Average Degree Of Substitution Research Articles

Comparison of ovalbumin glycation induced by high-temperature steaming and high-temperature baking: A study combining conventional spectroscopy with high-resolution mass spectrometry

High-temperature steaming (HTS) and high-temperature baking (HTB)-induced ovalbumin (OVA)-glucose glycation (140 °C, 1–3 min) were compared, and the different mechanisms were evaluated by changes in protein conformation, glycation sites and average degree of substitution per peptide molecule (DSP) values as well as the antioxidant activity of glycated OVA. Conventional spectroscopic results suggested that in comparison with HTB, HTS promoted protein expansion, increased β-sheet content and made OVA structure more orderly. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) analysis showed that 10 glycation sites were found under HTB, while 4 new glycation sites R111, R200, R219 and K323 appeared under HTS, and 2 of them (R219 and K323) were located in internal β-sheet chains. The antioxidant activities of glycated OVA increased with increasing treatment time, and HTS showed stronger enhancement effect than HTB. Furthermore, the DSP values were generally higher under HTS than HTB. Compared with HTB, HTS with high penetrability could enhance the change of OVA primary structure and spatial conformation, making the protein structure more unfolded and stable, leading to more protein-sugar collisions occurred in inner OVA molecular and significantly promoted glycation. In conclusion, HTS is a promising method for high-temperature short-time glycation reaction, with drastically increasing the protein antioxidant activities.

Efficient methodology for the preparation and fabrication of cation exchange membranes using trichloroacetic acid and cellulose biopolymer

This article presents a new method for preparing enhanced cation exchange membrane (CEM) for water treatment using cellulose biopolymer. The preparation methodology of CEM membranes was performed in two steps; functionalization followed by fabrication. Firstly, cellulose powder was functionalized with trichloroacetic acid at different reaction times to prepare carboxymethyl tricellulose (CMTC). In the second step, the exchange memberane was fabricated via phase inversion technique using the functionalized cellulosic material and polyethylene glycol as a pore former. The prepared CEM was fully characterized using FTIR, SEM, mechanical properties, and degree of substitution (DS) determination. The morphological microstructure of the CEM membrane was investigated and discussed. The microstructural analysis by FTIR confirmed the functionalization process. The tensile values obtained at different reaction times showed the effectiveness of using trichloroacetic acid in the carboxymethylation and consequently, the stability of the obtained functionalized cellulose. The obtained DS values are higher than that of the commercial CMC and also the published values. It has been observed that the prepared CEM have an average DS value of 1.5 and therefore much higher than the DS value of commercial CMC whose DS ranges between 0.7 and 1.2. The prepared CEM membranes were morphologically investigated by SEM. The SEM photos showed homogeneously distributed small pores on the entire surface of the membrane, and its cross-section is a multilayer with large pores.

The occurrence and structural heterogeneity of arabinoxylan in commercial pilsner beers and their non-alcoholic counterparts

The impact of arabinoxylan (AX) on the brewing process and beer characteristics depends on its content and structure and is often overlooked in research and industry. This paper reports on the occurrence and structural heterogeneity of AX in a set of commercial pilsner beers and their non-alcoholic counterparts. Fractionation by graded ethanol precipitation allowed us to isolate AX-rich fractions from beer with a number-average degree of polymerisation of 4 to 308 and an average degree of substitution in the range of 0.43 to 0.88. Pilsner beers had a higher content of high-molecular-weight AX than their non-alcoholic counterparts. The structural heterogeneity among the various commercial beers differed. By comparing the chemical composition of the beers, differences in beer production methods and ingredient selection were deduced and used to tentatively explain the differences in AX content and structural heterogeneity.

