Carbonate Units Research Articles

Photoredox-Enabled Dearomative [2π + 2σ] Cycloaddition of Phenols.

Dearomative photocycloaddition of monocyclic arenes is an appealing strategy for comprehending the concept of "escape from flatland". This brings the replacement of readily available planar aromatic hydrocarbon units with a 3D fused bicyclic core with sp3-enriched carbon units. Herein, we outline an intermolecular approach for the dearomative photocycloaddition of phenols. In order to circumvent the ground-state aromaticity and to construct conformationally restrained building blocks, bicyclo[1.1.0]butanes were chosen as coupling partners. This dearomative approach renders straightforward access to a bicyclo[2.1.1]hexane unit fused to a cyclic enone moiety, which further contributed as a synthetic linchpin for postmodifications. Mechanistic experiment advocates for a plausible onset from both the reactants, depending on the redox potential.

Global practices in financing environmental investment-construction projects

Research on global practices in "green" financing has revealed that the most common approach is a mixed financing model, incorporating "green" financing (funds, certificates, carbon units’ sales), financial market resources, as well as contributions from the private and public sectors. Direct financing of projects aimed at reducing greenhouse gas emissions is one of the state’s roles. This can be accomplished through the allocation of public funds or the establishment of special funds for financing such projects. The state can also participate in creating favorable investment climate for "green" projects. Additionally, the state may be involved in developing and implementing standards and methodologies for the projects’ assessment and certification, as well as establishing a system for the registration and accounting of carbon units.

Перспективы углеродной нейтральности в сельском хозяйстве России по сценариям SSP: анализ на уровне страны и региона

Sustainable development and reduction of the carbon footprint is an important issue on the development agenda of the Russian national economy and, in particular, the agricultural sector. The study of long-term trajectories of development of the agricultural economy and the conditions for achieving carbon neutrality should take into account the expected climatic and socio-economic changes in the world, which are enshrined in a number of widely used scenarios – ‘Shared Socioeconomic Pathways’ (SSPs) and, as a rule, are based on the use of integral multi-sector models land use dynamics. The study is focused on obtaining projections of climate change and scenarios SSP1, SSP2 and SSP3 on the dynamics of crop production in Russia until 2050, with an emphasis on the development of a large agricultural region of Siberia – Altai Krai, in the context of analyzing the timing and conditions for achieving carbon neutrality. The GLOBIOM model, adapted for modeling at the level of Russian regions, was used as a toolkit. The results of scenario modeling made it possible to assess changes in the scale of production and cropland structure, greenhouse gas emissions in carbon units and the overall dynamics of the carbon footprint as well as expected consequences for Russian economy and harnessing the export potential of crops. It has been revealed that achieving carbon neutrality on the regional level (Altai Krai) is a challenge that requires a significant change in the structure of sown areas, the introduction of environmentally-oriented technologies and a significant increase in the productivity of agricultural land. The results contribute to deepening the understanding of regional economic management processes using the example of the Altai Kray and ways to achieve sustainable development goals, in particular achieving carbon neutrality in crop production. The practice of such research can be transferred to other regions of Russia

Copper-catalyzed synthesis of primary amides through reductive N-O cleavage of dioxazolones.

A new method for the synthesis of primary amides is developed, in which dioxazolones are treated with a copper catalyst under mild reaction conditions. A broad scope of dioxazolones is exhibited as well as dioxazolones containing biologically active structural motifs. These robust and mild reaction conditions allow the transformation of dioxazolones to primary amides, in which sensitive functional groups such as hydroxyl, aldehyde, trialkylsilyl, and unsaturated carbon units are tolerated with excellent chemoselectivity.

