Concentration Of Paramagnetic Centers Research Articles

Relating Paramagnetic Properties to Molecular Parameters of Humic Acids Isolated from Permafrost Peatlands in the European Arctic.

Free radicals (FRs) are intermediate participants in the transformation process of soil organic matter, and free radical activity is a fundamental property of humic substances. The aim of this work was to conduct a comparative study of the paramagnetic properties of humic acids (HAs) isolated from Histosols by electron paramagnetic resonance (EPR) spectroscopy. The studied Histosols are found in permafrost peatlands in four natural geographic subzones of the European Arctic (from forest tundra to northern tundra). The results obtained showed that in anaerobic conditions on the peatlands in the tundra zone, the formation of semiquinone-type radicals occurs through the reduction of quinone fragments of HAs and leads to an increase in the concentration of paramagnetic centres within HAs. PCA analysis allowed us to reveal relationships between the properties of the initial raw peat samples, the molecular composition of the isolated HAs, and their paramagnetic parameters. It was found that FR localization occurs predominantly on aromatic fragments of lignin nature, which are confined to the low molecular weight fraction of HAs. The g-factor values of the EPR spectra of HAs indicate the presence of carbon- and oxygen-centred FRs in the HA structure, with a predominance of the latter.

Continuous-wave and pulsed EPR studies of glass-like carbon with high spin concentration: Evidence for triplet states

Glass-like carbons (GLCs) are a large group of disordered carbon materials which have applications in various fields, but not all their properties are well characterized. In particular, they have high concentration of paramagnetic centers (PCs) which are easily observed by electron paramagnetic resonance (EPR). However, an apparently simple EPR spectrum, together with its peculiarities caused by high electrical conductivity, make it difficult to identify the PCs and their origin remains unknown. To resolve these unsettled questions, in this work we use the vacuum Rabi splitting and Rabi oscillations which so far have not been applied to study these materials by the continuous wave (CW) and pulsed EPR. GLC produced by pyrolysis of phenol-formaldehyde resin at 1120 K was studied in the temperature range of 4.3–300 K. Using the Rabi splitting we found conditions for undistorted registration of CW EPR spectra and determined spin concentration (1×1020 spin/g). The temperature dependence of the EPR susceptibility shows the coexistence of Pauli paramagnetism due to conduction electrons and the Curie-type paramagnetism of thermally activated PCs with the activation energy of 5.7 cm-1. These PCs may be excited triplet states, the presence of which is revealed by Rabi oscillations in the pulsed EPR.

Method for determining the ultimate sorption capacity of coal matter by EPR-spectroscopy

Purpose. Improving the method for determining the ultimate sorption capacity of coal matter using EPR-spectroscopy (electron paramagnetic resonance) by adjusting the proportionality coefficient between the ultimate sorption capacity of coal and the concentration of paramagnetic centers and the conjugation coefficient in accordance with the degree of coalification. Methodology. The ultimate sorption capacity of the matter was estimated by EPR-spectroscopy, based on the content of paramagnetic centers (PMC) in coal, which are able to come into physical (sorption) interaction with molecules of paramagnetic gas (O2) when the pressure increases. Processing of the research results was carried out by methods of mathematical statistics. Findings. Analysis of long-term results for determining the ultimate sorption capacity of coal matter by EPR-spectroscopy was carried out. The analysis testified about the need to adjust the proportionality coefficient  between the ultimate sorption capacity of coal and the concentration of paramagnetic centers Na and the conjugation coefficient Ksc, depending on the coal rank metamorphism. The values of the proportionality coefficient  by hard coal ranks for the yield of volatile components Vdaf and the reflectivity of vitrinite R° were calculated. Appropriate changes were made to the express-method for estimating the ultimate sorption capacity of coal by the EPR method. Originality. It is proved that the proportionality coefficient β between the ultimate sorption capacity of coal and the concentration of paramagnetic centers Na and the conjugation coefficient Ksc is not a constant value, but changes (decreases) with the degree of metamorphism. It is established that this relationship is satisfactorily characterized by the sigmoid model, whose inflection (on the graph) is confined to the gas and fat ranks of coals (volatile-matter yield is 29 %) and is caused by the second main jump of coalification during a cardinal change in the molecular structure of coal, associated with the completion of the intensive decomposition of the polymer-lipoidin component in the coal matter. Practical values. The express-method was improved for estimating the ultimate sorption capacity of coal by the EPR-method, which differs by specified proportionality coefficients according to ranks in the series of coalification.