Synthesize of the chitosan-TPP coated betanin-quaternary ammonium-functionalized mesoporous silica nanoparticles and mechanism for inhibition of advanced glycation end products formation

Advanced glycation end products (AGEs) are harmful by-products of thermal-processing of food. Betanin is an antioxidant with the potential to inhibit AGEs formation. In this work, we encapsulated betanin in chitosan-sodium tripolyphosphate coated quaternary ammonium-functionalized mesoporous silica nanoparticles (CS@QAMSNPs) to enhance the ability of betanin to inhibit AGEs formation. The inhibition rate of betanin-CS@QAMSNPs was 70.29%, which was higher than that of betanin (39.48%). Compared with betanin (2.16%), betanin-CS@QAMSNPs can trap more methylglyoxal (18.7%), absorb formed AGEs, and retain the antioxidant capacity of betanin under high-temperatures. Betanin-CS@QAMSNPs can reduce the average degree of substitution per peptide molecule value (DSP) of some glycation sites in bovine serum albumin. The cell viability was over 80% in the presence of betanin-CS@QAMSNPs, indicating their good biocompatibility. In the biscuit model, the highest inhibition rate of AGEs formation by betanin-CS@QAMSNPs was 12.5%, and CS@QAMSNPs can further adsorb the AGEs generated during digestion.

Elongated Rodlike Particle Formation of Methyl Cellulose in Aqueous Solution.

The conformation and structure of methyl cellulose (MC) ether samples dissolved in pure water under dilute conditions were carefully reconsidered based on the results obtained using small-to-wide-angle neutron scattering (S-WANS), static light scattering (SLS), dynamic light scattering (DLS), and viscometric techniques. The examined MC samples possessed an average degree of substitution by methyl groups per glucose unit of ca 1.8 and weight average molar masses (Mw), ranging from 23 to 790 kg mol–1. S-WANS experiments clearly demonstrated that the samples possess highly elongated rigid rodlike local structures in deuterium oxide solutions with weak periodicities of ca 0.4 and 1.0 nm on a length scale, which correspond to the average intermolecular distance between molecular chain portions facing each other in the formed rodlike structure and the repeating length of the monomeric cellobiose unit of molecular chains, respectively. Ratios of the particle length (L) to the radius of gyration (Rg) determined by SLS techniques approximately showed the relationship LRg–1 = holding in rigid rods over the entire Mw range examined in this study. However, the folding number, defined as the ratio of the average molecular contour length (l) to L, remained at the value of lL–1 ∼ 2, representing an elongated one-folded hairpin structure, until Mw ∼ 300 kg mol–1 and increased substantially up to ca 4.9 at the highest Mw of 790 kg mol–1. The observed increase in the lL–1 value corresponded well with an increase in the diameter of the formed rod with increasing Mw observed in the S-WANS data. The Mw dependencies of the translational diffusion coefficient determined via DLS measurements and that of the intrinsic viscosity detected via viscometric techniques also distinctly demonstrated that particles formed by the MC samples dissolved in aqueous solution behave as elongated rigid rods irrespective of Mw.

The determination of Sulfobutylether [formula omitted]-Cyclodextrin Sodium (SBECD) by LC-MS/MS and its application in remdesivir pharmacokinetics study for pediatric patients

SBECD (Captisol®) with an average degree of substitution of 6.5 sulfobutylether functional groups (SBE = 6.5), is a solubility enhancer for remdesivir (RDV) and a major component in Veklury, which was approved by FDA for the treatment of patients with COVID-19 over 12 years old and weighing over 40 kg who require hospitalization. SBECD is cleared mainly by renal filtration, thus, potential accumulation of SBECD in the human body is a concern for patients dosed with Veklury with compromised renal function. An LC-MS/MS method was developed and validated for specific, accurate, and precise determination of SBECD concentrations in human plasma. In this method, the hexa-substituted species, SBE6, was selected for SBECD quantification, and the mass transition from its dicharged molecular ion [(M–2H)/2]2-, Molecular (parent) Ion (Q1)/Molecular (parent) Ion (Q3) of m/z 974.7/974.7, was selected for quantitative analysis of SBECD. Captisol-G (SBE‐γ‐CD, SBE = 3) was chosen as the internal standard. With 25 µL of formic-acid-treated sample and with a calibration range of 10.0–1000 µg/mL, the method was validated with respect to pre-established criteria based on regulatory guidelines and was applied to determine SBECD levels in plasma samples collected from pediatric patients during RDV clinical studies.

