L-aspartic Acid (l-aspartic + acid)

Distribution by Scientific Domains

Selected Abstracts

Stereoselective Syntheses of (+)-,- (Ia) and (-)-,-Conhydrine (Ib) from L-Aspartic Acid.

CHEMINFORM, Issue 40 2005
Satyendra Kumar Pandey
No abstract is available for this article. [source]

Expression and regulation of L-cystine transporter, system xc,, in the newly developed rat retinal Müller cell line (TR-MUL)

GLIA, Issue 3 2003
Masatoshi Tomi
Abstract The purpose of the present study was to elucidate the expression and regulation of the L-cystine transporter, system xc,, in Müller cells. In this study, newly developed conditionally immortalized rat Müller cell lines (TR-MUL) from transgenic rats harboring the temperature-sensitive SV 40 large T-antigen gene were used as an in vitro model. TR-MUL cells express large T-antigen and grow well at 33°C with a doubling time of 30 h, but do not grow at 39°C. TR-MUL cells express typical Müller cell markers such as S-100, glutamine synthetase, and EAAT1/GLAST, whereas EAAT2/GLT-1 and EAAT5 are not detected. TR-MUL cells also exhibit little or no expression of glial fibrillary acidic protein. We found that TR-MUL5 cells exhibited [14C]L-cystine uptake activity and expressed xCT and 4F2hc, which involve system xc,. The uptake of [14C]L-cystine was significantly inhibited by L-glutamic acid and L-aspartic acid, whereas L-leucine had no effect. Following diethyl maleate (DEM) treatment, the glutathione concentration in TR-MUL5 cells was reduced in the first 24 h, then gradually recovered for more than 24 h. The L-cystine uptake rate and the xCT expression level in TR-MUL5 cells were enhanced by DEM treatment. In contrast, the 4F2hc expression level was unchanged. In conclusion, TR-MUL cells have the properties of Müller cells and exhibit system xc, -mediated L-cystine uptake activity. The oxidative stress conditions following DEM treatment activate L-cystine transport in TR-MUL cells due to the enhanced transcription of the xCT gene. GLIA 9999:000,000, 2003. © 2003 Wiley-Liss, Inc. [source]

Nitrogen biomarkers and their fate in soil,

Wulf Amelung
Abstract More than 90,% of the nitrogen (N) in soils can be organically bound, but the mechanisms and rates by which it is cycled have eluded researchers. The objective of this research was to contribute to a better understanding of the origin and transformation of soil organic N (SON) by using amino sugars and the enantiomers of amino acids as markers for microbial residues and/or aging processes. Studied samples presented here comprised (1) soil transects across different climates, (2) arable soils with different duration of cropping, and (3) radiocarbon-dated soil profiles. The results suggested that increased microbial alteration of SON temporarily results in a sequestration of N in microbial residues, which are mineralized at later stages of SON decomposition. Microorganisms increasingly sequestered N within intact cell wall residues as frost periods shortened. At a mean annual temperature above 12,15,°C, these residues were mineralized, probably due to limitations in additional substrates. Breaking the grassland for cropping caused rapid SON losses. Microbial residues were decomposed in preference to total N, this effect being enhanced at higher temperatures. Hence, climate and cultivation interactively affected SON dynamics. Nevertheless, not all SON was available to soil microorganisms. In soil profiles, L-aspartic acid and L-lysine slowly converted into their D-form, for lysine even at a similar rate in soils of different microbial activity. Formation of D-aspartate with time was, therefore, induced by microorganisms while that of D-lysine was not. The racemization of the two amino acids indicates that SON not available to microorganisms ages biotically and abiotically. In native soils, the latter is conserved for centuries, despite N deficiency frequently occurring in living terrestrial environments. Climate was not found to affect the fate of old protein constituents in surface soil. When native grassland was broken for cropping, however, old SON constituents had become available to microorganisms and were degraded. Stickstoff-Biomarker und ihre Dynamik im Boden Über 90,% des Stickstoffs im Boden können organisch gebunden sein. Um zu einem besseren Verständnis der Norg -Dynamik im Boden beitragen zu können, analysierte ich Aminozucker und Aminosäure-Enantiomere als Marker für mikrobielle N-Rückstände und/oder Alterungsprozesse von Norg im Boden. Das hier vorgestellte Untersuchungsmaterial umfasste (1) Bodentransekte entlang unterschiedlicher Klimate, (2) Ackerböden mit verschiedener Nutzungsdauer und (3) 14C-datierte Bodenprofile. Die Ergebnisse zeigten, dass mit fortschreitender Umwandlung des Norg mikrobielle N-Rückstände nur vorübergehend im Boden akkumulieren, da sie in späteren Abbauphasen wieder mineralisiert werden. Mikroorganismen bauten zunehmend N in intakte Zellwandrückstände ein, wenn sich die Frostperioden verkürzten. Bei einer Jahresmitteltemperatur über 12,15,°C sank der Beitrag mikrobieller Rückstände zum N-Gehalt, vermutlich weil Mikroorganismen diese mangels anderer Substrate verstärkt mineralisierten. Umbrüche von Gras- zu Ackerland führten zu raschen N-Verlusten. Mikrobielle N-Rückstände wurden bevorzugt abgebaut, ein Effekt, den höhere Temperaturen verstärkten. Demnach steuerte das Klima die Intensität von Nutzungseffekten auf die Norg -Dynamik. Doch nicht der gesamte Norg war für Mikroorganismen zugänglich. Der D-Gehalt von Asparaginsäure und Lysin nahm mit steigendem Alter der organischen Bodensubstanz zu, Lysin racemisierte in den verschiedenen Böden sogar mit gleicher Geschwindigkeit. Anders als die Bildung von D-Asparaginsäure wurde die von Lysin also nicht durch Mikroorganismen beeinflusst. Die Racemisierung der beiden Aminosäuren deutet deshalb darauf hin, dass nicht-bioverfügbare Norg -Bestandteile biotisch und abiotisch im Boden altern. Klimaeinwirkungen auf den Verbleib alter Proteinrückstände ließen sich nicht feststellen. Mit Umbruch von Gras- zu Ackerland erhielten Mikroorganismen allerdings Zugang zu alten Norg -Verbindungen und bauten diese ab. [source]

