Sodium Malonate Research Articles

Addition of sodium malonate alters the morphology and increases the critical flux during tangential flow filtration of precipitated immunoglobulins.

Recent studies have demonstrated that one can control the packing density, and in turn the filterability, of protein precipitates by changing the pH and buffer composition of the precipitating solution to increase the structure/order within the precipitate. The objective of this study was to examine the effect of sodium malonate, which is known to enhance protein crystallizability, on the morphology of immunoglobulin precipitates formed using a combination of ZnCl2 and polyethylene glycol. The addition of sodium malonate significantly stabilized the precipitate particles as shown by an increase in melting temperature, as determined by differential scanning calorimetry, and an increase in the enthalpy of interaction, as determined by isothermal titration calorimetry. The sodium malonate also increased the selectivity of the precipitation, significantly reducing the coprecipitation of DNA from a clarified cell culture fluid. The resulting precipitate had a greater packing density and improved filterability, enabling continuous tangential flow filtration with minimal membrane fouling relative to precipitates formed under otherwise identical conditions but in the absence of sodium malonate. These results provide important insights into strategies for controlling precipitate morphology to enhance the performance of precipitation-filtration processes for the purification of therapeutic proteins.

Long-Term Protective Effects of Succinate Dehydrogenase Inhibition during Reperfusion with Malonate on Post-Infarction Left Ventricular Scar and Remodeling in Mice.

Succinate dehydrogenase inhibition with malonate during initial reperfusion reduces myocardial infarct size in both isolated mouse hearts subjected to global ischemia and in in situ pig hearts subjected to transient coronary ligature. However, the long-term effects of acute malonate treatment are unknown. Here, we investigated whether the protective effects of succinate dehydrogenase inhibition extend to a reduction in scar size and adverse left ventricular remodeling 28 days after myocardial infarction. Initially, ten wild-type mice were subjected to 45 min of left anterior descending coronary artery (LAD) occlusion, followed by 24 h of reperfusion, and were infused during the first 15 min of reperfusion with saline with or without disodium malonate (10 mg/kg/min, 120 μL/kg/min). Malonate-treated mice depicted a significant reduction in infarct size (15.47 ± 3.40% of area at risk vs. 29.34 ± 4.44% in control animals, p < 0.05), assessed using triphenyltetrazolium chloride. Additional animals were then subjected to a 45 min LAD ligature, followed by 28 days of reperfusion. Treatment with a single dose of malonate during the first 15 min of reperfusion induced a significant reduction in scar area, measured using Picrosirius Red staining (11.94 ± 1.70% of left ventricular area (n = 5) vs. 23.25 ± 2.67% (n = 9), p < 0.05), an effect associated with improved ejection fraction 28 days after infarction, as determined using echocardiography, and an attenuated enhancement in expression of the pro-inflammatory and fibrotic markers NF-κB and Smad2/3 in remote myocardium. In conclusion, a reversible inhibition of succinate dehydrogenase with a single dose of malonate at the onset of reperfusion has long-term protective effects in mice subjected to transient coronary occlusion.

The proceeded ammonia release from ammonium nitrate owing to sodium malonate addition: Dependence of RH, acidity and surfactant

The gas-particle partition of ammonia has strong effect on size, composition and hygroscopic property of atmospheric aerosols. However, how chemical reaction drives ammonia evaporation from particle is not well known. In this work, ammonium depletion is used to characterize the ammonia liberation from aqueous ammonium nitrate and sodium malonate/ammonium nitrate aerosols. The addition of sodium malonate promotes more ammonia liberation owing to inter-ingredients reaction. As the relative humidity (RH) decreases, ammonia release is enhanced. Moreover, NH3 evaporation is also impacted by aerosol acidity. At pH 1.93, malonate is directly converted into hydrogen malonate and malonic acid via protonation. Under the neutral/alkaline condition, higher pH is beneficial for component reactions. When cetyltrimethylammonium bromide is added into mixed aerosols, NH3 evaporation becomes slow. These results can provide a new perspective on the evolution mechanism of NH3–NH4+ buffer pairs for multicomponent aerosols.

