Distribution Of Carboxyl Groups Research Articles

The Antifungal Activities of Silver Nano-Aggregates Biosynthesized from the Aqueous Extract and the Alkaline Aqueous Fraction of Rhazya stricta against Some Fusarium Species.

Rhazya stricta is a major medicinal species used in indigenous medicinal herbal medications in South Asia, the Middle East, Iran, and Iraq to treat a variety of ailments. The current study aimed to investigate the antifungal properties of biosynthesized silver nanoparticles (AgNPs) made from R. stricta aqueous extract and its alkaline aqueous fraction. Fourier transform infrared spectroscopy (FTIR), UV-vis spectrophotometry, dynamic light scattering (DLS), and transmitted electron microscopy (TEM) were used to characterize AgNPs. The produced extracts and AgNPs were tested for their antifungal efficacy against four Fusarium spp. All of the characterization experiments proved the biosynthesis of targeted AgNPs. FTIR showed a wide distribution of hydroxyl, amino, carboxyl, and alkyl functional groups among all preparations. The DLS results showed that the produced Aq-AgNPs and the Alk-AgNPs had an average size of 95.9 nm and 54.04 nm, respectively. On the other hand, TEM results showed that the Aq-AgNPs and Alk-AgNPs had average diameters ranging from 21 to 90 nm and 7.25 to 25.32 nm. Both AgNPs absorbed UV light on average at 405 nm and 415 nm, respectively. Regarding the fungicidal activity, the highest doses of Aq-extract and Aq-AgNPs inhibited the mycelial growth of F. incarnatum (19.8%, 87.5%), F. solani (28.1%, 72.3%), F. proliferatum (37.5%, 75%), and F. verticillioides (27.1%, 62.5%), respectively (p < 0.001). Interestingly, the Alk-fraction had stronger inhibition than the biosynthesized AgNPs, which resulted in complete inhibition at the doses of 10% and 20% (p < 0.001). Furthermore, microscopic analysis demonstrated that both AgNPs caused obvious morphological alterations in the treated organisms when compared to the control. In conclusion, R. stricta's Aq-extract, alkaline fraction, and their biosynthesized AgNPs show substantial antifungal efficacy against several Fusarium spp. It is the first study to highlight the prospective biological activities of R. stricta Aq-extract and its alkaline fraction against F. incarnatum, F. proliferatum, and F. verticillioides. In addition, it is the first opportunity to deeply investigate the ultrastructural changes induced in the Fusarium species treated with R. stricta crude Aq-extract and its biosynthesized AgNPs. More studies are required to investigate their biological effect against other Fusarium or fungal species.

Fluid-fluid interfacial properties during low salinity waterflooding

Understanding the fluid–fluid interfacial interactions is critical to enhancing oil recovery, underground CO2 storage, and soil remediation. Fluid-fluid interfacial interactions were identified as key parameters to govern fluid–fluid interfacial properties. In this investigation, we aim to evaluate the properties of the oil-brine interface in function of fluid compositions during low salinity waterflooding (LSW). Specifically, the main target is to unravel the oil-brine structure, including orientation of the carboxylic group (–COOH), interfacial structure, and species distribution. We utilized molecular dynamics (MD) simulation to evaluate the species distribution and surface structure at the molecular scale. The MD results showed that the carboxylic group accumulated near the oil-brine interface. The orientation of C=O in the carboxylic group is closer to 90° in the brines with all salinity ranges, which is perpendicular to the oil-brine interface. The accumulation and orientation of the carboxylic group is, however, not sensitive to salinity variations. Furthermore, the oil-brine interfacial area turns to be wider with lowering salinity. Radial distribution function (RDF, g(r)) confirmed that lowering salinity decreases g(r) between –COOH and water and thus looses the affinity of oil to water. This investigation provides insights into the fluid–fluid interfacial properties of LSW at the molecular level.

An Integrally Formed Janus Hydrogel for Robust Wet-tissue Adhesive and Anti-postoperative Adhesion.

