Stimulation of pollen tube growthin vitro by dicarboxylic acids

Summary Effect of eight dicarboxylic acids and three monocarboxylic acids on pollen growth ofCamellia japonica was tested. While monocarboxylic acids inhibited pollen germination and pollen tube elongation, dicarboxylic acids, namely oxalic, succinic, suberic, adipic, sebacic, traumatic cis-1,2-cyclohexane dicarboxylic, and 3,3-diethyl glutaric acids stimulated pollen tube elongation stronger than indoleacetic acid.     

Metabolic engineering for the production of dicarboxylic acids and diamines

Microbial production of chemicals and materials from renewable carbon sources is becoming increasingly important to help establish sustainable chemical industry. In this paper, we review current status of metabolic engineering for the bio-based production of linear and saturated dicarboxylic acids and diamines, important platform chemicals used in various industrial applications, especially as monomers for polymer synthesis. Strategies for the bio-based production of various dicarboxylic acids having different carbon numbers including malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), sebacic acid (C10), undecanedioic acid (C11), dodecanedioic acid (C12), brassylic acid (C13), tetradecanedioic acid (C14), and pentadecanedioic acid (C15) are reviewed. Also, strategies for the bio-based production of diamines of different carbon numbers including 1,3-diaminopropane (C3), putrescine (1,4-diaminobutane; C4), cadaverine (1,5-diaminopentane; C5), 1,6-diaminohexane (C6), 1,8-diaminoctane (C8), 1,10-diaminodecane (C10), 1,12-diaminododecane (C12), and 1,14-diaminotetradecane (C14) are revisited. Finally, future challenges are discussed towards more efficient production and commercialization of bio-based dicarboxylic acids and diamines.     

Advances in bio‐based production of dicarboxylic acids longer than C4

Growing concerns of environmental pollution and fossil resource shortage are major driving forces for bio‐based production of chemicals traditionally from petrochemical industry. Dicarboxylic acids (DCAs) are important platform chemicals with large market and wide applications, and here the recent advances in bio‐based production of straight‐chain DCAs longer than C4 from biological approaches, especially by synthetic biology, are reviewed. A couple of pathways were recently designed and demonstrated for producing DCAs, even those ranging from C5 to C15, by employing respective starting units, extending units, and appropriate enzymes. Furthermore, in order to achieve higher production of DCAs, enormous efforts were made in engineering microbial hosts that harbored the biosynthetic pathways and in improving properties of biocatalytic elements to enhance metabolic fluxes toward target DCAs. Here we summarize and discuss the current advantages and limitations of related pathways, and also provide perspectives on synthetic pathway design and optimization for hyper‐production of DCAs.     

Retention behaviours and separation of carboxylic acids by ion-exchange chromatography

The use of high-performance suppressed ion chromatography for the separation of aliphatic carboxylic acids has become an attractive and viable method during the past years. This paper summarises and critically concludes that some new results have been achieved in separation and detection of low-molecular-mass organic anions. Theoretical and practical considerations of ion-exchange selectivity to control retention behaviour are presented. The major factors that determine the separation ability of ion-exchange chromatography (pK_a values, the aliphatic nature and valency of solutes, eluent pH and the chemical composition of stationary phases) are discussed. The question of isocratic vs. gradient elution and different separation modes are examined briefly. The potentials and limitations of the developed methods and their specific application areas are outlined.     

Anaerobic degradation of long-chain dicarboxylic acids by methanogenic enrichment cultures

Abstract Methanogenic enrichment cultures fermented the long-chain dicarboxylates adipate, pimelate, suberate, azelate, and sebacate (C₆-C₁₀) stoichiometrically to acetate and methane. After several transfers, the cultures contained cells of only a few morphologically distinguishable types. During anaerobic degradation of dicarboxylic acids with even-numbered carbon atoms, propionate accumulated intermediately, and butyrate was the intermediate product of degradation of those with an odd number of carbon atoms. Degradation of the long-chain dicarboxylates depended strictly on the presence of hydrogenotrophic methanogens. The primary attack in these processes was β-oxidation rather than decarboxylation. A general scheme of anaerobic degradation of long-chain dicarboxylic acids has been deduced from these results.     