Efficiency of oil separation and demulsification following sonication gel degradation: Influence of Cr(III) ions, NaCl concentrations, and sodium-based retarders

This study investigates the impact of chromium (III) ions, salinity, and retarders on demulsification efficiency and oil separation in oil–water emulsions stabilized by hydrolyzed polyacrylamide (HPAM) aqueous solutions. Two different concentrations of HPAM (1000 and 2000 ppm) and NaCl (0–200,000 ppm), along with two distinct retarders (sodium lactate and sodium malonate), were employed to prepare the emulsion samples. A comprehensive analysis of emulsion stability and demulsification duration was conducted under varying treatment conditions, such as the presence or absence of chromium (III) ions and resin application for chromium removal. Results demonstrate that the presence of chromium (III) ions significantly increases emulsion stability, while their removal leads to a marked reduction in demulsification duration. Notably, the impact of salinity was found to depend on the specific retarder used, with sodium lactate and sodium malonate exhibiting differing demulsification durations. As the HPAM concentration was raised from 1000 to 2000 ppm, the demulsification duration also, regardless of the presence or absence of chromium (III) ions. Additionally, the oil separation rates were higher in samples treated with a resin for chromium removal and are notably influenced by the choice of retarder. In particular, using sodium malonate as a retarder resulted in a significant improvement in the oil separation rate compared to sodium lactate under various salinity conditions. The findings of this study provide valuable insights into the optimization of oil–water separation processes, offering the potential for improved oil recovery and environmental sustainability. This study is particularly novel in its comprehensive investigation of the interplay between different factors (chromium, salinity, and retarders) in oil–water separation processes.

Effect of Flame Retardants and Electrolyte Variations on Li-Ion Batteries

Lithium-ion batteries are being increasingly used and deployed commercially. Cell-level improvements that address flammability characteristics and thermal runaway are currently being intensively tested and explored. In this study, three additives—namely, lithium oxalate, sodium fumarate and sodium malonate—which exhibit fire-retardant properties are investigated with respect to their incorporation into graphite anodes and their electro/chemical interactions within the anode and the cell material studied. It has been shown that flame-retardant concentrations of up to approximately 20 wt.% within the anode coating do not cause significant capacity degradation but can provide a flame-retardant effect due to their inherent, fire-retardant release of CO2 gas. The flame-retardant-containing layers exhibit good adhesion to the current collector. Their suitability in lithium-ion cells was tested in pouch cells and, when compared to pure graphite anodes, showed almost no deterioration regarding cell capacity when used in moderate (≤20 wt.%) concentrations.

Sodium Malonate Inhibits the AcrAB-TolC Multidrug Efflux Pump of Escherichia coli and Increases Antibiotic Efficacy.

There is an urgent need to find novel treatments for combating multidrug-resistant bacteria. Multidrug efflux pumps that expel antibiotics out of cells are major contributors to this problem. Therefore, using efflux pump inhibitors (EPIs) is a promising strategy to increase antibiotic efficacy. However, there are no EPIs currently approved for clinical use especially because of their toxicity. This study investigates sodium malonate, a natural, non-hazardous, small molecule, for its use as a novel EPI of AcrAB-TolC, the main multidrug efflux pump of the Enterobacteriaceae family. Using ethidium bromide accumulation experiments, we found that 25 mM sodium malonate inhibited efflux by the AcrAB-TolC and other MDR pumps of Escherichia coli to a similar degree than 50 μΜ phenylalanine-arginine-β-naphthylamide, a well-known EPI. Using minimum inhibitory concentration assays and molecular docking to study AcrB-ligand interactions, we found that sodium malonate increased the efficacy of ethidium bromide and the antibiotics minocycline, chloramphenicol, and ciprofloxacin, possibly via binding to multiple AcrB locations, including the AcrB proximal binding pocket. In conclusion, sodium malonate is a newly discovered EPI that increases antibiotic efficacy. Our findings support the development of malonic acid/sodium malonate and its derivatives as promising EPIs for augmenting antibiotic efficacy when treating multidrug-resistant bacterial infections.

Proteome-wide analyses reveal diverse functions of protein acetylation and succinylation modifications in fast growing stolons of bermudagrass (Cynodon dactylon L.)