Impact of Geomagnetic Fields on the Geochemical Evolution of Oil

Here, we reported on experimental studies related to the exposure of oil to a 50 Hz electromagnetic field (0.81 T strength) and examined the changes in the geochemical characteristics of oil: n-alkane distribution, isotopic composition (δ13C), and concentration of paramagnetic centers. We discovered that electromagnetic fields have impacts on the distribution of n-alkanes and on their individual isotopic composition, with the concentration of paramagnetic centers remaining unchanged. While discussing the results, we looked into the state-of-the-art of research on electromagnetic exposures of the bottom-hole formation zone and into natural electric and geomagnetic fields. We consequently hypothesized that natural geomagnetic fields can influence the geochemical evolution processes of oil. This hypothesis requires further studies to reveal the frequency and strength characteristics of natural geomagnetic fields.

Manufacture-affected asphaltene genesis in dispersion hardened bitumen-mineral compositions

The paper focuses on increasing the service life of the road pavement layers made of dispersion hardened organomineral mixtures through the aging intensity reduction of organic binder, which begins at the preparation stage of these mixtures and lasts during the structural layer operation. The organic binder generates adsorption-volute shells on the surface of mineral materials, which become more viscous and acquire increased brittleness. Crack formation becomes more intensive, pavement designed and built in accordance with the requirements destroys. Dispersion hardening of the pavement structural layers with chemical fibers from spent sorbents containing oil products, can be used to partially solve this problem. The purpose of the work is to study the aging intensity of the binder in organomineral mixtures using electron paramagnetic resonance methods. The aging intensity of the organic binder is evaluated by the concentration of paramagnetic centers, since asphaltenes are almost one hundred percent concentrate of paramagnets, which can serve as an indicator of the aging intensity of the petroleum dispersion system. It is shown that dispersion hardening of the pavement layers by chemical fibers from spent sorbents containing absorbed oil products, decreases the concentration of paramagnetic centers, which indicates to the higher concentration of asphaltenes, which, in turn, means a decrease in the aging intensity of the oil dispersion system.

Mechanochemical activation of Al/V2O5 composites: Thermal transformations

Thermal transformations of mechanochemically activated (MCA) thermites Al/V2O5 (mixtures of Al with bare coarse V2O5 as well as with highly defected nanosized n-V2O5) were analyzed by the methods of X-ray diffraction, calorimetry, EPR spectroscopy, adsorption and SEM. The influence of the treatment time of MCA on stages of thermal transformations during oxidation of aluminum in the reaction 10Al + 3V2O5 → 5Al2O3 + 6V was revealed and the optimal conditions of MCA were established. It was shown that the use of highly defected n-V2O5 does not lead to changing the ignition conditions of mixtures and the dynamics of thermal reactions. For the non-activated mixtures and at short-time of MCA, the intensive oxidation of Al occurred by the liquid-phase mechanism at Т > 680 °C, above melting temperatures of the both components. At the optimal conditions of MCA, transformations are started at temperatures only slightly above 150 °C by the solid-phase mechanism. Reduction of V2O5 occurs via several lower vanadium oxides: V2O5 → V4O9 → V6O13 → VO2-1 → VO2-2 → V3O5 → V2O3 → VO → V. Heating of mixtures is accompanied by the increase of concentrations of paramagnetic centers (PCs) VO2+ of two types up to 420 °C, and by their noticeable decrease at 520 °C. Assumptions concerning relations between PCs and phases V4O9, VO2-1, and on the effect of PCs on initiation of the solid-phase transitions are discussed. MCA treatment carried out upon optimal conditions promotes the explosive way of the reaction at firing the activated samples. Possibility of passing the reaction by the solid-phase mechanism as the result of MCA can be caused by the formation of large surface area of contacts ca. 7–8 m2/g, and also by the formation of vanadyl PCs clusters.

