Cryo-EM Structure of the Human Cannabinoid Receptor CB2-Gi Signaling Complex.

Drugs selectively targeting CB2 hold promise for treating neurodegenerative disorders, inflammation, and pain while avoiding psychotropic side effects mediated by CB1. The mechanisms underlying CB2 activation and signaling are poorly understood but critical for drug design. Here we report the cryo-EM structure of the human CB2-Gi signaling complex bound to the agonist WIN 55,212-2. The 3D structure reveals the binding mode of WIN 55,212-2 and structural determinants for distinguishing CB2 agonists from antagonists, which are supported by a pair of rationally designed agonist and antagonist. Further structural analyses with computational docking results uncover the differences between CB2 and CB1 in receptor activation, ligand recognition, and Gi coupling. These findings are expected to facilitate rational structure-based discovery of drugs targeting the cannabinoid system.

SLC25A39 is necessary for mitochondrial glutathione import in mammalian cells.

Glutathione (GSH) is a small-molecule thiol that is abundant in all eukaryotes and has key roles in oxidative metabolism1. Mitochondria, as the major site of oxidative reactions, must maintain sufficient levels of GSH to perform protective and biosynthetic functions2. GSH is synthesized exclusively in the cytosol, yet the molecular machinery involved in mitochondrial GSH import remains unknown. Here, using organellar proteomics and metabolomics approaches, we identify SLC25A39, a mitochondrial membrane carrier of unknown function, as a regulator of GSH transport into mitochondria. Loss of SLC25A39 reduces mitochondrial GSH import and abundance without affecting cellular GSH levels. Cells lacking both SLC25A39 and its paralogue SLC25A40 exhibit defects in the activity and stability of proteins containing iron-sulfur clusters. We find that mitochondrial GSH import is necessary for cell proliferation in vitro and red blood cell development in mice. Heterologous expression of an engineered bifunctional bacterial GSH biosynthetic enzyme (GshF) in mitochondria enables mitochondrial GSH production and ameliorates the metabolic and proliferative defects caused by its depletion. Finally, GSH availability negatively regulates SLC25A39 protein abundance, coupling redox homeostasis to mitochondrial GSH import in mammalian cells. Our work identifies SLC25A39 as an essential and regulated component of the mitochondrial GSH-import machinery.

Degradation of deoxynivalenol in wheat by double dielectric barrier discharge cold plasma: identification and pathway of degradation products.

BACKGROUND: Deoxynivalenol (DON) produced during the onset of fusarium head blight not only affects the quality and safety of wheat but also causes serious harm to human and livestock health. However, due to the high stability of DON, it is difficult to eliminate it or reduce it naturally after it has been produced. Cold plasma technology is a non-thermophysical processing technology that has been widely used for microbial inactivation and mycotoxin degradation. In this study, the degradation efficiency of double dielectric barrier discharge (DDBD) cold plasma on DON in aqueous solution and wheat was studied; the structures of degradation products of DON and its pathway were clarified, and the effect of DDBD plasma on wheat quality was evaluated. RESULTS: Double dielectric barrier discharge cold plasma was used for efficient degradation of DON (0.5 ~ 5 µgmL^-1) solution and achieved a degradation rate of 98.94% within 25 min under the optimal conditions (voltage 100 V, frequency 200 Hz, duty cycle 80%). Furthermore, 10 degradation products (C15 H24 O5 , C15 H22 O6 , C15 H22 O9 , C16 H22 O7 , C15 H20 O7 , C15 H20 O9 , C15 H18 O8 , C15 H22 O5 , C16 H24 O5 , and C15 H18 O9 ) were identified by ultra-performance liquid chromatography-time of flight-mass spectrometry (UPLC-TOF-MS/MS) combined with Metabolitepilot and Peakview software. The degradation pathway of DON was obtained based on the chemical structures and accurate mass of these products. The DON degradation rate of 61% in wheat was achieved after treatment for 15 min, which slightly affects the moisture content, proteins, and wheat starch. CONCLUSION: Applying DDBD to wheat could effectively reduce the level of DON contamination, which provides a theoretical basis for applying cold plasma to the degradation of DON in wheat. © 2022 Society of Chemical Industry.

Selective removal of Pb(II) from yellow rice wine using magnetic carbon-based adsorbent.

