Formation Of Ester Bonds Research Articles

Sustainable fragrance cum antimicrobial finishing on cotton: Indigenous essential oil

Fragrance finishing of textile has been enormously increased and used in domestic and industrial application. Fragrance can be synthesis chemically but available in natural and inorganic. The investigation of this research is to study the combined effect of fragrance and antimicrobial finishing on cotton fabric by lavender essential oil with the use of β-Cyclodextrin, Chitosan citrate and β-Cyclodextrin/Grafted Chitosan through pad-dry method. Fourier Transform Infrared spectroscopy (FTIR) was used to study the formation of ester bonds between β-cyclodextrin/grafted chitosan and cotton celluloses. For all the finished fabric samples fragrance release rate performance and antimicrobial properties were measure by standard test methods. The results revealed that β-CD was highly soluble in 0.6gpl NaOH solution and 80gpl β-CD and 6% essential lavender oil solutions were found to be a most suitable combination for fragrance and antimicrobial finishing. FTIR studies reveal about the formation of a carboxylic ester between cotton and β-Cyclodextrin/Grafted Chitosan at 1730cm−1 ester peak.

Paramagnetic epoxy resin

This work illustrates that macrocycles can be used as crosslinking agents for curing epoxy resins, provided that they have appropriate organic functionalities. As macrocycles can complex metal ions in their structure, this curing reaction allows for the introduction of that metal ion into the resin network. As a result, some characteristic physical properties of the metallomacrocycle could be transferred to the new material. The bisphenol A diglycidyl ether (BADGE, n = 0) and hemin (a protoporphyrin IX containing the Fe(III) ion, and an additional chloride ligand) have been chosen. The new material has been characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), Transmission Electron Microscopy (TEM), and magnetic susceptibility measurements). Fe(III) remains in the high-spin state during the curing process and, consequently, the final material exhibits the magnetic characteristics of hemin. The loss of the chlorine atom ligand during the cure of the resin allows that Fe(III) can act as Lewis acid, catalyzing the crosslinking reactions. At high BADGE n = 0/hemin ratios, the formation of ether and ester bonds occurs simultaneously during the process.

Hydrophilic Graphene Preparation from Gallic Acid Modified Graphene Oxide in Magnesium Self-Propagating High Temperature Synthesis Process.

Hydrophilic graphene sheets were synthesized from a mixture of magnesium and gallic acid (GA) modified graphene oxide (GO) in a self-propagating high-temperature synthesis (SHS) process, and hydrophilic graphene sheets displayed the higher C/O ratio (16.36), outstanding conductivity (~88900 S/m) and excellent water-solubility. GO sheets were connected together by GA, and GA was captured to darn GO structure defects through the formation of hydrogen bonds and ester bonds. In SHS process, the most oxygen ions of GO reacted with magnesium to prevent the escape of carbon dioxide and carbon monoxide to from the structure defects associated with vacancies, and GA could take place the high-temperature carbonization, during which a large-area graphene sheets formed with a part of the structure defects being repaired. When only GO was reduced by magnesium in SHS process, and the reduced GO (rGO) exhibited the smaller sheets, the lower C/O ratio (15.26), the weaker conductivity (4200 S/m) and the poor water-solubility because rGO inevitably left behind carbon vacancies and topological defects. Therefore, the larger sheet, less edge defects and free structure defects associated with vacancies play a key role for graphene sheets good dispersion in water.

Purification and Characterization of an Extracellular High Molecular Mass Esterase from Bacillus pumilus

Esterases (EC 3.1.1.x) represent a diverse group of hydrolases catalyzing the cleavage and formation of ester bonds and are widely distributed in animals, plants and microorganisms. The esterase was purified from cell-free culture broth to homogeneity by size exclusion chromatography with 7.7 fold purification and 22.5% yield. The Mr of the purified esterase of B. pumilus was 17 kDa by SDS-PAGE. The esterase appeared to be a novel decameric protein as it possessed a single band of M r 17 kDa in SDS PAGE and 170 kDa in Native PAGE. A Lineweaver-Burk plot was calibrated to determine K m (3.94 mM), V max (49.02 mM/mL/min), K cat (138.89 sec -1 ), K spec (35.28) and K si (26.58 mM) values of purified esterase of B. pumilus for its substrate p -nitrophenylacetate. Energy of activation (Ea) of purified esterase of Bacillus pumilus was 2.61 Jmol -1 as determined with the help of an Arrhenius plot. The DMSO drastically inhibited the activity of purified esterase while benzene and propan-2-ol were fairly tolerated by the esterase. The potential protease inhibitors such as PMSF, EDTA, SDS and DTT were found to decrease the activity of purified esterase. Thermostability of the purified esterase was checked at 45 o C. Purified esterase lost more than 50% of its initial activity at 45 o C after 6.5 h of incubation in a water-bath under shaking.

