Characterization of a highly Al3+‐selective fluorescence probe based on naphthalimide‐Schiff base and its application to practical water samples

A new fluorescent Al³⁺‐probe, N‐allyl‐4‐[3,3′‐((2‐aminoethyl)azanediyl)‐bis(N´‐(2‐hydroxybenzylidene)propanehy‐drazide)]‐1,8‐naphthalimide ( L ), was designed and synthesized based on 1,8‐naphthalimide. The probe L contains 1,8‐naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. The structure of L was determined by single crystal X‐ray. L emission at 526 nm increased on addition of Al³⁺ under excitation wavelength at 350 nm. L exhibited high selectivity and sensitivity fluorescence emission towards to Al³⁺ in ethanol/Tris–HCl buffer solution (1:1, v/v, pH = 7.2) as compared with other tested metal ions. A good linearity with a correlation coefficient (R²) of 0.99 was observed in the concentration range 2–10 μM. The binding constant and the detection limit of L for Al³⁺ were calculated to 2.6 × 10⁴ M^?1 and 0.34 μM, respectively. The results of experiments that including Job plot, ultraviolet–visible (UV–Vis) light titration, fluorescence titration, ESI‐MS and ¹H NMR titration, indicated a 1:1 stoichiometric complex between L and Al³⁺. L was highly effective in monitoring Al³⁺ in real‐life Yellow River and tap water samples.     

IL‐17 is Involved in Helicobacter pylori‐Induced Gastric Inflammatory Responses in a Mouse Model

Background: Helicobacter pylori (H. pylori) is the major cause of chronic active gastritis and peptic ulcer disease. Recent studies have shown that H. pylori produces various cytokines that are related to neutrophil or mononuclear cell accumulation. Interleukin‐17 (IL‐17) is the founding member of an emerging family of inflammatory cytokines whose biological activities remain incompletely defined. In this study, the contributions of IL‐17 to the induction of gastric inflammation and to the protection from H. pylori infection were investigated using IL‐17 gene‐knockout (IL‐17^?/–) mice. Materials and Methods: IL‐17^?/–and wild‐type C57BL/6 mice were challenged with H. pylori CPY2052 (2 × 10⁸ CFU/mL) and the histological and microbiological evaluation were carried out at specified times. IL‐17 and myeloperoxidase (MPO) protein levels in tissues were assayed in duplicate using ELISA kits. Results: In wild‐type mice, IL‐17 was undetected at baseline; however, the protein expression of IL‐17 was induced after infection with H. pylori. A severe infiltration of neutrophils appeared in the submucosa and the lamina propria in wild‐type mice. In contrast, the degree of neutrophil infiltration in IL‐17^?/– mice was significantly lower than that in wild‐type mice. Although wild‐type mice infected with H. pylori showed drastically higher MPO activity compared with uninfected wild‐type mice, any significant increase in the enzyme activity was not revealed in infected IL‐17^?/– mice. The number of H. pylori colonized in the stomach of IL‐17^?/– mice was significantly lower than that of wild‐type mice from 1 to 6 months after infection. Conclusions: These results suggest that IL‐17 may play an important role in the inflammatory response to the H. pylori infection and ultimately influence the outcome of the H. pylori‐associated disease.     

Luminescent properties of 4‐aminobenzo‐15‐crown‐5 after preferential binding of ferric ions in aqueous solutions

We report a combined approach that introduces the use of 4‐aminobenzo‐15‐crown‐5 (4AB15C5) for the detection of ferric(III) ions by colorimetric, ultraviolet (UV)–visible light absorption, fluorescence, and live‐cell imaging techniques along with density functional theory (DFT) calculations. We have found that 4AB15C5 is sensitive and selective for binding ferric(III) ions in aqueous solutions. DFT calculations using the polarizable continuum model have been used to explain the strong binding of the ferric ion by 4AB15C5 in aqueous solutions. The detection limit in the fluorescence quenching measurements was found to be as low as 50 μM for the ferric ion with a determined Stern–Volmer constant of 1.52 × 10⁴ M^?1. Fluorescence intensity did not change for other ions tested, Fe²⁺, Co²⁺, Mn²⁺, Mg²⁺, Zn²⁺, Ca²⁺, NH₄⁺, Na⁺, and K⁺ ions. Live‐cell fluorescence imaging was also used to check the intracellular variations in ferric ion levels. Our spectroscopic data indicated that 4AB15C5 can bind ferric ions selectively in aqueous solutions.     

