino acid composition and the amount of individual glycation compounds in hot trub formed during boiling of wort prepared from different malts. Compared to the initial amino acid composition of the used malts, some Maillard reaction products (namely MG-H1, pyrraline) and hydrophobic amino acids (leucine, isoleucine, valine, phenylalanine) accumulated in the hot trub, whereas hydrophilic amino acids remained in the boiled wort. For MG-H1, a threefold increase was observed during wort boiling, whereas the other Maillard reaction products, namely CML, CEL, pyrraline and maltosine increased only slightly (1.1–2-fold). Furosine as a hallmark for peptide-bound Amadori compounds showed a small decrease. The results suggest that mainly glycated amino acids derived from small dicarbonyl compounds such as methylglyoxal and glyoxal are formed during wort boiling. Furthermore, the studies indicate that the modification of the protein structure as a result of the Maillard reaction has an influence on the hydration of the denatured proteins during the wort boiling process, thus affecting the coagulation process and, therefore, precipitation of the hot trub. The work carried out contributes to the understanding of the chemical reactions influencing the amino acid and Maillard reaction product transfer from malt to beer. [ABSTRACT FROM AUTHOR]

Glyoxal (GL) is a physiological reactive α-oxoaldehyde metabolite, produced by lipid peroxidation and autoxidation of glucose. In this work, a specific mitochondria-targeting fluorescent probe Z-GL for glyoxal has been developed by an introducing isopropyl group on the recognition site to tune the selectivity toward glyoxal. The probe showed high selectivity and sensitivity for glyoxal in an aqueous system. Importantly, the probe was able to visualize exogenous and endogenous glyoxal in living cells. Furthermore, the probe was mitochondria-targetable, and could be used for monitoring the level of intracellular glyoxal. [ABSTRACT FROM AUTHOR]

N-Methylpyrrolidine catalyzed, concise and attractive synthesis of a new class of 3-hydroxy-3,5/6-di-aryl-1H-imidazo[1,2-a]imidazol-2(3H)-ones was attained with impressive yields, in the presence of EtOH as a solvent, by means of a convenient and elegant condensation reaction between different aryl glyoxal monohydrates and guanidine hydrochloride under reflux conditions. Some specific merits of the current procedure, including encompasses low operating cost, availability of the starting substrates, reasonable reaction times, high reaction yield, operational simplicity, cleaner reaction profile, no harmful by-products, and the isolated product is in pure form. Structures of all the freshly synthesized products have been deduced by their FT-IR, 1H-NMR, 13C-NMR, Mass spectrometry data and microanalysis. [ABSTRACT FROM AUTHOR]

Increased concern over the use of metal salts such as chromium, zirconium, and aluminum for tanning of hides and skins has made the leather production industry to be constantly on the lookout for organic tanning agents in place of the inorganic system. Though glutaraldehyde has been looked at as a viable option, it still lags in imparting superior strength properties to the leather and also it has been reported to have inherent toxicity. With that concept in view, this research work focuses on the usage of glyoxal along with synthetic tanning agents as a replacement for glutaraldehyde and other inorganic tanning systems. The offer level and starting pH for the glyoxal tanning process was optimized as 6% (w/w) and 5.0, respectively, and the shrinkage temperature of the collagen was found to be around 80 °C. Additionally, the controlled shrunken grain effect of the aldehyde tanning system was explored by changing the pH of the process, which helped to improve the thickness of low-grade thinner raw materials by up to 40%. The mechanism for the shrunken grain effect has also been proposed in this work by studying the dimensional changes occurring in the leather matrix upon treating skin/hide with glyoxal at different pH levels. The mechanical and strength properties of the leather were found to be better than the glutaraldehyde tanning system. The BOD/COD ratio of wastewater generated from the glyoxal process was found to be greater than 0.3 making them easily treatable. Considering all these factors, compact glyoxal-based tanning along with synthetic tanning agents can be a game-changing technology for the leather processing industry. [ABSTRACT FROM AUTHOR]

Glycation is a non-enzymatic reaction that occurs between the free amino group of proteins and reducing sugars and/or lipids, leading to the formation of advanced glycation end products (AGEs). The reaction also produces reactive oxygen species that have detrimental effects on cellular and extracellular proteins. Aminoguanidine is a known inhibitor of AGEs, and some fatty acids are known to have a beneficial role in vivo by reducing inflammation and oxidative stress. However, the role of fatty acids on AGE formation has not been thoroughly reported. We investigated the role of a range of fatty acids in the formation of AGEs and their reactive intermediates using an in vitro BSA-dicarbonyl model. The model assessed a time-dependent (0–72 h) and dicarbonyl concentration (0–2 mM) -dependent studies for the optimal formation of AGEs. A 72 h time point was found to be optimal for the reaction of BSA with either methylglyoxal (MGO) or glyoxal (GO) to generate AGE-BSA complexes. When arachidonic, eicosapentaenoic or docosahexaenoic acids were included in the reaction, a significant decrease in protein-bound fluorescent AGEs was seen compared to the respective controls. In contrast, saturated and 18 carbon polyunsaturated fatty acids showed no significant activity. Liquid chromatography–mass spectrometry (LC–MS/MS) analysis showed saturated fatty acids significantly decreased the production of Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL) from GO and MGO models, respectively, whilst increasing methylglyoxal-derived hydroimidazolone (MG-H1). In contrast, arachidonic, eicosapentaenoic and docosahexaenoic acids did not significantly change either CEL or MG-H1 compared to no treatment controls whilst significantly reducing CML levels. [ABSTRACT FROM AUTHOR]