BackgroundBermudagrass (Cynodon dactylon L.) is an important warm-season turfgrass species with well-developed stolons, which lay the foundation for the fast propagation of bermudagrass plants through asexual clonal growth. However, the growth and development of bermudagrass stolons are still poorly understood at the molecular level.ResultsIn this study, we comprehensively analyzed the acetylation and succinylation modifications of proteins in fast-growing stolons of the bermudagrass cultivar Yangjiang. A total of 4657 lysine acetylation sites on 1914 proteins and 226 lysine succinylation sites on 128 proteins were successfully identified using liquid chromatography coupled to tandem mass spectrometry, respectively. Furthermore, 78 proteins and 81 lysine sites were found to be both acetylated and succinylated. Functional enrichment analysis revealed that acetylated proteins regulate diverse reactions of carbohydrate metabolism and protein turnover, whereas succinylated proteins mainly regulate the citrate cycle. These results partly explained the different growth disturbances of bermudagrass stolons under treatment with sodium butyrate and sodium malonate, which interfere with protein acetylation and succinylation, respectively. Moreover, 140 acetylated proteins and 42 succinylated proteins were further characterized having similarly modified orthologs in other grass species. Site-specific mutations combined with enzymatic activity assays indicated that the conserved acetylation of catalase and succinylation of malate dehydrogenase both inhibited their activities, further implying important regulatory roles of the two modifications.ConclusionIn summary, our study implied that lysine acetylation and succinylation of proteins possibly play important regulatory roles in the fast growth of bermudagrass stolons. The results not only provide new insights into clonal growth of bermudagrass but also offer a rich resource for functional analyses of protein lysine acetylation and succinylation in plants.

PSEUDOMONAS FLUORESCENS IN SHEEP MILK GREEK YOGHURT FROM VLASINA – A BIOCHEMICAL CHARACTERIZATION

Pseudomonas fluorescens is an aerobic, rod-shaped, non-sporulating gram-negative bacteria, mostlyfound in soil, decaying organic matter and feces. This species contaminates the milk mainly through animal feeddust, silage, utensils and polluted water. In addition to casein digestion, this psychotropic and lipolytic speciesgenerates butyric and caproic acids by fermentation of milk fat, which release a strong unpleasant odor and give arancid and bitter taste to dairy products. In this study we tested 48 hours old sheep's sour milk, produced in ahousehold in Vlasina, southeastern Serbia, using traditional method. Standard bacteriological protocols were usedfor isolation and identification Pseudomonas fluorescens strains. Biochemical identification was performed usingthe commercial API 32GN E system, and 60473057073 profile was obtained (Pseudomonas fluorescens, %Id=99.5and T=0.74). Positive biochemical tests were: N-acetyl-glukosamine (NAG), D-Ribose (RIB), Sodium malonate(MNT), Sodium acetate (ACE), Lactic acid (LAT), L-Alanine (ALA), D-Mannitol (MAN), D-Glucose (GLU), LArabinose(ARA), Capric acid (CAP), Valeric acid (VALT), Trisodium citrate (CIT), L-Histidine (HIS), Potasium2-ketogluconate (2KG), 3-Hydroxybutyric acid (3OBU), 4-Hydroxybenzoic acid (pOBE), L-Serine (SER), LProline(PRO) and Oxidase (OX). Negative biochemical tests were: L-Rhamnose (RHA), Inositol (INO), DSaccharose(SAC), D-Maltose (MAL), Itaconic acid (ITA), Suberic acid (SUB), Salicin (SAL), D-Melibose (MEL),L-Fucose (FUC), D-Sorbitol (SOR), Propionic acid (PROP), Potasium 5-ketogluconate (5KG), Glycogen (GLYG)and 3-hydroxybenzoic acid (mOBE). Based on the example of the strain Pseudomonas fluorescens, the API ID 32GN system proved to be precise and very efficient in the identification of this lipolytic type. Given thatpasteurization and cooling processes do not entirely inhibit the enzym activity and growth of this psychotrophicbacteria, informing individual milk and milk product manufacturers in the Vlasina region about good manufacturingpractices would limit contamination and bacteriological deterioration.

