The malate-activated ALMT12 anion channel in the grass Brachypodium distachyon is co-activated by Ca2+/calmodulin

In plants, strict regulation of stomatal pores is critical for modulation of CO2 fixation and transpiration. Under certain abiotic and biotic stressors, pore closure is initiated through anionic flux, with calcium (Ca2+) playing a central role. The aluminum-activated malate transporter 12 (ALMT12) is a malate-activated, voltage-dependent member of the aluminum-activated malate transporter family that has been implicated in anionic flux from guard cells controlling the stomatal aperture. Herein, we report the characterization of the regulatory mechanisms mediating channel activities of an ALMT from the grass Brachypodium distachyon (BdALMT12) that has the highest sequence identity to Arabidopsis thaliana ALMT12. Electrophysiological studies in a heterologous cell system confirmed that this channel is malate- and voltage-dependent. However, this was shown to be true only in the presence of Ca2+ Although a general kinase inhibitor increased the current density of BdALMT12, a calmodulin (CaM) inhibitor reduced the Ca2+-dependent channel activation. We investigated the physiological relevance of the CaM-based regulation in planta, where stomatal closure, induced by exogenous Ca2+ ionophore and malate, was shown to be inhibited by exogenous application of a CaM inhibitor. Subsequent analyses revealed that the double substitutions R335A/R338A and R335A/K342A, within a predicted BdALMT12 CaM-binding domain (CBD), also decreased the channels' ability to activate. Using isothermal titration calorimetry and CBD-mimetic peptides, as well as CaM-agarose affinity pulldown of full-length recombinant BdALMT12, we confirmed the physical interaction between the CBD and CaM. Together, these findings support a co-regulatory mechanism of BdALMT12 activation by malate, and Ca2+/CaM, emphasizing that a complex regulatory network modulates BdALMT12 activity.

A Combination of Tri-Leucine and Angiopep-2 Drives a Polyanionic Polymalic Acid Nanodrug Platform Across the Blood-Brain Barrier

One of the major problems facing the treatment of neurological disorders is the poor delivery of therapeutic agents into the brain. Our goal is to develop a multifunctional and biodegradable nanodrug delivery system that crosses the blood-brain barrier (BBB) to access brain tissues affected by neurological disease. In this study, we synthesized a biodegradable nontoxic β-poly(l-malic acid) (PMLA or P) as a scaffold to chemically bind the BBB crossing peptides Angiopep-2 (AP2), MiniAp-4 (M4), and the transferrin receptor ligands cTfRL and B6. In addition, a trileucine endosome escape unit (LLL) and a fluorescent marker (rhodamine or rh) were attached to the PMLA backbone. The pharmacokinetics, BBB penetration, and biodistribution of nanoconjugates were studied in different brain regions and at multiple time points via optical imaging. The optimal nanoconjugate, P/LLL/AP2/rh, produced significant fluorescence in the parenchyma of cortical layers II/III, the midbrain colliculi, and the hippocampal CA1-3 cellular layers 30 min after a single intravenous injection; clearance was observed after 4 h. The nanoconjugate variant P/LLL/rh lacking AP2, or the variant P/AP2/rh lacking LLL, showed significantly less BBB penetration. The LLL moiety appeared to stabilize the nanoconjugate, while AP2 enhanced BBB penetration. Finally, nanoconjugates containing the peptides M4, cTfRL, and B6 displayed comparably little and/or inconsistent infiltration of brain parenchyma, likely due to reduced trans-BBB movement. P/LLL/AP2/rh can now be functionalized with intra-brain targeting and drug treatment moieties that are aimed at molecular pathways implicated in neurological disorders.

Synthesis and Structure Reassignment of Malylglutamate, a Recently Discovered Earthworm Metabolite

Malylglutamate, a newly identified metabolite in earthworms, was synthesized using a traditional peptide coupling approach for assembling the amide from protected malate and glutamate precursors. The proposed structure (1) and a diastereomer were synthesized, but their NMR spectra did not match the natural sample. Further analysis of the natural sample using HMBC spectroscopy suggested an alternative attachment of the malyl moiety, and β-malylglutamate (2) diastereomers were synthesized, L,L-2 and D,D-2. NMR spectra were an excellent match with the natural sample, and chiral-phase chromatography was employed to identify (-)-β-l-malyl-l-glutamate (2) as the isomer native to Eisenia fetida.

