Water stable colloidal lignin-PVP particles prepared by electrospray.

In this study, electrospray deposition has been used as a method to prepare lignin submicron spherical particles. Regularities of electrospraying of lignin solutions in DMSO were revealed. The influence of voltage, distance between electrodes, feed rate, temperature and concentration of lignin solution on the morphology, size and polydispersity of the obtained particles was determined. SEM, IR, TG-DSC, elemental analysis, dynamic light scattering, Zeta potential and nitrogen sorption were used to characterize the particles and to determine their properties. The aqueous colloidal solutions of the submicron particles of lignins from various plant sources were stabilized by preparing the lignin/polyvinylpyrrolidone polymeric complexes.

Characteristics of chemical structure of lignin biopolymer from Araucaria relict plant. Questions and answers of evolution.

New details of chemical structure of Araucaria lignin are the focus of this paper, since Araucaria is a relict plant which fossils are dated by the Permian period. Quantitative chemical analysis, FTIR, EPR and 2D NMR spectroscopies, Py-GC/MS and nitrobenzene oxidation have been used to characterize the Araucaria lignin. This work highlighted the structural features of the lignin of Araucaria, which distinguish it from modern coniferous (gymnosperm) lignins. This lignin exhibits pronounced paramagnetic properties with the concentration of paramagnetic centers of 3.0 × 1017 spin/g, the value of g-factor of 2.0036 corresponds to the phenoxyl radical. The Araucaria lignin is apparently unique since it does not belong to the known G, GS or GSH types. For the first time it was quantitatively proven that he lignin of Araucaria was assigned to compositionally heterogeneous GH lignins, which is not typical for modern lignins.

In vitro adsorption-desorption of aflatoxin B1 on Pepper's lignins isolated from grassy plants.

The aflatoxin B1 (AFB1) adsorption properties of several lignins isolated by the Pepper's method from grassy plants: Helianthus tuberosus (LS-1), Atriplex patula (LS-2), Rhododendron tomentosum (LS-3), Althaea officinalis (LS-4), Lavatera (LS-5), and from wood of spruce Pícea (LS-6) were studied. The adsorption was conducted in vitro in the modeled conditions of the gastrointestinal tract. The correlations between the values of adsorption-desorption and the parameters of surface-porous structure and chemical structure of the lignins were established. The relationships between the adsorption capacity and properties of the lignins led us to the conclusion that chemisorption play the most important role in the strong adsorption of aflatoxin B1. The contribution of the surface physical properties to the process of adsorption of aflotoxin B1 was not significant. It was shown that the sample of lignin isolated from stems of Althaea officinalis, was characterized by the highest value of strong adsorption of aflatoxin B1.

Comparative study of chemical and topological structure of macromolecules of lignins of birch (Betula verrucosa) and apple (Malus domestica) wood.

Recent advances in investigations of chemical structure of lignin give rise to questions about relationship between chemical structure and topology of the macromolecules. In this paper, we made a comparison of results of the studies of chemical and topological structures of lignins. The features of topological structure of lignins of birch and apple wood were identified on the basis of the study of dilute solutions of the lignins by the sedimentation-diffusion analysis and viscometry. The number of branches of macromolecules in the birch and apple lignins was calculated by the Zimm-Kilb equation. Quantitative characteristics of chemical structure of the lignins were obtained by 2D NMR spectroscopy and nitrobenzene oxidation. The structural analysis and the calculations based on the hydrodynamic data gave estimation of the degree of branching of macromolecules, which fit well in the theory on the role of dibenzodioxocin and 4'-O-5 structures in branching of lignin macromolecules.

High-Temperature Crystal Chemistry of α-, ß-, and γ-BiNbO4 Polymorphs.

