A well-defined diamine from lignin depolymerization mixtures for constructing bio-based polybenzoxazines

The demand for high-performance materials is increasing, and most of these materials are petrol based. Therefore, the development of highly efficient and selective catalytic methods that allow access to industrially relevant polymer building blocks from complex biomass depolymerization mixtures is essential. Here, we report on a robust catalytic strategy to obtain the industrially relevant 4,4′-methylenebiscyclohexanamine (MBCA) from lignin oxidation mixtures and its use for constructing fully bio-based polybenzoxazines. The strategy consists of two challenging catalytic steps: 1) the funneling of lignin-derived bisphenol mixtures into 4,4′-methylenebiscyclohexanol (MBC) and 2) the highly selective amination of MBC with ammonia to obtain MBCA. The renewable polybenzoxazines were prepared from MBCA and phenolic lignin platform chemicals. The most promising, cured poly (S-MBCA), shows high glass transition temperature Tg of 315°C, outstanding thermal stability (T10% = 400°C), and good storage modulus (E′25°C = 3.8 GPa), which is competitive with commercial resins

Fully lignocellulose-based PET analogues for the circular economy

Polyethylene terephthalate is one of the most abundantly used polymers, but also a significant pollutant in oceans. Due to growing environmental concerns, polyethylene terephthalate alternatives are highly sought after. Here we present readily recyclable polyethylene terephthalate analogues, made entirely from woody biomass. Central to the concept is a two-step noble metal free catalytic sequence (Cu20-PMO catalyzed reductive catalytic fractionation and Raney Ni mediated catalytic funneling) that allows for obtaining a single aliphatic diol 4-(3-hydroxypropyl) cyclohexan-1-ol in high isolated yield (11.7 wt% on lignin basis), as well as other product streams that are converted to fuels, achieving a total carbon yield of 29.5%. The diol 4-(3-hydroxypropyl) cyclohexan-1-ol is co-polymerized with methyl esters of terephthalic acid and furan dicarboxylic acid, both of which can be derived from the cellulose residues, to obtain polyesters with competitive Mw and thermal properties (Tg of 70–90 °C). The polymers show excellent chemical recyclability in methanol and are thus promising candidates for the circular economy.</p

A combination of experimental and computational methods to study the reactions during a Lignin-First approach

AbstractCurrent pulping technologies only valorize the cellulosic fiber giving total yields from biomass below 50 %. Catalytic fractionation enables valorization of both cellulose, lignin, and, optionally, also the hemicellulose. The process consists of two operations occurring in one pot: (1) solvolysis to separate lignin and hemicellulose from cellulose, and (2) transition metal catalyzed reactions to depolymerize lignin and to stabilized monophenolic products. In this article, new insights into the roles of the solvolysis step as well as the operation of the transition metal catalyst are given. By separating the solvolysis and transition metal catalyzed hydrogen transfer reactions in space and time by applying a flow-through set-up, we have been able to study the solvolysis and transition metal catalyzed reactions separately. Interestingly, the solvolysis generates a high amount of monophenolic compounds by pealing off the end groups from the lignin polymer and the main role of the transition metal catalyst is to stabilize these monomers by transfer hydrogenation/hydrogenolysis reactions. The experimental data from the transition metal catalyzed transfer hydrogenation/hydrogenolysis reactions was supported by molecular dynamics simulations using ReaXFF

The Russian database of HIV antiretroviral drug resistance

The development of sequencing technologies and bioinformatic analysis made it possible to conduct molecular and epidemiological studies, in which nucleotide sequences of the human immunodeficiency virus (HIV) are used as information added to the patient profile. From a practical perspective, studies of prevalence of HIV drug resistance (HIVDR) are of the highest significance. To promote such studies, different countries use databases that serve as repositories of genetic and epidemiological information. The Russian HIVDR database (https://hivresist.ru/) was created in 2009. Nevertheless, it was characterized by limited applicability for a long time. Since 2021, after the regulatory documents had been revised and updated, the entry of HIVDR research results into the Russian HIVDR database has been mandatory. Therefore, the priority attention has been given to upgrading the database and improving its functional capabilities. Different methods have been developed to enter clinical, epidemiological and genetic data. At the time of this study, the Russian database HIVDR contained 10,626 unique records about patients and 13,126 nucleotide sequences deposited by 10 institutions. The following functions have been provided for data analysis: quality control of the epidemiological and clinical information about a patient, quality control of nucleotide sequences, contamination check, subtyping, detection of DR mutations, identification of viral tropism and generation of standardized reports. The efforts toward further development of the Russian HIVDR database will be focused on designing tools for detection and analysis of molecular clusters, adaptation to routine application for epidemiological surveillance of HIV infection

Stabilization strategies in biomass depolymerization using chemical functionalization