Malic acid production from biodiesel derived crude glycerol using morphologically controlled Aspergillus niger in batch fermentation

In the present investigation, the effects of crude glycerol concentration, spore inoculum concentration, yeast extract concentration and shaking frequency on seed morphology of Aspergillus niger PJR1 on malic acid production were investigated and dispersed fungal mycelium with higher biomass (20.25 ± 0.91 g/L) was obtained when A. niger PJR1 grow on crude glycerol. Dry cell weight under dispersed fermentation was 21.28% higher than usual pellet fermentation. The optimal crude glycerol, nitrogen source and nitrogen source concentration were found to be 160 g/L, yeast extract and 1.5 g/L, respectively. Batch fermentation in a shake flask culture containing 160 g/L crude glycerol resulted in the yield of malic acid 83.23 ± 1.86 g/L, after 192 h at 25 °C. Results revealed that morphological control of A. niger is an efficient method for increased malic acid production when crude glycerol derived from biodiesel production is used as feedstock.

Conformational changes on substrate binding revealed by structures of Methylobacterium extorquens malate dehydrogenase

Three high-resolution X-ray crystal structures of malate dehydrogenase (MDH; EC 1.1.1.37) from the methylotroph Methylobacterium extorquens AM1 are presented. By comparing the structures of apo MDH, a binary complex of MDH and NAD+, and a ternary complex of MDH and oxaloacetate with ADP-ribose occupying the pyridine nucleotide-binding site, conformational changes associated with the formation of the catalytic complex were characterized. While the substrate-binding site is accessible in the enzyme resting state or NAD+-bound forms, the substrate-bound form exhibits a closed conformation. This conformational change involves the transition of an α-helix to a 310-helix, which causes the adjacent loop to close the active site following coenzyme and substrate binding. In the ternary complex, His284 forms a hydrogen bond to the C2 carbonyl of oxaloacetate, placing it in a position to donate a proton in the formation of (2S)-malate.

Structure of glyoxysomal malate dehydrogenase (MDH3) from Saccharomyces cerevisiae

Malate dehydrogenase (MDH), a carbohydrate and energy metabolism enzyme in eukaryotes, catalyzes the interconversion of malate to oxaloacetate (OAA) in conjunction with that of nicotinamide adenine dinucleotide (NAD+) to NADH. Three isozymes of MDH have been reported in Saccharomyces cerevisiae: MDH1, MDH2 and MDH3. MDH1 is a mitochondrial enzyme and a member of the tricarboxylic acid cycle, whereas MDH2 is a cytosolic enzyme that functions in the glyoxylate cycle. MDH3 is a glyoxysomal enzyme that is involved in the reoxidation of NADH, which is produced during fatty-acid β-oxidation. The affinity of MDH3 for OAA is lower than those of MDH1 and MDH2. Here, the crystal structures of yeast apo MDH3, the MDH3-NAD+ complex and the MDH3-NAD+-OAA ternary complex were determined. The structure of the ternary complex suggests that the active-site loop is in the open conformation, differing from the closed conformations in mitochondrial and cytosolic malate dehydrogenases.

