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A novel naphthalimide-based solid-phase fluorescence pH sensor (PS-Acyl-II) is prepared by immobilization of a small molecule probe (II) on polystyrene microspheres through an ester bond and is characterized by Fourier-transform infrared spectroscopy, optical microscope, scanning electron microscope, and conductiometric titrations. The sensor can determine the pH of a solution within the pH 4.0–7.0, free from interference of common metal ions, and can be reused several times. The geometries of II, PS-Acyl-II, and its product with H+ are optimized at the B3LYP/6-31G** level by density functional theory. The charge distribution, orbital interactions, and bonding characteristics are analyzed and compared in detail to discuss the recognition mechanism and structure–fluorescence property relationships.

The understanding of correlations between molecular details and macroscopic material behavior is a fundamental question of molecular chemistry/physics and offers practical interest in materials design with fine-property-tunability. Herein, we demonstrate extreme modulation of liquid crystal (LC) viscoelasticity triggered by a reversion of the ester bond direction in two series of sulfur-containing cyanobiphenyl-based LC dimers. They possess two oppositely directed ester linkages (i.e., COO or OCO), namely COOn and OCOn, respectively, and different carbon atom numbers of the short alkylene spacers (n = 4 and 6). Unexpectedly, it has been proven that the COOn homologs exhibit extraordinarily enhanced viscoelastic properties in the fluidic nematic (N) phase (up to about 1000 times) compared with their OCOn counterparts. Besides, dielectric spectroscopy revealed that the degree of the collective orientational fluctuation is significantly affected by reversing the ester bond direction, suggesting the existence of heliconical clusters embedded in the N state. Finally, we have proposed a novel eco-driving LC memory device based on a pulse-electric-field driving method using COO4 with an extremely high rotational viscosity.

Smart self-healing materials have attracted much attention due to their promising applications in biological and medical fields. Here, a tri-responsive and fast self-healing organogel based on a boronate ester bond, an acylhydrazone bond and a disulfide bond was prepared from polyvinyl alcohol (PVA), 4-formylphenylboronic acid (FPBA), and 3,3′-dithiobis (propionohydrazide) (DPH). PVA was selected as a gel skeleton to improve the mechanical property of the organogel. A tensile test indicated that the obtained organogel is highly stretchable. Due to the dynamic nature of reversible covalent chemistry, the organogel can respond to pH, glucose and redox to undergo gel–sol phase transition. Microscopy observation and tensile tests further indicate that the organogel can self-repair without external stimuli.

Resveratrol which is a natural polyphenol with good biological activity is mainly used in medicine, but it has poor photostability in vitro and short plasma half-life in vivo. Multi-armed poly(e-caprolactone) (PCL) has attracted great attention because the increased number of terminal group broadens the polymeric flexibility in biomedical application. In the work, six-armed PCL was coupled with resveratrol through the hydrolysable ester bond to solve its disadvantage and realize protection for more resveratrol. The synthesized product was characterized with 1H NMR, GPC and DSC. The molecular weight of the designed polymer was less than the experimental, and the polymeric distribution of molecular weight was narrow. In addition, resveratrol changed the physical form of six-armed PCL. The resveratrol coupling with six-armed PCL presented better photostability compared to original resveratrol. The concentration curve of the coupled resveratrol extended to the plain terrain after 80 min of irradiation, while the original resveratrol continued to decline. They were 72.10% and 52.35% at 2 h, respectively. Moreover, six-armed PCL could effectively protect resveratrol in vivo, and buy time for reaching the target site. The in vitro released amount of the original resveratrol was 52.89% within 3 h, while the coupled resveratrol was only 6.28%. Then this study provides a promising strategy for efficient usage of resveratrol.