Key message: Analysis of carotenoid-accumulating roots revealed that oxidative carotenoid degradation yields glyoxal and methylglyoxal. Our data suggest that these compounds are detoxified via the glyoxalase system and re-enter primary metabolic pathways. Carotenoid levels in plant tissues depend on the relative rates of synthesis and degradation. We recently identified redox enzymes previously known to be involved in the detoxification of fatty acid-derived reactive carbonyl species which were able to convert apocarotenoids into corresponding alcohols and carboxylic acids. However, their subsequent metabolization pathways remain unresolved. Interestingly, we found that carotenoid-accumulating roots have increased levels of glutathione, suggesting apocarotenoid glutathionylation to occur. In vitro and in planta investigations did not, however, support the occurrence of non-enzymatic or enzymatic glutathionylation of β-apocarotenoids. An alternative breakdown pathway is the continued oxidative degradation of primary apocarotenoids or their derivatives into the shortest possible oxidation products, namely glyoxal and methylglyoxal, which also accumulated in carotenoid-accumulating roots. In fact, combined transcriptome and metabolome analysis suggest that the high levels of glutathione are most probably required for detoxifying apocarotenoid-derived glyoxal and methylglyoxal via the glyoxalase pathway, yielding glycolate and d-lactate, respectively. Further transcriptome analysis suggested subsequent reactions involving activities associated with photorespiration and the peroxisome-specific glycolate/glyoxylate transporter. Finally, detoxified primary apocarotenoid degradation products might be converted into pyruvate which is possibly re-used for the synthesis of carotenoid biosynthesis precursors. Our findings allow to envision carbon recycling during carotenoid biosynthesis, degradation and re-synthesis which consumes energy, but partially maintains initially fixed carbon via re-introducing reactive carotenoid degradation products into primary metabolic pathways. [ABSTRACT FROM AUTHOR]

Reactive glucose degradation products (GDPs) are formed during heat sterilization of glucose-containing peritoneal dialysis fluids (PDFs) and may induce adverse clinical effects. Long periods of storage and/or transport of PDFs before use may lead to de novo formation or degradation of GDPs. Therefore, the present study quantified the GDP profiles of single- and double-chamber PDFs during storage. Glucosone, 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), 3,4-dideoxyglucosone-3-ene (3,4-DGE), glyoxal, methylglyoxal (MGO), acetaldehyde, formaldehyde, and 5-hydroxymethylfurfural (5-HMF) were quantified by two validated UHPLC-DAD methods after derivatization with o-phenylenediamine (dicarbonyls) or 2,4-dinitrophenylhydrazine (monocarbonyls). The PDFs were stored at 50 °C for 0, 1, 2, 4, 13, and 26 weeks. The total GDP concentration of single-chamber PDFs did not change considerably during storage (496.6 ± 16.0 µM, 0 weeks; 519.1 ± 13.1 µM, 26 weeks), but individual GDPs were affected differently. 3-DG (− 82.6 µM) and 3-DGal (− 71.3 µM) were degraded, whereas 5-HMF (+ 161.7 µM), glyoxal (+ 32.2 µM), and formaldehyde (+ 12.4 µM) accumulated between 0 and 26 weeks. Acetaldehyde, glucosone, MGO, and 3,4-DGE showed time-dependent formation and degradation. The GDP concentrations in double-chamber fluids were generally lower and differently affected by storage. In conclusion, the changes of GDP concentrations during storage should be considered for the evaluation of clinical effects of PDFs. [ABSTRACT FROM AUTHOR]

An incoherent broadband cavity-enhanced absorption spectrometer in open-path configuration (OP-IBBCEAS) was developed to measure glyoxal (CHOCHO), in the nocturnal atmosphere at the medium-sized coastal city of Calicut, India. The instrument mainly consists of a broadband light source, an open optical cavity formed by two high reflective mirrors, and a CCD array spectrometer. The instrument was operated in a continuous visible spectral range of 415–460 nm, and we report preliminary result from a measurement campaign in the autumn of 2018. Measurements were made between 10 PM and 6 AM, and focus was when diesel vehicles were found idling along about half a km stretch during 3–6 AM, while the loading/unloading of vegetables at sorting facility happens. Spectral measurements were averaged over 10 min, observed a passing plume of glyoxal that lasted ~ 1 h with a maximum concentration of ~ 16.9 ± 2.18 ppb. Transient plumes of another urban pollutant, nitrogen dioxide (NO2), were also observed simultaneously that recorded a concentration of ~ 74 ± 5.5 ppb at its maximum. [ABSTRACT FROM AUTHOR]