Role of organic acids in the integration of cellular redox metabolism and mediation of redox signalling in photosynthetic tissues of higher plants

Organic acids play a crucial role in numerous metabolic processes accompanied by transfer of electrons and protons and linked to the reduction/oxidation of major redox couples in plant cells, such as NAD, NADP, glutathione, and ascorbate. Fluxes through the pathways metabolizing organic acids modulate redox states in cell compartments, contribute to generation of reactive oxygen and nitrogen species, and mediate signal transduction processes. Organic acid metabolism not only functions to equilibrate the redox potential in plant cells but also to transfer redox equivalents between cell compartments supporting various metabolic processes. The most important role in this transfer belongs to different forms of malate dehydrogenase interconverting malate and oxaloacetate or forming pyruvate (malic enzymes). During photosynthesis malate serves as a major form of transfer of redox equivalents from chloroplasts to the cytosol and other compartments via the malate valve. On the other hand, mitochondria, via alterations of their redox potential, become a source of citrate that can be transported to the cytosol and support biosynthesis of amino acids. Citrate is also an important retrograde signalling compound that regulates transcription of several genes including those encoding the alternative oxidase. The alternative oxidase, which is activated by increased redox potential and by pyruvate, is, in turn, important for the maintenance of redox potential in mitochondria. The roles of organic acids in establishing redox equilibrium, supporting ionic gradients on membranes, acidification of the extracellular medium, and regulation of production of reactive oxygen and nitrogen species are discussed.

Effects of Fe(III)-fulvic acid on Cu removal via adsorption versus coprecipitation

This study compared the sorption and extractability of Cu following adsorption (SOR) and coprecipitation(CPT). The effect of solution pH, Fe: organic carbon (OC) ratios and fulvic acid (FA) on the combined removal of Cu was investigated in the batch tests using Fe(III) precipitates as a sorbent. Transmission electron microscope (TEM) images demonstrated that the coexisting FA reduced the particle size of ferrihydrites as expected. Generally, more Cu was eliminated in coprecipitation compared with adsorption and the dissolved Cu left in solutions decreased as the pH increased, most of dissolved Cu was trapped at pH 6 and above. Meanwhile, the inhibition or promotion of Cu removal really depended on the different Fe: OC ratios. The addition of FA led to a further decrease of Cu concentrations in CPT systems with Fe/OC ratio of 1:3, however, Cu removal was hindered in the presence of FA in SOR systems. In the case of extraction experiments, the addition of l-malic acid (MA), oxalic acid (OA) and citric acid (CA) resulted in lower extractability of coprecipitated Cu than adsorption samples. The gaps in extractions were seemed to be a consequence of tight Cu binding in CPT products, and the more feasible desorption of Cu from the surface of SOR samples. Based on the results of Cu adsorption and coprecipitation, coprecipitation of Cu with ferrihydrites was the more effective Cu sequestration mechanism in the removal of Cu. These results are helpful to understand the complicated interactions among Fe(III), FA and Cu (II) in the natural environment.

Sub-minute kinetics of human red cell fumarase: 1 H spin-echo NMR spectroscopy and 13 C rapid-dissolution dynamic nuclear polarization

Fumarate is an important probe of metabolism in hyperpolarized magnetic resonance imaging and spectroscopy. It is used to detect the release of fumarase in cancer tissues, which is associated with necrosis and drug treatment. Nevertheless, there are limited reports describing the detailed kinetic studies of this enzyme in various cells and tissues. Thus, we aimed to evaluate the sub-minute kinetics of human red blood cell fumarase using nuclear magnetic resonance (NMR) spectroscopy, and to provide a quantitative description of the enzyme that is relevant to the use of fumarate as a probe of cell rupture. The fumarase reaction was studied using time courses of 1 H spin-echo and 13 C-NMR spectra. 1 H-NMR experiments showed that the fumarase reaction in hemolysates is sufficiently rapid to make its kinetics amenable to study in a period of approximately 3 min, a timescale characteristic of hyperpolarized 13 C-NMR spectroscopy. The rapid-dissolution dynamic nuclear polarization (RD-DNP) technique was used to hyperpolarize [1,4-13 C]fumarate, which was injected into concentrated hemolysates. The kinetic data were analyzed using recently developed FmRα analysis and modeling of the enzymatic reaction using Michaelis-Menten equations. In RD-DNP experiments, the decline in the 13 C-NMR signal from fumarate, and the concurrent rise and fall of that from malate, were captured with high spectral resolution and signal-to-noise ratio, which allowed the robust quantification of fumarase kinetics. The kinetic parameters obtained indicate the potential contribution of hemolysis to the overall rate of the fumarase reaction when 13 C-NMR RD-DNP is used to detect necrosis in animal models of implanted tumors. The analytical procedures developed will be applicable to studies of other rapid enzymatic reactions using conventional and hyperpolarized substrate NMR spectroscopy.