First phosphorylated glycoconjugates were synthesized in three stages on the basis of isosteviol, d-arabinofuranose, and d-ribofuranose. In the first stage, isosteviol reacted with methyl 5-O-(p-tosyl)-2,3-di-O-benzoyl-d-ribofuranoside and methyl 5-O-(p-tosyl)-2,3-di-O-benzoyl-d-arabinofuranoside to give glycoconjugates in which the diterpenoid fragment is linked through ester bond to the carbohydrate C5 atom. In the second stage, the anomeric methoxy group in the furanoside fragment was replaced by bromine, and the resulting 2,3-di-O-benzoyl-d-ribofuranosyl and 2,3-di-O-benzoyl-d-arabinofuranosyl bromides were treated with dibutyl phosphate to afford the target phosphorylated derivatives.

To simplify the preparation process of a glucose-responsive microneedle patch, a cross-linking-density changeable microneedle patch was designed. The microneedle patch was made up of a hydrogel formed by phenylboronic acid-grafted polyallylamine and poly(vinyl alcohol) (PVA). The gel was cross-linked by boronate ester bonds between phenylboronic acid groups and PVA. It still had fluidity and could be filled into a mold to prepare microneedle patches. Moreover, insulin could be directly loaded into the microneedle patch by mixing with the gel. The boronate ester bond would be broken in the presence of glucose, resulting in a decrease in the cross-linking density. Therefore, the gel could achieve a greater swelling degree and insulin could be released faster. In addition, PVA chains were crystallized by repeatedly freezing and thawing to improve the mechanical strength of the microneedle patch. In terms of glucose-dependent insulin release, the gel showed good glucose-responsive insulin-release ability. Through additional ion cross-linking, the microneedle patch could also control the insulin release according to glucose concentration. In the hypoglycemic experiment of diabetic rats, the microneedle patch effectively pierced the skin and slowly released insulin.

Pectin of various strengths to gel or stabilize stocks, as well as pectin of various standards or derivatives with simple properties, is in high demand. While pectin is commonly used as a food ingredient in jellies, syrups, and dairy products for its densification, gelling, and emulsifying capabilities, it is also classified as a biodegradable polymer with natural sources, but its supply is limited. To get a significant yield of high-quality pectin, some factors, such as the extraction process requirements, must increase the stability of the reaction by releasing high solvent polymers with negative charges and hydrolyzing the glycoside or ester bond. Therefore, time, temperature, and HNO3 concentration are the autonomous factors. In this review, it is intended to provide a comprehensive overview of the current state of pectin research by focusing on recent studies of pectin recovery from plant materials (purification and fractionation) as well as advances in the physical, chemical, and functional properties of pectin.

Because of their involvement in various biological pathways, the sirtuin enzyme family members SIRT1, SIRT2, and SIRT3 play both tumor-promoting and tumor-suppressing roles, based on the context and experimental conditions. Thus, an interesting question is whether inhibiting one of them or inhibiting all of them would be better for treating cancers. Pharmacologically, this is difficult to address, due in part to potential off-target effects of different compounds. Compounds with almost identical properties but differing in SIRT1-3 selectivity will be useful for addressing this question. Here, we have developed a pan SIRT1-3 inhibitor (NH4-6) and a SIRT2-selective inhibitor (NH4-13) with very similar chemical structures, with the only difference being the substitution of an ester bond to an amide bond. Such a minimal difference allows us to accurately compare the anticancer effect of pan SIRT1-3 inhibition and SIRT2-selective inhibition in cellular and mouse models. NH4-6 showed stronger cytotoxicity than NH4-13 in cancer cell lines. In mice, both inhibitors showed similar anticancer efficacy. However, NH4-6 is toxic to mice, which hinders the use of higher dosages. These results highlight the advantage of SIRT2-selective inhibitors as potential anticancer therapeutics.