Universal Dependence of Nuclear Spin Relaxation on the Concentration of Paramagnetic Centers in Nano- and Microdiamonds.

An analysis of our data on 1H and 13C spin–lattice and spin–spin relaxation times and rates in aqueous suspensions of purified nanodiamonds produced by detonation technique (DNDs), DNDs with grafted paramagnetic ions, and micro- and nanodiamonds produced by milling bulk high-temperature high-pressure diamonds is presented. It has been established that in all the studied materials, the relaxation rates depend linearly on the concentration of diamond particles in suspensions, the concentration of grafted paramagnetic ions, and surface paramagnetic defects produced by milling, while the relaxation times exhibit a hyperbolic dependence on the concentration of paramagnetic centers. This is a universal law that is valid for suspensions, gels, and solids. The results obtained will expand the understanding of the properties of nano- and microdiamonds and will be useful for their application in quantum computing, spintronics, nanophotonics, and biomedicine.

Photoinduced Dynamics of Radicals in N- and Nb-Codoped Titania Nanocrystals with Enhanced Photocatalysis: Experiment and Modeling

Titanium dioxide (TiO2) nanocrystals are one of the most promising materials for modern photocatalysis applications, having unique properties such as a huge specific surface area and affordability of synthesis. However, the facile fabrication of TiO2-based photocatalysts active in regular daylight remains a major challenge. In this work, aiming to create such a nanocrystalline material by a very simple technology, we provide a detailed analysis of the paramagnetic centers (PCs) and their photoinduced reactions in N- and Nb-codoped TiO2 nanocrystals. The resulting powders show a surface area up to 170 m2/g and an intense visible-light photocatalysis of rhodamine 6G with reaction rate k = 0.087 min–1. Ti3+, N•, and O2– PCs are observed and studied using electron paramagnetic resonance spectroscopy. We also present a new approach to the study of photoinduced processes in nanocrystalline photocatalysts─a simple theoretical model of kinetics of these PCs, which well predicts their behavior and variations of their concentration under illumination. Our results indicate that the obtained Nb–N–TiO2 nanocrystals with a high concentration of PCs on the sample surface can be used in cutting-edge industries, paving the way for the most advanced photocatalytic systems operating in sunlight.

ELECTRONIC PARAMAGNETIC RESONANCE OF HUMIC AND HYMATOMELANIC ACIDS IN SAPROELS OF THE LAKE OF THE MIDDLE OB RIVER

The paper presents the results of a study of the paramagnetic activity of humic and hymatomelanic acids extracted from sapropels of ten small lakes on the right bank of the Ob River and ten small lakes on the left bank of the Ob River (Western Siberia). Quantitative studies were carried out by two methods: the ABS spins method and the method using a double resonator with respect to TEMPO. A comparison of the two methods is presented. The values ​​of the concentration of paramagnetic cents per gram of humic and hymatomelanic acids, as well as the molecular weights of the conditional paramagnetic molecules of humic and hymatomelanic acids were calculated. Based on the results obtained, a conclusion was made about the greater paramagnetic activity of humic acids relative to hymatomelanic acids. Differences in the paramagnetic activity of humic acids and hymatomelanic acids have been established. Three samples from lakes on the right bank of the Ob River and one sample from a lake on the left bank of the Ob River have the greatest differences in paramagnetic activity between HAs and their corresponding HMCs. The concentration of paramagnetic centers in the HAs of these samples is six times higher than in the corresponding MMCs. The contribution of the conjugated aromatic component to the structure of the macromolecules of these HAs is the greatest.

