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The Journal of Nutrition Sep 2020It is widely accepted that the tricarboxylic acid (TCA) cycle is a critical partner for gluconeogenesis (GNG) in hepatocytes. Although researchers in the 1950s showed,...
It is widely accepted that the tricarboxylic acid (TCA) cycle is a critical partner for gluconeogenesis (GNG) in hepatocytes. Although researchers in the 1950s showed, using radiolabeled long-chain fatty acids, that acetate derived from fatty acid β-oxidation contributes carbon to glucose, fatty acids are not included on lists of gluconeogenic precursors in many textbooks of biochemistry and nutritional biochemistry. Here, by following the flow of carbon atoms through the mitochondrial TCA cycle and into cytosolic GNG, it is shown that carbons in acetyl-CoA derived from fatty acid β-oxidation will be found in glucose. Specifically, it is evident that, after the condensation of acetyl-CoA and oxaloacetate (OAA) to make citrate at the start of the TCA cycle, the 2 carbons lost from the cycle as carbon dioxide come from OAA, not acetyl-CoA. Carbons from acetyl-CoA are retained as the cycle progresses toward malate, and when malate exits the mitochondrion for GNG, carbons that originated in acetyl-CoA and OAA are found to contribute equally to glucose. With influx of other critical precursors into the TCA cycle and efflux of malate into the cytosol for GNG, the TCA cycle is in balance. During fasting-induced GNG, there is a net gain of glucose in glucogenic cells; however, the fact that there is no net gain in the TCA cycle is irrelevant as far as precursors are concerned. Given the physiological importance of fat as a source of reserve energy, and knowing that some cell types rely on glucose as their primary supplier of energy, a role for fatty acids in glucose production aligns both with intuition and with evidence provided by a careful look at the biochemistry and older isotope studies. Hopefully, subsequent editions of textbooks will list fatty acids among the gluconeogenic precursors.
Topics: Carbon; Citric Acid Cycle; Fatty Acids; Gluconeogenesis; Glucose; Humans
PubMed: 32652038
DOI: 10.1093/jn/nxaa165 -
Environmental Pollution (Barking, Essex... Jan 2023Per- and polyfluorolkyl substances (PFAS) were measured in the water and fish from 20 coastal tourist resorts in China, to investigate their sources, seasonal...
Per- and polyfluorolkyl substances (PFAS) were measured in the water and fish from 20 coastal tourist resorts in China, to investigate their sources, seasonal differences, and bioconcentration. An oxidative method with hydroxyl radicals was used to extract potential perfluoroalkyl acid (PFAA) precursors in the water of resorts. The results indicated that the total concentrations of target chemicals (i.e., ΣPFAS) in the original water were 59.4-138, 32.7-77.2, and 14.6-29.9 ng L in December, April, and August, respectively. C-C perfluorocarboxlate (PFCA) and perfluorooctane sulfonate (PFOS) accounted for 67%-92% of the ΣPFAS contents in all water samples. The PFAS concentrations in the muscles and liver of fish were 16.0-162 ng g ww and 186-1240 ng g ww, respectively. The dominant compounds were perfluorobutanoate acid (PFBA) and PFOS in the water, and perfluorooctanoic acid (PFOA) and PFOS in fish tissues. High bioconcentration were observed for PFCA (C ≥ 8) and perfluorosulfonate (PFSA, C ≥ 6). After oxidative conversion, the water exhibited a noticeable increase in the ΣPFAS value. Precursors that generated C-C PFCA were more prevalent than precursors that generated other PFCA upon oxidation. The concentration of C-based precursor was higher than that of C-based precursor in wet and dry seasons. This study is the first to apply an oxidative method to investigate PFAS pollution in the water of coastal tourist resorts. The results verified that PFAA precursors exist in the water of coastal tourist resorts, and more attention should be given to the existence of PFAA precursors and the safety of water in coastal tourist resorts.
Topics: Animals; Fluorocarbons; Environmental Monitoring; Water Pollutants, Chemical; Carboxylic Acids; Alkanesulfonic Acids; Water; Fishes
PubMed: 36273687
DOI: 10.1016/j.envpol.2022.120460 -
Cellulose (London, England) 2021Polyacrylonitrile (PAN)-based carbon precursor is a well-established and researched material for electrodes in energy storage applications due to its good physical... (Review)
Review
Polyacrylonitrile (PAN)-based carbon precursor is a well-established and researched material for electrodes in energy storage applications due to its good physical properties and excellent electrochemical performance. However, in the fight of preserving the environment and pioneering renewable energy sources, environmentally sustainable carbon precursors with superior electrochemical performance are needed. Therefore, bio-based materials are excellent candidates to replace PAN as a carbon precursor. Depending on the design requirement (e.g. carbon morphology, doping level, specific surface area, pore size and volume, and electrochemical performance), the appropriate selection of carbon precursors can be made from a variety of biomass and biowaste materials. This review provides a summary and discussion on the preparation and characterization of the emerging and recent bio-based carbon precursors that can be used as electrodes in energy storage applications. The review is outlined based on the morphology of nanostructures and the precursor's type. Furthermore, the review discusses and summarizes the excellent electrochemical performance of these recent carbon precursors in storage energy applications. Finally, a summary and outlook are also given. All this together portrays the promising role of bio-based carbon electrodes in energy storage applications.
PubMed: 33897123
DOI: 10.1007/s10570-021-03881-z -
Nanomaterials (Basel, Switzerland) Jan 2021Bulk inorganic materials play important roles in human society, and their construction is commonly achieved by the coalescence of inorganic nano- or micro-sized... (Review)
Review
Bulk inorganic materials play important roles in human society, and their construction is commonly achieved by the coalescence of inorganic nano- or micro-sized particles. Understanding the coalescence process promotes the elimination of particle interfaces, leading to continuous bulk phases with improved functions. In this review, we mainly focus on the coalescence of ceramic and metal materials for bulk construction. The basic knowledge of coalescent mechanism on inorganic materials is briefly introduced. Then, the properties of the inorganic precursors, which determine the coalescent behaviors of inorganic phases, are discussed from the views of particle interface, size, crystallinity, and orientation. The relationships between fundamental discoveries and industrial applications are emphasized. Based upon the understandings, the applications of inorganic bulk materials produced by the coalescence of their particle precursors are further presented. In conclusion, the challenges of particle coalescence for bulk material construction are presented, and the connection between recent fundamental findings and industrial applications is highlighted, aiming to provide an insightful outlook for the future development of functional inorganic materials.
PubMed: 33477573
DOI: 10.3390/nano11010241 -
Frontiers in Physiology 2022In human cells, approximately 30% of all polypeptides enter the secretory pathway at the level of the endoplasmic reticulum (ER). This process involves cleavable... (Review)
Review
In human cells, approximately 30% of all polypeptides enter the secretory pathway at the level of the endoplasmic reticulum (ER). This process involves cleavable amino-terminal signal peptides (SPs) or more or less amino-terminal transmembrane helices (TMHs), which serve as targeting determinants, at the level of the precursor polypeptides and a multitude of cytosolic and ER proteins, which facilitate their ER import. Alone or in combination SPs and TMHs guarantee the initial ER targeting as well as the subsequent membrane integration or translocation. Cytosolic SRP and SR, its receptor in the ER membrane, mediate cotranslational targeting of most nascent precursor polypeptide chains to the polypeptide-conducting Sec61 complex in the ER membrane. Alternatively, fully-synthesized precursor polypeptides and certain nascent precursor polypeptides are targeted to the ER membrane by either the PEX-, SND-, or TRC-pathway. Although these targeting pathways may have overlapping functions, the question arises how relevant this is under cellular conditions and which features of SPs and precursor polypeptides determine preference for a certain pathway. Irrespective of their targeting pathway(s), most precursor polypeptides are integrated into or translocated across the ER membrane via the Sec61 channel. For some precursor polypeptides specific Sec61 interaction partners have to support the gating of the channel to the open state, again raising the question why and when this is the case. Recent progress shed light on the client spectrum and specificities of some auxiliary components, including Sec62/Sec63, TRAM1 protein, and TRAP. To address the question which precursors use a certain pathway or component in intact human cells, i.e., under conditions of fast translation rates and molecular crowding, in the presence of competing precursors, different targeting organelles, and relevant stoichiometries of the involved components, siRNA-mediated depletion of single targeting or transport components in HeLa cells was combined with label-free quantitative proteomics and differential protein abundance analysis. Here, we present a summary of the experimental approach as well as the resulting differential protein abundance analyses and discuss their mechanistic implications in light of the available structural data.
PubMed: 35899032
DOI: 10.3389/fphys.2022.833540 -
Angewandte Chemie (International Ed. in... Jun 2024Understanding the properties of the precursor can provide deeper insight into the crystallization and nucleation mechanisms of perovskites, which is vital for the...
Understanding the properties of the precursor can provide deeper insight into the crystallization and nucleation mechanisms of perovskites, which is vital for the solution-process device performance. In this work, we conducted a detailed investigation into the photophysics properties of all-inorganic perovskite (CsPbBr₃) precursors in a broad concentration and various solvents. The precursor gradually transformed from the solution state into the colloidal state and exhibited aggregation-induced emission (AIE) character as the concentration increased. The aggregative luminescence from the precursors originates from the polybromide plumbous that is formed through the coordination of solvent molecules to the lead metal center. Two adducts with monodentate (PbBr₂⋅solvent) and bidentate (PbB₂⋅2solvent) ligands can be obtained based on the coordination capability, accompanied by a red and green emission with photoluminescence peak at 610 and 565 nm, respectively. Furthermore, the aggregative luminescence intensity and color could be regulated by changing the solvent and precursor ratio. Besides, we discussed the difference between the molecular aggregate in the organic system and the ionic aggregate in the inorganic system. The fluorescence that is sensitive to Pb²⁺ coordination reported here could be applied to screen perovskite additives and judge the precursor aging.
PubMed: 38853460
DOI: 10.1002/anie.202408586 -
Chemosphere Sep 2022The composite materials based on graphitic carbon nitrides (g-CN) are remarkably better semiconductors, but the inherent photocatalytic performance in its generic... (Review)
Review
The composite materials based on graphitic carbon nitrides (g-CN) are remarkably better semiconductors, but the inherent photocatalytic performance in its generic synthesis form is not up to the mark. Eminence efforts have been made to improve its performance and photocatalytic efficiencies. Recently, extensive investigations have been performed to develop their texturally modified and highly porous structures to get around the big flaws of bulk g-CN. One significant disadvantage is the increase in the polycondensation while preparation at 550 °C results in g-CN materials with restricted specific surface area (SSA) (<10 m/g) and no textured pores. Textural modification has emerged as an efficient and progressive way to improve optical and electronic characteristics. The final texture and shape of CN are influenced by the precursor's interaction with the template. Researchers are interested in developing CN materials with high SSA and changeable textural properties (pore volume and pore size). Based on the literature review it is concluded that the soft templating approach is relatively simple, and straightforward to induce textural changes in the g-CN type materials. This review focused on improving the textural properties of bulk g-CN via templating method, and the major advances in the modified g-CN materials for the treatment of wastewater. The procedures and mechanisms of numerous approaches with varying morphologies are thoroughly explained.
Topics: Catalysis; Graphite; Nitriles; Nitrogen Compounds; Polymers; Water Purification
PubMed: 35533933
DOI: 10.1016/j.chemosphere.2022.134792 -
European Journal of Clinical... Dec 2023There are contradictory effects regarding the effect of NAD+ precursor on blood pressure and inflammation. In order to obtain a better viewpoint from them, this study... (Review)
Review
BACKGROUND
There are contradictory effects regarding the effect of NAD+ precursor on blood pressure and inflammation. In order to obtain a better viewpoint from them, this study aimed to comprehensively investigate the effects of NAD+ precursor supplementation on blood pressure, C-reactive protein (CRP) and carotid intima-media thickness (CIMT).
METHODS
PubMed/MEDLINE, Web of Science, SCOPUS and Embase databases were searched using standard keywords to identify all controlled trials investigating the effects of NAD+ precursor on blood pressure, CRP and CIMT. Pooled weighted mean difference (WMD) and 95% confidence intervals (95% CI) were achieved by random-effects model analysis for the best estimation of outcomes.
RESULTS
Twenty-nine articles (with 8664 participants) were included in this article. Results from meta-analyses of RCTs from random-effects models indicated a significant reduction in systolic (SBP) (weighted mean difference (WMD): -2.54 mmHg, p < .001) and diastolic blood pressure (DBP) (WMD: -2.15 mmHg, p < .001), as well as in CRP (WMD: -.93 mg/L, 95% CI -1.47 to -.40, p < .001) concentrations and CIMT (WMD: -.01 mm, 95% CI -.02 to -.00, p = .005) with the NAD+ precursors supplementation compared with the control group. In addition, a greater effect of supplementation with NAD+ precursors in reducing blood pressure (BP) were observed with the highest dose (≥2 g) and duration of the intervention (>12 weeks), as well as with NA supplementation when compared to NE.
CONCLUSIONS
Overall, these findings suggest that NAD+ precursor supplementation might have a beneficial effect on cardiovascular risk factors such as BP, CRP concentration and CIMT.
Topics: Humans; Blood Pressure; C-Reactive Protein; Carotid Intima-Media Thickness; NAD; Dietary Supplements; Randomized Controlled Trials as Topic
PubMed: 37593976
DOI: 10.1111/eci.14078 -
Frontiers in Physiology 2022Amino acids and fatty acids are the main precursors of volatile organic compounds (VOCs) in meat. The purpose of this study was to determine the main VOC components in...
Amino acids and fatty acids are the main precursors of volatile organic compounds (VOCs) in meat. The purpose of this study was to determine the main VOC components in chicken breast muscle (BM) and abdominal fat (AF) tissue, as well as the source of VOCs, to provide a basis for quality improvement of broilers. BM and AF served as experimental and control groups, and gas chromatography-mass spectrometry (GC-MS) and untargeted metabolomics were employed to identify the source of VOCs. The results revealed nine VOCs in BM and AF tissues, including hexanal, octanal, and nonanal. VOCs including 1-octen-3-ol, (E,E)-2, 4-nonadienal, and benzaldehyde were significantly elevated in BM compared with AF ( < 0.05), while heptane and diethyl disulphide showed the opposite trend ( < 0.05). Levels of hexanal, heptanal, and octanal were similar in the two tissues. Metabolites of VOCs in chicken BM were investigated by weighted co-expression network analysis. However, only blue module in BM tissue was positively correlated with hexanal ( = 0.66, = 0.01), heptanal ( = 0.67, = 0.008), and (E,E)-2,4-nonadienal ( = 0.88, = 3E-05). L-tyrosine, L-asparagine, adenosine, and valine were the main precursors of (E,E)-2,4-nonadienal and heptanal in BM tissue. Amino acids are the main precursors of 1-octen-3-ol, (E,E)-2, 4-nonadienal, and heptanal in chicken meat, while fatty acids are the main precursors of diethyl disulfide. However, hexanal can be synthesized from amino acids and small amounts of fatty acids as precursors. These findings expand our understanding of VOCs in chicken.
PubMed: 35874543
DOI: 10.3389/fphys.2022.927618 -
Molecular & Cellular Proteomics : MCP Feb 2023Data-independent acquisition (DIA) methods have become increasingly popular in mass spectrometry-based proteomics because they enable continuous acquisition of fragment...
Data-independent acquisition (DIA) methods have become increasingly popular in mass spectrometry-based proteomics because they enable continuous acquisition of fragment spectra for all precursors simultaneously. However, these advantages come with the challenge of correctly reconstructing the precursor-fragment relationships in these highly convoluted spectra for reliable identification and quantification. Here, we introduce a scan mode for the combination of trapped ion mobility spectrometry with parallel accumulation-serial fragmentation (PASEF) that seamlessly and continuously follows the natural shape of the ion cloud in ion mobility and peptide precursor mass dimensions. Termed synchro-PASEF, it increases the detected fragment ion current several-fold at sub-second cycle times. Consecutive quadrupole selection windows move synchronously through the mass and ion mobility range. In this process, the quadrupole slices through the peptide precursors, which separates fragment ion signals of each precursor into adjacent synchro-PASEF scans. This precisely defines precursor-fragment relationships in ion mobility and mass dimensions and effectively deconvolutes the DIA fragment space. Importantly, the partitioned parts of the fragment ion transitions provide a further dimension of specificity via a lock-and-key mechanism. This is also advantageous for quantification, where signals from interfering precursors in the DIA selection window do not affect all partitions of the fragment ion, allowing to retain only the specific parts for quantification. Overall, we establish the defining features of synchro-PASEF and explore its potential for proteomic analyses.
Topics: Tandem Mass Spectrometry; Proteomics; Proteome; Peptides
PubMed: 36566012
DOI: 10.1016/j.mcpro.2022.100489