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Substantial amounts of phenolic aldehydes, represented by the structures of syringaldehyde, vanillin, and 4-hydroxybenzaldehyde, are emitted to the atmosphere during biomass burning. The oxidative transformation of phenolic aldehydes during atmospheric transport has the potential to modify the physicochemical properties of particulates, which play a vital role in Earth's climate and human health. Herein, thin solid films made of syringaldehyde, vanillin, and 4-hydroxybenzaldehyde are oxidized in contact with O

The hypothesis of this study is that the complex organic load of landfill leachate could be reduced by supercritical water oxidation (SCWO) in a single stage, but this operation could lead to the formation of some undesired by-products of phthalate esters (PAEs). In this context, the fate of selected PAEs, butyl benzyl phthalate (BBP), di-2-ethylhexyl phthalate (DEHP) and di-n-octyl phthalate (DNOP), was investigated during the oxidation of leachate under subcritical and supercritical conditions. Experiments were conducted at various temperatures (250-500 °C), pressures (10-35 MPa), residence times (2-18 min) and dimensionless oxidant doses (DOD: 0.2-2.3). The SCWO process decreased the leachate's chemical oxygen demand (COD) from 34,400 mg/L to 1,120 mg/L (97%). Removal efficiencies of DEHP and DNOP with longer chains were higher than BBP. The DEHP, DNOP and BBP compounds were removed in the range of -35 to 100%, -18 to 92%, and 28 to 36%, respectively, by the SCWO process. Many non-target PAEs were qualitatively detected in the raw leachate apart from the selected PAEs. Besides, 97% of total PAEs including both target and non-target PAEs was mineralized at 15 MPa, 300 °C and 5 min. Although PAEs were highly mineralized during SCWO of the leachate, aldehyde, ester, amide and amine-based phthalic substances were frequently detected as by-products. These by-products have transformed into higher molecular weight by-products with binding reactions as a result of complex SCWO process chemistry. It has also been determined that some non-target PAEs such as 1,2-benzenedicarboxylic acid bis(2-methylpropyl)ester and bis(2-ethylhexyl) isophthalate can transform to the DEHP. Therefore, the suggested pathway in this study for PAEs degradation during the SCWO of the leachate includes substitution and binding reactions as well as an oxidation reaction.

Polymers with excellent optical and mechanical performance fabricated from renewable resources, have been paid an increasing attention in recent years. Here, high-performing polyurethane elastomers with significant mechanical properties, crystallinity, excellent stretchability and good transparency are prepared by a synergistic molecular design in the soft and hard segments. Using the liquid glycolysis degradation product (LGOP) as a chain extender, polyurethane elastomer is synthesized from polyethylene terephthalate (PET) waste bottles. The results suggest that the degradation products from waste PET can be directly used as feedstock for preparing polyurethane elastomers with significant performance. The polyurethanes exhibited excellent optical transparency of near 90%, and can be stretched up to 670% without any treatment to return to original size. It is assumed that the symmetrical hard domain composed of aromatic rings and ester groups in LGOP creates sufficient chain fluidity for the dynamic exchange of hydrogen bonds and urethane. This paper has devoted to achieve a complete and mature system from waste PET to polyurethane products, to create a closed loop of waste PET plastic recycling and regeneration, and to realize the polyurethane industrial chain of raw material self-supply.

We developed a copper-catalyzed enantio- and diastereoselective boron conjugate addition to α-alkyl α,β-unsaturated esters under base-free conditions. The approach showed excellent enantioselectivities (87-99% ee) and moderate to good conversions (51-99%), albeit with moderate diastereoselectivities (1 : 1-17 : 1 dr). The synthetic utility of this protocol was demonstrated.

Palladium-catalyzed Suzuki reactions of brominated flavin derivatives (5-deazaflavins, alloxazines, and isoalloxazines) with boronic acids or boronic acid esters that occur readily under mild conditions were shown to be an effective tool for the synthesis of a broad range of 7/8-arylflavins. In general, the introduction of an aryl/heteroaryl group by means of a direct C-C bond has been shown to be a promising approach to tuning the photophysical properties of flavin derivatives. The aryl substituents caused a bathochromic shift in the absorption spectra of up to 52 nm and prolonged the fluorescence lifetime by up to 1 order of magnitude. Moreover, arylation of flavin derivatives decreased their ability to generate singlet oxygen.

The influence of the two technological parameters, temperature (20 °C, 24 °C, 28 °C) and the inoculum amount of the yeast culture (2%, 3%, 4%) on the duration of the alcoholic fermentation and the ester-producing capacity of the Badachoni and the 24-6 strains of Saccharomyces cerevisiae species was studied. The yeast exhibited high fermentation activity. The intensity with which it initiated the process and the time for its completion was in correlation with the studied factors. The strains showed the best activity at 28 °C/4%. Neural networks were applied and mathematical models were derived, properly describing the fermentation process and the change in the total amount of esters in the course of the process, depending on the technological conditions. The rate in the dynamic of the esters during the process was monitored in 4 stages - onset, rapid fermentation, quiet fermentation, and after malolactic fermentation. The maximum quantity of esters was synthesized in the middle of the process. During alcoholic fermentation, the esters followed a tendency to increase with decreasing the temperature, increasing the amount of yeast culture and the time of the process. The Badachoni and the 24-6 strains demonstrated the highest ester-producing capacity under the temperature of 20 °C and with the 4% inoculum of the yeast culture. The Badachoni strain quantitatively produced more esters than the 24-6 strain. No strict correlation was found between the amount of esters and the organoleptic properties of the wines. The sample containing the most esters had the highest tasting score only in the variants of the 24-6 strain.