Structure and Magnetism of Few-Layer Nanographene Clusters in Carbon Microspheres

The solid-phase pyrolysis method was used to synthesize carbon microspheres, consisting of clusters of few-layer nanographene and amorphous carbon. Powders of metal-free phthalocyanine and polyethylene served as precursors of the synthesized carbon microspheres. The pyrolysis products of metal-free phthalocyanine samples SPc(700) and SPc(900) contained 4 and 1 atom % nitrogen, respectively, replacing carbon in the graphene lattice in pyrrolic and pyridinic coordination. There are no impurity nitrogen atoms in the products of the pyrolysis of polyethylene. The SPc(700) sample showed strong paramagnetism with a concentration of paramagnetic centers of ∼5 × 1019 spin g–1 and a temperature-independent diamagnetism susceptibility of χDia = −1 × 10–6 emu g–1 Oe–1. In a temperature range of 5–300 K, ferromagnetism was also revealed with a temperature dependence similar to that of ferromagnetic cluster spin glasses, with maximum saturation magnetization, MSFM = 3 × 10–2 emu g–1, and coercive force, Hc = 400 Oe, at Tsg = 25 K. It was shown that the ferromagnetism in the SPc(700) sample is due to π(p)-electrons of zigzag-type edge states as well as nitrogen impurity atoms. The experimental results are interpreted based on the temperature dependence of the spin correlation length. It was revealed that the temperature dependence of the integral of the magnetic resonance absorption intensity closely resembles the temperature behavior of the saturation magnetization of the ferromagnetic component.

The impact of geological factors on the sorption capacity of gas and fat ranks of coal in the krasnoarmeyskiy district

At present, based on the research of the conditions and factors of outburst hazard of coal beds, various predicting methods have been developed grounded on contemporary views concerning the nature and mechanism of gas-dynamic phenomena. One of the main factors affecting the outburst hazard of coals is gas saturation, which is determined by the sorption capacity of coals. The sorption properties of coal matter are significantly determined by the degree of coal transformation (metamorphism). Therefore, the analysis of the data obtained for a coal matter of the same rank makes it possible to reveal the role and importance of factors that have formed the parameters of the signals observed by EPR (electron paramagnetic resonance) spectroscopy. These signals define the features of the sorption coal-gas interaction for a particular sample. It is established that the average values of the concentration of paramagnetic centers are (2.29 ± 0.36) and of contingency - (0.476 ± 0.02), and the calculated value of the sorption capacity of coals (24.3 ± 0.29) can be considered basic for gas and fat ranks of coals in the Krasnoarmeyskiy district. Minor deviations from the basic parameters can be caused by various geological and technological factors. Significant deviations of the average values for the sorption capacity of coals can be caused by tectonic processes. The purposeis to research the impact of geological factors on the sorption properties of gas and fat ranks of coals determined by the EPR method in the mines of the Krasnoarmeyskiy district. During the research, the following parameters were defined: 1) the integrated intensity of the EPR spectrum - the concentration of paramagnetic centers (Na) in the matter under research, which characterizes the conjoint impact of external factors on the coal matter, and 2) the contingency coefficient (Ksc), i.e. the number and status of the conjugate system in the molecular structure of a matter, which characterizes the transmitting depth of structural transformations (a degree of structuredness) of fossil organics at the nanolevel. As a result, it is found that various factors acting in different directions affect the calculated value of the sorption methane capacity of coals. The average sorption capacity of gas and fat ranks of coals from the Krasnoarmeyskiy district is 24.3 ± 0.29 and mainly depends on the deformation conditions. The average concentrations of paramagnetic centers are (2.29 ± 0.36), and of contingency (0.476 ± 0.02). The calculated value of the sorption capacity of coals (24.3 ± 0.29) can be considered as the base one for the gas and fat ranks of coals in the Krasnoarmeyskiy district. Minor deviations from the basic parameters can be caused by various geological and technological factors. Significant deviations in the average values of the coals sorption capacity can be caused by tectonic processes.

Electron paramagnetic resonance in organic binder aging in dispersely reinforced substructures

Purpose: To study the intensity of binder aging in organo-mineral mixtures using electron paramagnetic resonance. The aging intensity of the organic binder is provided by its concentration in paramagnetic centers, since asphaltenes are almost one hundred percent of paramagnet concentration and indicate to the aging intensity of the petroleum dispersion system.Approach: Dispersed reinforcement of substructures with chemical fibers made of spent sorbents containing a controlled amount of absorbed oil products allows to partially solve the problem of crack formation and fracture of road pavements designed in accordance with the regulatory documents.Research implications: The service life of substructure made of dispersely reinforced organo-mineral mixtures reduces owing to organic binder aging, which begins at the stage of preparation of organo-mineral mixtures and continues during the substructure operation. Organic binder ageing results in the formation of solvation layers on the surface of mineral materials that become more viscous and brittle.Findings: The substructure dispersed reinforcement with chemical fibers made of spent sorbents containing a controlled amount of absorbed oil products decreases the concentration of paramagnetic centers. This indicates to a decrease in the asphaltene concentration, thereby reducing the aging intensity of the oil dispersion system.