A role for the human peroxisomal half-transporter ABCD3 in the oxidation of dicarboxylic acids

Peroxisomes play a major role in human cellular lipid metabolism, including fatty acid β-oxidation. Free fatty acids (FFAs) can enter peroxisomes through passive diffusion or by means of ATP binding cassette (ABC) transporters, including HsABCD1 (ALDP, adrenoleukodystrophy protein), HsABCD2 (ALDRP) and HsABCD3 (PMP70). The physiological functions of the different peroxisomal half-ABCD transporters have not been fully determined yet, but there are clear indications that both HsABCD1 and HsABCD2 are required for the breakdown of fatty acids in peroxisomes. Here we report that the phenotype of the pxa1/pxa2Δ yeast mutant, i.e. impaired oxidation of oleic acid, cannot only be partially rescued by HsABCD1, HsABCD2, but also by HsABCD3, which indicates that each peroxisomal half-transporter can function as homodimer. Fatty acid oxidation measurements using various fatty acids revealed that although the substrate specificities of HsABCD1, HsABCD2 and HsABCD3 are overlapping, they have distinctive preferences. Indeed, most hydrophobic C24:0 and C26:0 fatty acids are preferentially transported by HsABCD1, C22:0 and C22:6 by HsABCD2 and most hydrophilic substrates like long-chain unsaturated-, long branched-chain- and long-chain dicarboxylic fatty acids by HsABCD3. All these fatty acids are most likely transported as CoA esters. We postulate a role for human ABCD3 in the oxidation of dicarboxylic acids and a role in buffering fatty acids that are overflowing from the mitochondrial β-oxidation system.     

Molecular approach of gossypol-induced reproductive toxicity in male rabbits. Changes in seminal plasma amino acids and fatty acids

This study was done to evaluate the effects of two sublethal doses of gossypol (4 and 20 mg/kg of BW, every other day) on some amino and fatty acid concentrations in male rabbit seminal plasma. Rabbits were chosen as an experimental animal owing to the fact that they are excellent model for reproductive toxicological effects. The experiment lasted 16 weeks and included two periods: a treatment period (first 8 weeks) where the animals were given the tested product, and a recovery period (second 8 weeks) where all drugs were withdrawn. Results showed that total amino acids (TAA), total essential amino acids (EAA), total non-essential amino acids (non-EAA) and EAA/non-EAA ratio were decreased in a dose-dependent manner during gossypol treatment. The deleterious effect on TAA concentrations was mainly due to the reduction in total EAA. However, these concentrations regained their normal values after gossypol cessation. Basic, acidic, neutral amino acids and basic/acidic amino acids ratio decreased in a dose-dependent manner by gossypol treatment. Additionally, gossypol administration caused decreases in total unsaturated fatty acids (USFA) and increases in total saturated fatty acids (SFA) and the SFA/USFA ratio in a dose-dependent manner. During the recovery period, total SFA and USFA showed significant reduction and significant increase, respectively, after gossypol withdrawal. In conclusion, gossypol administration affected rabbit seminal plasma concentrations of amino and fatty acids in a dose-dependant manner. Gossypol reduced TAA, total EAA and total non-EAA. Additionally, gossypol caused decreases in total USFA and increases in total SFA. These deleterious effects were associated with poor-quality semen observed in our previous studies.     

生物可降解塑料单体二元羧酸的生物合成研究进展北大核心CSCD

塑料是最重要的聚合物材料之一,需求量巨大,但存在处理困难、污染大等缺点。环境友好型的生物可降解塑料有望成为目前塑料的替代品,以满足社会各界对于塑料制品日益增长的需求。二元羧酸是生物可降解塑料中重要的单体之一,可降解性强,应用广泛,并且可以通过全生物法合成。因此,本文重点选取了几种比较有代表性的二元羧酸,总结它们的生物合成途径以及其代谢改造手段,以期为中长链等复杂二元羧酸的生物法合成提供借鉴。     