The shoot epidermal cell wall in land-plants is associated with a polyester, cutin, which controls water loss and possibly organ expansion. Covalent bonds between cutin and its neighbouring cell-wall polysaccharides have long been proposed. However, the lack of biochemical evidence makes cutin–polysaccharide linkages largely conjectural. Here we optimised a portfolio of radiochemical assays to look for cutin–polysaccharide ester bonds in the epidermis of pea epicotyls, ice-plant leaves and tomato fruits, based on the hypothesis that a transacylase remodels cutin in a similar fashion to cutin synthase and cutin:cutin transacylase activities. Through in-situ enzyme assays and chemical degradations coupled with chromatographic analysis of the 3H-labelled products, we observed that among several wall-related oligosaccharides tested, only a xyloglucan oligosaccharide ([3H]XXXGol) could acquire ester-bonds from endogenous cutin, suggesting a cutin:xyloglucan transacylase (CXT). CXT activity was heat-labile, time-dependent, and maximal at near-neutral pH values. In-situ CXT activity peaked in nearly fully expanded tomato fruits and ice-plant leaves. CXT activity positively correlated with organ growth rate, suggesting that it contributes to epidermal integrity during rapid expansion. This study uncovers hitherto unappreciated re-structuring processes in the plant epidermis and provides a step towards the identification of CXT and its engineering for biotechnological applications.

Gram-positive pathogens can colonize on mucosal tissues stably withstanding large mechanical disturbance from coughing and sneezing by secreting special surface adhesion proteins. However, how these proteins resist mechanical unfolding remains unknown. In a recent work, using single molecule force spectroscopy, Cao et al. discovered that an ester bond containing surface adhesion protein from Gram-positive bacteria, Clostridium perfringenes, remains folded even under stretching forces of >2 nN, more stable than most proteins investigated to date. Such an outstanding mechanical stability is due to the coupling between ester bond and protein topologic structure and can be dynamically regulated by surrounding conditions. This work has been published in Nature Communications and can be reached at https://doi.org/10.1038/s41467-021-25425-6 .