Facile fabrication of asymmetrically adhesive hydrogel with robust wet tissue adhesion simultaneously with effective anti-postoperative adhesion still remains a great challenge. In this work, an integrally formed Janus hydrogel is facilely fabricated in one step by controlling the interfacial distribution of free carboxyl groups on the two sides of hydrogels. At a lower stirring speed, the generated bigger sized emulsion droplets mainly occupy the top surface of hydrogel, which effectively hinders the exposition of carboxyl groups on the top surface, driving them to be more distributed on the bottom surface, ultimately resulting in the poor adhesion of top surface but robust adhesion of bottom surface to various wet tissue even underwater. The difference in adhesive strength achieves as high as 20 times between the two surfaces. In vivo rabbit experiment outcomes clearly validate that the bottom surface of hydrogel firmly adheres to the stomach defect, and the other opposite surface can efficiently address the postoperative adhesion problem. Besides, this hydrogel exhibits superior mechanical toughness and conductivity which has been used as a highly adhesive strain sensor to real-time monitor the beating heart in vivo. This simple yet effective strategy provides a much more feasible approach for creating Janus hydrogels bio-adhesives. This article is protected by copyright. All rights reserved.

Additivity of ionic currents in mixed electrolyte solutions and confined geometries

Electrolyte mixtures in aqueous solutions are central to biophysical chemistry and chemical engineering. In many cases, ions are confined to nanoscale volumes with surface electrical charges. Here, we analyze experimentally the additivity of ionic currents across negatively charged conical nanopores in mixed electrolyte solutions. These pores show an asymmetric axial distribution of carboxylic acid groups on the pore surface, which gives rectified current (I)-voltage (V) curves when a single-pore membrane is bathed by two symmetrical aqueous solutions at neutral pH values. We consider KCl, LiCl, NaCl, CsCl, CaCl2, and K2SO4 pure electrolytes as well as the mixed electrolyte systems LiCl + KCl, NaCl + KCl, CsCl + KCl, CaCl2 + KCl, and K2SO4 + KCl for concentrations ranging from 2 to 500 mM and applied voltages between −2 V and 2 V. The difference between the sum of the pure electrolyte currents and the mixed electrolyte current is studied in terms of the electrolyte concentration, the sign of the applied voltage in the current–voltage curves, and the mixed electrolyte type.

Aromaticity Index with Improved Estimation of Carboxyl Group Contribution for Biogeochemical Studies.

Natural organic matter (NOM) components measured with ultrahigh-resolution mass spectrometry (UHRMS) are often assessed by molecular formula-based indices, particularly related to their aromaticity, which are further used as proxies to explain biogeochemical reactivity. An aromaticity index (AI) is calculated mostly with respect to carboxylic groups abundant in NOM. Here, we propose a new constrained AIcon based on the measured distribution of carboxylic groups among individual NOM components obtained by deuteromethylation and UHRMS. Applied to samples from diverse sources (coal, marine, peat, permafrost, blackwater river, and soil), the method revealed that the most probable number of carboxylic groups was two, which enabled to set a reference point n = 2 for carboxyl-accounted AIcon calculation. The examination of the proposed AIcon showed the smallest deviation to the experimentally determined index for all NOM samples under study as well as for individual natural compounds obtained from the Coconut database. In particular, AIcon performed better than AImod for all compound classes in which aromatic moieties are expected: aromatics, condensed aromatics, and unsaturated compounds. Therefore, AIcon referenced with two carboxyl groups is preferred over conventional AI and AImod for biogeochemical studies where the aromaticity of compounds is important to understand the transformations and fate of NOM compounds.

Structure and interfacial adsorption behavior of soy hull polysaccharide at the oil/water interface as influenced by pH

This paper attempted to investigate the micro structure and interfacial adsorption behavior of soy hull polysaccharide (SHPS) at the oil/water interface as influenced by pH. Initially, the particle size of SHPS at pH 5.0–7.0 is 2.73 nm, 5.80 nm and 5.84 nm, which are significantly lower than other samples. Therefore, it is show that the diffusion rate (Kdiff) of pH 5.0–7.0 is also significantly greater than other samples according the results of the interface expansion rheological dynamics model. Additionally, the enthalpy change of SHPS in the pH 5.0–9.0 is greater than 1200 J/g, it illustrates that the SHPS structure is more stretched. Meanwhile, pH (5.0–9.0) has a significant effect on the distribution of carboxyl groups on the SHPS molecular chain and hydroxyl groups on the side chain glycosidic bonds. These findings lay a foundation for the application of SHPS as, an emulsifier for the production and stabilization of emulsions.