Rice Husk Research: From Environmental Pollutant to a Promising Source of Organo-Mineral Raw Materials.

Rice husk is a large-tonnage waste left from rice production. It is not subject to humification and therefore becomes a serious environmental pollutant. Due to the presence of two essential elements—carbon and silicon—in its composition, rice husk is a promising organo-mineral raw material. The known methods for processing of rice husk are associated with the formation of even more aggressive waste. The creation of a waste-free technology for processing this plant material requires a detailed study. Rice husk of Kyzylorda oblast was studied using IR, SEM, TA, TPD-MS, EPR, and TEM methods. It was determined that under a temperature up to 500 °C, the ligno-carbohydrate component of rice husk decomposes almost completely. Three main peaks are recorded during the decomposition: hemicellulose at 200 °C, cellulose at 265 °C, and lignin at 350–360 °C. This process is endothermic. However, above of 300 °C the exothermic reactions associated with the formation of new substances and condensation processes in the solid residue begin to prevail. This explains the increase in the concentration of paramagnetic centers (PMCs) in products of rice husk carbonization in the range of up to 450 °C. Further increase in temperature leads to a decrease in the number of PMCs as a result of carbon graphite-like structures formation. The silicon–carbon product of rice husk carbonization (nanocomposite) is formed by interconnected nanoscale particles of carbon and silicon dioxide, the modification of which depends on the temperature of carbonization. The obtained data allow management of the rice husk utilization process while manufacturing products in demand based on ecofriendly technologies.

Antioxidant Properties of an Extract of Hermetia illucens Larvae

An aqueous extract was obtained from the biomass of Hermetia illucens larvae using the electro-pulse plasma-dynamic method. The extract was highly effective in quenching the chemiluminescence of luminol in the presence of hemoglobin and hydrogen peroxide. It contained the dark pigment melanin with a concentration of paramagnetic centers of 8.3 × 1016 spin/g of dry matter and antioxidant activity. The antiradical properties of the extract were confirmed on the model of oxidative stress of the nematode Caenorhabditis elegans in the presence of 40 mmol of paraquat: the introduction of the extract increased the median lifespan of the nematode by 25%. The antioxidant effect identified is associated with the presence of a complex of antioxidants in the extract and, possibly, antioxidant enzymes that destroy hydroperoxides.

Study Of Fossil Coals In The Kuznetsk Basin By Epr Spectroscopy

Fossil coals of the Kuznetsk Basin of varying degrees of metamorphism were studied by the method of electron paramagnetic resonance. It is shown that in the series from brown coal to anthracite, the g-factor of the EPR signal decreases, due to the aromatization of the carbon framework and a decrease in oxygen-containing and hydrogen-containing fragments in the coals. The maximum width of the EPR spectrum is observed for coals of the middle stage of metamorphism, which indicates the presence of both aliphatic and aromatic paramagnetic centers (PCs) in their structure. Also, in the series of coal metamorphism, the concentration of PCs increases. Thus, it has been shown that in the process of coal metamorphism, a change in the electronic structure occurs, associated with the rearrangement of the carbon skeleton of the organic mass of coal (OMC) and a decrease in the amount of oxygen-containing and hydrogen-containing radicals.

Biological Activity of Native and Modified Humic Acids

The samples of native and hydrogen peroxide–modified humic acids (HAs) separated from brown coals of the Tisul’skoe deposit in the Kansk-Achinsk Basin were obtained. The HA samples were characterized by instrumental methods: elemental and technical analysis and EPR spectroscopy. The modification of HAs affected the structural-group composition and decreased the concentration of paramagnetic centers (PMCs). The biological activity of native and modified humic acids was evaluated by phytotesting with the use of Iren varietal wheat seeds as an example. The highest biological activity was manifested at an HA concentration of 0.005%. A tendency toward a decrease in the biological activity with a decrease in the concentration of PMCs was revealed.