Synthesis, characterization and stabilization effect of antioxidant-functionalized celluloses

Phenolic antioxidants were immobilized on cellulose nanocrystals and microcrystalline cellulose to reduce their loss. The products were synthesized with antioxidant acid chlorides forming ester bonds, and some additionally grafted with aliphatic acid chlorides to improve their solubility in non-polar polymeric matrices. The products were fully characterized using FT-IR, solid-state NMR, X-ray diffraction, and thermogravimetric analysis. The quantity of grafted groups was determined through alkaline hydrolysis and subsequent titration of the excess of alkali. The stabilization effect of the products was verified by oxidation induction time measurements in squalane. Different mixing ratios to test the influence of stabilizer amount were used. The products are compared and influences on the stabilization effect discussed.

Preliminary Oligomerization in a Glycolic Acid-Glycine Mixture: A Free Energy Map.

Glycolic acid and glycine can potentially self-oligomerize or co-oligomerize in solution by forming ester and amide bonds. Using density functional theory with implicit solvent, we have mapped a baseline free energy landscape to compare the relative stabilities of monomers, dimers, and trimers in solution. We find that amide bond formation is favored over ester bond formation both kinetically and thermodynamically, although the differences decrease when zwitterionic species are taken into account. The replacement of ester linkages by amide bonds is favored over lengthening the oligomer, suggesting that one route to oligopeptide formation is utilizing oligoesters as a starting point. We also find that diketopiperazine, the cyclic dimer of glycine, is favored over the linear dimer; however, the linear trimers are favored over their cyclic counterparts. Because glycolic acid and glycine are dominant products from a Strecker synthesis starting from formaldehyde and HCN, this study sheds light on potential pathways to prebiotic formation of oligopeptides via oligoesters.

From Classical to High Throughput Screening Methods for Feruloyl Esterases: A Review.

Feruloyl esterases (FAEs) are a diverse group of hydrolases widely distributed in plants and microorganisms which catalyzes the cleavage and formation of ester bonds between plant cell wall polysaccharides and phenolic acids. FAEs have gained importance in biofuel, medicine and food industries due to their capability of acting on a large range of substrates for cleaving ester bonds and synthesizing highadded value molecules through esterification and transesterification reactions. During the past two decades extensive studies have been carried out on the production, characterization and classification of FAEs, however only a few reports of suitable High Throughput Screening assays for this kind of enzymes have been reported. This review is focused on a concise but complete revision of classical to High Throughput Screening methods for FAEs, highlighting its advantages and disadvantages, and finally suggesting future perspectives for this important research field.

Surface Modification of Talc Particles with Phthalimide: Study of Composite Structure and Consequences on Physical, Mechanical, and Optical Properties of Deinked Pulp

Commercial talc was modified with phthalimide to produce a composite filler, which was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray fluorescence spectroscopy (XRF), and scanning electron microscope (SEM). It was used as a papermaking filler, and its efficiency was compared with that of plain commercial talc and when mixed with additives (i.e., cationic polyacrylamide and alum-rosin size). The results showed that phthalimide could be linked appropriately to the surface of talc particles through forming ester bonds with the surface hydroxyl groups. The brightness of the composite filler was more than that of the commercial filler due to a reduction in the impurities and removal of the metal compounds. Unlike other treatments, the brightness of the papers filled with modified talc (MT) was enhanced with increases in filler loading. In spite of reducing the paper strength in all treatments, the reduction was significantly less in the MT treatment, which implies the enhancement in particle tendency to develop hydrogen bonds in the fiber network.