Role of carboxylic group pattern on protein surface in the recognition of iron oxide nanoparticles: A key for protein corona formation

The knowledge of protein-nanoparticle interplay is of crucial importance to predict the fate of nanomaterials in biological environments. Indeed, protein corona on nanomaterials is responsible for the physiological response of the organism, influencing cell processes, from transport to accumulation and toxicity. Herein, a comparison using four different proteins reveals the existence of patterned regions of carboxylic groups acting as recognition sites for naked iron oxide nanoparticles. Readily interacting proteins display a distinctive surface distribution of carboxylic groups, recalling the geometric shape of an ellipse. This is morphologically complementary to nanoparticles curvature and compatible with the topography of exposed FeIII sites laying on the nanomaterial surface. The recognition site, absent in non-interacting proteins, promotes the nanoparticle harboring and allows the formation of functional protein coronas. The present work envisages the possibility of predicting the composition and the biological properties of protein corona on metal oxide nanoparticles.

Boosting CO2 Conversion with Terminal Alkynes by Molecular Architecture of Graphene Oxide-Supported Ag Nanoparticles

Summary Carboxylation of terminal alkynes with CO2 via direct C–H bond activation is a highly appealing way to capture and convert CO2 but faces great challenges and difficulty. Here, we report an efficient catalyst that is prepared simply through introduction of p-tert-butylaniline into graphite oxide powders followed by localized growth of Ag nanoparticles (NPs). The bulky nature of p-tert-butylaniline facilitates the powder exfoliation, giving rise to mass production of uniform modified graphene oxide (tert-GO) nanosheets of 4 nm in thickness. Notably, Ag/tert-GO shows excellent catalytic activity for converting alkynes regardless of containing electron-donating or electron-withdrawing groups under mild reaction conditions. The synergy of the amide linkages on tert-GO nanosheets and the supported small-sized Ag NPs is recognized as the vital role in promoting adsorption of CO2 and subsequent conversion.

Emulsifier-free emulsion polymerization of acrylonitrile-butadiene-carboxylic acid monomers: a kinetic study based on polymerization pressure profile

Emulsion polymerization of acrylonitrile-butadiene-carboxylic acid monomers (XNBR latexes) in the absence of emulsifier is associated with thermodynamic and kinetic complexities and is very sensitive to colloidal stability. In this paper, polymerization pressure profiles were utilized for kinetic studies of emulsifier-free emulsion terpolymerization of acrylonitrile, butadiene and two carboxylic acid monomers (i.e., acrylic acid and methacrylic acid). It was found that the type and amount of acidic monomer have a great impact on the nucleation rate as well as particle size distribution and carboxyl group distribution of XNBR latexes. Also, the type of the acidic monomer affects the rates of entry and exit of radicals to and from particles and consequently the average number of radicals per particle, where a higher rate of polymerization was observed for methacrylic acid latexes. The reaction temperature has profound effects on polymerization rate, particle size distribution and colloidal stability of the latex. Partitioning of pressure profiles into four distinct regions in accordance with well-established intervals of Harkins model and analyzing particle size distribution and carboxyl group distribution, established a conceptual framework for kinetic studies in emulsion polymerization of XNBR latexes.

Experimental and modeling study of proton and copper binding properties onto fulvic acid fractions using spectroscopic techniques combined with two-dimensional correlation analysis

Fulvic acid (FA) significantly influences the bioavailability and fate of heavy metals in environments, while its acid-base characters and metal binding processes are still unclear. Here, spectroscopic techniques combined with multiple models (e.g., NICA-Donnan model) and two-dimensional correlation spectroscopy (2D COS) were applied to explore the proton and copper binding properties of FA sub-fractions (FA3-FA13). The charge densities, average contents of carboxylic and phenolic groups, average dissociation constants pKa1 and pKa2 of sub-fractions ranged 0–16 meq∙g∙C−1, 5.03–9.58 meq∙g∙C−1, 2.52–4.67 meq∙g∙C−1, 4.15–4.33 and 8.52–9.72, respectively. FA sub-fractions had a relatively narrow distribution of carboxyl group and a broad distribution of phenolic group. FA sub-fractions also exhibited roughly two phenolic hydroxyl groups per every 1–3 phenyl rings. Differential absorbance spectra (DAS) derived Gaussian bands were associated to the inter-chromophore interactions, the changes of molecular conformations and functional groups with copper addition. Differential spectra slopes (DSlope275-295&325-375) were more significant with higher copper concentration and copper amounts bonded to carboxylic groups. UV–Vis and fluorescence spectra with 2D heterospectral COS revealed the copper binding heterogeneities and sequential orders of chromophores and fluorophores, quantitatively confirming by the order of conditional stability constants (log KCu: 4.64–5.56). Salicylic-/polyhydroxyphenolic, hydroxyl and amino groups were strongly associated to the basic units for fluorophores. Sequential changes followed the order of humic-like→fulvic-like materials for FA3/FA5, humic-like→fulvic-like→tryptophan-like materials for FA7, and humic-like→tryptophan-like→fulvic-like→tyrosine-like materials for FA9/FA13. Spectroscopic techniques combined with various models (especially for 2D COS) are beneficial to elucidate the binding heterogeneity and sensitivity for metal-organic matters at the functional group level.