Simple plasma work-up for a fast chromatographic analysis of homocysteine,cysteine, methionine and aromatic amino acids

Simplified sample workup obviating protein precipitation and eluent evaporation commonly employed in earlier reports using chloroformate-mediated derivatization of aminothiols prior to mass spectrometric (MS) detection is presented. The reduction of disulfides in plasma is accomplished with dithiothreitol within minutes. A simultaneous derivatization with ethyl chloroformate (ECF) and extraction of derivatives into organic phase takes place within seconds. Along with S-amino acids, also aromatic amino acids can be determined during a 5-min run. Gas chromatography with flame ionization detection (GC-FID) proved to be sensitive enough to reach plasma homocysteine levels. A prerequisite for a reliable quantitation was fulfilled under the given conditions. Intra-assay precision was <5%, recoveries from spiked plasma complete (101.2%), detection and quantitation limits for homocysteine came to <1 and 3 micro mol/l. Our results were in full agreement with those obtained by liquid chromatography (r=0.999 for homocysteine and 0.987 for cysteine), and were close to two homocysteine immunoassays (r=0.991 and 0.939, respectively).     

Dicarboxylic acid transport in Rhizobium meliloti: isolation of mutants and cloning of dicarboxylic acid transport genes

The role of the dicarboxylic acid transport (dct) system in the Rhizobium meliloti-Alfalfa symbiosis was investigated. Mutants of R. meliloti CM2 unable to grow on medium containing succinate as the sole carbon source were isolated following chemical and transposon mutagenesis. These mutants were also unable to utilize malate or fumarate as the sole source of carbon. Transport studies with ¹⁴C-labelled succinate showed that the mutants were specifically defective in succinate transport. Revertants of both chemical and transposon mutants were obtained at a frequency of 10^-5–10^-6. The R. meliloti dct mutants were able to nodulate Alfalfa plants but the nodules formed were unable to fix nitrogen. Revertants of the mutants were fully effective on plants. The mutants unable to transport succinate were used to isolate dct genes from a R. meliloti gene bank. Two plasmids containing a common 26.5 Mdal insert were found to complement some of the mutants. The presence of this DNA insert in the complementing mutant strains restored their effectivenss of plants. This DNA fragment encoding succinate transport function(s) was used to produce genetically engineered R. meliloti strains with an increased rate of succinate uptake.Abbreviation dct dicarboxylic acid transport     

Arylboron complexes of the acids Ph2C(XH)CO2H (X = O, NH)

The acids Ph₂C(XH)CO₂H (X = O, NH) readily react with the triarylboron reagents BAr₃ (Ar = Ph, C₆F₅) to form the complexes [Ph₂C(O)CO₂BPh] (1) and [Ph₂C(NH₂)CO₂BPh₂] (2), Ph₂C(p-CH₃C₆H₄)CO₂H (3a) [in the presence of Et₃N the complex HNEt₃[Ph₂C(OH)CO₂B(C₆F₅)₃] (3b) was formed], and [Ph₂C(NH₃)CO₂B(C₆F₅)₃] (4), respectively. The synthesis and crystal structures of 1-4 (synchrotron radiation was necessary for 2) are reported.     

Catabolism of malate and related dicarboxylic acids in various Desulfovibrio strains and the involvement of an oxygen-labile NADPH dehydrogenase

Four out of five Desulfovibrio strains tested were able to oxidize l-malate to acetate in the presence of sulfate. Fumarate and succinate were also oxidized to acetate by these strains, but growth with the latter substrate was marginal. During growth on malate high NADP-dependent malic enzyme and NADPH DH activities were found in all strains. These activities were lower in lactate-or pyruvate-grown cells. An NADPH DH from D. gigas was partially purified. It was oxygen-labile, very sensitive to heavy metal ions and highly specific for NADPH. Growth yield studies indicated that energy conservation occurred during the transport of reducing equivalents from NADPH to the sulfate reduction pathway.Abbreviations DH dehydrogenase - DCPIP 2,6-dichlorophenolindophenol - MTT 3-(4,5-dimethylthiazol-2-yl)-2,4-diphenyltetrazolium bromide - HEPES 4-(2-hydroxyethyl-1-piperazine ethane sulfonic acid - PIPES piperazine-1,1-bis(2-ethane sulfonic acid) - MES 2-(N-morpholino)-ethane sulfonic acid - DTT dithiothreitol     