We report a combined experimental and mechanistic study on the Buchwald-Hartwig amination and C-S/S-H metathesis of aryl sulfides by selective activation of C-S bonds mediated by well-defined, air-and moisture-stable Pd(II)-NHC precatalysts, [Pd(NHC)(mu-Cl)Cl]2. This class of Pd(II)-NHC precatalysts displays excellent activity in the cross coupling of aryl sulfides. Most crucially, we unravel the unified mechanism for activation of C-S bonds in the C-N cross-coupling and C-S metathesis manifolds, where the inert C-S bond serves as a precursor to valuable amine or thioether products.

In this study of extracts of 100 food contact material (FCM) samples collected from South China, we identified 21 organophosphate esters (OPEs) by suspect screening and seven novel OPEs by characteristic fragments-based nontarget screening. Six organophosphite antioxidants (OPAs) were further identified using a suspect list derived from these identified OPEs. Of these compounds, 18 OPEs and 3 OPAs were found for the first time in the extracts of FCMs. (Semi-)quantification revealed that seven of the OPEs [triphenyl phosphate, tris(2,4-di

The biocide tetrakis(hydroxymethyl)phosphonium sulphate (THPS) and other members of the tetrakis(hydroxymethyl) phosphonium salts (THPX) family are associated with liver toxicity in several mammalian species and teratogenicity in rabbits. Malformations include skeletal changes and abnormalities in eye development and are very similar to those seen with vitamin A deficiency or excess. For this reason, it was hypothesized that teratogenicity of THPS(X) might be attributed to disturbances in retinol availability and/or metabolism as a result of maternal toxicity, for example, either due to insufficient dietary intake by the mothers or due to liver toxicity. Therefore, in the present study, liver toxicity and vitamin A homeostasis were studied in pregnant rabbits that were exposed to 13.8 or 46.0 mg/kg THPS during organogenesis and in precision-cut liver slices of rats and rabbits exposed to 0-70 mu M THPS. Results show that in vivo exposure to THPS leads to a marked reduction of food intake, increased plasma concentrations of gamma-glutamytransferase, degenerative changes in the liver and to changes in retinoid content in liver and plasma in the rabbits during organogenesis. In addition, THPS, both in vivo and ex vivo, caused a change in expression of proteins related to vitamin A metabolism and transport. Together, these observations could explain the birth defects observed in earlier teratogenicity studies.

Abstract: Plant derived natural products have multifaceted beneficial roles in human pathophysiology. Plant secondary metabolites have been used as an adjunct medicine for a long time and β- Glucogallin is one such pharmaceutically important plant derived natural product. Β-glucogallin (1-O-galloyl-β-d-glucopyranose), a plant-derived polyphenolic ester, is regarded as the primary metabolite in the biosynthesis of hydrolyzable tannins. It is majorly found in amla, pomegranate, strawberry etc. Owing to its free radical scavenging properties, β-glucogallin (BG) is believed to protect against several diseases like diabetes and related complications like retinopathy, glaucoma, inflammation, hepatic damage, skin damage from UV, etc. Several semisynthetic derivatives of β-Glucogallin are being developed, which have better pharmacokinetic and pharmacodynamic parameters than β-glucogallin. Studies have shown the prophylactic role of β-Glucogallin in developing defence mechanisms against the advent and progression of certain diseases. β- glucogallin formulations have shown a positive effect as a neutraceutical. In this manuscript, we have discussed β-glucogallin, its natural sources, biosynthetic pathways, its semi-synthetic derivatives, and the plethora of its pharmacological activities like antioxidant-antiinflammatory, antidiabetic, cataract-preventing, anti glaucoma, and UV protectant. We have also highlighted various biological pathways, which are modulated by β-glucogallin. The manuscript will convey the importance of β-glucogallin as a compound of natural origin, having multifaceted health benefits.

The accumulation of organic pollutants in vegetables is a major global food safety issue. The concentrations of pollutants in vegetables usually differ across different tissues because of different transport and accumulation pathways. However, owing to the limitations of conventional methods, in situ localization of typical organic pollutants such as phthalate esters (PAEs) in plant tissues has not yet been studied. Here, we developed a quick and efficient method for in situ detection and imaging of the spatial distribution of PAEs in a typical root vegetable, carrot, using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). The use of a 2,5-dihydroxybenzoic acid matrix with a spray-sublimation coating method led to the successful identification of PAEs ion signals. The IMS results showed that a typical PAE-di-(2-ethylhexyl)phthalate (DEHP) was broadly distributed in the cortex, phloem, and metaxylem, but was barely detectable in the cambium and protoxylem. Interestingly, MALDI-IMS data also revealed for the first time the spatial distribution of sugars and β-carotene in carrots. In summary, the developed method offers a new and practical methodology for the in situ analysis of PAEs and plant metabolites in plant tissues. As a result, it could provide a more intuitive understanding of the movement and transformation of organic pollutants in soil-plant systems.

A regioselective alkylation of β,γ-alkynyl-α-imino esters by visible-light photocatalysis has been developed. This method enables 1,2-addition of methyl, primary, secondary, and tertiary alkyl radicals to the conjugated imines under mild conditions to produce a variety of quaternary alkynyl α-amino acid and cyclic amino acid motifs. Alkyl radicals are generated from alkyl bis(catecholato)silicates with an organic photocatalyst. This process is effective under an air atmosphere, providing operational benefits compared to conventional alkylation using organometallic reagents.