Лесоклиматические проекты как новый приоритет стратегического развития лесного комплекса региона

In the context of modifications in external demand for Russian forest products, it became necessary to search for new directions for the strategic development of the forest complex at the national and regional levels. The proposed government support measures are aimed at stimulating domestic demand for traditional forest products. At the same time, in the context of the intensification of the global climate agenda in Russia, the transition to a low-carbon economy based on the reduction of greenhouse gas emissions is emerging as a new strategic priority. The article examines the possibilities of implementing forest climate projects as a new promising direction for the development of the forest complex in multi-forest regions, which include the territories of the Russian Far East. A methodological approach has been developed and an assessment has been made of the possible implementation of a forest climate project on reforestation in the Khabarovsk Territory, including the calculation of the possible volume of carbon absorption when planting various tree species, the number of carbon units for sale on the carbon market, potential income for the investor and the budget from this activity. It is shown that the implementation of the forest climate project provides both commercial and public effects

Hemp (cannabis sativa l.) Is an effective carbon-depositing crop

The article presents the results of a quantitative assessment of carbon deposition by sowing hemp (Cannabis sativa L.). Field studies were conducted in Khabibrakhmanov Peasant Farm Enterprise (Republic of Bashkortostan), the carbon content in plant biomass was determined by the CN 802 analyzer. It was found that cannabis crops form 7.87 t/ha aboveground biomass at the end of the growing season, including stems – 6.40 t/ha (81.3% of the aboveground mass), inflorescences – 0.77 t/ha (9.8% of the aboveground mass), seeds - 0.70 t/ha (8.9% of the aboveground mass), and roots - 1.02 t/ha. Of the total biomass, 8.19 t/ha is preserved. Sowing captures a relatively large amount of carbon dioxide from the atmosphere (14.78 t/ha) and, accordingly, carbon (4.03 t/ha). The effectiveness of cannabis in terms of decarbonization mainly consists in the conservation of a significant amount of accumulated carbon (91%) for a long time into long-term products and into the soil. The cultivation of hemp in carbon farms is recommended to reduce the carbon footprint and sell carbon units.

Sports Tournament Design as a Source of Economic Impact (Through the Example of Russian Premier League)

In today's restricted environment, sport continues to face a lack of funding and to be perceived as an industry that can survive without support. Meanwhile, numerous studies have proven that sport is not about significant investments only, but also creates an economic impact. The aim of this work is to consider such a specific driver of economic impact as tournament design and evaluate the corresponding impact through the example of the Russian Premier League (RPL). The research hypothesis states that changing the design of the RPL tournament will lead to an increase in the total revenue of participating teams, in consumption in the host cities and a reduction in greenhouse gas emissions, which together will lay the foundation for an economic impact at the country level and for individual regions. The paper examines three reform scenarios, which differ in the assumptions made. The authors have developed a calculation model that quantifies the economic impact of these reforms. The main triggers are the attendance at RPL matches and its derivatives (the number of away fans, the distance traveled by away fans), as well as monetary metrics: ticket & travel costs, carbon unit costs. The impact is calculated as the difference between the results achieved in the current tournament design and in potential scenarios. The study showed that the current RPL design has significant potential for economic impact. Thus, the implementation of the Optimum scenario, which does not require additional calendar reserves, will create a positive economic impact in the amount of 479 million rubles. With additional calendar opportunities and implementing the “Maximum” scenario, the effect will be 932 million rubles. This study may be useful for managers of sports competitions, heads of regional and municipal authorities, as well as sports leagues and federations.

A mitochondrial-targeted activity-based sensing probe for ratiometric imaging of formaldehyde reveals key regulators of the mitochondrial one-carbon pool.

Formaldehyde (FA) is both a highly reactive environmental genotoxin and an endogenously produced metabolite that functions as a signaling molecule and one-carbon (1C) store to regulate 1C metabolism and epigenetics in the cell. Owing to its signal-stress duality, cells have evolved multiple clearance mechanisms to maintain FA homeostasis, acting to avoid the established genotoxicity of FA while also redirecting FA-derived carbon units into the biosynthesis of essential nucleobases and amino acids. The highly compartmentalized nature of FA exposure, production, and regulation motivates the development of chemical tools that enable monitoring of transient FA fluxes with subcellular resolution. Here we report a mitochondrial-targeted, activity-based sensing probe for ratiometric FA detection, MitoRFAP-2, and apply this reagent to monitor endogenous mitochondrial sources and sinks of this 1C unit. We establish the utility of subcellular localization by showing that MitoRFAP-2 is sensitive enough to detect changes in mitochondrial FA pools with genetic and pharmacological modulation of enzymes involved in 1C and amino acid metabolism, including the pervasive, less active genetic mutant aldehyde dehydrogenase 2*2 (ALDH2*2), where previous, non-targeted versions of FA sensors are not. Finally, we used MitoRFAP-2 to comparatively profile basal levels of FA across a panel of breast cancer cell lines, finding that FA-dependent fluorescence correlates with expression levels of enzymes involved in 1C metabolism. By showcasing the ability of MitoRFAP-2 to identify new information on mitochondrial FA homeostasis, this work provides a starting point for the design of a broader range of chemical probes for detecting physiologically important aldehydes with subcellular resolution and a useful reagent for further studies of 1C biology.