A catalytic three-component synthesis of isoxazol-5(4H)-ones under green conditions

The three-component cyclocondensation of various aryl/heteroaryl aldehydes, hydroxylamine hydrochloride, and ethyl acetoacetate/ ethyl 4-chloro-3-oxobutanoate have been established for the synthesis of isoxazol-5(4 H )-ones using sodium malonate as an efficient catalyst. This reaction has been performed in water as a green reaction medium at 25°C. Optimization of the reaction conditions show that the reaction performs better in aqueous medium, at room temperature, and in the presence of 10 mol% of the catalyst. This procedure has several unique features, including shorter reaction times, easy separation of pure products, avoiding the hazardous organic solvents, simplicity of experimental procedures, operationally simple, and eco-friendly.

Effect of different organic salts on ammonia volatilization in ammonium nitrate

The ammonium salts and organic salts are the important components of atmospheric aerosols. The reaction between the two salts will cause the release of NH3, hence, affecting the budget of NH3 in the atmosphere. Furthermore, the equilibrium partitioning of NH3 in the gas and particle phases plays a key role in the evolution of chemical composition and size of fine atmospheric particles. In this work, the chemical composition evolution processes of mixed particles consisting of four different organic acid salts (sodium oxalate (SO), sodium malonate (SM), sodium succinate (SS), sodium pyruvate (SP)) with ammonium nitrate (AN) were measured by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The release of NH3 were gained by monitoring the changes in the absorbance of NH4 + in mixed organic acid salts/AN particles under 70% relative humidity (RH). After 127 minutes, the remaining ammonium content in the four mixed aerosols was 84.2%, 71.6%, 57.1%, and 28.7% for SO, SM, SS, and SP mixed with AN, respectively, which is lower than that in pure AN aerosol (97%). This study may help to further understand the conversion process between organic salts and AN in the atmosphere, as well as the NH3 cycles in the atmosphere.

Citric Acid Cycle Metabolites Predict Infarct Size in Pigs Submitted to Transient Coronary Artery Occlusion and Treated with Succinate Dehydrogenase Inhibitors or Remote Ischemic Perconditioning.

Succinate dehydrogenase (SDH) inhibition with malonate during reperfusion reduced myocardial infarction in animals, whereas its endogenous substrate, succinate, is detected in plasma from STEMI patients. We investigated whether protection by SDH inhibition is additive to that of remote ischemic perconditioning (RIC) in pigs submitted to transient coronary artery occlusion, and whether protective maneuvers influence plasma levels of citric acid cycle metabolites. Forty pigs were submitted to 40 min coronary occlusion and reperfusion, and allocated to four groups (controls, sodium malonate 10 mmol/L, RIC, and malonate + RIC). Plasma was obtained from femoral and great cardiac veins and analyzed by LC-MS/MS. Malonate, RIC, and malonate + RIC reduced infarct size (24.67 ± 5.98, 25.29 ± 3.92 and 29.83 ± 4.62% vs. 46.47 ± 4.49% in controls, p < 0.05), but no additive effects were detected. Enhanced concentrations of succinate, fumarate, malate and citrate were observed in controls during initial reperfusion in the great cardiac vein, and most were reduced by cardioprotective maneuvers. Concentrations of succinate, fumarate, and malate significantly correlated with infarct size. In conclusion, despite the combination of SDH inhibition during reperfusion and RIC did not result in additive protection, plasma concentrations of selected citric acid cycle metabolites are attenuated by protective maneuvers, correlate with irreversible injury, and might become a prognosis tool in STEMI patients.

A novel approach to detect barium in gunshot residue using a handheld device: a forensic application.