The aim of present investigation is survey reactivity of 2-aminopyridine and Meldrum's acid in the presence of aryl glyoxals or aryl aldehydes. The ethyl 2-(3-aryl imidazo[1,2-a]pyridin-2-yl)acetates were successfully synthesized by reaction of 2-aminopyridine, Meldrum's acid, and aryl glyoxals, while the ethyl 3-aryl-3-(pyridin-2-ylamino)propanoates were synthesized in the presence of aryl aldehydes. The reactions are performed in ethanol, catalyzed by acetic acid at reflux and microwave conditions. [ABSTRACT FROM AUTHOR]

Kaolin clay (KN) was employed as an inorganic filler to modify a cross-linked chitosan-glyoxal as Schiff's-based chitosan composite derivative (CTS-GLY). The resulting (CTS-GLY/KN) was found to be a promising composite synthetic biopolymer that can be potentially utilized for color removal as well as COD reduction of an industrial anionic dye (remazol brilliant blue R, RBBR). The surface porosity, crystallinity, morphology, functionality, charge, and amine content of the CTS-GLY/KN were studied using BET, XRD, SEM, FTIR, pHpzc and pH-potentiometric titration analyses, respectively. Response surface methodology-Box-Behnken design (RSM-BBD) was used to optimize the impact of the main input factors on the color removal and COD reduction of RBBR. The adsorptive performance CTS-GLY/KN towards RBBR was well-defined by both Langmuir and Freundlich isotherm models with highest adsorption capacity of 447.1 mg/g at 30 °C. This finding reveals that CTS-GLY/KN can be utilized as a promising, feasible, and environmentally friendly composite-biosorbent for color removal and COD reduction of textile dyes from aqueous medium. [ABSTRACT FROM AUTHOR]

Confined volume systems, such as microdroplets, Leidenfrost droplets, or thin films, can accelerate chemical reactions. Acceleration occurs due to the evaporation of solvent, the increase in reactant concentration, and the higher surface-to-volume ratios amongst other phenomena. Performing reactions in confined volume systems derived from mass spectrometry ionization sources or Leidenfrost droplets allows for reaction conditions to be changed quickly for rapid screening in a time efficient and cost-saving manner. Compared to solution phase reactions, confined volume systems also reduce waste by screening reaction conditions in smaller volumes prior to scaling. Herein, the condensation of glyoxal with benzylamine (BA) to form hexabenzylhexaazaisowurtzitane (HBIW), an intermediate to the highly desired energetic compound 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), was explored. Five confined volume systems were compared to evaluate which technique was ideal for forming this complex cage structure. Substituted amines were also explored as BA replacements to screen alternative cage structure intermediates and evaluate how these accelerated techniques could apply to novel reactions, discover alternative reagents to form the cage compound, and improve synthetic routes for the preparation of CL-20. Ultimately, reaction acceleration is ideal for predicting the success of novel reactions prior to scaling up and determining if the expected products form, all while saving time and reducing costs. Acceleration factors and conversion ratios for each reaction were assessed by comparing the amount of product formed to the traditional bulk solution phase synthesis. [ABSTRACT FROM AUTHOR]

A one-step convergent method was proposed for the synthesis of branched macromolecules in the presence of conjugated dinitrones (N,N-dimethylglyoxal dinitrone, N,N-di-tert-butylglyoxal dinitrone, and N,N- diphenylglyoxal dinitrone) under radical initiation. It was found that branched polystyrene macromolecules synthesized with participation of α-dinitrones have lower glass transition temperatures than their linear analogues. Modification methods for the prepared polymers containing alkoxyamine moieties with the goal to increase their thermal stability were developed. [ABSTRACT FROM AUTHOR]

This study was aimed to investigate effects of acetic acid (0.5%), ethanol (2%), and NaCl (2%) on the formation of protein-bound Nε-carboxymethyllysine (CML), Nε-carboxyethyllysine (CEL) and their precursors, glyoxal (GO) and methylglyoxal (MGO), in ground pork during commercial sterilization (121 °C, 10 min or 30 min). The commercial sterilization led to significant increases of CML and CEL in pork (raw: CML 2.91 ± 0.72, CEL 9.36 ± 3.22; 10 min heating: CML 15.30 ± 3.58, CEL 21.19 ± 5.70; 30 min heating: CML 40.05 ± 16.41, CEL 101.95 ± 42.24; all in mg/kg protein), regardless of the addition of an additive or not. However, all sterile pork (10 min heating) contained 5–31% less GO and 7–34% less MGO (except for the ethanol treated pork) as compared to their raw counterparts (GO: 2.48–4.65 mg/kg; MGO: 1.12–2.33 mg/kg). The addition of acetic acid led to an average of 33% more CML in sterile pork heated for 10 min in comparison with the control counterparts, but an average of 23% less CML and CEL in sterile pork heated for 30 min. The addition of ethanol or NaCl did not result in any obvious difference in the levels of CML and CEL in sterile pork. The amounts of CML and CEL had no direct relationship with the amounts of their precursors (GO and MGO) in sterile pork, which is possibly due to the high reactivity of the two α-dicarbonyl compounds that could rapidly react with other compounds like lysine to form more stable products (such as CML and CEL) during heating. [ABSTRACT FROM AUTHOR]