Properties,theoretical study and crystal structure of 3‐benzothiazole‐9‐ethyl carbazole

The title compound of 3‐benzothiazole‐9‐ethyl carbazole was synthesized by the reaction of 3‐aldehyde‐9‐ethyl carbazole and 2‐aminothiophenol. The compound was characterized by ¹H nuclear magnetic resonance (NMR) and mass spectrometry (MS). Its crystal structure was obtained and determined by single crystal X‐ray diffraction. The results showed that the crystal belongs to the orthorhombic crystal system and the cell parameters of space group P2(1)2(1)2(1) were a = 5.6626 (12) Å, b = 12.606 (3) Å, c = 22.639 (5) Å, α = 90°, β = 90°, γ = 90°, V = 1616.0 (6) ų, Z = 4, Dc = 1.350 mg/m³. The UV–vis and fluorescence spectra were also studied preliminarily. The fluorescence spectra of the title compound with bovine serum albumin (BSA) showed that BSA could be marked with the compound and the stability constant between them was 0.82 × 10⁷ M^?1. Meanwhile, the crystal and molecule were theoretically surveyed by density functional tight‐binding (DFTB). The results showed that there was an orbital overlap for lowest unoccupied molecular orbital (LUMO) between the neighbouring molecules for the crystal, which is different from the molecule structure. It was also showed that the crystal structure is a non‐conductor. Copyright © 2016 John Wiley & Sons, Ltd.     

Mapping of O‐linked β‐N‐acetylglucosamine modification sites in key contractile proteins of rat skeletal muscle

O‐linked β‐N‐acetylglucosamine (O‐GlcNAc) is a widespread modification of serine/threonine residues of nucleocytoplasmic proteins. Recently, several key contractile proteins in rat skeletal muscle (i.e., myosin heavy and light chains and actin) were identified as O‐GlcNAc modified. Moreover, it was demonstrated that O‐GlcNAc moieties involved in contractile protein interactions could modulate Ca²⁺ activation parameters of contraction. In order to better understand how O‐GlcNAc can modulate the contractile activity of muscle fibers, we decided to identify the sites of O‐GlcNAc modification in purified contractile protein homogenates. Using an MS‐based method that relies on mild β‐elimination followed by Michael addition of DTT (BEMAD), we determined the localization of one O‐GlcNAc site in the subdomain four of actin and four O‐GlcNAc sites in the light meromyosin region of myosin heavy chains (MHC). According to previous reports concerning the role of these regions, our data suggest that O‐GlcNAc sites might modulate the actin–tropomyosin interaction, and be involved in MHC polymerization or interactions between MHC and other contractile proteins. Thus, the results suggest that this PTM might be involved in protein–protein interactions but could also modulate the contractile properties of skeletal muscle.     

Effect of short‐term (0–72 h) fasting on serum biochemical characteristics in rainbow trout Oncorhynchus mykiss

An experiment was carried out to investigate the effects of short‐term fasting periods on the serum biochemical characteristics of rainbow trout, Oncorhynchus mykiss. For this purpose, fish were fasted 0, 6, 12, 24, 48 and 72 h before blood sampling. Thereafter the serum levels of thyroxine (T₄), 3,5,3′‐triiodothyronine (T₃), cortisol, glucose, lactate, triglyceride, cholesterol, total protein, albumin, globulin and albumin : globulin ration (A : G) were determined. Results show that serum levels of T₄ (4.60–8.77 ng ml^?1), T₃ (7.50–13.3 ng ml^?1), cortisol (7.91–24.5 ng ml^?1), glucose (18.5–80.1 mg dl^?1), lactate (12.7–29.6 mg dl^?1), triglyceride (171–500 mg dl^?1), and cholesterol (321–535 mg dl^?1) were significantly affected by the fasting period. However, there were no significant changes in serum total protein (3.03–3.68 g dl^?1), albumin (1.78–2.01 g dl^?1), globulin (1.15–1.70 g dl^?1) or A : G (1.13–1.93) among the fish fasted 0–72 h. Results clearly show the importance of a fasting period on the serum biochemical properties of rainbow trout. According to the results, 24 h fasting is suggested as a pre‐sampling fasting period in rainbow trout to measure serum levels of T₄, T₃, cortisol, glucose, lactate, triglyceride, and cholesterol. Potential mechanisms related to the changes in biochemical properties are discussed.     