The present manuscript describes an innovative handheld device for the rapid detection of barium (Ba2+) in Gunshot Residue (GSR) based on the use of gold nanomaterials capped with sodium malonate. The method depends on a shift in the Light Scattering Plasmon Resonance (LSPR) peak of malonate capped gold nanoparticles (AuNPs) from 526 nm to 610.5 nm, due to the carboxylate ion aggregation between the metal and the nanoparticles leading to a change in the color. Qualitative detection was realized by the change in the color, while for quantitative analysis a handheld device has been fabricated in-house. The results were then correlated with those of standard known methods such as UV-Vis Spectroscopy and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). The results showed better correlation between the fabricated device and standard methods with R2 = 0.98. It shows a linearity range from 0.01 mg mL-1 to 5 mg mL-1 with a Limit of Detection (LOD) of 0.2 mg mL-1. Furthermore, GSR samples were collected from cloth piece set at different range of shooting (i.e. 1 ft to 16.40 ft) using different ammunition to detect the presence of Ba2+ with the help of the developed device and results were found similar to those of the known methods. The hand-held device was found to be unaffected by other interfering agents (i.e. Pb2+, Sb3+, Ca2+, Cu2+, Hg2+, Mg2+, As3+, Cr3+, etc.). The results demonstrated here shows high selectivity, sensitivity and rapid method for Ba2+ detection in GSR, showing its greater potentiality in future.

Анодные окисные пленки на меди в нейтральном боратном буферном растворе и адсорбция на них малоната натрия

Анодные окисные пленки на меди в нейтральном боратном буферном растворе и адсорбция на них малоната натрия

Expression, purification, crystallization and X-ray diffraction studies of a novel root-induced secreted protein from Trichoderma virens.

Small secreted cysteine-rich proteins (SSCPs) from fungi play an important role in fungi-host interactions. The plant-beneficial fungi Trichoderma spp. are in use worldwide as biocontrol agents and protect the host plant from soil-borne as well as foliar pathogens. Recently, a novel SSCP, Tsp1, has been identified in the secreted protein pool of T. virens and is overinduced upon its interaction with the roots of the maize plant. The protein was observed to be well conserved in the Ascomycota division of fungi, and its homologs are present in many plant-pathogenic fungi such as Fusarium oxysporum and Magnaporthe oryzae. However, none of these homologs have yet been characterized. Recombinant Tsp1 protein has been expressed and purified using an Escherichia coli expression system. The protein, with four conserved cysteines, forms a dimer in solution as observed by size-exclusion chromatography. The dimerization, however, does not involve disulfide bonds. Circular-dichroism data suggested that the protein has a β-strand-rich secondary structure that matched well with the secondary structure predicted using bioinformatics methods. The protein was crystallized using sodium malonate as a precipitant. The crystals diffracted X-rays to 1.7 Å resolution and belonged to the orthorhombic space group P212121 (Rmeas = 5.4%), with unit-cell parameters a = 46.3, b = 67.0, c = 173.2 Å. The Matthews coefficient (VM) of the crystal is 2.32 Å3 Da-1, which corresponds to nearly 47% solvent content with four subunits of Tsp1 protein in the asymmetric unit. This is the first report of the structural study of any homolog of the novel Tsp1 protein. These structural studies will help in understanding the classification and function of the protein.

Sodium-salt adduct fullerenes prevent self-association and amyloid β fibril formation: molecular dynamics approach

ABSTRACT Aggregation of amyloid β peptides (AβP) forming fibrils and senile plaques is associated with numerous neurodegenerative disorders such as Alzheimer’s disease (AD). While there is no cure for AD, there is a possibility to retard and prevent the impairment. Inhibiting or interfering the aggregation of Aβ using fullerenes has shown to be a promising strategy to treat AD. The hydrophobic nature of fullerenes compromises its interaction with living cells inducing toxicity; thus, it is necessary to functionalize the molecule promoting its water solubility. In this study, we evaluate the structural and dynamical properties of six diethyl malonate C60 fullerene adducts and its corresponding sodium salts in aqueous solution by molecular dynamics simulations. By means of radial distribution functions, hydrogen bond counting, density profiles, and solvent-accessible surface area, we demonstrate that the sodium malonate fullerene adducts have higher hydration ability while the corresponding diethyl malonate adducts show a hydrophobic tendency, forming self-aggregates. Additionally, we calculate the density profiles of ternary systems including amyloid β peptide 1–42 (AβP42) monomers and found that bis-, tris-, tetra-, and pentaadducts of C60 with disodium malonate addends interact with amyloid molecules, blocking partially their self-aggregation. These data support the understanding of previous reports that indicated the efficiency of sodium malonate fullerene as inhibitors of AβP aggregation. Additionally, we performe measurements in vitro by dynamic light scattering and found that fullerene aggregation is independent of incubation time.