Thermal behavior of the orthorhombic (α) and triclinic (ß) polymorphs of BiNbO4 was studied by the methods of high-temperature powder X-ray diffraction (HTPXRD) and differential scanning calorimetry (DCS) in the temperature range 25-1200 °C. The study revealed the sequence of thermal phase transformations and the new high-temperature modification, γ-BiNbO4, which was formed above 1001 °C and existed up to the melting temperature of BiNbO4. The incongruent melting of BiNbO4 was characterized by the formation of the cubic phase with the approximate composition Bi3NbO7. The HTPXRD method was used in this study to evaluate thermal deformations and to calculate thermal-expansion coefficients (TEC) of the three modifications of BiNbO4 (α, ß, and γ). The average volumetric TECs of these three modifications were in the range 19-36 × 10-6 °C-1. The triclinic phase ß-BiNbO4 demonstrated the highest anisotropy of thermal expansion. α-BiNbO4 was characterized by the minimal TEC and anisotropy, which indicated its greatest stability. The crystal structure of γ-BiNbO4 was determined at 1100 °C using powder data and was refined using the Rietveld method (the α-LaTaO4 structural type, the space group Cmc21, a = 3.95440(3) Å, b = 15.0899(1) Å, c = 5.65524(5) Å, V = 337.458(5) Å3, Rwp = 4.82, RBragg = 3.61%). The methods of thermal analysis and high-temperature powder X-ray diffraction revealed that, during the heating, bismuth orthoniobate underwent the following sequence of phase transitions: α-BiNbO4 → γ-BiNbO4 → ß-BiNbO4 and ß-BiNbO4 → γ-BiNbO4 → ß-BiNbO4 or, at slow heating, ß-BiNbO4 → (α-BiNbO4) → γ-BiNbO4 → ß-BiNbO4, where γ-BiNbO4 is the high-temperature phase of bismuth orthoniobate.

Structural studies of biologically active pectin-containing polysaccharides of pomegranate Punica granatum.

The polysaccharide PGW was isolated from peels and membranes of fruits of pomegranate P. granatum by hot water extraction. The methods of ion exchange chromatography, partial acid hydrolysis, enzymatic hydrolysis and NMR spectroscopy were employed to establish the major elements of its structure. It was shown that this polysaccharide contained polymers with different structures, the main components among which were pectic polysaccharides, represented mainly by highly methyl-esterified and lowly acetylated 1,4-α-d-galactopyranosyluronan and a minor amount of partially 2-O- and/or 3-O-acetylated RG-I. The side carbohydrate chains of the branched region of RG-I were mainly represented by terminal, 5-O-, 3-O-, 2,5-di-O-, 3,5-di-O- and 2,3,5-tri-O-substituted α-l-Araf residues indicating the presence of branched 1,5-α-l-arabinan and minor regions of 1,4-ß-d-galactan or arabinogalactan type I. The degree of methylation of the isolated pectins varied depending on the method of treatment. As a result, peels and membranes of pomegranate fruits can be recommended as a source of highly and lowly methyl-esterified pectic polysaccharides.

Structure of acid-extractable polysaccharides of tree greenery of Picea abies.

The polysaccharide PAA was isolated from tree greenery of spruce Picea abies by the extraction with HCl solution. Monosaccharide analysis PAA revealed high content of uronic acid residues (45%), arabinose (19.5%) and galactose (8.6%). It was shown that this polysaccharide contained polymers of various structures. The major component of which were pectic polysaccharides represented mainly by partly methyl-esterified and partly acetylated 1,4-α-D-galacturonan and by minor parts of partly 2-O- and/or 3-O- acetylated rhamnogalacturonan-I (RG-I). The side carbohydrate chains of the branched region of RG-I were represented predominantly by highly branched 1,5-α-L-arabinan and minor portions of 1,4-ß-D-galactan. In addition to the dominant pectins, the isolated polysaccharide also contained arabinogalactan proteins (AGP) and binding glycans of the glucuronoarabinoxylan (GAX), glucomannan (GM) and xyloglucan classes, which indicated a close interaction of these polysaccharides in the cell walls. It can be concluded that, at least a part of the pectin is strongly associated with the AGP and binding glycans of the GAX and GM classes. However, neither GM nor GAX were associated with RG-I.

Structural studies of water-extractable pectic polysaccharides and arabinogalactan proteins from Picea abies greenery.