In this study, an analytical method for the determination of α-dicarbonyl compounds (α-DCs), including glyoxal (GO), methylglyoxal (MGO) and diacetyl (DA), in soy sauce was validated using gas chromatography–nitrogen-phosphorus detection. Through Maillard reaction various α-DCs, including GO, MGO and DA have been found in fermented food, dairy products and beverages. The analysis of α-DC was carried out by a derivatisation with o-phenylenediamine. The limit of detection and limit of quantitation were 0.04 and 0.12 μg/kg for GO, 0.04 and 0.13 μg/kg for MGO, and 0.07 and 0.22 μg/kg for DA. The intra- and inter-day accuracy ranged from 92.8 to 109% for GO, from 99.5 to 113% for MGO and from 93.6 to 102% for DA. The intra- and inter-day precision ranged from 3.38 to 12.1% for GO, from 0.67 to 7.65% for MGO and from 1.27 to 9.35% for DA. In 20 commercial soy sauces, α-DCs were found in concentration ranges of 5.60–31.7 μg/mL for GO, 14.4–116 μg/mL for MGO and 0.47–5.48 μg/mL for DA. The developed analytical method could be applied for the determination of α-DCs in soy sauce and motivate investigations related to reducing the content of α-DCs in soy sauce. [ABSTRACT FROM AUTHOR]

This study aims to investigate the formation mechanism of α-dicarbonyl compounds and glycation products in sesame seeds during roasting. The changes in the concentrations of sucrose, bound lysine, α-dicarbonyl compounds, N-ε-fructoselysine, N-ε-carboxymethyllysine and N-ε-carboxyethyllysine were observed in sesame samples roasted at 180, 200 and 220 °C for different time intervals to form a comprehensive kinetic model consisting of elementary steps for these products. Model results indicated that N-ε-carboxyethyllysine was originated from the reaction between methylglyoxal and bound lysine while N-ε-carboxymethyllysine formation was formed predominantly by the oxidation of N-ε-fructoselysine compared to the reaction of glyoxal with bound lysine. In addition, N-ε-fructoselysine was found to be mostly contributed to the formation of 1-deoxyglucosone, which was the most important precursor of methylglyoxal and diacetyl formation in roasted sesame seeds. 3-Deoxyglucosone and glyoxal were mainly formed from the glucose degradation. Among the reaction steps, the degradation of 1-deoxyglucosone was found to be the fastest one. In this study, the multiresponse kinetic modelling approach, which provided a better understanding the important pathways on the formation of advanced glycation end-products, was reported first in a real food system. [ABSTRACT FROM AUTHOR]

Bromine-containing polystyrene synthesized by atom transfer radical polymerization was used as a model to study coupling reactions in the presence of such free radical acceptors as conjugated dinitrones (N, N-dimethylglyoxaldinitrone, N, N-di-tert-butylglyoxaldinitrone, and N, N-diphenylglyoxaldinitrone). The influence of the reaction conditions, including the ratio of reagents, on the molecular weight characteristics of resulting products and the kinetics of the process was evaluated. It was shown that the proposed method allows one to synthesize polystyrene which contains in the middle of the chain an alkoxyamine functional group with a labile >C-ON< bond capable of further functionalization. The specified bond in the polymer modified by the coupling reaction in the presence of dinitrones cleaves at elevated temperatures, and the molecular weight of the polymer returns to the values characteristic of the original monobrominated polystyrene. It was found that in the case of the formation of dimeric products through recombination of macroradicals catalyzed by the system based on copper bromide and metallic copper in the absence of nitrones, the process follows the head-to-head pattern with the formation of a C-C bond. In this case, the polymer chain does not contain a nitroxyl functional group, which makes it inert to thermolysis under the conditions causing the >C-ON< bond cleavage formed in the presence of α-dinitrones. [ABSTRACT FROM AUTHOR]

A novel resin (DBGR) with α-hydroxy ketone groups was easily synthesized via condensation of 2,5-dihydroxy-1,4-benzoquinone with glyoxal, which was characterized by XPS, FTIR, SEM, TGA, EDS and BET. Experiments show that DBGR has a good uranium adsorption capacity of 741 mg g−1 and a high selectivity of uranyl ion in the presence of competing metal ions such as Ag+, Ca2+, Co2+, Mg2+, Sr2+ and Cs+. Adsorption isothermal and kinetic studies indicate that the uranium adsorption process of DBGR fits well with Langmuir isotherm and pseudo-second-order models. Analysis shows DBGR binds the uranyl ion via C=O, O–C–O and C–OH functional groups. [ABSTRACT FROM AUTHOR]