Sea spray aerosol formation: Results on the role of different parameters and organic concentrations from bubble bursting experiments

Submicron sea spray aerosol (SSA) particles play an essential role in atmospheric chemical processes and the Earth’s radiative balance. In this study, different combinations of NaCl, MgSO4, malonic acid (MA), d-fructose and sodium malonate were used to explore the effect of MA on submicron SSA generation. SSA particles were produced at room temperature by bubble bursting from an adjustable home-built SSA generator with sintered glass filters. We found that MA could promote the generation of SSA particles and make the geometric mean diameter (GMD) to decrease for MA concentrations ranging between 8 and 32 mM and then, to increase for MA concentrations in the range of 64–160 mM. d-fructose could improve the generation of SSA with increasing GMD. Interestingly, sodium malonate could significantly enhance the production of SSA, with the change of morphology. Besides, different parameters including flow rate, underwater depth, pore size and size span of sintered glass filter and salinity of water were tested to obtain the characterization of our self-made adjustable SSA generator. Three modes could be found among different SSA generation methods, and they exhibited an obvious accumulation mode around 100 nm. The SSA generation under different conditions was compared with oceanic measurements from the literature, which showed that the sintered glass filter has advantages in generating submicron SSA from film drops.

Expeditious Synthesis of 2-Amino-4H-chromenes and 2-Amino-4H-pyran-3- carboxylates Promoted by Sodium Malonate.

Chromenes and pyran annulated heterocycles are the most common frameworks existing in various biologically active molecules. Due to their beneficial and biological properties, they are eyecatching synthetic targets in the arsenal of organic chemistry. Thus, finding green and efficient methods, as well as searching for a new catalyst for the synthesis of these heterocycles is of interest to organic chemistry researchers. Sodium malonate as a readily available catalyst was employed aimed at the multicomponent synthesis of numerous 2-amino-4H-chromenes and 2-amino-4H-pyrans in water as a green medium reaction. The reaction was performed via treatment of aldehydes (1 mmol) with malononitrile/ethyl cyanoacetate (1 mmol) and β-dicarbonyl compounds (1 mmol)/or resorcinol (1 mmol) in water (4 mL) in the presence of sodium malonate (10 mol %) at 70°C. On completion of the reaction (monitored by TLC analysis), the reaction mixture was gradually cooled at room temperature, and the resulting precipitates were collected by filtration, washed with cold ethanol and air-dried to give the corresponding pure products. The solvent was evaporated from the filtrate to recover the catalyst, and the catalyst was reused for subsequent reactions. In the initial stages, we explored the best reaction conditions using three-component reaction of benzaldehyde, malononitrile, and dimedone as the model reaction. The effects of catalyst loading, temperature, and solvents were explored for this reaction. It was found that the best results were obtained for the synthesis of 2-amino-4H-chromenes and 2-amino-4H-pyran when the three-component reaction was carried out with equivalent molar quantities of each of the reactants in water containing 10 mol% sodium malonate at 70°C for 15 min in 96% yield. After finding optimal conditions, these conditions apply to other reactants and the target heterocyclic products were obtained with excellent yields. This study describes an efficient, environmentally benign, and clean one-pot, three-component synthesis of 2-amino-4H-chromenes and 2-amino-4H-pyran-3-carboxylates in the presence of sodium malonate as the commercially available catalyst in an aqueous medium at 70°C. High yields, mild reaction conditions, relatively shorter reaction times, use of simple reagents, and no requirement of the ultrasound, microwave, and ball milling techniques are the salient features and benefits of the present method. In addition, the present process is smooth and green.