Dissertação de mestrado integrado em Engenharia Biológica, Os processos vulgarmente usados para a alteração da forma do cabelo, envolvem o uso de componentes agressivos para com a fibra capilar, o consumidor e o meio ambiente. O objetivo desta dissertação visou desenvolver formulações alternativas à base de componentes menos agressivos que permitam a alteração da forma do cabelo. Estas formulações foram aplicadas em mechas de cabelo de origem asiática usando diferentes metodologias de aplicação em dois tipos de processos de esterificação in situ (a reação ocorre diretamente na fibra do cabelo): reação por condensação e por reação enzimática. Foi testada a aplicação de vários rácios molares de ácido (ácido cítrico e oxálico) e álcool (glicerol) para a formação do grupo éster, a altas temperaturas e a baixas temperaturas na presença da lipase. As mechas de cabelo foram avaliadas em termos de eficiência de encaracolamento após aplicação e após três lavagens com champô. As formulações compostas por ácido cítrico 1:1 glicerol, e por ácido oxálico 1:2 glicerol aplicadas a 170° C durante 2 min, exibiram os melhores resultados após três lavagens, cerca de 20 % e 31 %, respetivamente. No que diz respeito à aplicação das formulações na presença da lipase a baixas temperaturas, a lavagem pós tratamento, para inativação da enzima, com SDS 1% ou sulfato de amónio 0,5 mM demonstrou ser a mais eficaz para o efeito. A aplicação das formulações ácido cítrico 1:3 glicerol e ácido oxálico 1:2 glicerol obtiveram os melhores resultados após três lavagens, 17,5 % e 13 %, respetivamente. A caracterização físico-química das amostras de cabelo tratadas exibiu evidências da formação da ligação éster. Pelos espetros ESI-MS das formulações verificou-se a formação do dímero esperado e a análise FTIR-ATR evidenciou uma nova banda nas amostras tratadas, que diz respeito à formação da ligação éster. As imagens obtidas com MEV revelaram que a integridade estrutural da fibra capilar foi mantida após os tratamentos, resultados que corroboram os resultados obtidos pela percentagem de perda de massa nos ensaios de resistência ao desgaste. As amostras tratadas apresentaram perda de massa significativamente similar ao cabelo virgem, o que demonstrou que os tratamentos não danificaram a superfície da fibra, não alterando a taxa de degradação da fibra do cabelo. Relativamente à análise térmica da fibra capilar, as amostras tratadas de uma forma geral mantiveram a estabilidade térmica idêntica à do cabelo original sem tratamento. Estas formulações mostraram ser uma alternativa promissora, porém muito embrionária, aos produtos cosméticos, com um ligeiro efeito de encaracolamento. Este estudo estabelece uma boa base para o desenvolvimento de futuras formulações e estudo de sinergias com outros ingredientes para o cuidado e alteração da forma do cabelo., The processes commonly used to change the shape of hair, involve the use of aggressive components towards the hair fiber, the consumer and the environment. The aim of this dissertation was to develop alternative formulations based on less aggressive components that change the shape of the hair. These formulations were applied to Asian hair using different application methodologies in two types of in situ esterification processes: condensation reaction and enzymatic reaction. The application of various molar ratios of acid (citric and oxalic acid) and alcohol (glycerol) for the formation of the ester group, at high temperatures and at low temperatures in the presence of lipase, was tested. The locks of hair were evaluated in terms of curling efficiency after application and after three shampoo washes. Formulations composed of citric acid 1:1 glycerol, and oxalic acid 1:2 glycerol applied at 170 °C for 2 min, exhibited the best results after three washes, about 20 % and 31 %, respectively. With regard to the application of the formulations in the presence of lipase at low temperatures, washing after treatment, for enzyme inactivation, with 1% SDS or 0.5 mM ammonium sulphate, whichever is the most effective for the purpose. The application of the formulations citric acid 1: 3 glycerol and oxalic acid 1: 2 glycerol obtained the best results after three washes, 17.5 % and 13 %, respectively. The physicochemical characterization of the treated hair samples showed evidence of ester bond formation. The formation of the expected dimer was verified by the ESI-MS spectra of the formulations and the ATR-FTIR analysis showed a new band in the treated samples, which concerns the formation of the ester bond. The images obtained with SEM revealed that the structural integrity of the hair fiber was maintained after the treatments, results that corroborate the results obtained by the percentage of mass loss in the wear resistance tests. The treated samples showed significantly similar mass loss to virgin hair, which demonstrated that the treatments did not damage the fiber surface, not altering the rate of degradation of the hair fiber. Regarding the thermal analysis of the hair fiber, the treated samples generally maintained the same thermal stability as the original untreated hair. These formulations proved to be a promising but very embryonic alternative to cosmetic products, with a slight curling effect. This study lays a good foundation for the development of future formulations and the study of synergies with other ingredients for hair care and shape change.

Bioavailability of α-tocopherol varies with source, dose and duration of supplementation. The effect of source and dose of α-tocopherol on response of α-tocopherol stereoisomers in plasma and tissues of mink kits during the weaning period was studied. Twelve mink kits were euthanised in CO2 at the beginning of the experiment, and 156 mink kits (12 replicates per treatment group) were randomly assigned to thirteen treatment groups: no added α-tocopherol in the feed (0 dose) or four different doses (50, 75, 100 and 150 mg/kg of diet) of RRR-α-tocopherol (ALC), RRR-α-tocopheryl acetate (ACT) or all-rac-α-tocopheryl acetate (SYN). Six mink kits per treatment group were euthanised 3 weeks after initiation of the experiment, and the remaining six were euthanised 6 weeks after initiation of the experiment. The RRR-α-tocopherol content in plasma, liver, heart and lungs was affected by interaction between source and dose (P

Gram-positive bacteria can resist large mechanical perturbations during their invasion and colonization by secreting various surface proteins with intramolecular isopeptide or ester bonds. Previous studies showed that the isopeptide bond containing proteins are inextensible under mechanical load. However, compared to isopeptide bonds, ester bonds are prone to hydrolysis; it remains elusive whether ester bonds play similar roles as isopetide bonds to completely block mechanical extension, or alternatively dissipate mechanical energy by bond rupture. Here, we show that an ester bond containing protein, the C1 domain of Cpe0147, is not extensible even at forces > 2 nN. The ester bond locks the structure to a partially unfolded conformation, in which the ester bond remains largely water inaccessible. This allows the ester bond to withstand considerable mechanical forces and in turn prevent complete protein unfolding. Inspired by this design principle, we engineer a disulfide mutant resistant to mechanical unfolding under reducing conditions.