Lead binding to wild metal-resistant bacteria analyzed by ITC and XAFS spectroscopy

Metal-resistant bacteria can survive exposure to high metal concentrations without any negative impact on their growth. Biosorption is considered to be one of the more effective detoxification mechanisms acting in most bacteria. However, molecular-scale characterization of metal biosorption by wild metal-resistant bacteria has been limited. In this study, the Pb(II) biosorption behavior of Serratia Se1998 isolated from Pb-contaminated soil was investigated through macroscopic and microscopic techniques. A four discrete site non-electrostatic model fit the potentiometric titration data best, suggesting a distribution of phosphodiester, carboxyl, phosphoryl, and amino or hydroxyl groups on the cell surface. The presence of these functional groups was verified by the attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, which also indicated that carboxyl and phosphoryl sites participated in Pb(II) binding simultaneously. The negative enthalpy (−9.11 kJ mol−1) and large positive entropy (81.52 J mol−1 K−1) of Pb(II) binding with the bacteria suggested the formation of inner-sphere complexes by an exothermic process. X-ray absorption fine structure (XAFS) analysis further indicated monodentate inner-sphere binding of Pb(II) through formation of C−O−Pb and P−O−Pb bonds. We inferred that C−O−Pb bonds formed on the flagellar surfaces, establishing a self-protective barrier against exterior metal stressors. This study has important implications for an improved understanding of metal-resistance mechanisms in wild bacteria and provides guidance for the construction of genetically engineered bacteria for remediation purposes.

Influence of enzymatic and acidic demethoxylation on structure formation in sugar containing citrus pectin gels

Aim of the present study was to investigate the impact of different demethoxylation methods and the co-occuring side effects on the molecular properties and structure formation in pectin gels.A high-methoxylated citrus pectin (HMP) was demethoxylated using either hydrochloric acid or pectin methylesterases of plant (pPME) or fungal (fPME) origin. pPME treatment causes a more block-wise distribution of free carboxyl groups, fPME or acidic treatment a random distribution. Twelve pectin samples with four different degrees of methoxylation (DM) between 62% and 41% were prepared. The gelation process was studied by oscillatory measurements.In pectin samples from pPME treatment structure formation started at higher temperature and the final gels were more elastic in comparison to pectin from the two other modifications. The impact of the block-wise distribution of the free carboxyl groups became more evident with decreasing DM. The gelling process of pectin samples with random distribution was similar independent of DM.Side effects of all demethoxylation reactions were an altered sodium ion content (high in enzymatically treated pectin, close to zero in acidic treated) and a decrease of the molecular weight with increasing degree of demethoxylation. These side effects additionally altered the gelation process and the final gel properties in different ways.

Rheological surface properties of commercial citrus pectins at different pH and concentration

The interfacial activity of commercial low-methoxy (LM) and high-methoxy (HM) pectins from citrus peel was investigated at air-water interfaces by focusing on the role of their molecular weight (MW) and degree of methoxylation (DM). A pendant drop tensiometer was used to carry out transient interfacial tension measurements and small amplitude oscillations. Different pectin concentrations (ranging between 0.00001 g/100 g and 5 g/100 g) and pH conditions (4 and 6) were used during the tests. It was observed that citrus pectins are characterised by interesting surface properties that could allow potential practical uses. Experimental results evidenced that MW affects the diffusion of molecules towards the interface, whereas other investigated parameters (i.e. surface tension, adsorption rate, dynamic moduli) seem more dependent on DM and a clear dependence on MW was not observed. pH conditions modify intermolecular interactions in the bulk and surface layer, even if their effects are related to the fraction and distribution of carboxylic groups along the chain. As a consequence, a complex dependence on investigated parameters was observed and no clear relationship was obtained. Nevertheless, among tested commercial samples LM pectins exhibited the most interesting properties and this behaviour seems related to the intermolecular interactions occurring among them.