Effect of low-molecular-weight organic acids on hematite dissolution promoted by desferrioxamine B

Siderophores, as strong chelators specific to iron, have been intensively studied in relation to the facilitation of biological iron acquisition from iron oxides. In this study, the dissolution of hematite in the presence of the siderophore desferrioxamine B (DFOB) and three low-molecular-weight organic acids (LMWOAs, i.e., oxalic, citric, or malic acid) was investigated at three pH conditions (3.0, 5.5, and 9.0). Hematite dissolution was pH-dependent and LMWOA-specific. The adsorption of DFOB on hematite was significantly higher at pH 9.0 than at the other pH values. The adsorption of oxalic acid on hematite, however, showed a descending trend as pH was increased, and adsorption of citric and malic acids was not significantly affected by pH. The Fourier transform infrared (FTIR) results also indicated the occurrence of these ligands' adsorption. After acidification, dissolved iron was detected only in suspensions of hematite pre-adsorbed with oxalic acid at pH 5.5 and 9.0 or pre-adsorbed with citric acid at pH 5.5, indicating that these LMWOAs promoted the formation of labile iron on the hematite surface. Based on previous research and the results of this study, a hypothetical model is proposed. These results provide insight into the effect of LMWOAs on the dissolution of hematite promoted by DFOB.

Experience of correcting endothelial dysfunction in children-residents of radioactively contaminated areas by nitric oxide potential donator citrulline

OBJECTIVE

to determine the effectiveness of citrulline use for correcting endothelial dysfunction in children resi dents of radioactively contaminated areas.

MATERIALS AND METHODS

A group of children residents of radioactively contaminated areas with the presence of clinical and paraclinical signs of endothelial dysfunction was selected to assess the effectiveness of correcting endothelial dysfunction by the usage of NO potential donator - citrulline according to the data of selective screen ing. There were determined the biochemical parameters of the content of NO stable metabolites, L arginine, lipid peroxidation, antioxidant enzymes in the blood serum; the indices of cellular and humoral immunity; the instrumen tal indices of vascular endothelium dependent reaction on occlusion test, the lung ventilation capacity, the bioelec tric activity of the myocardium, the autonomic regulation of the cardiovascular system.Examined children were received a course of citrulline malate.

RESULTS AND CONCLUSIONS

An increased content of serum L arginine, nitrite, and amounts of NO metabolites was established in children with endothelial dysfunction who were received a course of citrulline malate. Bronchospasm elimination was noted in the significant part of examined patients after the drug use. Decreased recovery period and increased period of hypercompensation for thermographic circulation index in the test with post occlusion reac tive hyperemia were detected by an evaluation of indicators for vascular endothelium dependent vasodilatation using thermographic method indicating an increased endothelial vasomotor capacity. There was tendency to improve the processes of autonomic regulation of the heart rhythm and repolarization of the heart muscle. The antioxidant effect of used citrulline malate course was determined as: decreased content of serum LPO end products that react with thiobarbituric acid under elevated activity of antioxidant - catalase. An increase in the percentage of T lymphocyte, normalization of their subpopulation composition was noted in dynamics of citrulline malate application.

Phenolic compounds from Bletilla striata

Two new malic acid derivatives, namely eucomic acid 1-methyl ester (2) and 6'''-acetylmilitaline (7), together with ten known compounds (1, 3-6, 8-12), were isolated from the dry tubers of Bletilla striata (Thunb.) Reichb. F., a perennial traditional Chinese medicinal herb, which was used for the treatment of pneumonophthisis, pneumonorrhagia, tuberculosis, and hemorrhage of the stomach or lung. Their structures were elucidated by spectroscopic analyses, including 1D-, 2D-NMR, and HR-ESI-MS.