Resonance light‐scattering enhancement effect of the protein–Y3+–TTA–SLS system and its analytical application

In this paper, a sensitive resonance light scattering (RLS) method for the determination of protein is reported. In the Tris–HCl (pH 7.50) buffer, protein enhanced the RLS intensity of the Y³⁺–2‐thenoyltrifluoroacetone (TTA)–sodium dodecyl sulphate (SLS) system. The enhanced RLS intensities were in proportion to the concentrations of proteins in the range 8.0 × 10^?9–1.0 × 10^?5 g/mL for BSA, 1.0 × 10^–8–1.0 × 10^?5 g/mL for HSA and 1.0 × 10^–8–1.0 × 10^?6 g/mL for EA, and their detection limits were 5.0, 5.4 and 6.7 ng/mL, respectively. Actual samples were satisfactorily determined. The interaction mechanism was also studied. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of genistein on β‐catenin signaling and subcellular distribution of actin‐binding proteins in human umbilical CD105‐positive stromal cells

This study was performed to define the roles of actin‐binding proteins in the regulation of actin filament assembly associated with cellular signal transduction pathways in stromal cell proliferation. Genistein, a tyrosine protein kinase inhibitor, decreased the intracellular Ca²⁺ and attenuated cell proliferation and DNA synthesis through the β‐catenin and cyclin D1 pathway in human umbilical CD105‐positive cells. Immunoprecipitation studies using anti‐β‐actin antibody revealed that several actin‐binding proteins implicated in cells include formin‐2 (FMN‐2), caldesmon (CaD), tropomyosin (Tm), and profilin. Protein levels of these proteins in whole cell lysates were not significantly changed by genistein. Three Tm isoforms, Tm‐1, Tm‐2, and Tm‐4, were found to be present in cells. Genistein caused a reduction in levels of mRNAs coding for Tm‐1 and Tm‐4, but had no significant effect on Tm‐2 mRNA levels. Immunofluorescence confocal scanning microscopy indicated that changes in the subcellular distribution of Tm and CaD, in which the diffuse cytosolic staining was shifted to show colocalization with actin stress fibers. In contrast, genistein‐induced accumulation of FMN‐2 and profilin in the peri‐nuclear area. Silencing of FMN‐2 by small interfering RNA resulted in increases of intracellular Ca²⁺ and rendered genistein resistance in decreasing intracellular Ca²⁺ in cells. These results provide the novel findings that genistein acts by modulating the cellular distribution of actin‐binding proteins in association with alterations of cellular signal transduction pathways in human stromal cell proliferation. J. Cell. Physiol. 223: 423–434, 2010. © 2010 Wiley‐Liss, Inc.     

Luminescent thermometer based on Eu3+/Tb3+‐organic‐functionalized mesoporous silica

In this work we investigate a mesoporous silica (MS) decorated with dipyridyl‐pyridazine (dppz) ligands and further grafted with a mixture of Eu³⁺/Tb³⁺ ions (28.45%:71.55%), which was investigated as a potential thermometer in the 10–360 K temperature range. The MS material was prepared employing a hetero Diels–Alder reaction: 3,6‐di(2‐pyridyl)‐1,2,4,5‐tetrazine was reacted with the double bonds of vinyl‐silica (vSilica) followed by an oxidation procedure. We explore using the dppz‐vSilica material to obtain visible emitting luminescent materials and for obtaining a luminescent thermometer when grafted with Eu³⁺/Tb³⁺ ions. For the dppz‐vSilica@Eu,Tb material absolute sensitivity S_a of 0.011 K^?1 (210 K) and relative sensitivity S_r of 1.32 %K^?1 (260 K) were calculated showing good sensing capability of the material. Upon temperature change from 10 K to 360 K the emission color of the material changed gradually from yellow to red.     