Insight into the mechanism of d-allose in reducing the allergenicity and digestibility of ultrasound-pretreated α-lactalbumin by high-resolution mass spectrometry

The mechanism of d-allose in reducing the allergenicity and digestibility of ultrasound-pretreated α-lactalbumin (α-LA) was studied. The intensity reduction and peak red shift occurred in fluorescence spectra of glycated samples. Enzyme-linked immunosorbent assay and basophil degranulation analysis showed that d-allose significantly reduced the allergenicity of α-LA, and ultrasound-pretreated α-LA showed the lowest allergenicity after glycation. Compared with α-LA, the degree of hydrolysis decreased in glycated samples. Size-exclusion high-performance liquid chromatography showed that the glycated α-LA was resistant to digestive enzymes. The glycated sites and average degree of substitution per peptide molecule were determined using LC Orbitrap MS/MS. These results suggested that the masking of linear allergenic epitopes by glycation could reduce the allergenicity. Therefore, the combination of ultrasound pretreatment and glycation is a potential method to reduce protein allergenicity in food processing and provides a useful approach for the application of rare sugars in food processing.

β-Cyclodextrin-Polyacrylamide Hydrogel for Removal of Organic Micropollutants from Water

Water pollution by various toxic substances remains a serious environmental problem, especially the occurrence of organic micropollutants including endocrine disruptors, pharmaceutical pollutants and naphthol pollutants. Adsorption process has been an effective method for pollutant removal in wastewater treatment. However, the thermal regeneration process for the most widely used activated carbon is costly and energy-consuming. Therefore, there has been an increasing need to develop alternative low-cost and effective adsorption materials for pollutant removal. Herein, β-cyclodextrin (β-CD), a cheap and versatile material, was modified with methacrylate groups by reacting with methacryloyl chloride, giving an average degree of substitution of 3 per β-CD molecule. β-CD-methacrylate, which could function as a crosslinker, was then copolymerized with acrylamide monomer via free-radical copolymerization to form β-CD-polyacrylamide (β-CD-PAAm) hydrogel. Interestingly, in the structure of the β-CD-PAAm hydrogel, β-CD is not only a functional unit binding pollutant molecules through inclusion complexation, but also a structural unit crosslinking PAAm leading to the formation of the hydrogel 3D networks. Morphological studies showed that β-CD-PAAm gel had larger pore size than the control PAAm gel, which was synthesized using conventional crosslinker instead of β-CD-methacrylate. This was consistent with the higher swelling ratio of β-CD-PAAm gel than that of PAAm gel (29.4 vs. 12.7). In the kinetic adsorption studies, phenolphthalein, a model dye, and bisphenol A, propranolol hydrochloride, and 2-naphthol were used as model pollutants from different classes. The adsorption data for β-CD-PAAm gel fitted well into the pseudo-second-order model. In addition, the thermodynamic studies revealed that β-CD-PAAm gel was able to effectively adsorb the different dye and pollutants at various concentrations, while the control PAAm gel had very low adsorption, confirming that the pollutant removal was due to the inclusion complexation between β-CD units and pollutant molecules. The adsorption isotherms of the different dye and pollutants by the β-CD-PAAm gel fitted well into the Langmuir model. Furthermore, the β-CD-PAAm gel could be easily recycled by soaking in methanol and reused without compromising its performance for five consecutive adsorption/desorption cycles. Therefore, the β-CD-PAAm gel, which combines the advantage of an easy-to-handle hydrogel platform and the effectiveness of adsorption by β-CD units, could be a promising pollutant removal system for wastewater treatment applications.

Cellulose based cation-exchange fiber as filtration material for the rapid removal of methylene blue from wastewater

The development of eco-friendly adsorbent with perfect solid/liquid separation performance is of great practical importance for the efficient purification of dye-containing wastewater. Herein, cellulose based cation-exchange fibrous bio-adsorbent (CEF) was successfully obtained via an industrialized cellulose etherification process. The fiber morphology can be maintained with the average degree of substitution (DS) of CEF as about 0.19. The CEF showed high efficiency adsorption for methylene blue (MB): achieving 82% of equilibrium uptake (447.69 mg·g−1) within 5 min. Especially, the non-woven porous filter material, formed by CEFs and glass fibers, showed the praisable solid/liquid separation characteristics, fast water filtration rate (≈ 6.3 m3·m−2·h−1) and high removal rate (≈ 99.2%) when it was used to adsorb MB (150 ppm) from wastewater. In addition, CEF filter material can be regenerated via a simple method. This study demonstrates that green natural fiber materials are promising for the economical and efficient purification of dye-containing wastewater.