Enhanced recovery of valuable metals from spent lithium-ion batteries through optimization of organic acids produced by Aspergillus niger

In the present study, spent medium bioleaching method was performed using organic acids produced by Aspergillus niger to dissolve Ni, Co, Mn, Li, Cu and Al from spent lithium-ion batteries (LIBs). Response surface methodology was used to investigate the effects and interactions between the effective factors of sucrose concentration, initial pH, and inoculum size to optimize organic acid production. Maximum citric acid, malic acid, and gluconic acid concentrations of 26,478, 1832.53 and 8433.76ppm, respectively, and a minimum oxalic acid concentration of 305.558ppm were obtained under optimal conditions of 116.90 (gl^-1) sucrose concentration, 3.45% (vv^-1) inoculum size, and a pH value of 5.44. Biogenically-produced organic acids are used for leaching of spent LIBs at different pulp densities. The highest metal recovery of 100% Cu, 100% Li, 77% Mn, and 75% Al occurred at 2% (wv^-1) pulp density; 64% Co and 54% Ni recovery occurred at 1% (wv^-1) pulp density. The bioleaching of metals from spent LIBs can decrease the environmental impact of this waste. The results of this study suggest that the process can be used for large scale industrial purposes.

Influence of lead in the sorption of arsenate by municipal solid waste composts: metal(loid) retention, desorption and phytotoxicity

The ability of two municipal solid waste composts (MSW-C) to sorb As(V) in the presence of Pb(II) and in acidic conditions was investigated. Sorption isotherms and kinetics showed that both MSW-C were able to sorb As(V) in a similar way (∼0.24mmolg^-1 MSW-C), but only when Pb(II) was present (0.45mmolL^-1). The concomitant sorption of Pb(II) by both MSW-C (∼0.40mmolg^-1) suggested that the metal cation was likely acting as bridging element between the negatively charged functional groups of composts and As(V). SEM-EDX analysis of the MSW-C+Pb(II)+As(V) systems supported the association between Pb(II) and As(V), while sequential extraction procedures and organic acids treatment showed that As(V) was strongly retained by MSW-C+Pb(II) and suggested the presence of different interaction types between As(V) and Pb(II). Plant growth experiments highlighted the key role of Pb(II) in the reduction of As(V)-phytotoxicity for triticale plants (×Triticosecale Wittm.) in the presence of MSW-C.

Combined Use of S. pombe and L. thermotolerans in Winemaking. Beneficial Effects Determined Through the Study of Wines' Analytical Characteristics

The most common way to produce red wine is through the use of Saccharomyces cerevisiae strains for alcoholic fermentation and lactic acid bacteria for malolactic fermentation. This traditional winemaking methodology produces microbiologically stable red wines. However, under specific conditions off-flavours can occur, wine quality can suffer and human health problems are possible, especially after the second fermentation by the lactic acid bacteria. In warm countries, problems during the malolactic fermentation arise because of the high pH of the must, which makes it very difficult to properly control the process. Under such conditions, wines with high acetic acid and histamine concentrations are commonly produced. This study investigates a recent red wine-making technology that uses a combination of Lachancea thermotolerans and Schizosaccharomyces pombe as an alternative to the conventional malolactic fermentation. This work studies new parameters such as aroma compounds, amino acids, ethanol index and sensory evaluation. Schizosaccharomyces pombe totally consumes malic acid while Lachancea thermotolerans produces lactic acid, avoiding excessive deacidification of musts with low acidity in warm viticulture areas. This methodology also reduces the malolactic fermentation hazards in wines with low acidity. The main products are wines that contain less acetic acid, less biogenic amines and precursors and less ethyl carbamate precursors than the traditional wines produced via conventional fermentation techniques.