BACKGROUND: The non-distilled property and prolonged production period of yellow rice wine have significantly increased the metal residue problem, posing a threat to human health. In this study, a magnetic carbon-based adsorbent, named magnetic nitrogen-doped carbon (M-NC), was developed for the selective removal of lead(II) (Pb(II)) from yellow rice wine. RESULTS: The results showed that the uniformly structured M-NC could be easily separated from the solution, exhibiting a high Pb(II) adsorption capacity of 121.86 mg g-1 . The proposed adsorption treatment showed significant Pb(II) removal efficiencies (91.42-98.90%) for yellow rice wines in 15 min without affecting their taste, odor, and physicochemical characteristics of the wines. The adsorption mechanism studied by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) analyses indicated that the selective removal of Pb(II) could be attributed to the electrostatic interaction and covalent interaction between the empty orbital of Pb(II) and the π electrons of the N species on M-NC. Additionally, the M-NC showed no significant cytotoxicity on the Caco-2 cell lines. CONCLUSION: Selective removal of Pb(II) from yellow rice wine was achieved using magnetic carbon-based adsorbent. This facile and recyclable adsorption operation could potentially address the challenge of toxic metal pollution in liquid foods. © 2023 Society of Chemical Industry.

De novo assisted AFB1-Specific monoclonal antibody sequence assembly and comprehensive molecular characterization.

Despite their widely used and access as biological reagents in analytical methods, the detailed structural features for most of the antibodies were rarely known. Here, a new antibody for AFB1 with high specificity in constructing ELISA was studied in detail. The molecular structure and modification were elucidated mainly by nano-electrospray ionization mass spectrometry. The mass experiments, including MALDI-TOF MS, revealed complete and specific fragments, including antibody molecular weight, peptides, glycopeptide, and N-glycoform. By proteolytic treatment of pepsin and trypsin and high-resolution tandem-MS, the primary structure of the newly developed anti-AFB1 antibody was assembled by several rounds of Database search process assisted with the de novo results. The antibody CDR annotation and constraint-based multiple alignment tool were used to differentiate and align the sequences. The method uses only two proteases to generate numerous peptides for de novo sequencing. This artificial assembled AFB1-specific monoclonal antibody sequence was validated by comparison with the sequencing results of the immunoglobulin gene. The results showed that this method achieves full sequence coverage of anti-AFB1 monoclonal antibody, with an accuracy of 100% in the CDR regions of light chain and four amino acid mismatch in heavy chain. This simple and low-cost method was confirmed by treating a public dataset. The secondary structure information of intact antibody was also elucidated from the results of circular dichroism spectrum.

Analysis of multiple mycotoxins-contaminated wheat by a smart analysis platform.

This study describes a smart analysis platform capable of quantitative measurements using a multiplex lateral flow strip. Using the multi-mycotoxin strip, five fungal toxins were simultaneously and quantitatively detected in naturally contaminated wheat. First, a matrix-based standard curve was established for the detection of aflatoxin B1 (AFB1), fumonisin B1 (FB1), T-2, deoxynivalenol (DON), and zearalenone (ZEN). Established on an open android system, the platform is able to read 6 lines on the strip simultaneously. The platform is equipped with a Quick Response code scanning model, which reads the established standard curves, and then rapidly quantify mycotoxins in naturally contaminated wheat. All the data and sample information are stored on a central server through the platform which is linked to the cloud. The limits of detection (LOD) for AFB1, FB1, T-2, DON, and ZEN in wheat were 4, 20, 10, 200, and 40 µg/kg and the visual cut off values was 20, 1000, 200, 4000, and 400 µg/kg, separately. To validate the platform and the multi-mycotoxin detection method, 10 wheat samples were analyzed and the results were in a good agreement with those obtained by LC-MS/MS. The platform will be a powerful tool for crop monitoring services.

Development of an ELISA and immunochromatographic strip for highly sensitive detection of microcystin-LR.

A monoclonal antibody for microcystin-leucine-arginine (MC-LR) was produced by cell fusion. The immunogen was synthesized in two steps. First, ovalbumin/ bovine serum albumin was conjugated with 6-acetylthiohexanoic acid using a carbodiimide EDC (1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride)/ NHS (N-hydroxysulfosuccinimide) reaction. After dialysis, the protein was reacted with MC-LR based on a free radical reaction under basic solution conditions. The protein conjugate was used for immunization based on low volume. The antibodies were identified by indirect competitive (ic)ELISA and were subjected to tap water and lake water analysis. The concentration causing 50% inhibition of binding of MC-LR (IC50) by the competitive indirect ELISA was 0.27 ng/mL. Cross-reactivity to the MC-RR, MC-YR and MC-WR was good. The tap water and lake water matrices had no effect on the detection limit. The analytical recovery of MC-LR in the water samples in the icELISA was 94%-110%. Based on this antibody, an immunochromatographic biosensor was developed with a cut-off value of 1 ng/mL, which could satisfy the requirement of the World Health Organization for MC-LR detection in drinking water. This biosensor could be therefore be used as a fast screening tool in the field detection of MC-LR.

