Surfactant to dye binding degree based approach for the selective determination of L-glutamate in foodstuffs.
Pedraza, A., Sicilia, M. D., Rubio, S. & Pérez-Bendito, D. (2007). Analytical and Bioanalytical Chemistry, 389(7-8), 2297-2302.
A selective method for the determination of L-glutamate in foodstuffs has been developed. It was based on the competition established between the analyte and the dye Coomassie brilliant blue G (CBBG) to interact with the surfactant didodecyldimethylammonium bromide (DDABr). The measurement parameter was the amount of DDABr required to reach a given dye-to-surfactant binding degree. It was obtained by photometric titration on the basis of the changes observed in the spectral characteristics of the dye when CBBG–DDABr aggregates were formed. The calibration graph obtained was linear in the L-glutamate concentration interval 0.2–5 mM (detection limit 0.05 mM). The high selectivity of the proposed method (other amino acids and food additives did not interfere at the concentrations present in foodstuffs) permitted the direct analysis of food samples after dissolution of the analyte in hot water. The accuracy of the surfactant to the dye binding degree method was demonstrated by determining L-glutamate in different kinds of foodstuffs (liquid and dried soups, seasonings, pasta sauces and dried mushroom creams) and comparing the results obtained with those provided by the commercial Boehringer Mannheim essay.
Production of stable quinine nanodispersions using esterified γ-polyglutamic acid biopolymer.
Hoennscheidt, C., Kreyenschulte, D., Margaritis, A. & Krull, R. (2013). Biochemical Engineering Journal, 79, 259-266.
Novel methods are needed for the development of nanodispersed drug formulations to enhance bioavailability of many hydrophobic pharmaceuticals. The poorly water-soluble quinine is a well-known anti-malaria drug which can be used as a promising model compound for the development of novel nanodispersed formulations. In addition to hydrophobic drug's own affecting properties, surfactants play an important role for the enhancement of their low bioavailability by preparing stable dispersions. Amphiphilic compounds can efficiently be used to stabilize colloidal fragments by preventing the precipitation or crystallization of poorly water-soluble active ingredients during fabrication. A novel biopolymer derivative based on the biotechnologically produced γ-polyglutamic acid (γ-PGA) from Bacillus licheniformis cultivation was developed for encapsulation of the active ingredient. High-molecular γ-PGA is an anionic polyelectrolyte that was optimized and modified with hydrophobic L-phenylalanine ethyl ester (L-PAE) to form an amphiphilic comb polymer P(γ-GA-r-L-PAE) with surfactive properties. The approach of the nanodispersion polymer concentration, molecular weight and grafting degree enables the efficient stabilization of the poorly water-soluble model drug. The research presented in this report indicates the potential benefits of hydrophobically modified γ-PGA and suggests its potential role in forming stable dispersions for future pharmaceutical applications.
Gamma-amino butyric acid, glutamate dehydrogenase and glutamate decarboxylase levels in phylogenetically divergent plants.
Seher, Y., Filiz, O. & Melike, B. (2013). Plant Systematics and Evolution, 299(2), 403-412.
Gamma-amino butyric acid (GABA) is a nonprotein amino acid found in a wide range of organisms including plants. Several studies have shown that GABA plays different roles in plant metabolism including carbon–nitrogen metabolism, energy balance, signaling and development. It has been suggested that the occurrence of GABA and the enzymes related to GABA biosynthesis in prokaryotes and eukaryotes may be important in evolution and diversification. However, studies of GABA biosynthesis and GABA levels in an evolutionary context are restricted to sequenced plant genomes. In this study we aimed to compare the activities of GDH and GAD enzymes and total nitrogen, and the contents of total soluble protein, succinate, glutamate, proline and GABA in plants from different phylogenetic levels including Ulva lactuca, Pseudevernia furfuracea, Nephrolepsis exaltata, Ginkgo biloba, Pinus pinea, Magnolia grandiflora, Nymphaea alba, Urtica dioica, Portulaca oleraceae, Malva sylvestris, Rosa canina, Lavandula stoechas, Washingtonia filifera, Avena barbata and Iris kaempferi. The activities of GAD and GDH enzymes differed according to the species and were not always parallel to GABA levels. The discrepancy in the contents of succinate and GABA between higher and primitive plants was also prominent. Glutamate levels were high with a few exceptions and proline contents were at similar low values as compared to other amino acids. Our results support the hypothesis that the GABA shunt plays a key role in carbon and nitrogen partitioning via linking amino acid metabolism and the tricarboxylic acid cycle which is essential for higher plant species.
Astrocytic glutamate transporter-dependent neuroprotection against glutamate toxicity: An in vitro study of maslinic acid.
Qian, Y., Guan, T., Tang, X., Huang, L., Huang, M., Li, Y., Sun, H., Yu, R. & Zhang, F. (2011). European Journal of Pharmacology, 651(1-3), 59-65.
The astrocytic glutamate transporters GLAST/EAAT1 and GLT-1/EAAT2 are crucial for the removal of glutamate from the synaptic cleft and are essential for maintaining a low concentration of extracellular glutamate in the brain. Enhanced transporter expression is neuroprotective. In the present study, we tested the neuropotective effects of maslinic acid, a natural product from the Olea europaea plant, on cultures of primary neurons from the cerebral cortex. Studies showed that astrocyte-conditioned medium from maslinic acid-treated astrocytes dose-dependently promoted neuron survival during glutamate toxicity by enhancing extracellular glutamate clearance. Real-time PCR and western blot analysis revealed that maslinic acid pre-treatment significantly increased the expression of GLAST and GLT-1 at the protein and mRNA levels. In addition, this neuroprotection was abolished by the glutamate transporter inhibitor, L-Threohydroxy aspartate (THA), in a co-culture of astrocytes and neurons. These findings suggest that maslinic acid regulates the extracellular glutamate concentration by increasing the expression of astrocytic glutamate transporters, which may, in turn, provide neuroprotection.
The rice R2R3-MYB transcription factor OsMYB55 is involved in the tolerance to high temperature and modulates amino acid metabolism.
El-kereamy, A., Bi, Y. M., Ranathunge, K., Beatty, P. H., Good, A. G. & Rothstein, S. J. (2012). PloS one, 7(12), e52030.
Temperatures higher than the optimum negatively affects plant growth and development. Tolerance to high temperature is a complex process that involves several pathways. Understanding this process, especially in crops such as rice, is essential to prepare for predicted climate changes due to global warming. Here, we show that OsMYB55 is induced by high temperature and overexpression of OsMYB55 resulted in improved plant growth under high temperature and decreased the negative effect of high temperature on grain yield. Transcriptome analysis revealed an increase in expression of several genes involved in amino acids metabolism. We demonstrate that OsMYB55 binds to the promoter regions of target genes and directly activates expression of some of those genes including glutamine synthetase (OsGS1;2) glutamine amidotransferase (GAT1) and glutamate decarboxylase 3 (GAD3). OsMYB55 overexpression resulted in an increase in total amino acid content and of the individual amino acids produced by the activation of the above mentioned genes and known for their roles in stress tolerance, namely L-glutamic acid, GABA and arginine especially under high temperature condition. In conclusion, overexpression of OsMYB55 improves rice plant tolerance to high temperature, and this high tolerance is associated with enhanced amino acid metabolism through transcription activation.