Effect of different carboxylic acids in cyclodextrin functionalization of cellulose nanocrystals for prolonged release of carvacrol

Current investigations deal with new surface functionalization strategy of nanocrystalline cellulose-based substrates to impart active molecule release properties. In this study, cellulose nanocrystals (CNC) were surface-functionalized with β-cyclodextrin (β-CD) using succinic acid (SA) and fumaric acid (FA) as bridging agents. The main objective of this surface modification performed only in aqueous media was to obtain new active materials able to release antibacterial molecules over a prolonged period of time. The reactions were conducted by immersing the CNC film into a solution composed of β-CD, SA and FA, leading to CNC grafting. The materials were characterized by infrared spectroscopy (FT-IR), Quartz crystal microbalance-dissipation (QCM-D), AFM and phenolphthalein (PhP) was used to determine the efficiency of CNC grafting with β-CD. The results indicated that β-CD was successfully attached to the CNC backbone through the formation of ester bonds. Furthermore, carvacrol was entrapped by the attached β-CD and a prolonged release was confirmed. In particular, CNC grafted to β-CD in the presence of FA was selected as the best solution. The antibacterial activity and the controlled release were studied for this sample. Considerably longer bacterial activity against B. subtilis was observed for CNC grafted to β-CD compared to CNC and CNC-FA, confirming the promising impact of the present strategy.

Solid-Phase Synthesis of Cyclic Depsipeptides Containing a Tyrosine Phenyl Ester Bond.

The first solid-phase strategy for the synthesis of cyclic depsipeptides containing a phenyl ester linkage in their structure is described. The key steps of the synthesis were the formation of the phenyl ester bond and the on-resin head-to-side-chain cyclization. The amino acid configuration significantly influenced the formation and the stability of the cyclic depsipeptides. The presence of a l-Tyr(1) and a d-Tyr(7) led to the most stable sequences.

Synthesis of some glucose-fatty acid esters by lipase from Candida antarctica and their emulsion functions

The synthesis of glucose esters with palmitic acid, lauric acid and hexanoic acid using lipase enzyme was studied and their emulsion functionality in oil-in-water system were compared. Reactions at 3:1M ratio of fatty acids-to-glucose had the highest conversion percentages (over 90% for each of the fatty acid). Initial conversion rate increased as substrate solubility increased. Ester bond formation was confirmed by nuclear magnetic resonance technique that the chemical shifts of glucose H-6 and α-carbon protons of fatty acids in the ester molecules shifted to the higher fields. Contact angle of water on esters’ pelleted surface increased as the hydrophobicity increased. Glucose esters’ and commercial sucrose esters’ functionality as emulsifiers were compared. Glucose esters delayed, but did not prevent coalescence, because the oil droplets diameter doubled during 7days. Sucrose esters prevented coalescence during 7days since the droplets diameter did not have significant change.

Anti-wrinkle and UV protective performance of cotton fabrics finished with 5-(carbonyloxy succinic)-benzene-1,2,4-tricarboxylic acid

1,2,3,4-Butane tetracarboxylic acid (BTCA) has been considered as one of the most promising crosslinking agent to replace dimethylol dihydroxy ethylene urea (DMDHEU) for anti-wrinkle finishing on cotton fabrics. However, it could cause significant strength loss of the treated fabrics. In this study, a 5-(carbonyloxy succinic)-benzene-1,2,4-tricarboxylic acid (BSTA) was synthesized and applied as an effective crosslinking agent. The results show that fabrics treated with BSTA present the same or even better anti-wrinkle properties as that with BTCA. FTIR was employed to analyze ester bond formation process on cellulose. Finishing conditions such as agent concentration, curing temperature, and bath pH were also discussed to evaluate crosslinking effect of cellulose. BSTA, as a derivative of photo-active conjugated compound, can absorb ultraviolet lights and offer ultraviolet (UV) protective property on treated materials. The treated fabrics showed excellent UV protection performance due to the addition of aromatic conjugated system on fabrics.