A Novel Synthesis Technology of Ethyl-β-Cyclodextrin

A novel green synthesis process about ethyl-β-Cyclodextrin have been investigated through the reaction between β-cyclodextrin and diethyl carbonate by used anhydrous potassium carbonate as catalyst in DMF. The influence of experimental factors including reaction time, the molar ratio of β-cyclodextrin to diethyl carbonate, reaction temperature and contents of anhydrous potassium carbonate on the average degree of substitution of ethyl-β-cyclodextrin were carried out by a design method of orthogonal experiments. The results shown that the average degree of substitution of ethyl-β-cyclodextrin can be depend on the reaction temperature and the molar ratio of raw material primarily. The optimal maximum average degree of substitution of ethyl-β-cyclodextrin is 6.0 when the molar ratio of β-cyclodextrin to diethyl carbonate, reaction temperature, reaction time and dosage of catalyst are 1:28, 120°C, 24h and 2.0 g, respectively. The structures of ethyl-β-cyclodextrin were characterized by TLC, IR, MS, ¹H-NMR and ¹³C-NMR, and these results are concordant with former ones which synthesized ethyl-β-cyclodextrin by diethyl sulfate or ethyl iodide.

Characterising plasticised cellulose acetate-based historic artefacts by NMR spectroscopy: A new approach for quantifying the degree of substitution and diethyl phthalate contents

As one of the first semi-synthetic plastics produced industrially, cellulose acetate (CA)-based artefacts represent valued items in museum collections and archives which, however, present stability issues. High temperature and relative humidity conditions have long been known to promote changes in CA properties, for instance, due to the deacetylation of CA polymer chains and the loss of plasticiser from the polymer matrix. However, there is a need for improved methods for the quantification of plasticiser loss and CA deacetylation. In this context, this contribution presents a new approach for enabling the investigation of plasticiser loss and deacetylation degradation processes in historic plasticised CA-based artefacts which is based on high-resolution proton nuclear magnetic resonance spectroscopy (1H NMR). The proposed methods allow for simple and fast quantification of diethyl phthalate contents and average degree of substitution (DS), while requiring no need for extractive separation between the plasticiser and the CA polymer matrix prior to analysis. Both methods are demonstrated by their application towards a series of reference samples, historic artefacts and artificially aged plasticised CA materials. Our analysis indicates that plasticiser content and DS can be accurately quantified by using high-resolution 1H NMR and both methods have been compared to analyses performed using infrared spectroscopy.

Insight into the mechanism of urea inhibit ovalbumin-glucose glycation by conventional spectrometry and liquid chromatography-high resolution mass spectrometry

The inhibition effect of urea on ovalbumin (OVA) glycation was investigated, and the mechanism was evaluated through the changes in protein structure as well as glycation sites and average degree of substitution per peptide molecule (DSP) by conventional spectrometry and liquid chromatography-high resolution mass spectrometry (LC-HRMS). A urea concentration of 3 M was chosen as the optimum condition. Ultraviolet and fluorescence spectra suggested that both glycation and urea treatment could unfold the OVA, but urea inhibited the glycation-induced protein unfolding. Circular dichroism spectra showed that urea treatment could increase the β-sheet content and reduce the α-helix content of OVA. LC-HRMS indicated that the number of glycation sites was reduced from 15 to 3, and DSP values decreased with urea treatment. In conclusion, urea could significantly inhibit the OVA-glucose glycation, and the sites competition as well as structure unfolding inhibition resulted from urea could be the main factors.

Insight into the Mechanism of Reduced IgG/IgE Binding Capacity in Ovalbumin as Induced by Glycation with Monose Epimers through Liquid Chromatography and High-Resolution Mass Spectrometry.