This correction notice addresses mistakes in an article titled "NiFe-based Prussian blue analogue nanopolygons hybridized with functionalized glyoxal polymer as a voltammetric platform for the determination of amisulpride in biological samples." The correction includes changes to section headings, deletion of a sentence and phrase, and modifications to the description of sample sources. The original article's compliance with ethical guidelines and approval by the Egyptian Network of Research Ethics Committees is also clarified. The correction notice is provided by Marwa R. El-Zahry and Marwa F. B. Ali. [Extracted from the article]

We have studied the critical parameters of Micheletti's glycoluril synthesis starting from urea and glyoxal on a statistical and multivariate analysis basis [12]. The process is potentially highly useful for scaling-up glycoluril production, and needs to be optimized. We have come to a conclusion that H3PO4 could be used as well as P4O10 giving high yields at temperature around 95°C, using glyoxal without prior purification. All reactions have been completed in less than 25 min with the yield as high as 80% under the optimized conditions. [ABSTRACT FROM AUTHOR]

The elimination kinetics of carbonyl-modified low density lipoproteins (LDL) from rabbit bloodstream was studied using isolated LDL of rabbits and humans after preliminary biotinylation or labeling with FITC. Rabbit or human blood plasma LDL were isolated using differential ultracentrifugation in a density gradient; after labeling by biotinylation or by FITC, LDL were modified with various low molecular weight natural dicarbonyls: malondialdehyde (MDA), glyoxal or methylglyoxal. Native (control) and dicarbonyl-modified biotinylated or FITC-labeled LDL were injected into the ear vein of rabbits, and blood samples were taken at certain time intervals. The content of biotinylated LDL in blood plasma was determined by an enzyme immunoassay method; FITC-labeled LDL was determined from the fluorescence spectra. It has been found that glyoxal- and methylglyoxal-modified rabbit and human LDL circulate in the bloodstream of rabbits for almost the same period as native (unmodified) LDL. In contrast to this, MDA-modified rabbit and human LDL were very quickly eliminated from the rabbit bloodstream. Dicarbonyl-modified LDL from human blood plasma is not associated with red blood cells or endothelial cells. We found that using the Oxidized LDL ELISA kits (Mercodia, Sweden) it was possible to identify mainly MDA-modified LDL. The level of MDA-modified LDL in the blood plasma of CHD patients sharply decreased during therapy with evolocumab, the hypocholesterolemic inhibitor of PCSK9 (proprotein convertase of subtilisin/kexin type 9), which activates LDL reutilization in the liver cells. These results explain the extremely rapid clearance of MDA-modified LDL in our experiments by their increased utilization in hepatocytes. The results obtained indicate a high atherogenicity of glyoxal- and methylglyoxal-modified LDL, long-term circulating in the bloodstream. [ABSTRACT FROM AUTHOR]

A new method has been developed for the synthesis of 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione in 62% yield using etidronic acid [1-hydroxyethane-1,1-diylbis(phosphonic acid), HEDP] as a "green" catalyst. A plausible stepwise mechanism of the reaction has been proposed and partially confirmed by NMR data and studying model processes. The effects of the reaction medium and HEDP on particular species involved in the reaction, namely N,N′-dimethylurea, 4,5-dihydroxy-1,3-dimethylimidazolidin-2-one, and 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione, have been studied by 1H and 13C NMR spectroscopy in D2O, neutral and acidified solutions (acetic acid-d4), and solutions containing 1 equiv of HEDP. [ABSTRACT FROM AUTHOR]

A procedure was developed for preparing glyoxylic acid by glyoxal oxidation with nitric acid in the presence of hydrohalic acids with selective isolation of glyoxylic acid from the reaction mixture in the form of magnesium and calcium salts. Specific features of the synthesis of glyoxylic acid were demonstrated, and optimum conditions for each step of the process were determined. The highest yield of glyoxylic acid was obtained in oxidation of glyoxal with an HNO3 : HCl mixture. Oxidation in the presence of HF and HBr is characterized by lower yields because of low dissociation constant of HF and side redox reactions with HBr. Dilute solutions of glyoxylic acid were obtained by an exchange reaction of its calcium salt with a hydrofluoric acid solution at room temperature. An increase in the reaction temperature leads to an increase in the content of glycolic and oxalic acids formed by disproportionation of glyoxylic acid in the initial step of the exchange reaction. [ABSTRACT FROM AUTHOR]

New 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones were synthesized, and good-to-excellent yields were achieved through one-pot, three-component condensation of aryl glyoxal monohydrates, 4-hydroxyquinolin-2(1H)-one and 3-nitroaniline using sodium alginate and water/ethanol (1:1) as a green solvent at mild reaction conditions. The noticeable features of the present procedure are mild reaction conditions, economic procedure, availability of starting materials, very simple operation, easy isolation, no need for column chromatography separation and using sodium alginate as a natural polysaccharide that is a transition-metal-free, biodegradable, reusable and commercially affordable catalyst. In addition, sodium alginate was recycled up to five times with no remarkable loss of its catalytic properties. [ABSTRACT FROM AUTHOR]