A main chain biodegradable polyurethane with anti-protein adsorption and anti-bacterial adhesion performances.

Biofilms are initially formed by substances such as proteins secreted by bacteria adhering to a surface. To achieve a durable antibacterial material, biodegradable dihydroxyl-terminated poly[(ethylene oxide)-co-(ethylene carbonate)] (PEOC(OH)2) with anti-protein adsorption properties was synthesized in this study. Further polycondensation of PEOC(OH)2 and isophorone diisocyanate (IPDI) led to biodegradable polyurethane (PEOC-PU) with PEOC as the soft segment. For comparison, polyurethanes with polyethylene glycol (PEG-PU) and polypropylene glycol (PPG-PU) as soft segments were also synthesized. The chemical structures of the polyurethanes were characterized by 1H NMR and FTIR. The biodegradation behavior of PEOC-PU promoted by lipase due to the presence of ethylene carbonate units was also studied. Their resistance to proteins was studied using quartz crystal microbalance with dissipation (QCM-D) and the results revealed that PEOC-PU exhibited excellent nonspecific resistance to proteins. The colonization of microorganisms on PU in the liquid culture medium was further examined and the results showed that PEOC-PU exhibited excellent antibacterial adhesion performance due to its protein resistance and biodegradation.

OVERGROWN AGRICULTURAL LANDS AS A POTENTIAL FOR NATURAL DECARBONIZATION OF OIL AND GAS FIELDS

In the north-western part of the Republic of Bashkortostan there are a large number of oil and gas fields, which are located on abandoned agricultural lands. Taking into account the increased level of impact on forest phytocenoses of natural and artificial origin in this zone, it becomes necessary to study the volume of carbon uptake by woody vegetation. To fulfill this goal, the tasks of carrying out an inventory of overgrown agricultural lands, entering coordinates of the boundaries of oil and gas fields into geoinformation projects and applying the results of digitization of overgrown agricultural lands to the boundaries of oil and gas fields are set. The study covers 18 municipal districts: Askinsky, Bakalinsky, Baltachevsky, Belebeyevsky, Bizhbulyaksky, Blagoveshchensky, Buraevsky, Dyurtyulinsky, Ilishevsky, Kaltasinsky, Karaidelsky, Krasnokamsky, Kushnarenkovsky, Mishkinsky, Tatyshlinsky, Tuymazinsky. Sharansky, Yanaulsky. The Q-GIS program defines the areas of overgrown areas. According to satellite images, 4 stages of overgrowth have been identified: the fourth (the age of trees is 20 years or more), the third (the age of trees is about 15 years), the second (the age of trees is about 10 years) and the first (the age of trees is up to 5 years). The main breeds that ensure overgrowth are pine and birch. The results of the study demonstrate an increase from 1985 to 2022 for the forest area by 20.41% for the north of the Republic of Bashkortostan. Calculation of accumulated carbon with subsequent conversion into carbon units and assessment of their value showed that at the moment the stand of overgrown agricultural land has already accumulated about 182 thousand tons of carbon units. About 135 thousand tons of carbon units are deposited annually. The high dynamics of carbon accumulation by woody vegetation allows us to assume with a high degree of probability that agricultural lands overgrown with forest, when implementing certain forestry measures, can be the basis for the implementation of costeffective climate projects for both owners of licensed plots and other interested parties. According to the results of our work, the use of the Severo-Kushkul and Mishidinsky license areas of oil and gas fields is promising for forest-climatic projects.