Ovalbumin (OVA) is one of the major food allergens in hen eggs. In this work, it was demonstrated that glycation with d-glucose and its epimers, including d-mannose, d-allose, d-galactose, and l-idose, could effectively attenuate the IgG/IgE binding of OVA, which was attributed to the covalent masking by sugars and to its structural changes. The glycation sites were determined, and their average degree of substitution was found using liquid chromatography coupled with high-resolution mass spectrometry. Fluctuations in OVA conformation were monitored by conventional spectrometry. Compared to those of OVA-Man and OVA-Glu, OVA-All, OVA-Gal, and OVA-Ido showed a higher glycation extent, and the alterations on their steric layouts were more drastic, suggesting that the configuration of hydroxyl groups at positions C-3, C-4, and C-5 in sugars might be important for the glycation reactivity; as such, their capabilities in binding with IgG/IgE decreased more significantly. Attempts were made to provide valuable information for in-depth understanding of the differences in biochemical functionality among epimeric sugars. These insights would be helpful for designing sweetened food products with a desirable level of safety.

Conformational alteration and the glycated sites in ovalbumin during vacuum freeze-drying induced glycation: A study using conventional spectrometry and liquid chromatography–high resolution mass spectrometry

Ovalbumin (Oval)–ribose glycation induced by vacuum freeze-drying (VFD) was studied. The protein conformational changes based on fluorescence, ultraviolet and circular dichroism spectra were evident with the increase in VFD time. The glycated sites and the average degree of substitution per peptide molecule (DSP) were determined using LC–HRMS. Lysine was shown to be the sole glycated site. Two glycated sites and the minimum DSP values were found during the first 6 h of VFD and increased to nine and the maximum DSP values after 48 h of VFD. The glycated sites located on the protein surface were mostly more active than those in the folded or helical regions, and the hydrophilic/hydrophobic environment could also influence DSP values. This study gave relationships between VFD time and the conformational structure and glycated sites of VFD-treated Oval–ribose system, providing a theoretical basis for VFD technique-based protein food and drug industries.

Synthesis of cellulose acetate using as raw material textile wastes

Several tons of textiles are wasted annually in world, mainly composed of fibers or cotton, which are currently disposed of in landfills or incinerated. These textile wastes are a valuable resource, for being rich in cellulose, which through chemical processes can become value-added products. Considering the importance of reducing the environmental impact that these industries cause, it is necessary to investigate solutions to reuse of these materials. In this scenario, the production of cellulose derivatives has been extremely important. The cellulose can be esterified to obtain cellulose acetate (CA), which is one of the most important commercial cellulose derivatives due to its wide industrial applications. Thus, this study aimed to evaluate the use of textile wastes provided by a textile industry of Portugal, in the synthesis of CA. The CA was produced through the homogeneous acetylation method and characterized by Fourier transform infrared spectroscopy (FTIR) and degree of substitution (DS). The CA produced presented an average DS of 2.69. The FTIR spectra showed the appearance of new bands which proved that acetylation occurred. These results showed that is possible to obtain CA, without any previous purification steps, by a simple method.

Synthesis and characterization of dicarboxymethyl cellulose

Synthesis of dicarboxymethyl cellulose (DCMC) under heterogeneous conditions was examined. Cellulose was etherified using sodium bromomalonate in isopropanol/water in the presence of NaOH. The reaction was performed with five different NaOH concentrations (5–30 w/v %) and the products were characterized by anion-exchange high-performance liquid chromatography (AE-HPLC), inductively coupled plasma atomic emission- (ICP-AES), Fourier transform infrared- (FTIR), and nuclear magnetic resonance (1D-/2D-NMR) spectroscopy. Adjusting the amount of NaOH resulted in increasing functionalization of the cellulose achieving an average degree of substitution (DS) between 0.05 and 0.51. Both ICP-AES and AE-HPLC gave comparable DS values. NMR spectroscopic analysis showed that etherification occurred preferably at O-6 and, to a certain extent, at the secondary positions depending on the reaction conditions.