Removal of lead by apatite and its stability in the presence of organic acids

In this study, lead sorption and desorption tests were conducted with apatite and organic acids (i.e. citric, malic, and formic acids) to understand lead removal by apatite in the presence of an organic acid and lead dissolution from the lead- and organic-acid-sorbed apatite by such organic acid exposure. The lead sorption test showed that the amount of lead removed by apatite in the presence of organic acid varied depending on the type of acid used. The molar amounts of calcium dissolved from apatite in the presence and absence of organic acid were exactly the same as those of lead removed even under different pH conditions as well as different organic acid concentrations, indicating that the varying amount of lead removal in the presence of different organic acids resulted from the magnitude of the dissolution of apatite and the precipitation of lead phosphate minerals. The percentages of lead dissolved from the organic-acid-sorbed and non-organic-acid-sorbed apatite by all the organic acid extractions were equal and higher than those by water extraction. In particular, the highest extractions were observed in the non-organic-acid-sorbed apatite by citric and malic acids. These results suggest that to immobilize lead by the use of apatite in the presence of organic acids, much more apatite must be added than in the absence of organic acid, and that measures must be taken to ensure that the immobilized lead is not dissolved.

Dietary linseed oil with or without malate increases conjugated linoleic acid and oleic acid in milk fat and and gene expression in mammary gland and milk somatic cells of lactating goats

Supplementary dietary plant oils have the potential to alter milk fatty acid composition in ruminants as a result of changes in the amount and kind of fatty acid precursors. We hypothesized that linseed oil in combination with malate (a key propionate precursor in the rumen) would increase ∆9 unsaturated fatty acids and specific gene expression in somatic cells and mammary glands of lactating goats. Twelve lactating goats were used in a 3 × 3 Latin square design. Treatments included the basal diet (CON), the CON plus 4% linseed oil (LO), and the CON plus 4% linseed oil and 2% -malate (LOM). Relative to CON, the LO and LOM supplements increased the daily intake of palmitic (16:0), stearic (18:0), oleic (18:1-9), linoleic (18:2-6), α-linolenic (18:3-3), and γ-linolenic acids (18:2-6); α-linolenic acid intake was increased over 9-fold, from 6.77 to over 51 g/d ( < 0.02). The LO and LOM supplements increased daily milk yield, milk fat yield, and milk fat percentage ( < 0.05). The LOM supplement also increased milk lactose percentage and daily yield ( = 0.03). Both the LO and LOM supplements increased plasma glucose and total cholesterol and decreased plasma β-hydroxbutyrate concentrations ( = 0.03). The LO and LOM supplements increased concentrations of stearic acid; -vaccenic acid (TVA; 18:1-11); -9, -11 CLA; -10 -12 CLA; and α-linolenic acid in rumen fluid and increased the concentrations of oleic acid; TVA; -9, -11 CLA; -10, -12 CLA; and α-linolenic acid in plasma lipids and milk fat ( < 0.05). Conversely, the LO and LOM supplements decreased short- and medium-chain SFA, including lauric (12:0), myristic (14:0), and palmitic acids, in plasma and milk fat ( < 0.05). Relative mRNA levels for and () gene expression were increased in somatic cells and mammary gland tissue by LO and LOM ( < 0.05). We conclude that the higher intake and ruminal production of stearic acid promoted SCD gene expression in somatic cells and mammary tissue. Furthermore, milk somatic cells are a suitable substitute for documenting treatment effects of dietary oils on gene expression in goat mammary tissue.

Impact of low molecular weight organic acids (LMWOAs) on biochar micropores and sorption properties for sulfamethoxazole

The interaction between biochar (BC) and antibiotics with the presence of low molecular weight organic acids (LMWOAs) is largely unknown, although it is crucial for understanding the role of BC in reducing the bioavailability of antibiotics in rhizosphere. The impacts of two typical LMWOAs (citric and malic acids) on sorption of sulfamethoxazole (SMX) by crop-straw BCs produced at 300 °C (BCs300) and 600 °C (BCs600), respectively, were examined. The sorption of SMX on BCs increased more than 5 times with the concentration of LMWOAs increasing from 0 to 100 mmol/L, which was mainly attributed to the elevated microporosity of BCs (measured by CO2) after treated by LMWOAs. The pore development of BCs was mainly derived from the release of dissolved organic residues from BC by LMWOA washing. For H2O2-oxidized BCs, however, LMWOAs had little effect on SMX sorption by BCs300 but greatly increased that by BCs600, which can be explained by the distinct sorption mechanisms of SMX on BCs300 and BCs600. These results indicate that the impact of LMWOAs on SMX sorption is highly dependent on the properties of BCs and LMWOAs, as well as their interaction mechanisms.