Molar Mass and Structural Characteristics of Poly[(lactide- co -(aspartic acid)] Block Copolymers

Ida Poljan
Abstract Summary: We report on various synthetic procedures for the preparation of biodegradable and biocompatible poly(lactide- co -aspartic acid) block copolymers based on natural monomeric units , lactic acid and aspartic acid. Multiblock poly(lactide- co -aspartic acid) copolymers of different comonomer composition were synthesized by heating a mixture of L-aspartic acid and L,L-lactide in melt without the addition of any catalyst or solvent and with further alkaline hydrolysis of the cyclic succinimide rings to aspartic acid units. Diblock poly(lactide- co -aspartic acid) copolymers with different block lengths were prepared by copolymerization of amino terminated poly(, -benzyl-L-aspartate) homopolymer and L,L-lactide with subsequent deprotection of the benzyl protected carboxyl group by hydrogenolysis. The differences in the structure, composition, molar mass characteristics, and water-solubility of the synthesized multiblock and diblock poly(lactide- co -aspartic acid) copolymers are discussed. [source]

Intracerebroventricular injection of L-aspartic acid and L-asparagine induces sedative effects under an acute stressful condition in neonatal chicks

ABSTRACT The present study was conducted to clarify the central functions of L-aspartic acid (Asp) and L-asparagine (Asn) during an acute stressful condition in chicks. Intracerebroventricular (i.c.v.) injection of Asp and Asn (0.84 µmol) attenuated the vocalization that normally occurs during social separation stress. Asp decreased the time spent in active wakefulness and induced sedation. Asn had a similar effect to Asp, although somewhat weaker. However, i.c.v. injection of Asp and Asn further enhanced plasma corticosterone release under social separation stress. Taken together, the i.c.v. injection of Asp and Asn has sedative effects under an acute stressful condition, which does not involve the hypothalamic-pituitary-adrenal axis. [source]

Health-Affecting Compounds in Brassicaceae

Muhammad Jahangir
ABSTRACT:,Brassicaceae vegetables are considered to be a staple food in many areas all over the world. Brassica species are not only known for their high fat and protein contents for human and animal consumption, but Brassicaceae vegetables are recognized as a rich source of nutrients such as vitamins (carotenoids, tocopherol, ascorbic acid, folic acid), minerals (Cu, Zn, P, Mg, among others), carbohydrates (sucrose and glucose), amino acids (for example, L-alanine, L-aspartic acid, L-glutamic acid, L-glutamine, L-histidine, L-methionine, L-phenylalanine, L-threonine, L-tryptophan, and L-valine), and different groups of phytochemicals such as indole phytoalexins (brassinin, spirobrassinin, brassilexin, camalexin, 1-methoxyspirobrassinin, 1-methoxyspirobrassinol, and methoxyspirobrassinol methyl ether), phenolics (such as feruloyl and isoferuloylcholine, hydroxybenzoic, neochlorogenic, chlorogenic, caffeic, p -coumaric, ferulic, and sinapic acids, anthocyanins, quercetin, and kaempferol), and glucosinolates (mainly glucoiberin, glucoraphanin, glucoalyssin, gluconapin, glucobrassicanapin, glucobrassicin, gluconasturtiin, and neoglucobrassicin). All of these phytochemicals contribute to the reported antioxidant, anticarcinogenic, and cardiovascular protective activities of Brassica vegetables. However, not all members of this family are equal from a nutritional viewpoint, since significant qualitative variations in the phytochemical profiles of Brassica species and varieties suggest differences in the health-promoting properties among these vegetables. In this article, Brassica phytochemicals with their nutritional value and health-promoting activities are discussed to give an overview of the literature for Brassica as a staple crop. [source]