STUDIES OF THE ORGANIC ORIGIN CHEMICAL COMPOUNDS OF BROWN COALS AND CARBONIZED PLANT RESIDUES FROM NORTHERN TIMAN

The results of the physical and chemical studies of the organic matter of Devonian brown coals and rocks with carbonized plant residues from Northern Timan (Russian Arctic) are presented. We used a complex of physical and chemical methods, including IR spectroscopy, EPR spectroscopy, quantitative chemical analysis, pyrolytic gas chromato-mass spectrometry. For comparative studies we used Devonian (Middle Timan) and Jurassic (Griva, Komi Republic, Russia) carbonized plant residues and lignins, isolated from modern wood and non-wood plants. Organic structures of aromatic nature, which are products of the metamorphic transformation of lignins of coal-forming plants, were found in the investigated samples. It was shown that lignin’s relics show pronounced paramagnetic properties, mainly due to the presence of phenoxyl radicals. The concentration of paramagnetic centers reaches a value that is close to the maximum value nорг for carbonaceous substances. Based on quantitative analysis of phenolic products of pyrolysis the composition of lignin relics was calculated, taking into account the ratio of the main structural H, G and S units. Experimental data allowed to put forward the hypothesis that in the composition of Devonian coal-forming plants, as one of the first representatives of forest communities on the planet, included compositionally homogeneous protolignins of H-type, built mainly from p-coumaric structural units.

Ommochromes from the Compound Eyes of Insects: Physicochemical Properties and Antioxidant Activity.

The objective of this study was screening of ommochromes from the compound eyes of insects and comparison of their antioxidant properties. Ommochromes were isolated in preparative quantities from insects of five different families: Stratiomyidae, Sphingidae, Blaberidae, Acrididae, and Tenebrionidae. The yield of ommochromes (dry pigment weight) was 0.9-5.4% of tissue wet weight depending on the insect species. Isolated pigments were analyzed by high-performance liquid chromatography and represented a mixture of several ommochromes of the ommatin series. The isolated ommochromes displayed a pronounced fluorescence with the emission maxima at 435-450 nm and 520-535 nm; furthermore, the emission intensity increased significantly upon ommochrome oxidation with hydrogen peroxide. The ommochromes produced a stable EPR signal consisting of a singlet line with g = 2.0045-2.0048, width of 1.20-1.27 mT, and high concentration of paramagnetic centers (> 1017 spin/g dry weight). All the investigated ommochromes demonstrated high antiradical activity measured from the degree of chemiluminescence quenching in a model system containing luminol, hemoglobin, and hydrogen peroxide. The ommochromes strongly inhibited peroxidation of the photoreceptor cell outer segments induced by visible light in the presence of lipofuscin granules from the human retinal pigment epithelium, as well as suppressed iron/ascorbate-mediated lipid peroxidation. The obtained results are important for understanding the biological functions of ommochromes in invertebrates and identifying invertebrate species that could be used as efficient sources of ommochromes for pharmacological preparations to prevent and treat pathologies associated with the oxidative stress development.

Comparative Analysis of the Composition of Carbon-Rich Rocks from Domanik Deposits and the Oil–Water Contact Zone Exemplified by Tatarstan’s Bavly Oilfield

Samples of carbon-rich rocks from domanik deposits and the oil–water contact zone of the Bavly field of the Republic of Tatarstan (Russia), as well as extracts from them, have been studied by thermal analysis, IR and EPR spectroscopy, and gas–liquid chromatography. Significant differences have been revealed in the chemical composition and physicochemical properties of both soluble and insoluble organic matter from various areas of the Bavly field. Compared with bitumens from the oil–water contact zone, bitumoids from domanik deposits are heavier; they are enriched in oxidized structures and contain elevated levels of isoprenoid hydrocarbons and light normal alkanes. Bitumoid asphaltenes are enriched in sulfur and nitrogen, depleted in oxygen, and characterized by an increased concentration of paramagnetic centers. These differences have to be taken into account when testing technologies for the development of domanik deposits.

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.