Synthesis and DNA‐binding study of imidazole linked thiazolidinone derivatives

A novel series of imidazole‐linked thiazolidinone hybrid molecules were designed and synthesized through a feasible synthetic protocol. The molecules were characterized with Fourier transform infrared (FT‐IR), ¹H nuclear magnetic resonance (NMR), ¹³C NMR and high‐resolution mass spectrometry (HRMS) techniques. In vitro susceptibility tests against Gram‐positive (S. aureus and B. subtilis ) and Gram‐negative bacteria (E. coli and P. aeruginosa ) gave highly promising results. The most active molecule (3e) gave a minimal inhibitory concentration (MIC) value of 3.125 μg/mL which is on par with the reference drug streptomycin. Structure–activity relationships revealed activity enhancement by nitro and chloro groups when they occupied meta position of the arylidene ring in 2‐((3‐(imidazol‐1‐yl)propyl)amino)‐5‐benzylidenethiazolidin‐4‐ones. DNA‐binding study of the most potent molecule 3e with salmon milt DNA (sm‐DNA) under simulated physiological pH was probed with UV–visible absorption, fluorescence quenching, gel electrophoresis and molecular docking techniques. These studies established that compound 3e has a strong affinity towards DNA and binds at DNA minor groove with a binding constant (K_b) 0.18 × 10² L mol^?1. Molecular docking simulations predicted strong affinity of 3e towards DNA with a binding affinity (ΔG) ‐8.5 kcal/mol. Van der Waals forces, hydrogen bonding and hydrophobic interactions were predicted as the main forces of interaction. The molecule 3e exhibited specific affinity towards adenine–thiamine base pairs. Copyright © 2016 John Wiley & Sons, Ltd.     

4‐Hydroxy‐benzoic acid (4‐diethylamino‐2‐hydroxy‐benzylidene)hydrazide: DFT,antioxidant, spectroscopic and molecular docking studies with BSA

The Schiff base 4‐hydroxy‐benzoic acid (4‐diethylamino‐2‐hydroxy‐benzylidene) hydrazide (SL) was synthesized and characterized. Its antioxidant activity was evaluated using 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical scavenging action. Being a potent antioxidant its binding ability to the transport protein bovine serum albumin (BSA) was studied using fluorescence quenching and circular dichroism (CD) studies. The binding distance has been calculated by fluorescence resonance energy transfer (FRET) to be 1.85 Å and the Stern–Volmer quenching constant has been calculated to be (3.23 ± 0.45) × 10⁵ M^–1. Quantum chemical analysis was carried out for the Schiff base using DFT with B3LYP and 6–311G** and related to the experimentally obtained results. For a deeper understanding of the mechanism of the interaction, the experimental data were complemented by protein–Schiff base docking calculations using Argus Lab. Copyright © 2015 John Wiley & Sons, Ltd.     

SPECIFICITY AND FUNCTION OF GLYCERALDEHYDE‐3‐PHOSPHATE DEHYDROGENASE IN A FRESHWATER DIATOM,ASTERIONELLA FORMOSA (BACILLARIOPHYCEAE)1

The plastidic glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) catalyzes the only reductive step in the Calvin cycle and exists as different forms of which GapC1 enzyme is present in chromalveolates, such as diatoms. Biochemical studies on diatoms are still fragmentary, and, thus, in this report, GAPDH from the freshwater diatom Asterionella formosa Hassall has been purified and kinetically characterized. It is a homotetrameric enzyme with a molecular mass of ~150 ± 15 kDa. The enzyme showed Michaelis–Menten kinetics with respect to both cofactors, NADPH and NADH, with a 16‐fold greater catalytic constant for NADPH. The K_m for NADPH was 140 μM, the lowest affinity reported, while the catalytic constant, 815 s^?1, is the highest reported. The K_m for NADH was 93 μM, and the catalytic constant was 50 s^?1, both are similar to reported values for other types of GAPDH. The GapC1 enzyme, like the Chlamydomonas reinhardtii A₄ GAPDH, exhibits a cooperative behavior toward the substrate, 1,3‐bisphosphoglyceric acid (BPGA), with both cofactors. Mass spectrometry analysis showed that when GapC1 enzyme was purified without reducing agents, it copurified with a small protein with a mass of 8.2 kDa. This protein was recognized by antibodies against CP12. When associated with this protein, GAPDH displayed a lag that disappeared upon incubation with reducing agent in the presence of either BPGA or NADPH as a consequence of dissociation of the GAPDH/CP12 complex. Thus, as in other species of algae and higher plants, regulation of GapC1 enzyme in A. formosa may occur through association‐dissociation processes linked to dark‐light transitions.     