In this study, a search for synthetic routes to never-before-seen tetrabenzylglycoluril was made and two synthetic strategies were examined: condensation of 1,3-dibenzylurea with glyoxal, and N-alkylation of glycoluril and its disubstituted derivative. The first synthetic approach furnished only a condensation product, 3,3′-bi(6,8-dibenzyl-2,4-dioxa-9,8-diazabicyclo[3.3.0]octan-7-one, bearing the dioxolane moiety, in 24% yield. The second method in which 2,6-dibenzylglycoluril was reacted with BnCl in acetonitrile in the presence of KOH for 3 h afforded the target product tetrabenzylglycoluril in over 60% yield. [ABSTRACT FROM AUTHOR]

Purpose: Chemical fixation is a critical step to retaining cellular targets as naturally as possible. Recent developments in microscopy allow sophisticated detection and measuring techniques with which spatio-temporal molecular alterations are conceivable. In this study, we compare two members of aldehyde fixatives [i.e., glyoxal (Gly) and paraformaldehyde (PFA)] to determine whether Gly, a less toxic dialdehyde fixative that is considered to retain immunoreactivity could provide a successful and consistent cell fixation in favor of PFA in various cell preparations and types. Methods: We document the fixation competence of Gly and PFA side-by-side (with or without Triton X-100 permeabilization) in live- and fixed-cell preparations in mouse oocytes, embryos, and human somatic cells (human umbilical cord-derived mesenchymal stromal cells) using protein quantification by Western blot assay and super-resolution microscopy. Results: Although Gly seemed to act faster than PFA, catastrophic consequences were found not acceptable, especially in oocytes and embryos. Due to cell lysate and immunocytochemistry surveys, it was obvious that PFA is superior to Gly in retaining cellular proteins in situ with little/no background staining. In many samples, PFA revealed more reliable and consistent results regarding the protein quantity and cellular localization corresponding to previously defined patterns in the literature. Conclusion: Although the use of Gly is beneficial as indicated by previous reports, we concluded that it does not meet the requirement for proper fixation, at least for the tested cell types and proteins. However, PFA alone with no addition of TX displayed a significant cytoplasmic loss by generating membrane blebs during fixation. [ABSTRACT FROM AUTHOR]

In situ formation of 2-methylimidazole as a result of 2,4,6-trimethyl-1,3,5-hexahydrotriazine trihydrate and glyoxal interaction in an aqueous solution is studied for the first time using NMR spectroscopy. In addition to the reactants and products, the reaction mixture is shown to contain stable intermediate products of the trimer decomposition as well as glycolic acid. [ABSTRACT FROM AUTHOR]

Sustainable leather processing is viable through conventional organic tanning processing that provides scopes for quality to match with the chrome-tanned leathers. Hence, there is a need to develop sustainable tanning technology for leather processing. Glyoxal alone and in combination with wattle extract has been tried to establish a new tanning system. Glyoxal as the solo-tanning agent, optimized at the level of 5%, can produce shrinkage temperature up to a level of 72 °C, whereas the combination tanning system with the help of wattle extract yielded leather with shrinkage temperature of 92 °C. The tanned leather was further processed into crust leather, and organoleptic properties are evaluated. Thermogravimetric analyses revealed better thermal stability at 113.52 °C, with a residue of 86.94%, in comparison with the leather tanned with combination tanning system using wattle extract showing stability at 110 °C and residue of 87.29%. The visual assessment results showed that the leathers produced from experiments were soft, with smoother grain, uniform dyeing properties and overall comparable strength properties. The plausible mechanism for present tanning systems has been elucidated. The results of scanning electron microscopic analysis revealed that leather produced from glyoxal tanning was of empty type where the fibers are tightly bounded, however, having less angle of weave as compared to control sample. The reduction in Bio-chemical oxygen demand and Chemical oxygen demand values from effluent stream in the case of solo tanning showed 64–70% and 68–71%, respectively. [ABSTRACT FROM AUTHOR]

Silkworm silk protein fibroin is widely exploited to develop novel silk-based biomaterials due to its stable β-sheet structure, providing high crystallinity and tensile strength. The polymorphic behaviour of silk fibroin provides a window to modulate its structural transitions during self-assembly for different functional outcomes. Most studies are therefore mainly focused on formation of well-developed β-sheet structure and self-assembly of silk fibroin which are regulated by many parameters. Glyoxal, a highly reactive α-oxoaldehyde, reacts with different proteins to form advanced glycation end products (AGEs) following Maillard-like reaction. Considering the significance of protein modification by glyoxal-derived AGEs, in the present study the effect of glyoxal (250, 500 and 1000 μM) on the structure of silk fibroin has been investigated. CD and fluorescence studies reveal that higher concentrations of the α-oxoaldehyde induce considerable alterations of secondary and tertiary structure of the protein leading to aggregation following incubation with for 3 weeks. The aggregates exhibit fibrillar morphology with amyloidal nature as evident from SEM, FTIR and XRD experiments. The findings highlight that glycation-induced modification can be a possible approach for modulating the conformation of the silk protein which may be relevant in connection to clinical, biomedical or synthetic biology based applications. [ABSTRACT FROM AUTHOR]