Antibacterial Mechanism of d-Cysteine/Polyethylene Glycol-Functionalized Gold Nanoparticles and Their Potential for the Treatment of Bacterial Infections.

Bacterial infection has always posed a severe threat to public health. Gold nanoparticles (Au NPs) exhibit exceptional biocompatibility and hold immense potential in biomedical applications. However, their antibacterial effectiveness is currently unsatisfactory. Herein, a chiral antibacterial agent with high stability was prepared by the modification of Au NPs with d-cysteine with the assistance of polyethylene glycol (PEG). The as-synthesized d-cysteine/PEG-Au NPs (D/P-Au NPs) exhibited a stronger (99.5-99.9%) and more stable (at least 14 days) antibacterial performance against Gram-negative (Escherichia coli and Listeria monocytogenes) and Gram-positive (Salmonella enteritidis and Staphylococcus aureus) bacteria, compared with other groups. The analysis of the antibacterial mechanism revealed that the D/P-Au NPs mainly affected the assembly of ribosomes, the biosynthesis of amino acids and proteins, as well as the DNA replication and mismatch repair, ultimately leading to bacterial death, which is significantly different from the mechanism of reactive oxygen species-activated metallic antibacterial NPs. In particular, the D/P-Au NPs were shown to effectively accelerate the healing of S. aureus-infected wounds in mice to a rate comparable to or slightly higher than that of vancomycin. This work provides a novel approach to effectively design chiral antibacterial agents for bacterial infection treatment.

Visual sensor for the detection of trace Cu(II) ions using an immunochromatographic strip.

A rapid and simple immunochromatography method based on a gold nanoparticle-labeled monoclonal antibody was developed for the on-site detection of copper (Cu) in water samples. This monoclonal antibody, obtained by a cell fusion technique, recognized the Cu-ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) complex, but not metal-free EDTA, with high sensitivity and specificity. In optimized conditions, the visual limit of detection for qualitative detection of Cu(II) ions was 10 ng/mL and the LOD for semi-quantitative detection decreased to 0.45 ng/mL with the help of a scanning reader system. The detection process was achieved within 10 min with no cross-reactivity from other heavy metal ions. The recovery of the test samples ranged from 98% to 109%. To our knowledge, this antibody-based test strip for Cu(II) ions has not been previously reported. Based on the above results, this strip sensor could be used as an alternative tool for screening heavy metal pollution in the environment.

Rapid and highly sensitive detection of lead ions in drinking water based on a strip immunosensor.

In this study, we have first developed a rapid and sensitive strip immunosensor based on two heterogeneously-sized gold nanoparticles (Au NPs) probes for the detection of trace lead ions in drinking water. The sensitivity was 4-fold higher than that of the conventional LFA under the optimized conditions. The visual limit of detection (LOD) of the amplified method for qualitative detection lead ions was 2 ng/mL and the LOD for semi-quantitative detection could go down to 0.19 ng/mL using a scanning reader. The method suffered from no interference from other metal ions and could be used to detect trace lead ions in drinking water without sample enrichment. The recovery of the test samples ranged from 96% to 103%. As the detection method could be accomplished within 15 min, this method could be used as a potential tool for preliminary monitoring of lead contamination in drinking water.

Degradation of carbendazim in aqueous solution by dielectric barrier discharge cold plasma: Identification and toxicity of degradation products.

Dielectric barrier discharge (DBD) cold plasma, as a new nonthermal technology, has attracted increasing attention in pesticide degradation. In this study, DBD plasma was used to degrade carbendazim (MBC) in aqueous solution. Under the optimal conditions (160 kv, 50 Hz), MBC solution (0.5 µg/mL) was degraded by 89.04% after plasma treatment for 10 min. Four MBC degradation products were identified, one of which was a common oxidative degradation product (5-hydroxycarbendazim, m/z 208.07); the others were identified (m/z 118.06, m/z 132.08 and m/z 104.05) to have formed by the cleavage of the benzimidazole heterocyclic ring. The degradation pathways were obtained by analysis of degradation products at different treatment times. The toxicity of the degradation products was estimated based on the survival rate of yeast, indicating much lower toxicity levels compared to that of MBC. This study provides a theoretical basis for the application of DBD plasma in the degradation of benzimidazole pesticides in foods.

Arsenic Contents, Speciation and Toxicity in Germinated Rice Alleviated by Selenium.