Suspension-cultured cells of a bamboo species (Bambusa multiplex; Bm) produce 3-O-feruloylquinic acid (3-FQA) and 3-O-p-coumaroylquinic acid (3-pCQA) by treatment with the histone deacetylase inhibitor suberoyl bis-hydroxamic acid (SBHA). Acyltransferases catalyzing the formation of 5-O-hydroxycinnamoylquinic acid esters by transesterification from hydroxycinnamoyl-CoAs to the C-5 hydroxy group of quinic acid (hydroxycinnamoyl-CoA:quinate hydroxycinnamoyltransferase, HQT) have been identified in the biosynthesis of chlorogenic acids and monolignols; however, an HQT that catalyzes the acylation of the C-3 hydroxy group of quinic acid has not been identified previously. In the present study, we purified a native HQT from SBHA-treated Bm cells. The purified enzyme preferentially accepted feruloyl-/p-coumaroyl-CoAs as acyl-donors and quinic acid as the acyl-acceptor, and the enzyme specifically formed 3-FQA and 3-pCQA but not 5-O-hydroxycinnamoylquinic acid esters or esters with shikimic acid. A cDNA (BmHQT1) encoding this HQT was isolated. Although BmHQT1 is a phylogenetically unique member of the BAHD acyltransferase superfamily that does not cluster with other HQTs, functional characterization of the recombinant enzyme verified that BmHQT1 catalyzes the regiospecific formation of 3-O-hydroxycinnamoylquinic acid esters. Transcript levels of BmHQT1 markedly increased in Bm cells cultured in the presence of SBHA. Moreover, elevated acetylation levels of histone H3 were observed in the coding region of BmHQT1 in the presence of SBHA, indicating that the induced accumulation of 3-FQA/3-pCQA by SBHA is caused by transcriptional activation of BmHQT1 by the action of SBHA as a histone deacetylase inhibitor. The results demonstrate the utility of HDAC inhibitors for discovery of cryptic secondary metabolites and unknown biosynthetic enzymes.

Several classes of ribosomally synthesized and post-translationally modified peptides (RiPPs) are composed of multiple macrocycles. The enzymes that assemble these macrocycles must surmount the challenge of installing a single specific set of linkages out of dozens of distinct possibilities. One class of RiPPs that includes multiple macrocycles are the graspetides, named after the ATP-grasp enzymes that install ester or amide linkages between pairs of nucleophilic and electrophilic side chains. Here, using heterologous expression and NMR spectroscopy, we characterize the connectivity and structure of amycolimiditide, a 29 aa graspetide with a stem-loop structure. The stem includes four esters and extends over 20 Å. The loop of amycolimiditide is distinguished by the presence of an aspartimide moiety, installed by a dedicated

ConspectusTransition-metal-catalyzed cross-coupling reactions are widely used in both academia and industry for the construction of carbon-carbon and carbon-heteroatom bonds. The vast majority of cross-coupling reactions utilize aryl (pseudo)halides as the electrophilic coupling partner. Carboxylic acid derivatives (RC(O)X) represent a complementary class of electrophiles that can engage in decarbonylative couplings to produce analogous products. This decarbonylative approach offers the advantage that RC(O)X are abundant and inexpensive. In addition, decarbonylative coupling enables both intramolecular (between R and X of the carboxylic acid derivative) as well as intermolecular bond-forming reactions (in which an exogeneous nucleophile is coupled with the R group derived from RC(O)X). In these intermolecular reactions, the X-substituent on the carboxylic acid can be tuned to facilitate both oxidative addition and transmetalation, thus eliminating the need for an exogeneous base. This Account details our group's development of a diverse variety of base-free decarbonylative coupling reactions catalyzed by group 10 metals. Furthermore, it highlights how catalyst design can be guided by stoichiometric organometallic studies of these systems.Our early studies focused on

The first copper-catalyzed enantioselective [4 + 1] annulation of yne-allylic esters with 1,3-dicarbonyl compounds was realized through an elegant remote stereocontrol strategy. The very remote ε regioselective nucleophilic substitution was developed by employing a novel chiral copper-vinylvinylidene species from the new C4 synthon yne-allylic esters. Thus, greatly diverse spirocycles were obtained with ample scope and excellent levels of chemo-, regio-, and enantioselectivities. Moreover, detailed mechanistic studies suggest an yne-allylic substitution and Conia-ene cascade pathway on the remote stereochemical induction progress.

Aim and Objective: The syntheses of glucuronide metabolites of phenolic xenoestrogens triclosan and 2-phenylphenol, namely triclosan-O-glucuronide (TCS-G; 1), and 2-phenylphenol-O-glucuronide (OPP-G; 2), were achieved for use as analytical standards. Methods: Under classical conditions previously reported for glucuronide synthesis, the final basic hy-drolysis of the peracylated ester intermediate leading to the free glucuronides is often a limiting step. Indeed, the presence of contaminating by-products resulting from ester elimination has often been ob-served during this step. This is particularly relevant when the sugar unit is close to a crowded envi-ronment as for triclosan and 2-phenylphenol. Results: To circumvent these problems, we proposed mild conditions for the deprotection of peracety-lated glucuronate intermediates. Conclusion: A new methodology using a key imidate following a two-step protocol for acetates and methyl ester hydrolysis was successfully applied to the preparation of TCS-d3 (1) and OPP-G (2) as well as deuterated isotopomers TCS-d3-G (1-d3) and OPP-d5-G (2-d5).