Scavenging of superoxide anion radical and hydroxyl radical by novel thiazolyl‐thiazolidine‐2,4‐dione compounds

The antioxidant behavior of a series of new synthesized substituted thiazolyl‐thiazolidine‐2,4‐dione compounds (TZDs) was examined using chemiluminescence and electron paramagnetic resonance spin trapping techniques. 5,5‐Dimethyl‐1‐pyrroline‐N‐oxide (DMPO) was used as the spin trap. The reactivity of TZDs with superoxide anion radical (O) and hydroxyl radical (HO^?) was evaluated using potassium superoxide/18‐crown‐6 ether dissolved in dimethylsulfoxide, and the Fenton‐like reaction (Fe²⁺ + H₂O₂), respectively. The results showed that TZDs efficiently inhibited light emission from the O generating system at a concentration of 0.05–1 mmol L^?1 (5–94% reductions were found at 1 mmol L^?1 concentration). The TZD compounds showed inhibition of HO^?‐dependent DMPO–OH spin adduct formation from DMPO (the amplitude decrease ranged from 8 to 82% at 1 mmol L^?1 concentration). The findings showed that examined TZDs had effective activities as radical scavengers. Copyright © 2009 John Wiley & Sons, Ltd.     

Melatonin alleviates lipopolysaccharide‐compromised integrity of blood–brain barrier through activating AMP‐activated protein kinase in old mice

Blood–brain barrier (BBB) dysfunction is considered to be an early event in the pathogenesis of a variety of neurological diseases in old patients, and this could occur in old people even when facing common stress. However, the mechanism remains to be defined. In this study, we tested the hypothesis that decreased melatonin levels may account for the BBB disruption in old mice challenged with lipopolysaccharide (LPS), which mimicked the common stress of sepsis. Mice (24–28 months of age) received melatonin (10 mg kg^?1 day^?1, intraperitoneally, i.p.) or saline for one week before exposing to LPS (1 mg kg^?1, i.p.). Evan's blue dye (EB) and immunoglobulin G (IgG) leakage were used to assess BBB permeability. Immunostaining and Western blot were used to detect protein expression and distribution. Our results showed that LPS significantly increased BBB permeability in old mice accompanied by the degradation of tight junction proteins occludin and claudin‐5, suppressed AMP‐activated protein kinase (AMPK) activation, and elevated gp91^phox protein expression. Interestingly, administration of melatonin for one week significantly decreased LPS‐induced BBB disruption, AMPK suppression, and gp91^phox upregualtion. Moreover, activation of AMPK with metformin significantly inhibited LPS‐induced gp91^phox upregualtion in endothelial cells. Taken together, our findings demonstrate that melatonin alleviates LPS‐induced BBB disruption through activating AMPK and inhibiting gp91^phox upregulation in old mice.     

Concentration‐ and flux‐based dose–responses of isoprene emission from poplar leaves and plants exposed to an ozone concentration gradient

Concentration‐ and flux‐based O₃ dose–responses of isoprene emission from single leaves and whole plants were developed. Two poplar clones differing in O₃ sensitivity were exposed to five O₃ levels in open‐top chambers for 97 d: charcoal‐filtered ambient air (CF), non‐filtered ambient air (NF) and NF plus 20 ppb (NF + 20), 40 ppb (NF + 40) and 60 ppb (NF + 60). At both leaf and plant level, isoprene emission was significantly decreased by NF + 40 and NF + 60 for both clones. Although intra‐specific variability was found when the emissions were up‐scaled to the whole plant, both leaf‐ and plant‐level emissions decreased linearly with increasing concentration‐based (AOT40, cumulative exposure to hourly O₃ concentrations >40 ppb) and flux‐based indices (POD_Y, cumulative stomatal uptake of O₃ > Y nmol O₃ m^?2 PLA s^?1). AOT40‐ and POD₇‐based dose–responses performed equally well. The two clones responded differently to AOT40 and similarly to POD_Y (with a slightly higher R² for POD₇) when the emission was expressed as change relative to clean air. We thus recommend POD₇ as a large‐scale risk assessment metric to estimate isoprene emission responses to O₃ in poplar.     