Emulsions stabilized by pH-responsive PNIPAM-based microgels: Effect of spatial distribution of functional carboxylic groups on the emulsion stability

Abstract Poly(N-isopropylacrylamide-co-Methacrylic acid) (PNIPAM-MAA) microgels with different spatial distribution of functional carboxylic (COOH) groups were synthesized by a combination of semi-batch and temperature-programmed surfactant-free precipitation polymerization. This synthetic approach enabled functional COOH groups and crosslinks to be controlled in a better way so that they were either predominately concentrated at the periphery, leading to a functional dense-shell (DS), or mainly located inside the microgel, resulting in a functional dense-core (DC) particle. Because of the specially designed internal structures of these two microgels, we were able to investigate the effect of the charge group distribution on the corresponding Pickering emulsions. By examining the emulsion stability at different pH values and particle concentration using these two microgel samples as particular emulsifiers, our results showed that the soft, negatively charged microgel with a pure PNIPAM shell is the best emulsion stabilizer since the microgel is very hydrophilic and also retains its interfacial activity at the same time. On the other hand, the functional DS microgel lost most of its interfacial activity due to the dramatic increase in hydrophilicity, particularly in alkaline condition. Nevertheless, it is still capable of stabilizing oil/water emulsion by its high volume fraction in the continuous phase. Although the particles are not strongly adsorbed to the interface, the movement of the particles is significantly restrained. Therefore, they are still separating the oil droplets from coalescence.

Analysis of competitive binding of several metal cations by graphene oxide reveals the quantity and spatial distribution of carboxyl groups on its surface.

The sorption capacity of graphene oxide (GO) toward different metal cations has been the subject of several recent studies. However, the reported quantitative data are controversial, and the mechanism of chemical bonding between GO and metal cations is poorly understood. Clarifying these questions can eventually help to reveal the fine chemical structure of GO that remains ambiguous. In this work, we study the binding of Gd3+ and Mn2+ by GO in the presence of several competing metal cations by the 1H NMR relaxation method. As a general trend, the efficiency of the metal cations to bind to GO increases with ionic charge, and depends on their ability to form coordinate-covalent bonds with GO oxygen groups. The efficiency of the competing metal cations to "replace" Gd3+ and Mn2+ increases in the order Na+ < Cs+ < Ca2+ < Sr2+ < Ga3+ < Lu3+. GO contains two different types of binding sites, bonding to which results in either high or low NMR relaxivity of the resulting Gd3+-GO and Mn2+-GO solutions. Gd3+ and Mn2+, being replaced from the high-relaxivity sites by the large excess of competing cations, are not released into the bulk solution, but only migrate to the low-relaxivity sites, remaining covalently bonded to GO. The absolute majority of the existing carboxyl groups in GO are located at tiny few-carbon-atom-vacancy defects on the major planes. The density of these vacancy defects is estimated as one per every 200 carbon atoms.

Immobilization of phosphotungstic acid on multiwalled carbon nanotubes with cetyltrimethyl ammonium bromide as the molecular linker for enhanced oxidation of hydroxylamine

Hydroxylamine, widely used as reducing agent in chemical and pharmaceutical industries, has been recognized as a mutagen. Modest levels of hydroxylamine are toxic to humans, animals and even plants. The development of a sensitive method for the detection of HA is very important. In this work, phosphotungstic acid (PTA)/cetyltrimethyl ammonium bromide (CTAB)/multiwalled carbon nanotube (MWCNT) nanocomposite with sandwich structure was prepared by means of the immobilization of PTA on carboxylated MWCNT. CTAB acts as the molecular bridge to immobilize PTA molecules on the surface of MWCNT. The surface of the MWCNT is negatively charged owing to the abundant distribution of carboxyl groups. PTA is a strong acid, which ionizes completely in aqueous solutions by losing protons. CTAB is a quaternary ammonium surfactant, which is positively charged in aqueous solutions. The formation of PTA/CTAB/MWCNT nanocomposite is due to the electrostatic attraction between CTAB, PTA and MWCNT. PTA/CTAB/MWCNT shows excellent electrocatalytic ability towards the oxidation of hydroxylamine (HA) by significantly enhancing its oxidation current. On PTA/CTAB/MWCNT modified glassy carbon electrode (GCE) (PTA/CTAB/MWCNT/GCE), the oxidation current of HA is linear with its concentration in the range of 0.3–100μM with a detection limit of 0.06μM.