Exploiting aromatic π-interaction for the stabilization of polyaromatic anticancer drugs at the core of the polymer nanoassemblies is an elegant approach for drug delivery in cancer research. To demonstrate this concept, here we report one of the first attempts on enzyme-responsive polymers from aryl-unit containing amino acid bioresources such as l-tyrosine and 3,4-dihydroxy-l-phenylalanine (l-DOPA). A silyl ether protection strategy was adopted to make melt polymerizable monomers, which were subjected to solvent free melt polycondensation to produce silyl-protected poly(ester-urethane)s. Postpolymerization deprotection yielded phenol- and catechol-functionalized poly(ester-urethane)s with appropriate amphiphilicity and produced 100 ± 10 nm size nanoparticles in an aqueous solution. The aromatic π-core in the nanoparticle turns out to be the main driving force for the successful encapsulation of anticancer drugs such as doxorubicin (DOX) and topotecan (TPT). The electron-rich catechol aromatic unit in l-DOPA was found to be unique in stabilizing the DOX and TPT, whereas its l-tyrosine counterpart was found to exhibit limited success. Aromatic π-interactions between l-DOPA and anticancer drug molecules were established by probing the fluorescence characteristics of the drug-polymer chain interactions. Lysosomal enzymatic biodegradation of the poly(ester-urethane) backbone disassembled the nanoparticles and released the loaded drugs at the cellular level. The nascent polymer was nontoxic in breast cancer (MCF7) and WT-MEF cell lines, whereas its DOX and TPT loaded nanoparticles showed remarkable cell growth inhibition. A LysoTracker-assisted confocal microscopic imaging study directly evidenced the polymer nanoparticles' biodegradation at the intracellular level. The present investigation gives an opportunity to design aromatic π-interaction driven drug stabilization in l-amino acid based polymer nanocarriers for drug delivery applications.

Glycopolymers are synthetic macromolecules having pendant sugar moieties and widely utilized to target cancer cells. They are usually considered as a hydrophilic segment of amphiphilic block copolymers to fabricate micelles as drug carriers. A novel amphiphilic block copolymer, namely, poly(2-deoxy-2-methacrylamido-d-glucose

By applying the aroma extract dilution analysis, 13 esters were found to have high FD factors in the

Heteroaryl sulfoxides are an integral part of several bioactive molecules and pharmaceuticals. We have described a transition-metal-free route for the direct sulfinylation of 2-halobenzothiazoles and 2-halobenzimidazoles using β-sulfinyl esters as the source of the sulfenate ion in the presence of a Brønsted base such as LiO

Growth suppression and defence signalling are simultaneous strategies that plants invoke to respond to abiotic stress. Here, we show that the drought stress response of poplar trees (Populus trichocarpa) is initiated by a suppression in cell wall derived methanol (MeOH) emissions and activation of acetic acid (AA) fermentation defences. Temperature sensitive emissions dominated by MeOH (AA/MeOH

Synthetic methods of unnatural α-amino acids have always been the focus of extensive research due to their significant bioactivities. However, convenient transition-metal-free catalyzed methods are still in demand. Herein, we report a novel strategy for the construction of an unnatural α-amino acid skeleton via intramolecular rearrangement of carbamates, which are readily available from amines and their common protecting groups. This rearrangement could afford a variety of amino ester products in up to 98% yield, even in gram-scale reaction. The reaction mechanism was studied in detail through experiments and theoretical calculations. The complex-induced proximity effect (CIPE) from the 2-pyridyl group is shown to be indispensable for this transformation.

Random and rational mutagenesis of an α-amino acid ester acyl transferase from Sphingobacterium siyangensis AJ2458 (SAET) was conducted to examine the production of aspartame, an α-l-aspartyl-l-phenylalanine methyl ester. We previously reported aspartame production via combination of enzymatic and chemical methods. However, the productivity of the aspartame intermediate by SAET was approximately one-fifth that of l-alanyl-l-glutamine (Ala-Gln), whose production method has already been established. Here, to improve the enzymatic activity of SAET, we performed random mutagenesis in the gene encoding SAET and obtained 10 mutations that elevated the enzymatic activity (1.2- to 1.7-fold increase) relative to that of wild-type SAET. To further improve the activity, we performed mutagenesis to optimize the combination of the obtained mutations and finally selected one SAET variant with 10 amino acid substitutions (M35-4 SAET). An Escherichia coli strain overexpressing M35-4 SAET displayed a 5.7-fold higher activity than that of the wild-type SAET, which was almost equal to that of Ala-Gln by an E. coli strain overexpressing wild-type SAET. The Vmax value of M35-4 SAET was 2.0-fold greater, and its thermostability was higher than those of wild-type SAET. These results suggest that the obtained SAET variants contribute to improvement in aspartame production.

Quercetin monoesters were prepared via a one-step enzymatic transesterification. The main acylation products were eight quercetin ester derivatives, respectively, consisting of varying acyl groups ranging from 2 to 18 carbon atoms (acetate, butyrate, caproate, caprylate, caprate, laurate, myristate, and stearate). The purified quercetin esters were structurally characterized by LC-ESI-ToF and NMR HSQC. Meanwhile, several classical chemical (DPPH, ABTS, FRAP, and Fe

The oxidation of volatile organic compounds (VOCs), which are emitted to the atmosphere from natural and anthropogenic sources, leads to the formation of ozone and secondary organic aerosol (SOA) particles that impact air quality and climate. In the study reported here, we investigated the products of the reactions of five biogenic monoterpenes with OH radicals (an important daytime oxidant) under conditions that mimic the chemistry that occurs in polluted air, and developed mechanisms to explain their formation. Experiments were conducted in an environmental chamber, and information on the identity of gas-phase molecular products was obtained using online mass spectrometry, while liquid chromatography and two methods of functional group analysis were used to characterize the SOA composition. The gas-phase products of the reactions were similar to those formed in our previous studies of the reactions of these monoterpenes with NO