Simple and rapid quantitative high-performance liquid chromatographic analysis of plasma amino acids

A simple and rapid high performance liquid chromatographic method for the determination of plasma amino acids was developed. The method uses minimal sample volume and automated online precolumn derivitization of amino acids with o-phthalaldehyde and fluorescent detection. Amino acids are separated by a simplified gradient without column heating. The assay is linear from 5 to 1000 micromol/L for all amino acids. Recovery of amino acids was between 91 and 108%, intra-assay coefficient of variation (CV) was 1-7%, and inter-assay CV was 2-12%. The simple sample preparation and minimal sample volume make the method useful for the quantitation of amino acids in both patient and experimental animal samples.     

A Cl channel in Ascaris suum selectivity conducts dicarboxylic anion products of glucose fermentation and suggests a role in removal of waste organic anions

The permeability of organic anions (produced from anaerobic fermentation of glucose) through a nonselective membrane Cl channel was examined. Single channel recording techniques were used to study the permeabilities of the anions: oxalate, succinate, oxaloacetate, malate, lactate and pyruvate in Ascaris muscle cell membranes. All of the anions, except malate, were found to be conducted through the channel. The relative permeability of most anions could be predicted from the component structure of the anions. The failure of the channel to conduct malate prevents an energy drain on the cell. These studies further the hypothesis that a Cl channel functions to transport waste organic anions across the cell membrane. This mechanism does not require specific exchange carriers for the anions. Channels with properties like the nonselective anion channels of Ascaris, are suitable for transport of carboxylic anions through cell membranes, down a concentration or potential gradient.This work was financed by the Scientific and Engineering Research Council (S.E.R.C.).     

Membrane engineering via trans unsaturated fatty acids production improves Escherichia coli robustness and production of biorenewables

Constructing microbial biocatalysts that produce biorenewables at economically viable yields and titers is often hampered by product toxicity. For production of short chain fatty acids, membrane damage is considered the primary mechanism of toxicity, particularly in regards to membrane integrity. Previous engineering efforts in Escherichia coli to increase membrane integrity, with the goal of increasing fatty acid tolerance and production, have had mixed results. Herein, a novel approach was used to reconstruct the E. coli membrane by enabling production of a novel membrane component. Specifically, trans unsaturated fatty acids (TUFA) were produced and incorporated into the membrane of E. coli MG1655 by expression of cis-trans isomerase (Cti) from Pseudomonas aeruginosa. While the engineered strain was found to have no increase in membrane integrity, a significant decrease in membrane fluidity was observed, meaning that membrane polarization and rigidity were increased by TUFA incorporation. As a result, tolerance to exogenously added octanoic acid and production of octanoic acid were both increased relative to the wild-type strain. This membrane engineering strategy to improve octanoic acid tolerance was found to require fine-tuning of TUFA abundance. Besides improving tolerance and production of carboxylic acids, TUFA production also enabled increased tolerance in E. coli to other bio-products, e.g. alcohols, organic acids, aromatic compounds, a variety of adverse industrial conditions, e.g. low pH, high temperature, and also elevated styrene production, another versatile bio-chemical product. TUFA permitted enhanced growth due to alleviation of bio–product toxicity, demonstrating the general effectiveness of this membrane engineering strategy towards improving strain robustness.     