The Oko Limestones: a Late Miocene-Pliocene fluvial to palustrine-lacustrine carbonate wetland enclosed in the South Pyrenean Thrust Front (Navarre, Spain)

This work presents the sedimentological study of the Upper Miocene-Pliocene Oko Limestones, exposed in the Antzin-Murieta Basin, in Navarre. Two stratigraphic sections of the carbonate unit have been studied: the Oko cemetery and Ega road sections. The former exposes facies that characterize a fluvial carbonate environment, with a distinct development of microbial oncolitic deposits. The coeval deposits exposed in the Ega road section, instead, largely represent a palustrine-lacustrine setting that evolved under alternating conditions of ponding and desiccation. Data integration from these sections and the intermediate areas, allows the interpretation of a fluvial to palustrine-lacustrine wetland with a marked east-southeast trend, which developed coevally to the uplift of the Piedramillera thrust sheet.

Economic effect of carbon storage due to forest management intensification: analysis and forecast for the Republic of Karelia

Objective: to assess the economic potential of carbon storage for a group of companies in the Republic of Karelia in the context of intensive forest management.Methods: SWOT analysis; assessment of a forest management project according to the VM10 international methodology, Verified Carbon Standard 2016 and forecast of revenues from selling carbon units.Results: the potential of Russian forest management in the context of the Paris Agreement is not disputed, but the assessment of the economic potential of carbon storage of individual economic entities at the moment remains open for discussion. The study estimates the effect of selling carbon units from forest management intensification projects, taking into account the maximum lease term for the area of 2.25 million hectares. This effect can reach an average of 23 million rubles per year from 2023 to 2034 and an average of 42 million rubles per year from 2023 to 2050, excluding the capital costs of logging and preparation, validation, verification and registration of the climate project, and field observations to ensure monitoring. The study proves that long-term investments in forest management intensification and a longer period of the climate project can lead to higher income per hectare from selling carbon units.Scientific novelty: it consists in the economic evaluation of regulatory restrictions on the price of carbon unit for forest climate projects, taking into account the maximum lease term stipulated by national legislation. The obtained results substantiate the economic challenges associated with the current regulations and provide information on the variability of project efficiency depending on the selected term of its implementation.Practical significance: the main results of the research can be used in the practical activity of economic entities, as well as by the bodies forming the policy of forest management.

Article Review/ The Tectonic Evolution of Erbil Area (Ne Iraq) as a Part of the Northeastern Margin of the Arabian-Nubian Plate Throughout Albian-Early Eocene

The Albian-Early Eocene tectonic evolution of the Zagros Foreland Basin of the High Folded Zone in the Iraqi Kurdistan region has been studied based on the recent foreland basin system concept. This study showed that during the cretaceous (Albian – Cenomanian) there was a geodynamic shift from a passive margin to a foreland basin system phase, not to an active margin phase as mentioned in the previous studies. The advance of the continental margin of the Arabian-Nubian Plate (ANP) toward the subduction zone imposed a tectonic load leading to the form of a flexural wave. The consequences of the last tectonic event were reflected by the continuous deposition of the Balambo Formation. in a foredeep depozone. This happened concomitantly with a flexural emergence of the continental shelf further to the west forming a forebulge depozone represented by the deposition of reefal facies of the Qamchuqa Formation. These geodynamic changes are considered here to represent the Megasequence boundary between the Tectonic Megasequence (TMS) of AP8 and AP9. The last sequence of the passive margin was the Qamchuqa Formation Which is called the Pre-Orogenic Carbonate Platform and was separated from the Bekhme Formation by regional unconformity (Megasequence boundary). The latter is represented by the Lower Sequence of the foreland basin system, which is called the Syn-Orogenic Carbonate Platform (SCP). During the Middle Campanian, the Zagros foreland basin started with the underfilled stage, and it was entirely clear by the end of the Cretaceous comprising a broad threefold subdivision of depositional realms that translated into three stratigraphic units known as trinity underfilled units of foreland basin system. The lower carbonate unit, the pelagic and hemipelagic unit, and the upper flysch clastic unit are represented by Bekhme, Shiranish, and Tanjero Formations respectively. All of these units were superimposed during basin depocenter migration and became younger toward the southwest in front of progressing the orogenic wedge toward the Arabian Craton. During the late Maastrichtian to Paleocene – Early Eocene, the Zagros foreland basin underwent a transition from underfill to fill the stage. Deep exhumation of the orogenic wedge and ophiolite assemblage had supplied the clastic sediment of the Kolosh Formation into the basin covering the foredeep and most of the forebulge and backbulge depozones.