X-ray Crystal Structure of Dichromium-transferrin with Synergistic Anion Malonate (P24-061-19)

ObjectivesTransferrin, Tf, the protein that transports iron, as Fe(III) from the blood to the tissues via endocytosis, is believed to also transport chromium(III), Cr(III). Under physiological conditions, transferrin binds Fe(III) and Cr(III), but can bind other metal ions such as titanium(IV), Ti(IV), such as in the blood of patients with Ti-containing implants. Questions have arisen whether similar protein and non-protein ligands are bound to the alternative metal ions in transferrin. MethodsHuman serum Cr(III)2-Tf was prepared in a buffered solution at pH 7.4 containing 25 mM bicarbonate at 37°C. The hanging drop vapor diffusion method was used for crystallization. The crystallization conditions contained 100 mM Hepes (pH 7.0, 20 mM disodium malonate, 14% PEG3350, 20% glycerol, and 55 mg/mL transferrin. ResultsCr(III)2-Tf crystallized in the space group C2221 with unit cell dimensions a = 137.05 Å, b = 158.01 Å, and c = 107.14 Å and α = β = γ = 90°. The C-terminal lobe is in the closed confirmation, while the N-terminal lobe is in the open confirmation. The C-terminal metal-binding site has four protein-provided ligands (two tyrosines, one histidine, and one aspartate) to the Cr(III) center, while six coordination is completed by two oxygens from a malonate anion. Thus, under the crystallization conditions, malonate displaces `the synergistic bicarbonate anion normally at the metal-binding site. The N-terminal metal binding site possesses only one protein-provided ligand (tyrosine) while the other binding sites about the Cr(III) center are filled by a (bi)carbonate anion and water molecules. ConclusionsUnder the conditions of crystallization, the C-terminal lobe of transferrin binds Cr(III) in a similar fashion to Fe(III) and Ti(IV), although the ligation at the N-terminal binding site varies. These similarities and differences in coordination have implications for the relative ability of transferrin to bind and release Fe, Cr, and Ti. Funding SourcesThe University of Alabama College of Arts and Sciences Research Award.

Analysis of the L-malate biosynthesis pathway involved in poly(β-L-malic acid) production in Aureobasidium melanogenum GXZ-6 by addition of metabolic intermediates and inhibitors.

Poly(β-L-malic acid) (PMA) is a promising polyester formed from L-malate in microbial cells. Malate biosynthesis is crucial for PMA production. Previous studies have shown that the non-oxidative pathway or oxidative pathway (TCA cycle) is the main biosynthetic pathway of malate in most of PMA-producing strains, while the glyoxylate cycle is only a supplementary pathway. In this study, we investigated the effect of exogenous metabolic intermediates and inhibitors of the malate biosynthetic pathway on PMA production by Aureobasidium melanogenum GXZ-6. The results showed that PMA production was stimulated by maleic acid (a fumarase inhibitor) and sodium malonate (a succinate dehydrogenase inhibitor) but inhibited by succinic acid and fumaric acid. This indicated that the TCA cycle might not be the only biosynthetic pathway of malate. In addition, the PMA titer increased by 18.1% upon the addition of glyoxylic acid after 72 h of fermentation, but the PMA titer decreased by 7.5% when itaconic acid (an isocitrate lyase inhibitor) was added, which indicated that malate for PMA production was synthesized significantly via the glyoxylate cycle rather than the TCA cycle. Furthermore, in vitro enzyme activities of the TCA and glyoxylate cycles suggested that the glyoxylate cycle significantly contributed to the PMA production, which is contradictory to what has been reported previously in other PMA-producing A. pullulans.

Development and benefit evaluation of fermentation strategies for poly(malic acid) production from malt syrup by Aureobasidium melanogenum GXZ-6

Malt syrup, as a low-cost substrate without any pretreatment, was proved to be able to replace maltose for ploymalic acid (PMA) production by Aureobasidium melanogenum GXZ-6. The PMA titer of 55.53 ± 1.72 g/L was obtained by batch fermentation in a 10-L fermentor with addition of malate, citrate and sodium malonate. Then, a higher PMA titer of 124.07 ± 2.28 g/L was obtained in fed-batch fermentation, which increased by 123.43% than that from batch fermentation. Moreover, repeated-batch fermentation with three batches gave a PMA titer of 64.06 g/L on average with a higher yield of 0.81 g/g and productivity of 0.56 g/L·h. Fermentation process and economics analysis were performed by SuperPro Designer for a 2000 metric tons plant. Results showed that PMA production cost was as low as $ 1.716/kg by fed-batch fermentation, which provides an economical strategy for large-scale PMA production.