An asymmetric 1,2-dicarbofunctionalization of unactivated alkenes with aryl iodides and aryl/alkenylboronic esters under nickel/bioxazoline catalysis is disclosed. A wide array of aryl and alkenyl nucleophiles are tolerated, furnishing the products in good yield and with high enantioselectivity. In addition to terminal alkenes, 1,2-disubstituted internal alkenes participate in the reaction, establishing two contiguous stereocenters with high diastereoselectivity and moderate enantioselectivity. A combination of experimental and computational techniques shed light on the mechanism of the catalytic transformation, pointing to a closed-shell pathway with an enantiodetermining migratory insertion step, where stereoinduction arises from synergistic interactions between the sterically bulky achiral sulfonamide directing group and the hemilabile bidentate ligand.

An iron-catalyzed four-component sulfonylthiocyanation between α,β-unsaturated amides/esters, TMSNCS, aryldiazonium tetrafluoroborates, and sulfur dioxide (from SOgen) is demonstrated. This protocol is characterized by mild reaction conditions, good functional group compatibility, broad substrate scope, and good to excellent yields, providing a feasible method for the preparation of

Depsides are polyphenolic molecules comprising two or more phenolic acid derivatives linked by an ester bond, which is called a depside bond in these molecules. Despite more than a century of intensive research on depsides, the biosynthetic mechanism of depside bond formation remains unclear. In this study, we discovered a polyketide synthase, DrcA, from the fungus

Relationships between chemical structure and conductivity in ordered polymers (OPs) are difficult to probe using bulk samples. We propose that conductance measurements of appropriate molecular-scale models can reveal trends in electronic coupling(s) between repeat units that may help inform OP design. Here, we apply the scanning tunneling microscope-based break-junction (STM-BJ) method to study transport through single-molecules comprising OP-relevant imine, imidazole, diazaborole, and boronate ester dynamic covalent chemical bridges. Notably, solution-stable boron-based compounds dissociate

Herein, we report a convenient solvent-controlled regioselective esterification to access two types of carboxylate esters without any additive or non-green activation strategy. In this transformation, 2-methyleneaziridines served as an ester reagent, providing two alternative electrophilic carbon centers. Notably, this protocol is suitable for some structure-complicated clinical molecules with a carboxylic acid group, presenting remarkable application potential.

Corn bran is an abundant coprocessing stream of corn-starch processing, rich in highly substituted, diferuloyl-cross-linked glucurono-arabinoxylan. The diferuloyl cross-links make the glucurono-arabinoxylan recalcitrant to enzymatic conversion and constitute a hindrance for designing selective enzymatic upgrading of corn glucurono-arabinoxylan. Here, we show that two bacterial feruloyl esterases, wtsFae1A and wtsFae1B, each having a carbohydrate-binding module of family 48, are capable of cleaving the ester bonds of the cross-linkages and releasing 5-5', 8-5', 8-5' benzofuran, and 8

Antibody conjugates are extensively used for diagnostics and therapeutics, and as a tool for molecular biology. To prepare such conjugates N-hydroxysuccinimide (NHS) esters are most often used due to the straightforward experimental procedure and the commercial accessibility of the reagents. Such conjugates are however highly heterogeneous, since only the reactivity of the lysines determines the distribution of labels. This has inspired the development of methods that experimentally are as facile but produce conjugates of higher quality. Herein, we report the development of a reagent that can, in one step, be activated with an NHS ester of choice and subsequently can be directly used for site-directed labeling of antibodies. The reagent can be prepared in three synthetic steps and produces conjugates with similar ease as for NHS esters, however in a site-directed manner. We show that the reagent is quantitatively activated by a variety of NHS esters, and we use these to functionalize IgG1, IgG2, and IgG4 antibodies.

Pyrethroids, which are synthetic organic insecticides, are widely used in agriculture and households to resist pests and control disease transmission. However, pyrethroids have inevitably caused environmental pollution, leading to concerns for food safety and human health. Bioremediation has emerged as one of the most promising methods to eliminate pyrethroids compounds. Pyrethroid-degrading microorganisms and the relevant enzymes have shown an efficient ability in degrading pyrethroids by hydrolyzing the ester linkage. In this review, a wide variety of pyrethroid-degrading strains were presented and classified from different sources, such as wastewater, soils, and oceans. In addition, the recombinant expression, enzyme identification, and molecular modification of these microbial pyrethroid-degrading enzymes were also compared and discussed in detail. Moreover, the potential applications of pyrethroid-degrading enzymes, including immobilization and biodegradation towards a series of pyrethroids, were also presented. All of the positive results obtained from this review could be a good guideline for the other research in this field. KEY POINTS: • Distribution of pyrethroid-degrading strains in different sources was summarized. • Enzymatic properties including pH, temperature, and substrate specificity were compared. • Promising molecular modification and immobilization of hydrolases were present.