Sequence design in terpolymerization of ε-caprolactone, CO2 and cyclohexane oxide: Random ester-carbonate distributions lead to large-span tunability

It is of great interest to make a degradable material widely tailorable to replace petroleum-derived products among diverse applications. Here, we report the construction of a new multi-purpose degradable material for the first time via a simple ternary copolymerization system comprising ε-caprolactone (ε-CL), cyclohexane oxide (CHO) and CO2. Under low pressure of 1 bar ∼5 bar, the ring-opening polymerization (ROP) of ε-CL and ring-opening copolymerization (ROCOP) of CO2 and CHO can simultaneously proceed. The carbonate units are randomly distributed on the polymer chain. These random terpolymers have controllable molar mass (10–106 kDa) and compositions (4–33 mol% CO2). And the obtained materials show large-span tunability from tough plastic to elastomer and even adhesive.

Negative δ13Ccarb excursions within early part of the Lomagundi event recorded in the Paleoproterozoic sedimentary carbonates, Aravalli Supergroup, Rajasthan India: Chemostratigraphy and basin evolution

High resolution stable isotopic (C and O) and geochemical studies of Paleoproterozoic carbonates were carried out in the Umra sub-basin of the Aravalli Supergroup, Rajasthan, India. All the sections, Umra-Dedkiya (UM), Umra-Jampa (BD), and Matoon (MU and GU), have yielded characteristic Lomagundi type positive values, with δ13Ccarb > 4 ‰ VPDB (maximum up to 6.86 ‰). Samples of two sections (UM and BD) have also yielded several distinct negative δ13Ccarb values (up to −6.14 ‰ VPDB). Geochemical validation of trace element and REE data indicate both these types of excursions to be of pristine character, with no signature of organic-remineralisation or hypersaline depositional condition. Mineralogical assemblages lack hypersalinity indicator minerals, such as Na-tourmaline, Na-Albite or scapolite, in the positive δ13C bearing carbonate samples. This supports the inference regarding the observed positive δ13C excursions mimicking the global Paleoproterozoic Lomagundi event. Chemostratigraphic correlation within the basin and with one of the global strato-type Paleoproterozoic carbonate unit from Paso Severino Formation, Uruguay, indicate interruptions in the initial part of the Lomagundi episode marked by several negative δ13C excursion events before achieving a stable positive δ13C character. This phenomenon is also evident from variation in paleoproductivity proxies, such as TOC, TN, Ba and P values, consistent with δ13C fluctuations. Mathematical model calculations have corroborated such a conclusion. All these observations motivated us to present a modified version of the global Paleoproterozoic δ13Ccarb curve and a six stage basin evolution model to explain the evolution of δ13C vis-à-vis variation in atmospheric oxygen.

Universal high-performance bulk graphites from natural flake graphite by rapid sintering

High performance graphites (HPGs) are a key material in modem industries; however, prevailing HPGs are short of comprehensive properties in many aspects, i.e., a specific property of HPGs is always achieved at the cost of other properties. And the production of HPGs is highly costly and causes severe environmental problems. Current HPGs are derived from various carbonaceous precursors, excluding nature flake graphite (NFG), the best graphite source. Typically, NFG-based bulk graphite has poor mechanical properties because NFG is difficult to sinter. Here we report the preparation and comprehensive properties of a new family of universal HPGs (U-HPGs) that can be mass-produced with moderate conditions by sintering NFG slightly mixed with diamond, where units of onion carbon (OC) with NFG (OC@NFG) act as building blocks. OC@NFG creates a strong interfacial network between the NFGs, giving the U-HPGs outstanding strength and moderate hardness. With U-HPGs being more than 93 % graphitization, the flexural strength exceeds 100 MPa, far superior to mainstream commercial graphites. OC@NFG also bestows U-HPGs with excellent thermal conductivity(＞125 W m−1 K−1 at room temperature). For such structure provides a 3D path for electrons inside U-HPGs, the as-produced material has significant electronical conductivity. This work presents new insights into this old yet important material and allows for innovative design of HPGs for various applications.