Lipases are enzymes that catalyze the ester bond hydrolysis in triglycerides with the release of fatty acids, mono- and diglycerides, and glycerol. The microbial lipases account for $400 million market size in 2017 and it is expected to reach $590 million by 2023. Many biotechnological processes are expedited at high temperatures and hence much research is dealt with thermostable enzymes. Cold active lipases are now gaining importance in the detergent, synthesis of chiral intermediates and frail/fragile compounds, and food and pharmaceutical industries. In addition, they consume less energy since they are active at low temperatures. These cold active lipases have not been commercially exploited so far compared to mesophilic and thermophilc lipases. Cold active lipases are distributed in microbes found at low temperatures. Only a few microbes were studied for the production of these enzymes. These cold-adapted enzymes show increased flexibility of their structures in response to freezing effect of the cold habitats. This review presents an update on cold-active lipases from microbial sources along with some structural features justifying high enzyme activity at low temperature. In addition, recent achievements on their use in various industries will also be discussed.

Plasmalogens are a special class of polar glycerolipids containing a vinyl-ether bond and an ester bond at sn-1 and sn-2 positions of the glycerol backbone, respectively. In animals, impaired biosynthesis and regulation of plasmalogens may lead to certain neurological and metabolic diseases. Plasmalogens deficiency was proposed to be strongly associated with neurodegenerative and metabolic diseases, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD), and appropriate supplement of plasmalogens could help to prevent and possibly provide therapy of these diseases. Plasmalogens evolved first in anaerobic bacteria with an anaerobic biosynthetic pathway. Later, an oxygen-dependent biosynthesis of plasmalogens appeared in animal cells. This review summarizes and updates current knowledge of anaerobic and aerobic pathways of plasmalogens biosynthesis, including the enzymes involved, steps and aspects of the regulation of these processes. Strategies for increasing the expression of plasmalogen synthetic genes using synthetic biology techniques under specific conditions are discussed. Deep understanding of plasmalogens biosynthesis will provide the bases for the use of plasmalogens and their precursors as potential therapeutic regimens for age-related degenerative and metabolic diseases.

A novel 3D Cd(II) coordination polymer {[Cd(ddpa)(2,2′-bpy)]·H2O}n (1) (H2ddpa = 5,10-dioxo-5,10-dihydro-4,9-dioxapyrene-2,7-dicarboxylic acid, 2,2′-bpy = 2,2′-bipyridine) is hydrothermally synthesized in situ, and the influencing factors and mechanism for the in situ reaction are briefly discussed. The synthesis of 1 requires the formation of a new C–O ester bond. This current study confirms that metal ions and N-donor ligands play important roles in the domination of the in situ ligand from 6,6′-dinitro-2,2′,4,4′-biphenyltetracarboxylic acid (H4dbta). Furthermore, the structure, thermal stability and photoluminescent property of 1 are also investigated.

According to the mechanism of hydrazine to ester bond elimination, a novel ratiometric fluorescent probe (FCP) based on the fluorescein-coumarin structure is designed and synthesized for detecting hydrazine. The obvious red shift in the absorption and fluorescence spectrum is caused by the hydrolysis of the ester bond of FCP by upon mixing with hydrazine. The proposed FCP probe is shown to have linear detection ranges from 0 to 250 nM for hydrazine, and LOD is 0.364 nM. In addition, this promising probe possesses high sensitivity and selectivity for monitoring the intracellular hydrazine, thus, has great potential to be applied in early diagnosis of disease. Meanwhile, it has been successfully applied to the detection and cell imaging of hydrazine in actual water samples.