PH-induced conformational changes of comb-like polycarboxylate investigated by experiment and simulation

Four types of polycarboxylate ether (PCE) polymers with consistent backbone length and side-chain (poly(ethylene glycol) monomethyl ether methacrylate MAA-M2000) length but different ratios of acrylic acid (AA) to methacrylic acid (MAA) were synthesized. The ratio of the methyl group would directly affect the backbone stiffness and hydrophobicity of the PCE. Laser light scattering (LLS) and molecular dynamic (MD) simulations were used to investigate the conformations of PCE at various pH values. It was found that the conformation of PCE remained more extended with the decrease of ratio of the backbone methyl group, which resulted in a low exposed extent of carboxylic groups on the backbone at the same ionization degree. The complexation of the carboxylic oxygen atoms of PCE with Ca2+ indicated that the differences of the complexing capacity resulted from the differences in the spatial distribution of carboxylic groups, which depended on the solution conformation of PCE molecules.

Copolymeric hexyl acrylate-methacrylic acid microspheres – surface vs. bulk reactive carboxyl groups. Coulometric and colorimetric determination and analytical applications for heterogeneous microtitration

Copolymeric acrylate microspheres were prepared from hexyl acrylate using different amounts of methacrylic acid, resulting in a series of microspheres of gradually changing properties. The distribution of carboxyl groups – between surface and bulk of microspheres was evaluated. Bulk reactive carboxyl groups were determined using reverse coulometric titration with H+ ions, following hydroxide ions have been generated and allowed to react with microspheres in the first step. It was found that the number of reactive carboxyl groups available in copolymeric microspheres is lower compared to number of methacrylic acid units used for polymerization process. Moreover, there is correlation between the number of groups introduced and found to be reactive in microspheres. On the other hand, the number of surface reactive groups was proportional to the number of groups introduced in course of polymerization. Thus, the surface reactive groups can be used as reagent, in novel heterogeneous microtitration procedure, in which a constant number of microspheres of different carboxyl groups contents is introduced to the sample to react with the analyte. The applicability of novel proposed method was tested on the example of Ni2+ determination.

Tailoring interlayer structure of molecular layer-by-layer assembled polyamide membranes for high separation performance

A molecular layer-by-layer (mLbL) technique was recently developed to fabricate polyamide (PA) thin film composite (TFC) membranes for water purification. In this study, the interlayer structure between the selective and support layers of the mLbL-assembled TFC membrane was tailored to achieve high performance applicable to seawater desalination. Introducing interlayers on porous supports prior to mLbL deposition allowed the effective PA growth by preventing monomer deposition within the support pores. The PA layers were grown via mLbL on supports coated by a series of interlayers: poly(piperazine-amide), cross-linked poly(ethyleneimine) (PEI) and a polyelectrolyte bilayer of PEI and poly(acrylic acid) (PAA) (PEI/PAA). The density and distribution of surface carboxyl groups of the interlayer were found to be key parameters that determine the structure and performance of the mLbL-assembled membranes. Among the interlayers examined, the PEI/PAA interlayer not only yielded membranes with superior performance but also with a highly smooth surface beneficial for antifouling.

Modification and physico-chemical properties of citrus pectin – Influence of enzymatic and acidic demethoxylation

Aim of the present study was to investigate the effect of the method of demethoxylation on the particle structure and techno-functional properties of pectins with different degree of methoxylation and distribution of free carboxyl groups. Two groups of model pectins, one with 57% and one with 42% degree of methoxylation have been prepared from one single commercial pectin. Modifications were performed by an acidic and two enzymatic methods using fungal and plant-derived pectin methyl esterases. Thermal stability was investigated by thermal analysis and water uptake was determined by a sorption and a capillary sucking method.The enzyme-treated pectins were thermally less stable than the acid-treated. The water uptake of enzyme-treated pectins was higher than in acid-treated samples in the sorption method and lower in the capillary sucking tests. The different behaviour is explained by differences in pH during demethoxylation and a co-occurring variation in sodium content. Both parameters affected intermolecular interactions of the pectin macromolecules in solution, which resulted in differences in the particle morphology. The effect of the distribution of free carboxyl groups (statistical or block-wise) on the techno-functional properties was more pronounced in high-methoxylated pectins than in low-methoxylated pectins.