Carboniferous-Permian sequences of the western margin of Sibumasu Block: Implications for new lithostratigraphic correlation in the eastern Highlands of Myanmar

The Eastern Highlands of Myanmar are characterized by Precambrian to Mesozoic rock formations, with Carboniferous-Permian sequences prominently present in the Shan Scarp and Shan Plateau zones. These sequences are particularly concentrated in the western margin of the Sibumasu Block. Although Permian sequences are abundant in this region, they are complicated by geological faults. Consequently, a lithostratigraphic study was conducted to establish correlations across an extensive area spanning 1200 km from Mandalay City in the north to Kawthaung City in the south and 250 km wide, bordered by the Sagaing Fault to the west and Inle Lake to the east. The Permian sequences can be categorized into lower siliciclastic units and upper carbonate units. These siliciclastic units encompass the Mergui Group, locally referred to as the Lebyin Group, Mawchi Series, Taungnyo Group, and Mergui Group, as well as the Yinyaw Formation. Additionally, there is a carbonate unit known as the Moulmein Formation in the Thaton, Hpa-an, and Mawlamyine areas, and the Tenasserim Formation in the Myeik and Bokepyin areas within the Shan Scarp zone. In the late Lower Permian sequences, the Mwedaw Beds are exclusively found in the Linwe area. However, the Thitsipin Formation, which is an equivalent of the Moulmein Formation, and the Nwabangyi Formation are also exposed in the Shan Plateau zone. Lower Carboniferous sequences, such as the Loikaw Beds, are sporadically visible in the Loikaw area but are overlain by the Thitsipin Formation. This study elucidates the presence of a diamictite unit (Mergui Group) and its associated units (Yinyaw and Thitsipin/Moulmein Formations) in the geo-structurally complex zones of the Shan Plateau and Shan Scarp through lateral lithostratigraphic correlation, shedding light on the Carboniferous-Permian period at the western margin of the Sibumasu Block.

Photocatalytic conversion of cellulose into C5 oligosaccharides

Cellulose is made up of linear polymers of glucose monomers that could be a crucial source for valuable chemicals and sustainable liquid fuels. Cellulose is however, very stable and its conversion to a useful fuel or platform chemical products remains a significant challenge (Kimura et al 2015 Sci. Rep. 5 16266; Xia et al 2016 Nat. Commun. 7 11162). Photocatalysis is a versatile technology which has demonstrated potential for solar driven processes such as water splitting or solar fuels production and has also been applied to the degradation of pollutants in air and water and for the production of useful products from biomass. Here, we focus on the products that are produced from cellulose (a glucose (C6) based polymer) photocatalysis that compliment hydrogen production. Probing the initial steps via UV-TiO2 photocatalysis, we remarkably find that an array of oligosaccharides containing only five (C5) carbon units is initially produced. As the process continues, C6 oligo oligosaccharides grow to dominate. The photocatalytic process is generally not viewed as a controllable synthetic process; however, these findings show, on the contrary that photocatalysis at semiconductor surfaces can achieve novel reaction pathways yielding new products.