The present study reports the successful synthesis of two important and abundant functional groups "ester and amide" by N,N′-diisopropylcarbodiimide (DIC) in water as a green solvent. A wide range of substrates could be employed with high functional group tolerance. The products were obtained in high yields after short reaction times. This method provides an efficient, economic, simple and very mild protocol for ester and amide bond formation in aqueous media. In addition, this work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water.

Tocopheryl fatty acid esters (TFAE) consist of tocopherols esterified to fatty acids, but only little is known about this substance class. In this study, twelve vegetable groups were screened on TFAE and contents of (free) tocopherols and TFAE were determined in red bell pepper, red chili pepper, cucumber and walnut (n = 5, respectively). Intact TFAE were separated by solid phase extraction from free tocopherols and analyzed by GC/MS. Highest TFAE values were determined in chili pepper (4.0–16 mg/100 g fresh weight, FW) and walnut (4.1–12 mg/100 g FW), followed by bell pepper (1.3–1.5 mg/100 g FW) and cucumber (0.06–0.2 mg/100 g FW). Contribution of TFAE to the total tocopherol content ranged from 7–84%. Neither the treatment with artificial digestion juices nor exposure to sunlight showed degradation of TFAE. This substance class might represent a hitherto overlooked storage form for free tocopherols in plants as they occur to be more stable. But as the ester bond in medium chain TFAE seems not to be fissile in the human body, they might not contribute in the same way as free tocopherols to the vitamin E activity of vegetables and might have to be determined separately.

The digestibility and molecular structure of corn starch mixed with amino acid modified by low-pressure treatment (LPT) was investigated. Amino acid induced a significant increase in the slowly digestible starch (SDS) and decrease in the rapidly digestible starch (RDS) after LPT. The reason is the formation of ester bond between the molecular chains of amino acid and starch. Low pressure treatment altered greatly the morphology of corn starch mixed with or without amino acid. After LPT, less ordered Maltese and more granule fragments were observed for starch-amino acid complex. An increase in size distribution was obvious after LPT and the size distribution curves provided from a new variety. We found that higher enthalpy and relative crystallinity of the starch-amino acid complex were associated with a higher SDS content. It can be inferred that LPT had a greater impact on the digestion and structural characterization of corn starch mixed with amino acids.

(±)-7-O-galloyltricetiflavan (1a) was synthesized successfully in five steps from the commercially available trihydroxyacetophenone (2) and trimethoxybenzoyl chloride (3). The flavone 4a was prepared in a one-pot reaction and it gave hex-O-methylflavan 6 followed by acylation and reduction. However, the demethylation of flavan 6, 5-O-acetylflavan 10 and 5-O-phenylacetylflavan 11 by BBr3 gave all the hydrolyzed fragments 7 and 8 as the major products. By contrast, in the same condition, hept-O-methylflavan 9 could provide the desired product (±)-7-O-galloyltricetiflavan (1a) in 91% yield. The additional 5-O-B-Br2 complex may stabilize the ester bond during the demethylation process.

Ester-linked ubiquitinated proteins have been reported by several groups to be involved in ubiquitin signalling. However, due to the lack of the suitable tools to homogeneously produce such conjugates, their exact physiological roles and biochemical behavior remain enigmatic. Here, we report for the first time on the development of a novel synthetic strategy based on total chemical synthesis of proteins to construct ubiquitinated proteins, where ubiquitin is linked to the substrate via an ester bond. In this study, we prepared ester- and isopeptide-linked ubiquitinated α-globin and examined their relative behaviors with various deubiquitinases. We found that deubiquitinases are able to cleave the ester linkage with different efficiency relative to the isopeptide-linked substrate. These results may indicate that ester-linked ubiquitinated proteins are natural substrates for deubiquitinases.

With the ability to switch transform the mechanical stimuli of epidermal deformations to electrical signals, epidermal strain sensors can be widely applied to monitor physiological signals, detect body movements and control robots. Epidermal strain sensors are required to conform to the human body under complex motions typically from tiny epidermal deformations (