The liver X receptor is a nuclear hormone receptor that regulates lipid metabolism. Previously, we had demonstrated the antiviral properties of a liver X receptor antagonist associated with the hepatitis C virus and severe acute respiratory syndrome coronavirus 2. In this study, we screened a chemical library and identified two potential liver X receptor antagonists. Spectroscopic analysis revealed that the structures of both antagonists (compounds 1 and 2) were cyclic dimer and trimer of esters, respectively, that consisted of phthalate and 1,6-hexane diol. This study is the first to report the structure of the cyclic trimer of phthalate ester. Further experiments revealed that the compounds were impurities of solvents used for purification, although their source could not be traced. Both phthalate esters exhibited anti-hepatitis C virus activity, whereas the cyclic dimer showed anti-severe acute respiratory syndrome coronavirus 2 activity. Cyclic phthalate derivatives may constitute a novel class of liver X receptor antagonists and broad-spectrum antivirals.

Protein therapy targeting the intracellular machinery holds great potentials for disease treatment, and therefore, effective cytosolic protein delivery technologies are highly demanded. Herein, we developed reactive oxygen species (ROS)-degradable, branched poly(β-amino ester) (PBAE) with built-in phenylboronic acid (PBA) in the backbone and terminal-pendent arginine for the efficient cytosolic protein delivery. The PBAE could form stable and cell-ingestible nanocomplexes (NCs) with proteins via electrostatic interaction, nitrogen-boronate (N-B) coordination, and hydrogen bonding, while it can be degraded into small segments by the over-produced H

Glycoconjugates are major constituents of mammalian cells that are formed

A pharmacophore-directed retrosynthetic (PDR) strategy was applied to the first total synthesis of the cembranoid, rameswaralide, in order to simultaneously achieve a total synthesis while also developing a structure-activity relationship profile throughout the synthetic effort. The synthesis utilized a Diels-Alder-Lactonization, including a rare kinetic resolution to demonstrate the potential of this strategy for an enantioselective synthesis providing both 5,5,6- and, through a ring expansion, the 5,5,7-tricyclic ring systems present in several Sinularia soft coral cembranoids. A pivotal synthetic intermediate, a tricyclic epoxy α-bromo cycloheptenone, displayed high cytotoxicity with interesting selectivity toward the HCT-116 colon cancer cell line. This intermediate enabled the pursuit of three unique D-ring annulation strategies including a photocatalyzed intramolecular Giese-type radical cyclization and a diastereoselective, intramolecular enamine-mediated Michael addition with the latter annulation constructing the final D-ring to deliver rameswaralide. The discovery of a serendipitous oxidation state transposition of the tricyclic epoxy cycloheptenone proceeding through a presumed doubly vinylogous, E1-type elimination, enabled facile introduction of the required α-methylene butyrolactone. Preliminary biological tests of rameswaralide and precursors demonstrated weak cytotoxicity however the comparable cytotoxicity of a simple 6,7-bicyclic β-keto ester, corresponding to the CD-ring system of rameswaralide, to the natural product itself suggests that such bicyclic β-ketoesters may constitute an interesting pharmacophore that warrants further exploration.

Site-selective acetylation of a single lysine residue in a protein that reaches a lysine acetyltransferase's accuracy, precision, and reliability is challenging. Here, we report a peptide-guided, proximity-driven group transfer reaction that acetylates a single lysine residue, Lys 248, of the fragment crystallizable region (Fc region) in the heavy chain of the human Immunoglobulin G (IgG). An Fc-interacting peptide bound with the Fc domain and positioned a phenolic ester close to Lys 248, which induced a nucleophilic reaction and resulted in the transfer of an acetyl group to Lys 248. The acetylation reaction proceeded to a decent yield under the physiological condition without the need for deglycosylation, unnatural amino acids, or catalysts. Along with acetylation, functional moieties such as azide, alkyne, fluorescent molecules, or biotin could also be site-selectively installed on Lys 248, allowing IgG's further derivatization. We then synthesized an antibody-lipid conjugate and constructed antibody-conjugated liposomes (immunoliposomes), targeting HER2-positive (HER2+) cancer cells. We also built a bispecific antibody complex (bsAbC) covalently linking an anti-HER2 antibody and an anti-CD3 antibody. The bsAbC showed

A neighboring boronate group in the substrate provides a dramatic rate acceleration in transmetalation to copper and thereby enables organoboronic esters to participate in unprecedented site-selective cross-couplings. This cross-coupling operates under practical experimental conditions and allows for coupling between vicinal bis(boronic esters) and allyl, alkynyl, and propargyl electrophiles as well as a simple proton. Because the reactive substrates are vicinal bis(boronic esters), the cross-coupling described herein provides an expedient new method for the construction of boron-containing reaction products from alkenes. Mechanistic experiments suggest that chelated cyclic ate complexes may play a role in the transmetalation.

Aqueous hexavalent chromium (Cr(VI)) treatment and chromium resource recovery toward Cr-containing wastes are of significant importance and necessity to both wastewater remediation and resource recovery. Herein, via mild photoreaction conditions with isopropanol (IPA) as an electron donor, a catalyst-free strategy for aqueous Cr(VI) extraction to form an insoluble polyhydroxy Cr(V) complex is developed for the first time. Aqueous Cr(VI) with concentration from 5 to 150 ppm can be efficiently extracted with high selectivity even in the presence of coexisting ions, and the total Cr concentration in residue solution can be as low as 0.5 ppm. The Cr resource could be efficiently recovered as pure Cr

A useful protocol for achieving decarboxylative cross-coupling (DCC) of redox-active esters (RAE, isolated or generated in situ) and halo(hetero)arenes is reported. This pragmatically focused study employs a unique Ag-Ni electrocatalytic platform to overcome numerous limitations that have plagued this strategically powerful transformation. In its optimized form, coupling partners can be combined in a surprisingly simple way: open to the air, using technical-grade solvents, an inexpensive ligand and Ni source, and substoichiometric AgNO