A central feature of most lignocellulosic-biomass-valorization strategies is the depolymerization of all its three major constituents: cellulose and hemicellulose to simple sugars, and lignin to phenolic monomers. However, reactive intermediates, generally resulting from dehydration reactions, can participate in undesirable condensation pathways during biomass deconstruction, which have posed fundamental challenges to commercial biomass valorization. Thus, new strategies specifically aim to suppress condensations of reactive intermediates, either avoiding their formation by functionalizing the native structure or intermediates or selectively transforming these intermediates into stable derivatives. These strategies have provided unforeseen upgrading pathways, products and process solutions. In this Review, we outline the molecular driving forces that shape the deconstruction landscape and describe the strategies for chemical functionalization. We then offer an outlook on further developments and the potential of these strategies to sustainably produce renewable-platform chemicals.Deconstructing plant-derived polymers into small molecules is necessary for biomass valorization but gives intermediates that undergo undesirable reactions. This Review describes how the intermediates can be converted into stable derivatives as renewable-platform chemicals

Pd/C-Catalyzed Hydrogenolysis of Dibenzodioxocin Lignin Model Compounds Using Silanes and Water as Hydrogen Source

A mild Pd/C-catalyzed hydrogenolysis of the C–O bond of model compounds representing the dibenzodioxocin motif in lignin using polymethylhydrosiloxane (PMHS) and water as hydrogen sources was developed. The efficiency of the reaction is highly dependent on both water concentration and the addition of a base. The results from mechanistic studies showed that the benzylic C–O bond is cleaved faster than the terminal C–O bond, which only cleaves upon the presence of the neighboring phenol. We propose a hydrogen bond formation between an oxygen atom of an ether group and a proton of a neighboring phenol under the employed mild reaction conditions, which facilitates cleavage of the C–O bond

Longitudinal variation in the ionosphere-plasmasphere system at the minimum of solar and geomagnetic activity: Investigation of temporal and latitudinal dependences

International audienceWe use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) as the first-principle calculation of the physical system state, the quick-run ionospheric electron density model (NeQuick) as the climatology background, and the International Reference Ionosphere-based Real-Time Assimilative Model for a global view of the ionospheric weather during a quiet period of the December 2009 solstice. The model computations are compared to the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation profiles, CHAMP and Gravity Recovery and Climate Experiment in situ densities, and GPS total electron content (TEC). It is shown that the plasma density in the ionosphere is generally larger in the American/Atlantic longitudinal sector at any local time. The high-latitude density enhancements are visible in the GSM TIP output at different altitudes but are not reproduced by the NeQuick empirical model. Given that observational data confirm an existence of the high-latitude areas where ionospheric densities are elevated in the altitude range between 300 and 480 km, we conclude that the NmF2 maximum in the GSM TIP output can be trusted. Indeed, such high-latitude NmF2, ionospheric electron content, and TEC maxima in the American longitude sector form on the proper places as shown by the GSM TIP data, COSMIC and GPS observations. According to our results, the high-latitude maximum of NmF2 (1) manifests itself only when the integration over LT or UT of the global maps for 22 December 2009 includes nighttime, i.e., supporting an argument of its close association with the Weddell Sea Anomaly, and (2) also appears in the Ne distribution at altitudes above the F2 peak

Efficacy of Mitochondrial Antioxidant Plastoquinonyl-decyl-triphenylphosphonium Bromide (SkQ1) in the Rat Model of Autoimmune Arthritis

Rheumatoid arthritis is one of the most common autoimmune diseases. Many antioxidants have been tested in arthritis, but their efficacy was, at best, marginal. In this study, a novel mitochondria-targeted antioxidant, plastoquinonyl-decyl-triphenylphosphonium bromide (SkQ1), was tested in vivo to prevent and cure experimental autoimmune arthritis. In conventional Wistar rats, SkQ1 completely prevented the development of clinical signs of arthritis if administered with food before induction. Further, SkQ1 significantly reduced the fraction of animals that developed clinical signs of arthritis and severity of pathological lesions if administration began immediately after induction of arthritis or at the onset of first symptoms (day 14 after induction). In specific pathogen-free Wistar rats, SkQ1 administered via gavage after induction of arthritis did not reduce the fraction of animals with arthritis but decreased the severity of lesions upon pathology examination in a dose-dependent manner. Efficacious doses of SkQ1 were in the range of 0.25–1.25 nmol/kg/day (0.13–0.7 μg/kg/day), which is much lower than doses commonly used for conventional antioxidants. SkQ1 promoted apoptosis of neutrophils in vitro, which may be one of the mechanisms underlying its pharmacological activity. Considering its low toxicity and the wide therapeutic window, SkQ1 may be a valuable additional therapy for rheumatoid arthritis