An IGDT-based a low-carbon dispatch strategy of urban integrated energy system considering intermittent features of renewable energy

The current global energy crisis has prompted a significant rise in the use of low carbon units, making it a crucial research trend in the field of urban energy system, especially in terms of addressing the intermittency of renewable energy generation. This study proposes an integrated energy system planning model (UIES) for urban areas. In addition, to tackle the issue of carbon emissions, a reward and punishment ladder-type carbon transaction model is presented, which aims to control the level of carbon emissions within urban areas. To evaluate the performance of the UIES model, the authors develop an objective function that integrates the sum of equipment operation and maintenance costs, equipment daily acquisition costs, purchased energy costs, carbon trading costs, and integrated demand response (IDR) costs. The stochastic features of renewable energy sources are taken into account in the proposed approach, and an information gap decision theory (IGDT) based strategy is designed to quantify the uncertainty interval and intermittent fluctuations associated with renewable energy. This approach also aims to mitigate any negative effects and variations that may occur during the urban energy system's IDR process. Finally, the simulation tests to demonstrate that the average decrease in operating cost of both models based on IGDT strategy are 7.36 %, and the peak of electrical (EL), heating (HL) and cooling load (CL) are reduced by 20.45 %, 12.38 % and 5.02 % respectively. in conclusion, the energy service providers in urban areas can effectively manage renewable energy fluctuations by independently adjusting the operation sequence of equipment, and the economy and stability of the UIES can be effectively improved by the proposed dispatch strategy.

Chemical Expansion of the Methyltransferase Reaction: Tools for DNA Labeling and Epigenome Analysis.

DNA is the genetic matter of life composed of four major nucleotides which can be further furnished with biologically important covalent modifications. Among the variety of enzymes involved in DNA metabolism, AdoMet-dependent methyltransferases (MTases) combine the recognition of specific sequences and covalent methylation of a target nucleotide. The naturally transferred methyl groups play important roles in biological signaling, but they are poor physical reporters and largely resistant to chemical derivatization. Therefore, an obvious strategy to unlock the practical utility of the methyltransferase reactions is to enable the transfer of "prederivatized" (extended) versions of the methyl group.However, previous enzymatic studies of extended AdoMet analogs indicated that the transalkylation reactions are drastically impaired as the size of the carbon chain increases. In collaborative efforts, we proposed that, akin to enhanced SN2 reactivity of allylic and propargylic systems, addition of a π orbital next to the transferable carbon atom might confer the needed activation of the reaction. Indeed, we found that MTase-catalyzed transalkylations of DNA with cofactors containing a double or a triple C-C bond in the β position occurred in a robust and sequence-specific manner. Altogether, this breakthrough approach named mTAG (methyltransferase-directed transfer of activated groups) has proven instrumental for targeted labeling of DNA and other types of biomolecules (using appropriate MTases) including RNA and proteins.Our further work focused on the propargylic cofactors and their reactions with DNA cytosine-5 MTases, a class of MTases common for both prokaryotes and eukaryotes. Here, we learned that the 4-X-but-2-yn-1-yl (X = polar group) cofactors suffered from a rapid loss of activity in aqueous buffers due to susceptibility of the triple bond to hydration. This problem was remedied by synthetically increasing the separation between X and the triple bond from one to three carbon units (6-X-hex-2-ynyl cofactors). To further optimize the transfer of the bulkier groups, we performed structure-guided engineering of the MTase cofactor pocket. Alanine replacements of two conserved residues conferred substantial improvements of the transalkylation activity with M.HhaI and three other engineered bacterial C5-MTases. Of particular interest were CpG-specific DNA MTases (M.SssI), which proved valuable tools for studies of mammalian methylomes and chemical probing of DNA function.Inspired by the successful repurposing of bacterial enzymes, we turned to more complex mammalian C5-MTases (Dnmt1, Dnmt3A, and Dnmt3B) and asked if they could ultimately lead to mTAG labeling inside mammalian cells. Our efforts to engineer mouse Dnmt1 produced a variant (Dnmt1*) that enabled efficient Dnmt1-directed deposition of 6-azide-hexynyl groups on DNA in vitro. CRISPR-Cas9 editing of the corresponding codons in the genomic Dnmt1 alleles established endogenous expression of Dnmt1* in mouse embryonic stem cells. To circumvent the poor cellular uptake of AdoMet and its analogs, we elaborated their efficient internalization by electroporation, which has finally enabled selective catalysis-dependent azide tagging of natural Dnmt1 targets in live mammalian cells. The deposited chemical groups were then exploited as "click" handles for reading adjoining sequences and precise genomic mapping of the methylation sites. These findings offer unprecedented inroads into studies of DNA methylation in a wide range of eukaryotic model systems.