The effect of U speciation in cultivation solution on the uptake of U by variant Sedum alfredii

In the present study, five plant species were screened for uranium uptake using a hydroponic experimental set-up. The effect of the U concentration, pH, as well as the presence of carbonates, phosphates, and organic acids (lactic acid, malic acid, citric acid) on the uptake of U by variant S. alfredii (V S. alfredii) and wild S. alfredii (W S. alfredii) were investigated. Results showed that V S. alfredii exhibited higher U content in the roots than the other four plants and with the increase of U concentration in the solution, the U uptake by V S. alfredii and W S. alfredii increased. The results also showed that different U speciation in different cultivation solution took an important role on the uptake of U in variant Sedum alfredii: at pH 6.5, U hydrolysis species (UO2)3(OH)5 (+)is predominant and the U concentrations in V S. alfredii roots reached a maximum value (3.7 × 10(4) mg/kg). U complexation with carbonates, phosphates, and some organic acids in the solution resulted in a decrease in the U content in the roots except for lactic acid. Our researches highlight the correlations between U speciation and the uptake on V S. Alfredii, which will be helpful for improved removal of U from the groundwater using phytoremediation method.

[Influence of Three Low-Molecular-Weight Organic Acids on the Adsorption of Phenanthrene in Purple Soil]

The effects of three low-molecular-weight organic acids (citric acid, malic acid and oxalic acid) on the adsorption of phenanthrene in purple soil were studied by static adsorption experiment. The results showed that the adsorption kinetic process of phenanthrene in purple soil could be described by the second-order kinetic model, and the adsorption rate constant would significantly decrease in the presence of the three low-molecular-weight organic acids ( LMWOAs). The adsorption thermodynamic process could be well described by linear adsorption model, which was dominated by distribution role. The three LMWOAs could promote the adsorption of phenantherene in purple soil when their concentrations were less than 5 mmol · L⁻¹, whereas inhibit the adsorption when their concentrations were more than 10 mmol · L⁻¹, and the inhibition would increase with increasing concentrations. Moreover, the inhibitory ability displayed a decreasing order of citric acid, oxalic acid, and malic acid when their concentrations were 20 mmol · L⁻¹, which is related to the molecular structure and acidity of the three LMWOAs. Compared with the control, the content of dissolved organic matter (DOM) released from purple soil showed a trend of first decrease and then increase with increasing LMWOAs concentration, and the adsorption capacity of phenanthrene in purple soil was negatively related to DOM content.

Mobilization of soil-borne arsenic by three common organic acids: Dosage and time effects

A batch experiment was conducted to investigate the mobilization of soil-borne arsenic by three common low-molecular-weight organic acids with a focus on dosage and time effects. The results show that oxalic acid behaved differently from citric acid and malic acid in terms of mobilizing As that was bound to iron compounds. At an equivalent molar concentration, reactions between oxalic acid and soil-borne Fe were kinetically more favourable, as compared to those between either citric acid or malic acid and the soil-borne Fe. It was found that reductive dissolution of soil-borne Fe played a more important role in liberating As, as compared to non-reductive reactions. Prior to the 7th day of the experiment, As mobility increased with increasing dose of oxalic acid while there was no significant difference (P > 0.05) in mobilized As among the treatments with different doses of citric acid or malic acid. The dosage effect on soil-borne As mobilization in the citric acid and malic acid treatments became clear only after the 7th day of the experiment. Soluble Ca present in the soils could cause re-immobilization of As by competing with solution-borne Fe for available organic ligands to form practically insoluble organic compounds of calcium (i.e. calcium oxalate). This resulted in transformation of highly soluble organic complexes of iron (i.e. iron oxalate complexes) into slightly soluble organic compounds of iron (i.e. iron oxalate) or free ferric ion, which then reacted with the solution-borne arsenate ions to form practically insoluble iron arsenates in the latter part of the experiment.