Water-extractable arabinogalactan proteins (AGP) (the main constituent) and pectic polysaccharides were isolated from tree greenery of Picea abies. The carbohydrate part of AGP macromolecules consisted of AG-II, the side chains of which were represented by 1,6- and 1,3,6-ß-d-Galp, T-α-l-Araf, 1,3- and 1,5-α-l-Araf, T-ß-D-GlcpA and 1,4-ß-D-GlcpA, T-α-l-Rhap, T-α-l-Fucp and 4-O-Me-α-l-Fucp residues. It was established that the unusual 4-O-Me-α-l-Fucp monosaccharide are located on the non-reducing ends of the side chains of carbohydrate part of AGP macromolecules, and are bound to 1,4-ß-d-GlcpA residues by 1,4-bonds. The backbone of pectin macromolecules consisted mostly of 1,4-α-d-galactopyranosyluronan and RG-I, which side chains were represented by highly branched 1,5-α-l-arabinan. It was shown that RG-I is characterized mainly by short segments, which are alternated with the regions of the non-acetylated and non-methyl-esterified galacturonan. The study revealed that at least a part of the pectin is strongly associated with AGP. It was indicated that the RG-I segments are separated from the AGP-bound pectin by regions of 1,4-α-d-galactopyranosyluronane.

Structural characteristics of water-soluble polysaccharides from Norway spruce (Picea abies).

Arabinogalactan proteins and pectic polysaccharides were isolated from greenery of Picea abies by water extraction. Main elements of their structure were determined by ion-exchange chromatography, partial acid and enzymatic hydrolysis, and NMR spectroscopy. It was established that the backbone of pectin macromolecules of greenery of P. abies is represented by segments of partially methyl-esterified and acetylated 1,4-α-d-galactopyranosyluronan, and partially 2-O- and/or 3-O-acetylated RG-I with side chains consisting of highly-branched 1,5-α-l-arabinan segments. The carbohydrate part of AGP of greenery of P. abies consists of AG-II, the main chain of which is represented by 1,3-ß-d-Galp and 1,3,6-ß-d-Galp residues. The side chains of AG-II are formed of 1,6- and 1,3,6-ß-d-Galp, 1,3- and 1,5-α-l-Araf, ß-d-GlcpA and 1,4-ß-d-GlcpA, T-α-l-Araf, T-α-l-Rhap and T-α-l-Fucp residues. The AGPs of P. abies are also characterized by the presence of an unusual 4-O-Me-α-l-Fucp monosaccharide, which, as far as we know, was not found in pectins or AGP earlier.

Seasonal dynamics of polysaccharides in Norway spruce (Picea abies).

Annual dynamics of accumulation and changes in the monosaccharide composition of pectin-, arabinan- and galactan-containing polysaccharides and binding glycans isolated from greenery (thin branches with needles) of Norway spruce were investigated in this study. The polysaccharides were compared with polysaccharides of Siberian fir according to the yields, composition and content of typical components. It was shown that Norway spruce greenery contains lowly methyl-esterified pectin extracted with ammonium oxalate, which is a part of protopectic complex and is bound with components of cell walls via ionic bonds. In contrast, Siberian fir greenery contains mainly water-extracted highly methyl-esterified pectin, weakly bound to cell wall components. It was concluded that an autumn-winter period is the optimal time for harvesting Norway spruce and Siberian fir greenery for isolation of the pectic polysaccharides. The revealed regularities indicate that there is a certain biorhythm of accumulation of the compounds, probably determined by genetic factors.

Structural characteristics of oxalate-soluble polysaccharides of Sosnowsky's hogweed (Heracleum sosnowskyi Manden).

Arabinogalactan proteins (AGP) and pectic polysaccharides were isolated from above-ground parts of Heracleum sosnowskyi. The structural study has shown that a linear region of the pectic macromolecules consists of 1,4-α-d-galactopyranosyluronan blocks partially methyl esterified and acetylated. The branched region consists of 3-O- and partially 2-O-acetylated rhamnogalacturonan I. Side chains of the RG-I backbone include the regions of arabinogalactan I and branched 1,5-α-l-arabinan. The carbohydrate part of AGP consists of arabinogalactan II with a 1,3-ß-d-Galp main chain. The side chains of the branched area of AG-II are composed of 1,6-ß-d-Galp, 1,5-, 1,3,5-α-l-Araf, 4-O-Me-ß-d-GlcA and 1,4-ß-d-GlcpA, and non-reducing ends residues of ß-d-Galp, α-l-Araf, α-l-Rhap and α-l-Fucp. The branch points of the main and side chains are formed by 3,6-di-O-substituted ß-d-Galp. It was found that at least a portion of pectin is probably covalently linked to AGP, wherein AGP is linked to RG-I, but not with galacturonan.