Hepatocyte-Targeted Delivery of siRNA Polyplex with PEG-Modified Lactosylated Dendrimer/Cyclodextrin Conjugates for Transthyretin-Related Amyloidosis Therapy

Targeted drug delivery system (DDS) is required for RNA interference (RNAi) therapy to increase the therapeutic effect and to reduce the adverse effect. Especially in transthyretin (TTR)-related amyloidosis, hepatocyte specific delivery is desired because TTR mainly expresses in hepatocyte. Herein, we report on a hepatocyte-specific small interfering RNA (siRNA) delivery system using polyethylene glycol (PEG)-modified lactosylated dendrimer (generation 3; G3) conjugates with α-cyclodextrin (PEG-LαCs (G3)) for TTR-related amyloidosis therapy, and investigated the in vitro and in vivo gene silencing effect of PEG-LαCs (G3)/siRNA polyplexes. PEG-LαC (G3, average degree of substitution of PEG (DSP) 2)/TTR siRNA (siTTR) polyplex exhibited the asialoglycoprotein receptor (ASGPR)-mediated cellular uptake, high endosomal escaping ability and localization of the siRNA in cytoplasm, resulting in significant TTR silencing in HepG2 cells. In vivo studies showed that PEG-LαC (G3, DSP2)/siTTR polyplex led to a significant TTR silencing effect in liver after systemic administration to mice. Furthermore, safety evaluation revealed that PEG-LαC (G3, DSP2)/siTTR polyplex had no significant toxicity both in vitro and in vivo. These findings suggest the utility of PEG-LαC (G3, DSP2) as a promising hepatocyte-specific siRNA delivery system both in vitro and in vivo, and as a therapeutic approach for TTR-related amyloidosis.

Cellulosic fibres modified by chitosan and synthesized ecofriendly carboxymethyl chitosan from prawn shell waste

The present study investigates preparation, characterization, and application of chitosan (Ch) and its derivative, carboxymethyl chitosan (CMCh), on jute and cotton fibres through the eco-friend modification avoiding chemical modifier. Chitosan is a deacetylated product of chitin. CMCh was produced from prepared chitosan (89% degree of deacetylation) by carboxymethylation process, and confirmed by Fourier transform infrared (FTIR) spectroscopy. CMCh had an average degree of substitution ranging from 0.62 to 1.20 was determined by titrimetric analysis. X-ray diffraction of CMCh showed a less ordered arrangement than chitosan. Moisture content and ash content of Ch and CMCh were 10%, 9% and 2.33%, 14.39%, respectively which affect cellulosic fibre properties. Extracted chitosan and CMCh were used as surface modifier for natural cellulosic fibres. Modification of jute and cotton through sorption of chitosan and CMCh introduces amino (1610 cm−1) and carboxyl groups (1737 cm−1) on the cellulose chain of fibre surface, causes functionalization. The modified fibres were characterized by FTIR, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Again, dyed modified fibres showed 10–15% higher dye exhaustion, and better fastness properties than that of unmodified fibres.

Studies About the Acylation of Starch in Dipolar Aprotic Solvents

Starch laurates with average degrees of substitution (DS) from 0.63 to 2.52 are obtained applying three equivalents lauroyl chloride per anhydroglucose unit (AGU). Different solvents, that is, N,N‐dimethylacetamide (DMAc), DMAc/LiCl, and N,N‐dimethylformamide (DMF)/LiCl are studied as reaction medium without and with a base. In the presence of pyridine, products of highest DS and degree of polymerization (DP) are accessible. Nuclear magnetic resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR) reveal the presence of acetate moieties that could be caused by O‐acyl‐dimethylacetiminium generated from DMAc in a side reaction. No side reaction is found to occur in the presence of triethylamine and triphenylphosphane. Furthermore, no side reactions are detected in DMF/LiCl as solvent.

Investigation of the Mechanism of Conformational Alteration in Ovalbumin as Induced by Glycation with Different Monoses through Conventional Spectrometry and Liquid Chromatography High-Resolution Mass Spectrometry.

Glycation between ovalbumin (OVA) and different monoses under mild dry heating at 37 °C was studied. The content of free amino groups decreased dramatically, and the conformational changes based on fluorescence and circular dichroism spectra were evident in glycated OVA. The glycated sites and the average degree of substitution per peptide molecule per site were determined using liquid chromatography high-resolution mass spectrometry. Lysine and arginine were the predominant glyaction sites, in which Lys207 was a relatively reactive site for glycation in all of the conjugates. In general, the extent of glycation of aldose was higher, and its alterations on the steric layouts of protein were more drastic than those of ketose. The configuration of hydroxyl groups at C-4 in sugar epimers might be important for the glycation reactivity and conformational modification in the glycated proteins. These insights would have important implications for the creation of sweetened food products with desirable structures and excellent quality control.