Silkworm silk protein fibroin is widely exploited to develop novel silk-based biomaterials due to its stable β-sheet structure, providing high crystallinity and tensile strength. The polymorphic behaviour of silk fibroin provides a window to modulate its structural transitions during self-assembly for different functional outcomes. Most studies are therefore mainly focused on formation of well-developed β-sheet structure and self-assembly of silk fibroin which are regulated by many parameters. Glyoxal, a highly reactive α-oxoaldehyde, reacts with different proteins to form advanced glycation end products (AGEs) following Maillard-like reaction. Considering the significance of protein modification by glyoxal-derived AGEs, in the present study the effect of glyoxal (250, 500 and 1000 μM) on the structure of silk fibroin has been investigated. CD and fluorescence studies reveal that higher concentrations of the α-oxoaldehyde induce considerable alterations of secondary and tertiary structure of the protein leading to aggregation following incubation with for 3 weeks. The aggregates exhibit fibrillar morphology with amyloidal nature as evident from SEM, FTIR and XRD experiments. The findings highlight that glycation-induced modification can be a possible approach for modulating the conformation of the silk protein which may be relevant in connection to clinical, biomedical or synthetic biology based applications. [ABSTRACT FROM AUTHOR]

A series of mesoporous silica (KIT-6, MCM-41 and SBA-15) supported Pd catalysts were successfully synthesized and applied for selective oxidation of glyoxal. All of these catalysts exhibited significantly higher activity than commercial Pd/C. Among them, Pd/KIT-6 exhibited the best activity and selectivity with 41.3% glyoxal conversion and 57.0% selectivity to glyoxalic acid. The better performance of Pd/KIT-6 was attributed to its three-dimensional mesoporous structure. The three-dimensional mesoporous structure of KIT-6 could enhance Pd dispersion, providing sufficient accessible active sites which improved the conversion of glyoxal. Meanwhile, the better mass transfer capability of Pd/KIT-6 allowed glyoxalic acid to leave the catalyst easily, reducing the probability of over-oxidation. The ratio of kI (rate constant of initial oxidation reaction) to kII (rate constant of over-oxidation) was compared among three catalysts. The kI/kII of Pd/KIT-6 (0.50) was higher than that of Pd/MCM-41 (0.39) and Pd/SBA-15 (0.34), which reflected its best selectivity from kinetic aspect. [ABSTRACT FROM AUTHOR]

The values and nature of induction periods (IP) for the oxidation of commercial glyoxal (CG) to glyoxylic acid (GA) by HNO3—HCl mixtures were studied under diff erent reaction conditions. The physicochemical interpretation of the IP enables one to control the oxidation of CG to target GA. It was established by UV spectroscopy that the addition of HCl favored the disintegration of n-mers of CG and simultaneous accumulation of structures with aldehyde groups (SAG), which are active forms of CG during its oxidation to GA. The rate constants and activation energies of SAG accumulation were determined. The theoretical UV spectra, which are well consistent with the experimental curves, and thermochemistry of equilibria of the CG forms were calculated in the Gaussian/09 program package. The IP values at varied temperature, ratio of CG to hydrochloric acid, and time of storage of the reaction mixture were determined on the Arduino-based unit with a temperature sensor. The IP value is almost halved with an increase in the amount of HCl. The IP is also nearly halved as the time of storage of a CG—HCl mixture increases by three times. The obtained regularities indicate that the character of the IP of CG oxidation is related to the continuous disintegration of n-mers in CG solutions, i.e., to the permanent accumulation of SAG, which are fi nally oxidized to GA. [ABSTRACT FROM AUTHOR]

We report the development of a fast and accurate fluorescence-based assay for amidine linked to cellulose membranes and Sepharose gel. The assay is founded on the glyoxal reaction, which involves reaction of an amidine group with glyoxal and an aromatic aldehyde, leading to the formation of a fluorophore that can be analyzed and quantified by fluorescence spectroscopy and imaging. While the assay has been reported previously for aromatic amidine estimation in solution phase, here we describe its adaptation and application to amidine linked to diverse forms of solid matrices, particularly benzamidine Sepharose and benzamidine-linked cellulose membranes. These functionalized porous matrices find important application in purification of serine proteases. The efficacy of a protein separation device is determined by, among other factors, the ligand (amidine) density. Hence, a sensitive and reproducible method for amidine quantitation in solid phase is needed. The glyoxal reaction was carried out on microbead-sized Sepharose gel and cellulose membranes. Calibration curves were developed for each phase, which established linearity in the range of 0–0.45 μmol per mL amidine for free amidine in solution, 0–0.45 μmol amidine per mL Sepharose gel, and 0–0.48 μmol per mL cellulose membrane. The assay showed high accuracy (~ 3.4% error), precision (RSD < 2%), and reproducibility. Finally, we show how this fluorescent labeling (glyoxal) method can provide a tool for imaging membranes and ligand distribution through confocal laser scanning microscopy. Graphical abstract [ABSTRACT FROM AUTHOR]