Rice can accumulate more organic and inorganic arsenic (iAs) than other crop plants. In this study, the localization of As in rice grains was investigated using High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry (HPLC-ICP-MS) based on 26 rice varieties collected from two provinces. In all the samples, the total As contents in polished rice were 0.03-0.37 mg/kg, with average values of 0.28 and 0.21 mg/kg for two sample sets. The results of the determination of arsenic speciation in different components of rice grain showed that in the polished and brown rice the mean value of arsenite (As(III)) was nearly twice than that of arsenate (As(V)). The regional difference was observed in both total As contents and As speciation. The reason may be that As(III) is more mobile than As(V) in a dissociated form and because of soil properties, rice varieties, and the growing environment. The proportion of iAs and the total As in rice bran was higher than that in polished rice, and this is because As tends accumulate between the husk and the endosperm. In our study, selenium could alleviate the risk of arsenic toxicity at the primary stage of rice growth. Co-exposure to As and Se in germinated rice indicated that the reduction in As accumulation in polished rice reached 73.8%, 76.8%, and 78.3% for total As, As(III), and As(V) when compared with rice treated with As alone. The addition of Se (0.3 mg/kg) along with As significantly reduced the As amount in different parts of germinated rice. Our results indicated that Se biofortification could alleviate the As accumulation and toxicity in rice crops.

Modification of soy protein isolate using dielectric barrier discharge cold plasma assisted by modified atmosphere packaging.

In this study, soy protein isolate (SPI) was treated by modified atmosphere packaging (MAP) assisted dielectric barrier discharge (DBD) cold plasma (CP) to improve its functional properties. For this reason, SPI powders were treated with DBD-CP at the oxygen ratio of 20 %, 30 %, 40 %, 50 % and 60 %, respectively. The results showed that with the increase of oxygen content, the structure of SPI was destroyed, protein macromolecule depolymerized. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed that the primary structure of SPI was not disrupted. In addition, when the oxygen content was greater than 40 %, the solubility, water holding capacity, gelling, emulsifying and foaming properties of SPI were significantly improved (p < 0.05). The results showed that high-oxygen packaging can increase the active particles generated during processing, thereby optimizing the structural and functional properties of SPI. Therefore, MAP can serve as a more efficient method for DBD-CP to modify soybean protein.

Recent design strategies and applications of organic fluorescent probes for food freshness detection.

Food spoilage poses a significant risk to human health, making the assessment of food freshness essential for ensuring food safety and quality. In recent years, there has been rapid progress in the development of fast detection technologies for food freshness. Among them, organic fluorescent probes have garnered significant attention in the field of food safety and sensing due to their easy functionalization, high sensitivity, and user-friendly nature. To comprehensively examine the latest advancements in organic fluorescent probes for food freshness detection, this review summarized their applications within the past five years. Initially, the fundamental detection principles of organic fluorescent probes are outlined. Subsequently, the recent research progress in utilizing organic fluorescent probes to detect various chemical indicators of freshness are discussed. Finally, the challenges and future directions for organic fluorescent probes in food freshness detection are elaborated upon. While, organic fluorescent probes have demonstrated their effectiveness in evaluating food freshness and possess great potential for practical applications, further research is still needed to enable their widespread commercial utilization. With continued advancements in synthesis and functionalization techniques, organic fluorescent probes will contribute to enhancing the efficiency of food safety detection.

Effects of food components and processing parameters on plant-based meat texture formation and evaluation methods.

Meat is the main source of protein nutrition for humans. However, given the increasing population and environmental pressure, a shortage of meat is expected in the future. The preparation of plant-based (meat) products using existing processing methods represents a breakthrough to solve the shortage of traditional animal meat in the future, and texture is a key issue determining whether plant-based (meat) products can replace traditional animal meat. Therefore, this review highlights recent progress in the texture of plant-based (meat) products. First, the texture changes in plant-based (meat) products were reviewed based on components (proteins, starch, lipids, food additives) and processing methods (processing factors, instrumental factors). Then, the current methods used to analyze the texture of plant-based (meat) products were summarized based on sensory evaluation and instrumental analysis (mechanical analysis, spectral analysis, and image analysis). Finally, this review outlined methods to improve the texture quality of plant-based (meat) products and analytical evaluation methods and provided an outlook on future research priorities.

Development and application of lateral flow strip with three test lines for detection of deoxynivalenol in wheat.