Synthesis of adsorbents with dendronic structures for protein hydrophobic interaction chromatography

Here, we introduced a new technology based on the incorporation of dendrons—branched chemical structures—onto supports for synthesis of HIC adsorbents. In doing so we studied the synthesis and performance of these novel HIC dendron-based adsorbents. The adsorbents were synthesized in a facile two-step reaction. First, Sepharose 4FF (R) was chemically modified with polyester dendrons of different branching degrees i.e. third (G3) or fifth (G5) generations. Then, butyl-end valeric acid ligands were coupled to dendrons via ester bond formation. UV–vis spectrophotometry and FTIR analyses of the modified resins confirmed the presence of the dendrons and their ligands on them. Inclusion of dendrons allowed the increment of ligand density, 82.5±11 and 175.6±5.7μmol ligand/mL resin for RG3 and RG5, respectively. Static adsorption capacity of modified resins was found to be ∼60mg BSA/mL resin. Interestingly, dynamic binding capacity was higher at high flow rates, 62.5±0.8 and 58.0±0.5mg/mL for RG3 and RG5, respectively. RG3 was able to separate lipase, β-lactoglobulin and α-chymotrypsin selectively as well as fractionating of a whole proteome from yeast. This innovative technology will improve the existing HIC resin synthesis methods. It will also allow the reduction of the amount of adsorbent used in a chromatographic procedure and thus permit the use of smaller columns resulting in faster processes. Furthermore, this method could potentially be considered as a green technology since both, dendrons and ligands, are formed by ester bonds that are more biodegradable allowing the disposal of used resin waste in a more ecofriendly manner when compared to other exiting resins.

Evaluation of structural and functional properties of chitosan⿿chlorogenic acid complexes

The objectives of the present study were to first synthesize chitosan⿿chlorogenic acid (CA) covalent complex and then compare structural and functional properties between chitosan⿿CA covalent complex and physical complex. First, chitosan⿿CA covalent complex was synthesized and its total phenolic content was as high as 276.5±6.2mg/g. Then structural and functional properties of chitosan⿿CA covalent and physical complexes were analyzed. The covalent reaction induced formation of both amide and ester bonds in chitosan. Data of X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the complexations of CA changed crystallinity and morphology of chitosan, and covalent complexation induced a larger change of physical structure than physical complexation. In terms of functional properties, chitosan⿿CA covalent complex exhibited better thermal stability than physical complex in terms of antioxidant activity, and the viscosity of chitosan was significantly increased by covalent modification.

Biotin-encoded Pullulan-Retinoic Acid Engineered Nanomicelles: Preparation, Optimization and In Vitro Cytotoxicity Assessment in MCF-7 Cells

Biotin and retinoic acid grafted pullulan conjugate was synthesized using carbodiimide activation ester bond formation strategy for biotin targeted delivery of doxorubicin in breast cancer chemotherapy using micelle formulation. The conjugate structure was evaluated and confirmed by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. Critical micelle concentration of final conjugate was determined using the pyrene fluorescence method. Doxorubicin-loaded micelles were prepared using the direct dissolution method. Physical parameters of optimized micelles comprising particle size, zeta potential, drug loading efficacy, and drug release profile were determined. The results reveal that the nanomicelles have formed with mean particle size of 191 nm and zeta potential of -9.45 mv. The drug loading efficacy of 92% and release efficiency of 81% during 24 h, are also obtained. The structure of the micelles was studied by transition electron microscopy technique. The cytotoxicity of doxorubicin-loaded micelles was studied in MCF-7 cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The results of in vitro cell culture cytotoxicity assay showed that the doxorubicin-loaded biotin grafted retinoic acid-pullulan micelles were more cytotoxic in comparison to the non-targeted pullulan and free doxorubicin.

Designing Visible Light-Cured Thiol-Acrylate Hydrogels for Studying the HIPPO Pathway Activation in Hepatocellular Carcinoma Cells.

Various polymerization mechanisms have been developed to prepare peptide-immobilized poly(ethylene glycol) (PEG) hydrogels, a class of biomaterials suitable for studying cell biology in vitro. Here, a visible light mediated thiol-acrylate photopolymerization scheme is reported to synthesize dually degradable PEG-peptide hydrogels with controllable crosslinking and degradability. The influence of immobilized monothiol pendant peptide is systematically evaluated on the crosslinking of these hydrogels. Further, methods are proposed to modulate hydrogel crosslinking, including adjusting concentration of comonomer or altering the design of multifunctional peptide crosslinker. Due to the formation of thioether ester bonds, these hydrogels are hydrolytically degradable. If the dithiol peptide linkers used are susceptible to protease cleavage, these thiol-acrylate hydrogels can be designed to undergo partial proteolysis. The differences between linear and multiarm PEG-acrylate (i.e., PEGDA vs PEG4A) are also evaluated. Finally, the use of the mixed-mode thiol-acrylate PEG4A-peptide hydrogels is explored for in situ encapsulation of hepatocellular carcinoma cells (Huh7). The effects of matrix stiffness and integrin binding motif (e.g., RGDS) on Huh7 cell growth and HIPPO pathway activation are studied using PEG4A-peptide hydrogels. This visible light poly-merized thiol-acrylate hydrogel system represents an alternative to existing light-cured hydrogel platforms and shall be useful in many biomedical applications.