The review summarizes approaches, known from the literature, to the synthesis, isolation, and crystallization of glyoxylic acid (GA), which is an important component in fine organic synthesis and is widely used in pharmaceutical, food, and perfume industry. The review describes the research dealing with GA synthesis from aqueous solutions of glyoxal by catalytic, electrochemical, and enzymatic methods and by ozonolysis of maleic acid in solution. Alternative methods for GA synthesis are considered, for example, from glycolic acid in the presence of glycolate oxidase, oxalic acid, ethyl alcohol, and from various halogenated acetic acid derivatives. Approaches to GA isolation from the products of synthesis depending on the starting compound are considered, including extraction with amines or alcohols, the use of cation or anion exchange resins at elevated temperatures, and precipitation as insoluble alkaline earth metal salts. Methods for GA crystallization using various experimental techniques are presented. [ABSTRACT FROM AUTHOR]

A convenient method was developed for the synthesis of previously unknown 1,2-diketones, based on the condensation of 5-hydroxy-2-methyl-4H-pyran-4-one with arylglyoxals. The study demonstrated the possibility of using these compounds to synthesize nitrogen-containing hetero cyclic systems bearing the 3-hydroxypyran-4-one moiety. [ABSTRACT FROM AUTHOR]

A convenient method for the synthesis of previously unknown substituted 2-(2-aryl-4-oxo-4H-furo[3,2-c]chromen-3-yl)acetic acids, 2-(2-aryl-6-methyl-4-oxo-4H-furo[3,2-c]pyran-3-yl)acetic acids, and 2-(2-aryl-6-methyl-4-oxo-4,5-dihydrofuro[3,2-c]pyridin-3-yl)acetic acids based on multicomponent condensation of heterocyclic enols with arylglyoxals and Meldrum's acid was developed. [ABSTRACT FROM AUTHOR]

Two organic compounds, namely, 7a-(2-chlorophenyl)-7a,8a,9,10,11,12a-hexadronaptho-[1',2':4,5]furo[3,2-d]pyrrolo[2,1-b]oxazole (I) and 2-(4-fluorophenyl)-2-hydroxynaptho[2,1-b]furan- 1(2H)-one (II), were synthesised via microwave reaction using commercially available glyoxal monohydrate, β-Naphthol, pyrrolidine, and Cu(OAc)2 · H2O, and their crystal structures were determined by X-ray diffraction technique. The crystals of compound I are orthorhombic, sp. gr. P212121, a = 6.8750(5) Å, b = 8.2248(9) Å, c = 31.720(3) Å, and Z = 4, while the crystals of compound II are monoclinic, sp. gr. P21/c, a = 7.4038(9) Å, b = 18.592(2) Å, c = 10.4589(12) Å, β = 107.492(13)°, and Z = 4. The inter molecular O-H···O, C-H···O, and C-H···F hydrogen interactions play significant role in stabilizing the crystal structure in the compound II. In addition, aromatic π-π interactions are also observed in the structure of the compound II. [ABSTRACT FROM AUTHOR]

It was found that the condensation of two equivalents of 4-hydroxy-6-methyl-2H-pyran-2-one or 4-hydroxycoumarin with arylglyoxals in boiling formic acid leads to 4H-furo[3,2-c]-pyran-4-ones or 4H-furo[3,2-c]chromen-4-ones, respectively. [ABSTRACT FROM AUTHOR]

Two different types of commercial tannins, namely chestnut (a hydrolysable tannin) and mimosa (a condensed flavonoid tannin), were used with two different types of hardener, namely hexamine and glyoxal, to upgrade soy-based adhesives for bonding of wood particleboard. Different soy-based adhesive formulations were tested by differential scanning calorimetry (DSC) and by thermomechanical analysis (TMA). The physical properties of different adhesive formulations such as viscosity, solid contents, acidity and density were also measured. One-layer laboratory particleboards bonded with the experimental adhesive formulations were prepared and tested. Based on the results obtained, tannins appear to decrease effectively soy-based adhesives' viscosity. The TMA analysis showed that chestnut tannin extract appeared to react well with soy flour and to improve the soy flour adhesion properties. The TMA results also showed that both tannin types shorten the adhesives gel time and gel temperature. The DSC analysis also showed that tannin changes the thermal properties of soy-based adhesive and decreases both its glass transition temperature (Tg) and its denaturation temperature (Td). Moreover, particleboard bonded with tannin-modified adhesives showed internal bond strength results higher than particleboard bonded with unmodified soy adhesive. Thickness swelling and water absorption of the boards decreased when using tannins in soy-based adhesive formulations. [ABSTRACT FROM AUTHOR]

By application of acid-catalyzed condensation of propane-2-, benzene- and methanesulfonamides with glyoxal a series of new derivatives of oxaazaisowurtzitanes were obtained, in particular, new heterocyclic systems: 2,4,6,8,12-pentaoxa-10-aza- and 2,4,8,12-tetraoxa-6,10-diazatetracyclo[5.5.0.0.0]-dodecanes. [ABSTRACT FROM AUTHOR]