Lateral flow strip was widely used and their qualitative and quantitative performance was in continuous improvement. However, the traditional strip was in a single-test-line format, which restricted operators to making a semi-quantitative judgment around a desired threshold concentration. Herein, a single strip with three test lines (TTLS) was developed for the semi-quantitative and quantitative determination of deoxynivalenol (DON). Four visual detection thresholds were obtained under optimized conditions and 35 wheat samples with DON content from 45 µg/kg to 2841 µg/kg were used to verify the method. The detection results were compared with that of the traditional strip and UPLC-MS/MS. In a three-test-line format, TTLS could reveal at least 200, 500, 1000, and 2000 µg/kg DON existed in different samples by the naked eye. The agreement analysis and statistical results indicated the new TTLS can be used as a useful tool for quantitative detection of DON with wide dynamic range.

Grain quality evaluation of japonica rice effected by cultivars, environment, and their interactions based on appearance and processing characteristics.

Appearance and processing characteristics of 45 japonica rice samples, collected from different regions in Jiangsu province, were investigated and evaluated in this study. Specifically, the chalkiness degree had been presented significant differences among different cultivars and regions. The average chalkiness degree varied from 6.81% to 15.34% for different regions and from 1.93% to 28.31% for different cultivars. The minimum head rice rate of cultivars from four regions, NJ9108 (HA), was 80.5%. The AC of CNG10, HD5, and PJ surpassed 13.68% and lower than 11.33% for the others. The protein content ranged from 6.1% to 11%, and the taste value was significantly different among cultivars. In addition, the RVA curves of the samples were similar, but the peak viscosities of NG8 and NJ5055 were higher than others, and there were significant differences in RVA traits among regions. Cultivars were the main reasons for the difference in appearance and processing quality of japonica rice, while environmental factors had leaded to the change of rice composition, texture, and gelatinization.

Fate of Fe3O4@NH2 in soil and their fixation effect to reduce lead translocation in two rice cultivars.

The fate of nanoparticles in the ecological chain of agriculture has been concerned as their potential pollution and biological effect to humans with rapid development and massive emission of nanomaterials. Here, we found that two rice cultivars (Oryza sativa L) have different heavy metal accumulation results in the roots and shoots after 15 days growth. Two rice cultivars (Oryza sativa L), grown in soil containing magnetite (Fe3O4@NH2) nanoparticles and heavy metal simultaneous, showed less Pb uptake in the roots and shoots, compared with that without Fe3O4@NH2 added. The shape and magnetic properties of Fe3O4@NH2 have no obvious change; however, the transmission electron microscope (TEM) results showed the shell of Fe3O4@NH2 could be broken in the process of interaction with soil. These results suggested that magnetite nanoparticles, such as Fe3O4@NH2, could potentially be used as the recyclable heavy metal fixation materials for alleviating heavy metal poisoning to plant.

Gold nanostars-enhanced Raman fingerprint strip for rapid detection of trace tetracycline in water samples.

Rapid and accurate detection of antibiotics at trace levels in food represents a great challenge. Tetracycline (TC), as a sort of broad-spectrum antibiotic, has been extensively used in animal infection therapy and animal husbandry as growth promoters. Large amounts of TC residues in animal-derived foods affect food quality and safety, and cause undesirable side effects such as allergic reactions and bacterial antibiotic resistance. Here, a Raman fingerprint strip sensor was reported based on surface-enhanced Raman scattering technology and demonstrated for ultrasensitive detection of TC. In this approach, 4-aminothiophenol (4-ATP) modified gold nanostars (GNSs) were used as a strong Raman reporter, which was coated with anti-TC monoclonal antibody serving as a biorecognition to acquire both visual and Raman signals on the test line. To demonstrate the performance of this strip, TC standard solutions with concentrations ranging from 0.5 to 50 ng/mL was detected, the limit of the detection (LOD) for the Raman signal was 0.04 ng/mL, which was 100 times more sensitive than those of color intensity quantifications. The other analogues, oxytetracycline, and chlortetracycline were detected using this method, making them suitable for the samples with TC analogues screening.

Time-Domain NMR Applied to Sitophilus zeamais Motschulsky/Wheat Detection.

Time-domain nuclear magnetic resonance (NMR) is used for the characterization of wheat infested with Sitophilus zeamais. NMR parameters (T21, T22, P21, P22, and A21/22) were achieved by biexponential analysis combined with a discrete method. Sound wheat, S. zeamais, and S. zeamais/wheat binary mixture are all explored by this method to find the changes in the process of the number increase and growth stage. Based on different sets of NMR parameters, the classification and quantification of the stage and number are made by linear discriminant analysis and partial least squares regression with very high accuracy. The weight and moisture content information lack will make the misclassification rate increase but not by more than 7%. This NMR-based hidden-insect detection method, with fast and nondestructive advantages, was confirmed by X-ray and had a high potential to be equipped in the online analysis system.