UV Light-Induced Generation of Reactive Oxygen Species and Antimicrobial Properties of Cellulose Fabric Modified by 3,3',4,4'-Benzophenone Tetracarboxylic Acid.

3,3',4,4'-Benzophenone tetracarboxylic acid (BPTCA) could directly react with hydroxyl groups on cellulose to form ester bonds. The modified cotton fabrics not only provided good wrinkle-free and ultraviolet (UV) protective functions, but also exhibited important photochemical properties such as producing reactive oxygen species (ROS) including hydroxyl radicals (HO(•)) and hydrogen peroxide (H2O2) under UV light exposure. The amounts of the produced hydroxyl radical and hydrogen peroxide were measured, and photochemical reactive mechanism of the BPTCA treated cellulose was discussed. The results reveal that the fabrics possess good washing durability in generation of hydroxyl radicals and hydrogen peroxide. The cotton fabrics modified with different concentrations of BPTCA and cured at an elevated temperature demonstrated excellent antimicrobial activities, which provided 99.99% antibacterial activities against both E. coli and S. aureus. The advanced materials have potential applications in medical textiles and biological material fields.

Glucose-Responsive Hybrid Nanoassemblies in Aqueous Solutions: Ordered Phenylboronic Acid within Intermixed Poly(4-hydroxystyrene)-block-poly(ethylene oxide) Block Copolymer.

Coassembly behavior of the double hydrophilic block copolymer poly(4-hydroxystyrene)-block-poly(ethylene oxide) (PHOS-PEO) with three amphiphilic phenylboronic acids (PBA) differing in hydrophobicity, 4-dodecyloxyphenylboronic acid (C12), 4-octyloxyphenylboronic acid (C8), and 4-isobutoxyphenylboronic acid (i-Bu) was studied in alkaline aqueous solutions and in mixtures of NaOHaq/THF by spin-echo (1)H NMR spectroscopy, dynamic and electrophoretic light scattering, and SAXS. The study reveals that only the coassembly of C12 with PHOS-PEO provides spherical nanoparticles with intermixed PHOS and PEO blocks, containing densely packed C12 micelles. NMR measurements have shown that spatial proximity of PHOS-PEO and C12 leads to the formation of ester bonds between -OH of PHOS block and hydroxyl groups of -B(OH)2. Due to the presence of PBA moieties, the release of compounds with 1,2- or 1,3-dihydroxy groups loaded in the coassembled PHOS-PEO/PBA nanoparticles by covalent binding to PBA can be triggered by addition of a surplus of glucose that bind to PBA competitively. The latter feature has been confirmed by fluorescence measurements using Alizarin Red as a model compound. Nanoparticles were proved to exhibit swelling in response to glucose as detected by light scattering.

Anti-crease finishing of cotton fabrics based on crosslinking of cellulose with acryloyl malic acid

Maleic acid (MA) has been explored to replace formaldehyde-based dimethylol dihydroxy ethylene urea (DMDHEU) for cotton anti-crease finishing. However, the resilience of treated fabrics was not satisfactorily improved. In this study, acryloyl malic acid (AMA) was synthesized and applied on fabrics as a novel crosslinking agent. The results showed that both crease recovery angle and whiteness index of treated samples were higher than those of MA in the presence/absence of catalyst sodium hypophosphite (SHP). Chemical structure of AMA was confirmed by NMR and MS spectra. The possible crosslinking mechanism between AMA and cellulose was investigated by means of 13C NMR, MS, FTIR and phosphorus content analyses. It was found that AMA could form ester bonds with cellulose by formation of anhydride intermediate. Meanwhile, additional reaction of double bonds on AMA with another molecule or PH of SHP residual has also contributed to the crosslinking. A reaction equation was proposed based on the analyses.

Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide.

An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules.