Partitioning Of Acids Research Articles

Long-term nitrogen fertilization alters the partitioning of amino acids between citrus leaves and fruits.

The growth of evergreen fruit trees is influenced by the interaction of soil nitrogen (N) and leaf amino acid contents. However, information on free amino acid contents in leaves of fruiting and non-fruiting branches during long-term N fertilizer application remains scarce. Here, a four-year field experiment (2018-2021) in a citrus orchard revealed consistently lower total N and amino acid contents in leaves of fruiting compared to non-fruiting branches. Appropriate N fertilizer application increased free amino acid and total N contents in leaves of both types of branches and fruits, but excessive amounts led to decreases. Correlation analysis showed that, in the early stage of fruit development, leaves on both types of branches can meet the N requirements of the fruit (R²=0.77 for fruiting, R²=0.82 for non-fruiting). As fruits entered the swelling stage, a significant positive correlation emerged between fruiting branch leaves and fruit total N content (R²=0.68), while the R² for leaves on non-fruiting branches dropped to 0.47, indicating a shift in N supply towards leaves on fruiting branches. Proline and arginine are the most abundant amino acids in these leaves. At fruit maturity, these amino acids account for more than half of the total amino acids in the fruit (29.0% for proline and 22.2% for arginine), highlighting their crucial role in fruit development. Further research is needed to investigate amino acid transport and distribution mechanisms between citrus leaves and fruits.

Spectral Bipartition via Gap Cut on DNA Sequences

Deoxyribonucleic Acid (DNA) and graph partitioning are two distinct fields of study which can be linked in the structure of biological networks. Graph partitioning has been extensively studied but not its application in the biological field. This research explored on the application of spectral graph partitioning in DNA splicing, aiming to simulate the cleavage of DNA by performing spectral bipartition on DNA sequences in a DNA splicing system. This research incorporates Fiedler theory and algebraic graph theory, which are commonly utilized in network analysis and the analysis of graph connectivity. Some DNA sequences of even length are selected and expressed in graphical representations. The adjacency matrix, Laplacian matrix, and degree matrix are computed from the graphs, as well as the Fiedler value and Fiedler vector associated with the graphs. Gap cut is used as a method of spectral bipartition which produces two partitions of DNA sequence of unequal lengths. The generalizations of gap cut on DNA sequences of even length are provided as lemmas and theorem.

Plasma Endocannabinoids Are Independently Associated With the Metabolic Function of White Adipose Tissue

Abstract Context Little is known about the link between the endocannabinoid (EC) system and the in vivo metabolic function of white adipose tissue (WAT). Objective We aimed to evaluate whether ECs are linked to postprandial fatty acid metabolism and WAT metabolic function. Methods Men and women, with (IGT, n = 20) or without impaired glucose tolerance (NGT, n = 20) underwent meal testing with oral and intravenous stable isotope palmitate tracers and positron emission tomography with intravenous [11C]-palmitate and oral [18F]-fluoro-thia-heptadecanoic acid to determine systemic and organ-specific dietary fatty acid (DFA) and nonesterified fatty acid (NEFA) metabolism and partitioning. We determined fasting and postprandial plasma levels of EC by ultra-high performance liquid chromatography–tandem mass spectrometry. Results All ECs of the 2-monoacylglycerol (2-MAG) family displayed a progressive postprandial increase up to 360 minutes after meal intake that was more pronounced in women with IGT. N-acylethanolamine (NAE) levels decreased between fasting and 180 minutes, followed by a return to preprandial values at 360 minutes and were also increased in women with IGT. Postprandial area under the curve (AUC) of palmitate appearance rate was significantly and independently associated with postprandial AUC of anandamide (AEA; P = .0003) and total energy expenditure (P = .0009). DFA storage in abdominal subcutaneous adipose tissue was positively predicted by fasting 2-arachidonoylglycerol (2-AG; P < .04). Conclusion EC levels of the NAE family independently follow plasma NEFA metabolism, whereas 2-MAG closely follow the spillover of triglyceride-rich lipoprotein intravascular lipolytic products. Whether these associations are causal requires further investigation.

The partitioning of fatty acids between membrane and storage lipids controls ER membrane expansion.

The biogenesis of membrane-bound organelles involves the synthesis, remodelling and degradation of their constituent phospholipids. How these pathways regulate organelle size, remains still poorly understood. Here we demonstrate that a lipid degradation pathway inhibits the expansion of the endoplasmic reticulum (ER) membrane. Phospholipid diacylglycerol acyltransferases (PDATs) use endogenous phospholipids as fatty acyl donors to generate triglyceride stored in lipid droplets. The significance of this non-canonical triglyceride biosynthetic pathway has remained elusive. We find that the activity of the yeast PDAT Lro1 is regulated by a membrane-proximal domain facing the luminal side of the ER bilayer. To reveal the biological roles of PDATs, we engineered an Lro1 variant with derepressed activity. We show that active Lro1 mediates the retraction of ER membrane expansion driven by phospholipid synthesis. Furthermore, the subcellular distribution and membrane turnover activity of Lro1 are controlled by diacylglycerol, produced by the activity of Pah1, a conserved member of the lipin family. Collectively, our findings reveal a lipid metabolic network that regulates endoplasmic reticulum biogenesis by converting phospholipids into storage lipids.

Experimental investigation of carbamide-assisted smart water flooding for enhancing heavy oil recovery from carbonate reservoirs

This study explores the impact of carbamide at different concentrations on smart water flooding into carbonate reservoirs. The aim is to find out how the presence of carbamide can influence the mechanisms of smart water flooding at rock/brine and oil/brine interfaces. The results revealed that interfacial tension (IFT) reduces as the carbamide concentration increases in the brine. Indeed, the carbamide decomposes at elevated temperatures, and in-situ surface active agents are formed at the oil/brine interface, reducing IFT values. Further, while the dilution of seawater (SW) is unable to change the oil-wet wettability, the carbamide can make the carbonate surface more water-wet by elevating its concentration. Additionally, the corresponding mechanisms of this wettability alteration would be the formation of in-situ surface active agents, electrostatic interactions, and hydrogen bond formation at the rock/brine interface. Among K+, Mg2+, and SO42−, adjusting the concentration of sulfate ions in SW leads to greater IFT reduction in the presence of carbamide. In addition, the contact angle is further reduced as K+ concentration is doubled in the solution; however, this reduction is not significant as compared to Mg2+ and SO42−. Also, ten-times diluted seawater (10dsw) produced more micro-dispersions in the oil phase. Nevertheless, the presence of carbamide in 10dws had a negative impact on the micro-dispersion formation, which is one of the driving mechanisms of smart water flooding. At a lower carbamide concentration (1000 ppm), more carboxylic acids and ketones were observed in the brines due to the partitioning and dissociation of naphthenic acids. On the contrary, as carbamide concentration increased to 10000 ppm, amounts of carboxylic acids declined due to the production of in-situ surface active agents at the oil/brine interface. Bottle test experiments indicated that water-in-oil emulsions were generated in the presence of carbamide. The mean water droplet size grew as carbamide concentration rose to 25000 ppm; nonetheless, further increase in the carbamide concentration resulted in mean droplet size reduction. Calcite-coated micromodel flooding illustrated that oil recovery of 21.6, 24, and 27.2 % was found at carbamide concentrations of 1000, 10000, and 100000 ppm. Furthermore, a three-time increase in SO42− concentration at 10000 ppm of carbamide offered a better performance in boosting oil recovery than tuning K+ and Mg2+ concentrations in carbamide/SW solutions. The findings of this study underscore the promising prospects of leveraging carbamide to enhance the efficacy of smart water solutions in carbonate reservoirs, particularly regarding IFT modification, wettability alteration, and oil recovery enhancement.

Partition of Chlorogenic and Nicotinic Acids Using Eco-Friendly ATPSs Containing Ethyl Lactate at 298.15 K and 0.1 MPa

Partition of Chlorogenic and Nicotinic Acids Using Eco-Friendly ATPSs Containing Ethyl Lactate at 298.15 K and 0.1 MPa

Fate and partition of perfluoroalkyl acids (PFAAs) driven by particles in mangrove ecosystems: Mechanistic insights and environmental implications

A critical gap in understanding emerging pollutants in mangrove ecosystems should be addressed. Despite their ecological importance, the state of environmental quality in fragmented mangrove patches, especially emerging contaminants, remains largely uncharted. Our research presented an in-depth analysis of the distribution of perfluoroalkyl acids (PFAAs) across porewater, suspended particles, and sediment in these small, fragmented mangroves, revealing the mechanisms behind their distribution. The findings indicated that PFAA concentrations in sediments were generally lower than in suspended particles, except for C12–C14 perfluorinated carboxylic acids (PFCAs) and C4–C6 perfluorinated sulfonic acids (PFSAs). A comparison of contamination levels in different mangrove patches concurred with conventional water quality assessments and crab burrow surveys, showing that large artificially planted patches were less contaminated, while areas with intense human activity were more polluted. Notably, no significant differences were observed in the concentrations of long-chain PFAAs and PFCAs between patches (p > 0.1). Elevated crab burrowing activity and higher concentrations of perfluorobutanoic acid (PFBA) and perfluorohexane sulfonic acid (PFHxS) in suspended particles in low intertidal zones suggested that seafood, particularly crabs and shellfish, might be at risk of PFAA pollution. Rainfall-runoff was identified as the primary source of PFAA pollution in porewater and suspended particle systems in these areas. The transport of PFAAs and organic carbon in mangroves was influenced by the concentrations and properties of suspended particles. These insights were critical for developing targeted environmental management strategies to mitigate the impact of PFAAs and preserve the ecological integrity of mangrove ecosystems.

Bacteria in clouds biodegrade atmospheric formic and acetic acids

Abstract. Formic and acetic acids are major organic species in cloud water and affect precipitation acidity. In atmospheric models, their losses are limited to chemical oxidation in the gas and aqueous phases and deposition processes. Previous lab studies suggest that these acids can be efficiently biodegraded in water by atmospherically relevant bacteria. However, the importance of biodegradation as a loss process in the atmospheric multiphase system has not been fully assessed. We implemented biodegradation as a sink of formic and acetic acids in a detailed atmospheric multiphase chemistry model. In our model, biodegradation is considered in 0.1 % of cloud droplets according to atmospheric bacteria concentrations of 0.1 cm−3. We predict that up to 20 ppt h−1 formic acid and 5 ppt h−1 acetic acid are biodegraded. This translates into a concentration change of 20 % and 3 % in addition to that caused by chemical losses. Our sensitivity studies suggest that acetic acid is most efficiently biodegraded at pH > 5, whereas biodegradation is least efficient for formic acid under such conditions. This trend can be explained by the fact that formic acid partitions more efficiently into the aqueous phase due to its higher Henry's law constant (KH,eff(HCOOH)=2×105 M atm−1 vs. KH,eff(CH3COOH)=3×104 M atm−1 at pH = 5). Therefore, under such conditions, formic acid evaporates less efficiently from bacteria-free droplets, resulting in less formic acid in the gas phase for dissolution bacteria-containing droplets to replenish biodegraded acid. Our analysis demonstrates that previous estimates of the importance of atmospheric biodegradation were often biased high as they did not correctly account for such uptake limitation in bacteria-containing droplets. The results suggest that, under specific conditions, biological processes can significantly affect atmospheric composition and concentrations in particular volatile, moderately soluble organics.

Layer-specific mechanisms of perfluoroalkyl acid (PFAA) transport and partition in estuarine environments: Unveiling the depth-dependent differences

Understanding of characteristics and transport of perfluoroalkyl acids (PFAAs) in heterogeneous estuarine environments is limited. Furthermore, the role of suspended particles (SPS) in different layers remains unclear. This study explores the multiphase distribution process and mechanism of PFAAs controlled by SPS across surface and bottom layers in five small estuaries. Peaks in PFAA concentrations are consistently observed at strongly stratified sites. Concentrations of the PFAAs in both surface and bottom SPS decreased as the degree of mixing increased from strongly stratified levels to well-mixed levels. The water-SPS partitioning of some short-chain PFAAs (PFBS, PFHxA, and PFHpA) is influenced by environmental factors (pH, depth, temperature, and salinity) due to electrostatic interactions, while the sorption of some long-chain PFAAs (PFOA, PFOS, and PFNA) is controlled by SPS and dissolved organic carbon (OC), driven by hydrophobic interactions. Additionally, SPS dominates OC transport in estuarine systems, except in sandy sediment environments. SPS plays a dominant role in PFAA partitioning in both surface and bottom water-SPS systems (p < 0.05), and salinity only significantly affects PFBS in bottom layer (p < 0.01). These findings are critical for understanding the drivers of PFAA partitioning and the roles of SPS in different layers, underscoring the necessity of considering particle-associated PFAA fractions in future coastal environmental management.

Description of the fasted serum metabolomic signature of lean and obese cats at maintenance and of obese cats under energy restriction.

This study aimed to investigate the serum metabolomic profile of obese and lean cats as well as obese cats before and after energy restriction for weight loss. Thirty cats, 16 obese (body condition score 8 to 9/9) and 14 lean (body condition score 4 to 5/9), were fed a veterinary weight loss food during a 4-week period of weight maintenance (L-MAINT and O-MAINT). The 16 obese cats were then energy restricted by a 60% energy intake reduction with the same food for a 10-week period (O-RESTRICT). Fasted serum metabolites were measured using nuclear magnetic resonance and direct infusion mass spectrometry after the maintenance period for L-MAINT and O-MAINT cats and after the energy restriction period for O-RESTRICT and compared between groups using a two-sided t-test. Obese cats lost 672 g ± 303 g over the 10-week restriction period, representing a weight loss rate of 0.94 ± 0.28% per week. Glycine, l-alanine, l-histidine, l-glutamine, 2-hydroxybutyrate, isobutryric acid, citric acid, creatine, and methanol were greater in O-RESTRICT compared to O-MAINT. There was a greater concentration of long-chain acylcarnitines in O-RESTRICT compared to both O-MAINT and L-MAINT, and greater total amino acids compared to O-MAINT. Glycerol and 3-hydroxybutyric acid were greater in O-MAINT compared to L-MAINT, as were several lysophosphatidylcholines. Thus, energy restriction resulted in increased dispensable amino acids in feline serum which could indicate alterations in amino acid partitioning. An increase in lipolysis was not evident, though greater circulating acylcarnitines were observed, suggesting that fatty acid oxidation rates may have been greater under calorie restriction. More research is needed to elucidate energy metabolism and substrate utilization, specifically fatty acid oxidation and methyl status, during energy restriction in strict carnivorous cats to optimize weight loss.

Partition of humic acids using alkaline aqueous two‐phase systems constituted of alcohol and hydroxides

AbstractBACKGROUNDHumic acids (HAs) are macromolecules classified within the group of humic substances that are mainly related to the agricultural and environmental sectors, but they have attracted interest from the medicine, pharmaceutical and cosmetic industries. However, these latter sectors depend on developing extraction and purification technologies for adequate use. Thus, this paper aims to study the partitioning and recovery of HA using alkaline two‐phase aqueous systems (ATPSs) based on alkali metal‐based hydroxides and alcohols. Initially, the influence of alcohols (methanol, ethanol, 1‐propanol, and 2‐propanol) and hydroxides [sodium (NaOH), potassium (KOH) and lithium (LiOH)] in the phase diagrams construction was addressed.RESULTSThe phase formation is correlated to an increase in the hydrophobicity of alcohols and hydroxides, which allows for the enlargement of the biphasic region. In the proposed systems, HA is always partitioned to the hydroxide‐rich phase. Increasing the hydrophobicity of the alcohol favors the migration of HA to the opposite phase, while increasing the hydrophilicity of the hydroxides leads to better partition and recovery values. It was observed that increasing TLL favors the recovery of HA. Furthermore, there was a decrease in alcohol concentration in the hydroxide‐rich phase with an increase in the alkyl chain and TLL, improving the recovery. Finally, the best reached‐recovery value was 98.18 ± 0.41% (KHA = 0.038 ± 0.02) for ATPS formed by 1‐propanol + NaOH with TLL ≈ 55 at 298 K.CONCLUSIONSAlkaline systems can be a novel route for recovering humic substances from the environment. © 2024 Society of Chemical Industry (SCI).

UMAMIT44 is a key player in glutamate export from Arabidopsis chloroplasts.

Selective partitioning of amino acids among organelles, cells, tissues, and organs is essential for cellular metabolism and plant growth. Nitrogen assimilation into glutamine and glutamate and de novo biosynthesis of most protein amino acids occur in chloroplasts; therefore, various transport mechanisms must exist to accommodate their directional efflux from the stroma to the cytosol and feed the amino acids into the extraplastidial metabolic and long-distance transport pathways. Yet, Arabidopsis (Arabidopsis thaliana) transporters functioning in plastidial export of amino acids remained undiscovered. Here, USUALLY MULTIPLE ACIDS MOVE IN AND OUT TRANSPORTER 44 (UMAMIT44) was identified and shown to function in glutamate export from Arabidopsis chloroplasts. UMAMIT44 controls glutamate homeostasis within and outside of chloroplasts and influences nitrogen partitioning from leaves to sinks. Glutamate imbalances in chloroplasts and leaves of umamit44 mutants impact cellular redox state, nitrogen and carbon metabolism, and amino acid (AA) and sucrose supply of growing sinks, leading to negative effects on plant growth. Nonetheless, the mutant lines adjust to some extent by upregulating alternative pathways for glutamate synthesis outside the plastids and by mitigating oxidative stress through the production of other amino acids and antioxidants. Overall, this study establishes that the role of UMAMIT44 in glutamate export from chloroplasts is vital for controlling nitrogen availability within source leaf cells and for sink nutrition, with an impact on growth and seed yield.

Multiple Myeloma Induced IL-6 Reprograms Lipid Metabolism through a CD36 Dependent Mechanism

Multiple Myeloma (MM) requires a high metabolic turnover to allow for expansion and paraprotein production. MM metabolism is complex relying on various metabolic pathways to fuel its survival including fatty acid (FA) oxidation (1, 2). The liver is a master regulator of fatty acid metabolism and distribution. It also stores FA as lipid droplets during steady state or produces ketone bodies during a starvation state (3). This study aimed to determine whether MM alters FA uptake within the liver and by what mechanism this occurs. To investigate the role of FA metabolism we used a mouse model of MM (5TGM1 (GFP) cells into KaLwRij mice). Analysis of serum from 5TGM1 (GFP) engrafted KaLwRij mice showed increased FFA when compared to control animals. RT-qPCR of RNA isolated from liver samples showed a decrease in genes involved in FA uptake and metabolism. These genes included the long chain fatty acid transporter CD36, which belongs to the class B scavenger receptors and is essential for uptake of LCFA in hepatocytes. In vitro modelling showed that primary hepatocytes cultured in conditioned media from 5TGM1 cells had significantly reduced expression of CD36. Furthermore, serum isolated from MM patients (n=6) downregulated CD36 expression in the human hepatocarcinoma cell line, HepG2. These data support the hypothesis that MM induces a factor that alters lipid metabolism in the liver. To detemine the factor that MM secretes, and which regulates FA uptake in the liver, a cytokine array of the serum from 5TGM1 (GFP) engrafted KaLwRij mice was compared to control serum. Pathway analysis revealed interleukin-6 (IL-6) as possible key factor involved in regulating liver FA uptake. In vitro gene expressions analysis of mouse primary hepatocytes revealed that addition of IL-6 to the medium inhibited expression of CD36 and also showed that primary hepatocytes had decreased reliance on FA oxidation when treated with IL-6. Furthermore. 5TGM1 (GFP) engrafted KaLwRij mice showed increased serum IL-6 levels compared to controls. Finally, using the IL-6 neutralising antibody, we observed that this blocked CD36 downregulation in HepG2 cultured with MM patient serum. Here we demonstrate that MM changes FA metabolism in the liver through upregulation of IL-6. Gene expression of FA genes identifies CD36 is down regulated in hepatocytes in response to IL-6. These data suggest that MM is able to redirect FFA away from the liver by down regulating CD36, which mediates FFA uptake in the liver. References Panaroni C, Fulzele K, Mori T, Siu KT, Onyewadume C, Maebius A, et al. Multiple myeloma cells induce lipolysis in adipocytes and uptake fatty acids through fatty acid transporter proteins. Blood. 2022;139(6):876-88.Tirado-Vélez JM, Joumady I, Sáez-Benito A, Cózar-Castellano I, Perdomo G. Inhibition of fatty acid metabolism reduces human myeloma cells proliferation. PLoS One. 2012;7(9):e46484.Hodson L, Gunn PJ. The regulation of hepatic fatty acid synthesis and partitioning: the effect of nutritional state. Nat Rev Endocrinol. 2019;15(12):689-700.

Fatty acids and inflammatory stimuli induce expression of long-chain acyl-CoA synthetase 1 to promote lipid remodeling in diabetic kidney disease

Fatty acid handling and complex lipid synthesis are altered in the kidney cortex of diabetic patients. We recently showed that inhibition of the renin-angiotensin system without changes in glycemia can reverse diabetic kidney disease (DKD) and restore the lipid metabolic network in the kidney cortex of diabetic (db/db) mice, raising the possibility that lipid remodeling may play a central role in DKD. However, the roles of specific enzymes involved in lipid remodeling in DKD have not been elucidated. In the present study, we used this diabetic mouse model and a proximal tubule epithelial cell line (HK2) to investigate the potential relationship between long-chain acyl-CoA synthetase 1 (ACSL1) and lipid metabolism in response to fatty acid exposure and inflammatory signals. We found ACSL1 expression was significantly increased in the kidney cortex of db/db mice, and exposure to palmitate (PA) or tumor necrosis factor (TNF-α) significantly increased Acsl1 mRNA expression in HK-2 cells. In addition, PA treatment significantly increased the levels of long-chain acylcarnitines and fatty acyl CoAs in HK2 cells, and these increases were abolished in HK2 cell lines with specific deletion of Acsl1(Acsl1KO cells), suggesting a key role for ACSL1 in fatty acid β-oxidation. In contrast, TNF-α treatment significantly increased the levels short-chain acylcarnitines and long-chain fatty acyl CoAs in HK2 cells but not in Acsl1KO cells, consistent with fatty acid channeling to complex lipids. Taken together, our data demonstrate a key role for ACSL1 in regulating lipid metabolism, fatty acid partitioning, and inflammation.

Tithonia diversifolia Improves In Vitro Rumen Microbial Synthesis of Sheep Diets without Changes in Total Gas and Methane Production

Among the alternatives identified as capable of making livestock farming a more efficient activity and reducing its environmental impact, the use of feeds with high digestibility and the use of non-conventional fodder species can be highlighted. Tithonia diversifolia (Hemsl.) A. Gray (TD) has already gained attention as a feed for ruminants. Nonetheless, there has been little discussion about the impacts of this plant on the rumen dynamics that lead to better animal performance. The aim of this study was to assess how increasing levels of TD could affect ruminal microbial biomass synthesis, degradability, and in vitro gas production (IVGP) of diets. Four diets were evaluated: a control diet (TD0: 400 g kg−1 soybean meal and maize grain, and 600 g kg−1 Tifton 85 hay (Cynodon spp.)) and three increasing levels of TD (TD9: 90, TD27: 270, and TD45: 450 g kg−1–dry matter basis) as a replacement for dietary roughage. A 96 h IVGP assay was carried out and five incubation times (2, 4, 10, 24, and 96 h) were used for degradability determination. Gas produced, methane (CH4), degradability of organic matter (IVDOM), short-chained fatty acid (SCFA) production, partitioning factor (PF), and microbial biomass (MB) were evaluated among treatments. There was no significant effect (p &gt; 0.05) between TD inclusion and IVGP at most incubation times; only at 6 h of incubation did gas production increase linearly with TD inclusion (R2 = 0.19; p &lt; 0.05). TD inclusion had no effects on CH4. IVDOM increased linearly with TD inclusion at 6 and 10 h, with TD45 being more degradable than the control diet at 6 h only. There was a positive linear relationship (R2 = 0.20; p &lt; 0.05) between TD inclusion and PF. TD45 had significantly higher PF values than the control. MB also increased linearly (R2 = 0.30; p &lt; 0.05) with TD inclusion, and all diets with TD had significantly more MB than the control diet. The inclusion of TD at the levels used in this work was revealed to have a positive impact on microbial protein synthesis, which could be related to the higher microbial efficiency of increased substrate quality.

An acute upregulation of hepatic de novo lipogenesis does not attenuate the partitioning of polyunsaturated fatty acids into oxidation pathways

An acute upregulation of hepatic de novo lipogenesis does not attenuate the partitioning of polyunsaturated fatty acids into oxidation pathways

Daylength variation affects growth, photosynthesis, leaf metabolism, partitioning, and metabolic fluxes.

Daylength, a seasonal and latitudinal variable, exerts a substantial impact on plant growth. However, the relationship between daylength and growth is nonproportional, suggesting the existence of adaptive mechanisms. Thus, our study aimed to comprehensively investigate the adaptive strategies employed by plants in response to daylength variation. We grew false flax (Camelina sativa) plants, a model oilseed crop, under long-day (LD) and short-day (SD) conditions and used growth measurements, gas exchange measurements, and isotopic labeling techniques, including 13C, 14C, and 2H2O, to determine responses to different daylengths. Our findings revealed that daylength influences various growth parameters, photosynthetic physiology, carbon partitioning, metabolic fluxes, and metabolite levels. SD plants employed diverse mechanisms to compensate for reduced CO2 fixation in the shorter photoperiod. These mechanisms included enhanced photosynthetic rates and reduced respiration in the light (RL), leading to increased shoot investment. Additionally, SD plants exhibited reduced rates of the glucose 6-phosphate (G6P) shunt and greater partitioning of sugars into starch, thereby sustaining carbon availability during the longer night. Isotopic labeling results further demonstrated substantial alterations in the partitioning of amino acids and TCA cycle intermediates between rapidly and slowly turning over pools. Overall, the results point to multiple developmental, physiological, and metabolic ways in which plants adapt to different daylengths to maintain growth.

Role of Dgat2 in Glucose Uptake and Fatty Acid Metabolism in C2C12 Skeletal Myotubes.

Acyl-coenzyme A (CoA):diacylglycerol acyltransferase 2 (DGAT2) catalyzes the last stage of triacylglycerol (TAG) synthesis, a process that forms ester bonds with diacylglycerols (DAG) and fatty acyl-CoA substrates. The enzymatic role of Dgat2 has been studied in various biological species. Still, the full description of how Dgat2 channels fatty acids in skeletal myocytes and the consequence thereof in glucose uptake have yet to be well established. Therefore, this study explored the mediating role of Dgat2 in glucose uptake and fatty acid partitioning under short interfering ribonucleic acid (siRNA)-mediated Dgat2 knockdown conditions. Cells transfected with Dgat2 siRNA downregulated glucose transporter type 4 (Glut4) messenger RNA (mRNA) expression and decreased the cellular uptake of [1-14C]-labeled 2-deoxyglucose up to 24.3% (p < 0.05). Suppression of Dgat2 deteriorated insulininduced Akt phosphorylation. Dgat2 siRNA reduced [1-14C]-labeled oleic acid incorporation into TAG, but increased the level of [1-14C]-labeled free fatty acids at 3 h after initial fatty acid loading. In an experiment of chasing radioisotope-labeled fatty acids, Dgat2 suppression augmented the level of cellular free fatty acids. It decreased the level of re-esterification of free fatty acids to TAG by 67.6% during the chase period, and the remaining pulses of phospholipids and cholesteryl esters were decreased by 34.5% and 61%, respectively. Incorporating labeled fatty acids into beta-oxidation products increased in Dgat2 siRNA transfected cells without gene expression involving fatty acid oxidation. These results indicate that Dgat2 has regulatory function in glucose uptake, possibly through the reaction of TAG with endogenously released or recycled fatty acids.

L-Phenylalanine Partitioning Mechanisms in Model Biological Membranes.

Time-resolved fluorescence spectroscopy in combination with differential scanning calorimetry (DSC) was used to study the chemical interactions that occur when l-phenylalanine is introduced to solutions containing phosphatidylcholine vesicles. Studies reported in this work address open questions about l-Phe's affinity for lipid vesicle bilayers, the effects of l-Phe partitioning on bilayer properties, l-Phe's solvation within a lipid bilayer, and the amount of l-Phe within that local solvation environment. DSC data show that l-Phe reduces the amount of heat necessary to melt saturated phosphatidylcholine bilayers from their gel to liquid-crystalline state but does not change the transition temperature (Tgel-lc). Time-resolved emission shows only a single l-Phe lifetime at low temperatures corresponding to l-Phe remaining solvated in aqueous solution. At temperatures close to Tgel-lc, a second, shorter lifetime appears that is assigned to l-Phe already embedded within the membrane that becomes hydrated as water starts to permeate the lipid bilayer. This new lifetime is attributed to a conformationally restricted rotamer in the bilayer's polar headgroup region and accounts for up to 30% of the emission amplitude. Results reported for dipalmitoylphosphatidylcholine (DPPC, 16:0) lipid vesicles prove to be general, with similar effects observed for dimyristoylphosphatidylcholine (DMPC, 14:0) and distearoylphosphatidylcholine (DSPC, 18:0) vesicles. Taken together, these results create a complete and compelling picture of how l-Phe associates with model biological membranes. Furthermore, this approach to examining amino acid partitioning into membranes and the resulting solvation forces points to new strategies for studying the structure and chemistry of membrane-soluble peptides and selected membrane proteins.

Abundant nitrogen oxide and weakly acidic environment synergistically promote daytime particulate nitrate pollution

Nitrate is formed through the chemical production of gas-phase nitric acid and subsequent partitioning to the aerosol phase during the daytime. Many studies in the past separated these two aspects, even though they occur simultaneously in the atmosphere. To better understand the nitrate formation mechanism and effectively mitigate its production, it is necessary to consider the synergy between these two mechanisms. For this, we analyze hourly-speciated ambient observations data, with EK&TMA (Empirical Kinetic & Thermodynamic Modeling Approach) map to comprehensively explore the factors controlling nitrate production. Results show that precursor NO2 concentration and aerosol pH, which are related to anthropogenic activities, are the two major factors for chemical kinetics production and gas/particle thermodynamic partitioning processes respectively. Abundant NO2 and weakly acidic environments are favorable conditions for daytime particulate nitrate pollution, thus collaborative control of coal source, vehicle source, and dust source is needed to alleviate nitrate pollution.