Preventing bacterial infections and accelerating wound closure are essential in the process of wound healing. Current wound dressings lack enough mechanical properties, self-healing ability, and tissue adhesiveness, and the bacterial killing also relies on the use of antibiotic drugs. Herein, a well-designed hybrid hydrogel dressing is constructed by simple copolymerization of acrylamide (AM), 3-acrylamido phenylboronic acid (AAPBA), chitosan (CS), and the nanoscale tannic acid (TA)/ferric ion (Fe

In this study, the high voltage electric field (HVEF) method was used for deodorization of sunflower oil to omit drawbacks of an established industrial method including long time, high energy, chemicals and water consumption, loss of bioactive compounds, and formation of some contaminants due to exposure to heat. Response surface methodology (RSM) was employed to find the optimal values of processing parameters. The effects of voltage (5-15 kV), clay (0-1%), electrolyte concentration (0-50 mM), the number of electrodes (1-5 pairs), and electrodes distance (1-3 cm) on the volatile compounds and tocopherols content were investigated by HS-SPME-GC/MS and HPLC, respectively. The optimal processing conditions were determined to be a voltage of 5 kV, a distance of 1 cm between the electrodes and a number of five pairs of electrodes. The amount of bleaching clay and electrolyte concentration were zero under optimal conditions. The refining process by HVEF removed 32.33% of the volatile compounds from crude sunflower oil, while the industrial refining process reduced the volatile compounds by only 17.78%. Results indicated no change was observed in the tocopherols content of refined sunflower oil by HVEF method. Based on PCA results, HVEF-treated sample not only contained the lowest concentration of volatile compounds but also was the most similar to crude sample in terms of volatile compounds composition. PRACTICAL APPLICATION: The oil refining process consists of four main stages, the last of which is deodorization. This step involves injecting steam at a temperature of about 240°C, under vacuum for about 50 min. High voltage electric field (HVEF) was able to reduce the number of volatile compounds, while no change was made in the tocopherol content of sunflower oil samples. It also does not form contaminant such as 3-monochloropropane-1,2-diol fatty acid esters and glycidyl fatty acid esters. There is no need to apply the vacuum in HVEF refining, which reduces the production cost and makes the process flow straightforward as well as rapid. This research helps to propagate green refining procedures of vegetable oils in food plants.

Injectable, self-healing hydrogels with enhanced solubilization of hydrophobic drugs are urgently needed for antimicrobial intravaginal therapies. Here, we report the first hydrogel systems constructed of dynamic boronic esters cross-linking unimolecular micelles, which are a reservoir of antifungal hydrophobic drug molecules. The selective hydrophobization of hyperbranched polyglycidol with phenyl units in the core via ester or urethane bonds enabled the solubilization of clotrimazole, a water-insoluble drug of broad antifungal properties. The encapsulation efficiency of clotrimazole increases with the degree of the HbPGL core modification; however, the encapsulation is more favorable in the case of urethane derivatives. In addition, the rate of clotrimazole release was lower from HbPGL hydrophobized via urethane bonds than with ester linkages. In this work, we also revealed that the hydrophobization degree of HbPGL significantly influences the rheological properties of its hydrogels with poly(acrylamide

Pulsed electron-electron double resonance (PELDOR) spectroscopy, X-ray scattering interferometry (XSI), and single-molecule Förster resonance energy transfer (smFRET) are molecular rulers that provide inter- or intramolecular pair-wise distance distributions in the nanometer range, thus being ideally suitable for structural and dynamic studies of biomolecules including RNAs. The prerequisite for such applications requires site-specific labeling of biomolecules with spin labels, gold nanoparticles, and fluorescent tags, respectively. Recently, site-specific labeling of large RNAs has been achieved by a combination of transcription of an expanded genetic alphabet containing A-T/G-C base pairs and NaM-TPT3 unnatural base pair (UBP) with post-transcriptional modifications at UBP bases by click chemistry or amine-NHS ester reactions. However, due to the bulky sizes of functional groups or labeling probes used, such strategies might cause structural perturbation and decrease the accuracy of distance measurements. Here, we synthesize an α-thiophosphorylated variant of rTPT3TP (rTPT3

Ferroptosis, as a new regulated mode of cell death, is mainly characterized by iron-dependent accumulation of lipid peroxides related to reactive oxygen species (ROS). However, the changes of peroxynitrite (ONOO

Controlling catalytic asymmetric space has received increasing attention for the on-demand synthesis of chiral molecules of interest. However, the identification of the key parameters controlling the stereo-determining step in transition metal catalysis is challenging and involves the thorough characterization of the rate- and stereo-determining transition state(s). In this paper, we describe the computational analysis of the (3 + 2) cycloaddition of Ni(II)-enolate with cyclic (E)-nitrone to provide a comprehensive analysis of how the bond-forming processes are regulated in the two-electron manifold in the triplet state. Our molecular orbital analysis, in particular, reveals the occurrence of the singly occupied molecular orbital-highest occupied molecular orbital (SOMO-HOMO) level inversion in the Ni(II)-enolate. Further, distortion and interaction analysis are also used to explain the substrate-dependent diastereodivergence in this reaction by alternating the structure of the nitrone. Using a range of computational analyses, we show that the rate- and stereo-determining step in the (3 + 2) cycloaddition of (E)-nitrone is regulated integrally by (1) isomerism of the octahedral Ni(II) complex, (2) E/Z isomerism of the Ni(II)-enolate, and (3) steric repulsion between the reactants and ligand.