Ultra‐stable phosphoglucose isomerase through immobilization of cellulose‐binding module‐tagged thermophilic enzyme on low‐cost high‐capacity cellulosic adsorbent

One‐step enzyme purification and immobilization were developed based on simple adsorption of a family 3 cellulose‐binding module (CBM)‐tagged protein on the external surface of high‐capacity regenerated amorphous cellulose (RAC). An open reading frame (ORF) Cthe0217 encoding a putative phosphoglucose isomerase (PGI, EC 5.3.1.9) from a thermophilic bacterium Clostridium thermocellum was cloned and the recombinant proteins with or without CBM were over‐expressed in Escherichia coli. The rate constant (k_cat) and Michaelis–Menten constant (K_m) of CBM‐free PGI at 60°C were 2,765 s^?1 and 2.89 mM, respectively. PGI was stable at a high protein concentration of 0.1 g/L but deactivated rapidly at low concentrations. Immobilized CBM (iCBM)‐PGI on RAC was extremely stable at ～60°C, nearly independent of its mass concentration in bulk solution, because its local concentration on the solid support was constant. iCBM‐PGI at a low concentration of 0.001 g/L had a half‐life time of 190 h, approximately 80‐fold of that of free PGI. Total turn‐over number of iCBM‐PGI was as high as 1.1 × 10⁹ mole of product per mole of enzyme at 60°C. These results suggest that a combination of low‐cost enzyme immobilization and thermoenzyme led to an ultra‐stable enzyme building block suitable for cell‐free synthetic pathway biotransformation that can implement complicated biochemical reactions in vitro. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011.     

Shifts in reciprocal river‐riparian arthropod fluxes along an urban‐rural landscape gradient

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A fluorimetric study on the interaction between a Trp‐containing beta‐strand peptide and amphiphilic polymer‐coated gold nanoparticles

Owing to the inevitability of nanoparticles encountering proteins/peptides in current bio‐nano‐medicine development, it is important to know how they interact with each other in vitro before developing in vivo applications. To this end, a model de novo β‐sheet‐forming peptide and typical biocompatible nanoparticles were selected to study thermodynamic aspects of their interactions via a fluorescence quenching method. The results showed that Pep11 and AuNPs spontaneously formed conjugates, mainly driven by a coulombic interaction with a binding affinity of ~ 0.1 µM^?1; the physical adsorption process was cooperative. These results deepen our quantitative understanding of nanoparticle–peptide interactions. The results may also be helpful in further nanoparticle–peptide hybrid nanofabrication and also useful for the application of nanoparticles in the treatment of amyloid diseases. Copyright © 2015 John Wiley & Sons, Ltd.     

Soil carbon sequestration due to post‐Soviet cropland abandonment: estimates from a large‐scale soil organic carbon field inventory

The break‐up of the Soviet Union in 1991 triggered cropland abandonment on a continental scale, which in turn led to carbon accumulation on abandoned land across Eurasia. Previous studies have estimated carbon accumulation rates across Russia based on large‐scale modelling. Studies that assess carbon sequestration on abandoned land based on robust field sampling are rare. We investigated soil organic carbon (SOC) stocks using a randomized sampling design along a climatic gradient from forest steppe to Sub‐Taiga in Western Siberia (Tyumen Province). In total, SOC contents were sampled on 470 plots across different soil and land‐use types. The effect of land use on changes in SOC stock was evaluated, and carbon sequestration rates were calculated for different age stages of abandoned cropland. While land‐use type had an effect on carbon accumulation in the topsoil (0–5 cm), no independent land‐use effects were found for deeper SOC stocks. Topsoil carbon stocks of grasslands and forests were significantly higher than those of soils managed for crops and under abandoned cropland. SOC increased significantly with time since abandonment. The average carbon sequestration rate for soils of abandoned cropland was 0.66 Mg C ha^?1 yr^?1 (1–20 years old, 0–5 cm soil depth), which is at the lower end of published estimates for Russia and Siberia. There was a tendency towards SOC saturation on abandoned land as sequestration rates were much higher for recently abandoned (1–10 years old, 1.04 Mg C ha^?1 yr^?1) compared to earlier abandoned crop fields (11–20 years old, 0.26 Mg C ha^?1 yr^?1). Our study confirms the global significance of abandoned cropland in Russia for carbon sequestration. Our findings also suggest that robust regional surveys based on a large number of samples advance model‐based continent‐wide SOC prediction.