Ultrafast Photoprotecting Sunscreens in Natural Plants

We explore the ultrafast photoprotective properties of a series of sinapic acid derivatives in a range of solvents, utilizing femtosecond transient electronic absorption spectroscopy. We find that a primary relaxation mechanism displayed by the plant sunscreen sinapoyl malate and other related molecular species may be understood as a multistep process involving internal conversion of the initially photoexcited 1(1)ππ* state along a trans-cis photoisomerization coordinate, leading to the repopulation of the original trans ground-state isomer or the formation of a stable cis isomer.

A comparative evaluation of different types of microbial electrolysis desalination cells for malic acid production

The aim of this study was to investigate different microbial electrolysis desalination cells for malic acid production. The systems included microbial electrolysis desalination and chemical-production cell (MEDCC), microbial electrolysis desalination cell (MEDC) with bipolar membrane and anion exchange membrane (BP-A MEDC), MEDC with bipolar membrane and cation exchange membrane (BP-C MEDC), and modified microbial desalination cell (M-MDC). The microbial electrolysis desalination cells performed differently in terms of malic acid production and energy consumption. The MEDCC performed best with the highest malic acid production rate (18.4 ± 0.6 mmol/Lh) and the lowest energy consumption (0.35 ± 0.14 kWh/kg). The best performance of MEDCC was attributable to the neutral pH condition in the anode chamber, the lowest internal resistance, and the highest Geobacter percentage of the anode biofilm population among all the reactors.

Effects of organic acids on cadmium and copper sorption and desorption by two calcareous soils

Low molecular weight organic acids (LMWOAs) present in soil alter equilibrium pH of soil, and consequently, affect heavy metal sorption and desorption on soil constitutes. This study was conducted to investigate the effects of different concentrations (0.1, 1, 2.5, 5, 10, 30, 40, 50, 70, and 100 mM) of citric, malic, and oxalic acids on sorption and desorption of cadmium (Cd) and copper (Cu) in two calcareous soils. Increasing the concentrations of three LMWOAs decreased the equilibrium pH of soil solutions. The results indicated that increase in organic acids concentrations generally reduced Cd and Cu sorption in soils. Increase concentrations of LMWOAs generally promoted Cd and Cu desorption from soils. A valley-like curve was observed for desorption of Cu after the citric acid concentration increment in soil 2. Increasing the concentrations of three LMWOAs caused a marked decrease in Kd(sorp) values of Cd and Cu in soils. In general, citric acid was the most effective organic acid in reducing sorption and increasing desorption of both metals, and oxalic acid had the minimal impact. The results indicated that LMWOAs had a greater impact on Cu sorption and desorption than Cd, which can be attributed to higher stability constants of organic acids complexes with Cu compared to Cd. It can be concluded that by selecting suitable type and concentration of LMWOAs, mobility, and hence, bioavailability of heavy metals can be changed. So, environmental implications concerning heavy metals mobility might be derived from these findings.

Curcumin Targeted, Polymalic Acid-Based MRI Contrast Agent for the Detection of Aβ Plaques in Alzheimer's Disease

Currently, there is no gadolinium-based contrast agent available for conventional magnetic resonance imaging (MRI) detection of amyloidal beta (Aβ) plaques in Alzheimer's disease (AD). Its timely finding would be vital for patient survival and quality of life. Curcumin (CUR), a common Indian spice effectively binds to Aβ plaques which is a hallmark of AD. To address this binding, we have designed a novel nanoimaging agent (NIA) based on nature-derived poly(β-l-malic acid) (PMLA) containing covalently attached gadolinium-DOTA(Gd-DOTA) and nature-derived CUR. The all-in-one agent recognizes and selectively binds to Aβ plaques and is detected by MRI. It efficiently detected Aβ plaques in human and mouse samples by an ex vivo staining. The method can be useful in clinic for safe and noninvasive diagnosis of AD.