The paper is devoted to the study of the physicochemical properties of aviation biofuels, in particular, to the substantiation of the influence of bio-additives based on various vegetable oils on the properties of jet fuels and to the assessment of the possibility of using new bio-additives to produce aviation biofuels. The aviation industry's current state is considered and its development's key directions are presented. Considering the tasks of minimizing the environmental impact of aviation, decarbonizing the aviation sector and increasing its energy efficiency, one of the industry's main priorities is the development of technologies for the production of alternative aviation fuels and their practical use. This paper considers alternative aviation fuels (biofuels), which are a mixture of traditional aviation fuels and bio-additives derived from various vegetable oils. Taking into account the trends of active transition from first-generation biofuels to second- and third-generation biofuels, the article considers new types of plant raw materials for obtaining bio-additives to fuels. In particular, the possibilities of using bio-additives based on palm kernel and coconut oils to produce second-generation biofuels are considered. The chemical composition and physicochemical properties of bio-additives based on various vegetable oils were investigated and analyzed. It is shown that the quantitative and qualitative composition of bio-additives determines their physicochemical properties. Further, the physicochemical properties of aviation biofuel samples based on petroleum aviation fuel and bio-additives were investigated. It is shown that the introduction of bio-additives into the composition of petroleum aviation fuels leads to changes in their properties, in particular, to an increase in density, viscosity, and crystallization temperature. The experimental results substantiate that bio-additives based on palm kernel and coconut oils have better characteristics than the previously studied bio-additives (based on rapeseed and castor oils), in particular, regarding the possibility of their use as components of aviation biofuels. Thus, the new bio-additives can be successfully used for further research on the development of alternative aviation fuels. Робота присвячена дослідженню фізико-хімічних властивостей авіаційних біопалив, зокрема, обґрунтуванню впливу біодобавок на основі різних рослинних олій на властивості палив для ГТД та оцінці можливості використання нових біодобавок для одержання авіаційних біопалив. Розглянуто сучасний стан авіаційної галузі та наведено ключові напрями її розвитку. Враховуючи завдання щодо мінімізації впливу авіації на навколишнє середовище, декарбонізації авіаційного сектору та підвищення його енергоефективності, одним із основних пріоритетів галузі є розвиток технологій виробництва альтернативних авіаційних палив та упровадження їх у практичне використання. У рамках роботи розглянуто альтернативні авіаційні палива (біопалива), що є сумішшю традиційного авіаційного палива та біодобавок, одержаних з різноманітних рослинних олій. Ураховуючи тенденції щодо активного переходу від біопалив першого покоління до біопалив другого та третього поколінь у статті розглядаються нові види рослинної сировини для одержання біодобавок до палив. Зокрема, розглянуто можливості використання біодобавок на основі пальмоядрової та кокосової олій для одержання біопалив другого покоління. У роботі досліджено та проаналізовано хімічний склад та фізико-хімічні властивості біодобавок на основі різних рослинних олій. Показано, що кількісний та якісний склад біодобавок визначає їх фізико-хімічні властивості. Надалі, досліджено фізико-хімічні властивості зразків авіаційних біопалив на основі нафтового авіаційного палива та біодобавок. Показано, що введення біодобавок до складу нафтових авіаційних палив призводить до зміни їх властивостей, зокрема до підвищення густини, в’язкості та температури кристалізації. За результатами експериментальних обґрунтовано, що біодобавки на основі пальмоядрової та кокосової олій мають кращі характеристики порівняно з біодобавками, що вивчалися раніше (на основі ріпакової та рижієвої олій), зокрема, з огляду можливості їх використання як компонентів авіаційних біопалив. Таким чином, нові біодобавки можуть успішно використовуватися для подальших досліджень щодо розроблення альтернативних авіаційних палив.

Trans-p-hydroxycinnamic acid and its esters in the leaves of Ligustrum robustum might be a new resource to prevent diabetes and its complications. In the present study, a new HPLC-UV method using hydrolyzation with sodium hydroxide for quantitation of trans-p-hydroxycinnamic acid and total trans-p-hydroxycinnamic acid esters in the leaves of L. robustum was developed, since it was difficult and troublesome to analyze no less than 34 trans-p-hydroxycinnamic acid esters by usual HPLC. The extract of L. robustum was hydrolyzed with sodium hydroxide at 80 °C for 2 h, and then, hydrochloride was added. HPLC analysis was performed in reverse phase mode using a C-18 column, eluting with methanol-0.1% acetic acid aqueous solution (40:60, v/v) in isocratic mode at a flow rate of 1.0 mL·min−1 and detecting at 310 nm. The linear range for trans-p-hydroxycinnamic acid was 11.0–352.0 μg·mL−1 (r2 = 1.000). The limit of detection and limit of quantification were 2.00 and 6.07 μg·mL−1, respectively. The relative standard deviations of intra-day and inter-day variabilities for trans-p-hydroxycinnamic acid were less than 2%. The percentage recovery of trans-p-hydroxycinnamic acid was 103.3% ± 1.1%. It is the first HPLC method using hydrolyzation for quantification of many carboxylic esters. Finally, the method was used successfully to determine trans-p-hydroxycinnamic acid and total trans-p-hydroxycinnamic acid esters in various extracts of the leaves of L. robustum. The 60–70% ethanol extracts of L. robustum showed the highest contents of free trans-p-hydroxycinnamic acid (3.96–3.99 mg·g−1), and the 50–80% ethanol extracts of L. robustum displayed the highest contents of total trans-p-hydroxycinnamic acid esters (202.6–210.6 mg·g−1). The method can be applied also to the quality control of the products of L. robustum.