Effect of monoethanolamine salt-containing dicarboxylic acid and plant growth regulators on the absorption and accumulation of mercury

In the modern world, mercury has become an extremely dangerous pollutant due to intensive human activity. Currently, sources of mercury are wastes from chemical industries, as well as mines, oil combustion products, and household waste. Phytoextraction of heavy metals from soil is considered one of the most promising and cost-effective technologies. The efficiency of this process can be increased by introducing various amendments. The use of additives in phytoextraction can enhance the absorption of heavy metals and increase their concentration in various parts of the plant. This article presents the results of a study of various chelating agents for effective phytoextraction of mercury with white clover (Trifolium repens L.) and watercress (Lepidium sativum). In the present study, the monoethanolamine salt of dithiodiacetic acid (MEDBA) was used. The optimal concentration of MEDBA on watercress and creeping clover has been determined for highly efficient phytoextraction of mercury. Research has been carried out with a complex of exogenous growth regulators (GA / IAA / Fe-EDDHA). The results showed that the use of phytohormones and plant growth regulators led to a synergistic effect in combination with thiosulfate, but a pronounced inhibitory effect was observed with the use of MEDBA.     

Changes of plasma insulin, urea, amino acids and rumen metabolites in somatotropin treated dairy cows

Summary An experiment was performed to evaluate the effects of somatotropin on plasma free amino acid, urea and insulin concentrations and rumen fermentation pattern and to assess their relationships. Four Italian Friesian dairy cows fitted with rumen cannulae were used in a switch-back design. Slow releasing recombinant bovine somatotropin (640 mg/cow) was injected every 28 days for two consecutive periods. Rumen fluid and blood samples were collected before and after feeding at 0, 7 and 21 days after rbST injection. Exogenous rbST increased plasma insulin concentration and the insulin response to feeding, and decreased plasma urea and free essential and branched chain amino acid concentrations. rbST did not affect rumen fermentation pattern. No correlation was found between rumen and plasma parameters measured after feeding. Our results are consistent with the notion that the main effect of somatotropin is post-absorptive.     

Spectroscopic study of lanthanide(III) complexes with aliphatic dicarboxylic acids

The complexation of trivalent lanthanides with aliphatic dicarboxylic acids (malonic, succinic, glutaric and adipic) were studied at 25°C and 0.1 M (NaClO₄) ionic strength by luminescence and absorption spectroscopy and luminescence lifetime measurements. The luminescence spectra and decay constants indicate that ML and ML₂ complexes were formed. The stability constants of Eu(III) complexes with the dicarboxylic acids were calculated from the changes of the ⁵D₀←⁷F₀ excitation spectra of Eu(III). For the four dicarboxylic acids studied, both the stability constant and the number of water molecules released from the inner sphere of Eu(III) upon complexation decrease from malonate to adipate for both the ML and ML₂ complexes. The results are interpreted as reflecting an increasing tendency from chelation to monodentation as the carbon chain length increases between carboxylate groups. The trend in the oscillator strength in the hypersensitive transition of the Nd(III)and Ho(III) complexes is the same as that in the ligand basicity.     

Neurochemical,pharmacological, and developmental studies on cerebellar receptors for dicarboxylic amino acids

Specific binding ofl-[³H]glutamate ([³H]Glu) andl-[³H]asparate ([³H]Asp) to cerebellar membranes represented a time-, temperature- pH- and protein-dependent interaction which was both saturable and reversible. Binding sites for both radioligands appeared maximally enriched in synaptosomal fractions isolated by gradient centrifugation. Kinetically derived dissociation constant (K _off/K _on=K _d) for [³H]Glu binding to this fraction indicated high-affinity (443 nM). Competition experiments employing analogs of excitatory amino acids, including new antagonists, helped identify binding sites for [³H]Glu and [³H]Asp as receptors with differential pharmacological, specificities. Membrane freezing reduced numbers of both receptor types, but binding activity could be recovered partially by incubation at 37°C. Glu receptors exhibited a pronounced deleterious sensitivity to thiol modifying reagents andl-Glu (50–1000 M) provided protection, against these compounds during co-incubation with cerebellar membranes. It is suggested that cold storage may induce partially reversible receptor inactivation by promoting sulfhydryl group/bond modification. Rat cerebellar glutamatergic function (endogenous Glu content, Glu uptake and receptor sites) exhibited an apparent ontogenetic peak between days 8–12 postpartum with a plateauing profile from day 30 to adulthood. The accelerated development (days 8–12) coincides with the first demonstrable Glu release and kainic acid neurotoxicity, as described previously.