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Neutral Amino Acids (neutral + amino_acids)

Distribution by Scientific Domains
Earth and Environmental Science50%

Selected Abstracts

Amino acids in Quaternary soil horizons from southwest Poland

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2003
A. Szponar
Summary Aminostratigraphy has proved to be a useful approach for dating fossils from the Quaternary. In these studies the amino acids in Quaternary soil formations were determined in an attempt to establish their stratigraphical relationships and relative ages. The sampling sites are in the southwest of Poland, in the Trzebnickie Hills. Three samples of fossil soils and two of recent soils were analysed. The absolute age of the soil samples was estimated by radiocarbon dating. We found that the total amount of amino acids decreased with the increasing age of soil. The smallest amounts of amino acids were found in the oldest fossil soil of Denekamp (Vistulian) age dated 29 600 ± 760 years bp. A sample of recent loess soil contained the most total amino acids, whereas the fossil soil of Lower Atlantic age, dated 3540 ± 230 years bp, was intermediate in respect of the total amount of amino acids, oxidation state and degree of biochemical transformation. Neutral amino acids formed a majority of all the amino acids studied. The method we describe could be useful in relative chronostratigraphical identification of fossil soils. [source]

Bound amino acids in humic acids from arable cropping systems

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2004
Lech Szajdak
Abstract We investigated the varying concentrations of bound amino acids in humic acids (HA) extracted from soils under both crop rotation and continuous cropping of rye. The experiment was created in 1957. Since then, winter rye had been grown continuously and also the sequence of the 7 yr rotation had been started: potato, spring barley, alfalfa, alfalfa, oil seed rape, winter rye, and winter rye. Soils were fertilized with NPK and manure. Continuous cropping of rye increased total acidity of soils and the contents of carboxylic and phenolic groups in HA. The total amounts of the bound amino acids in HA from soils under crop rotation were higher than from continuous cropping of rye. Fertilization with NPK increased the contents of bound amino acids more than manure. Neutral amino acids dominated in all samples of HA, and basic amino acids had the lowest concentrations. In both types of cultivation, glutamic acids, glycine, alanine, valine, and lysine dominated. The proline contents in HA from continuous rye cropping were higher than in HA from soils under crop rotation. The concentrations of ,-alanine and lysine were higher in HA from crop rotation indicating a higher microbial biomass since these compounds are typical constituents of bacteria cell walls. In Huminsäuren gebundene Aminosäuren aus Böden unterschiedlicher Anbausysteme In Bodenproben aus Feldern mit Roggen-Monokultur und Fruchtwechsel wurde die Konzentration von Anminosäuren in Huminsäuren untersucht. Der Feldversuch wurde im Jahre 1957 angelegt. Auf einem Teil des Feldes wurde Winterroggen in Monokultur angebaut, auf dem anderen Teil wurde eine Fruchtfolge aus Kartoffeln, Sommergerste, Luzerne, Raps, Winterroggen und Winterrogen angebaut. Die Böden wurden mit NPK und Stallmist gedüngt. Unter der Roggen-Monokultur vergrößerten sich die Gesamtazidität des Bodens und die Anteile von Karboxyl- und phenolischen OH-Gruppen in den Huminsäuren. Die Aminosäuregehalte der Huminsäuren waren bei Fruchtfolge höher als unter Monokultur. Bei Nutzung von Mineraldüngern war die Konzentration der Aminosäuren höher als bei Stallmist. Die neutralen Aminosäuren waren immer in größeren Gehalten vorhanden als die sauren Aminosäuren. Unabhängig von den Pflanzen dominierten immer Glutaminsäure, ß-Alanin, Valin und Lysin. Bei Monokultur war die Menge an Prolin höher als bei der Fruchtfolge. Die Gehalte an ß-Alanin und Lysin verhielten sich umgekehrt, was durch eine höhere mikrobielle Biomasse erklärt wird, da ,-Alanin und Lysin in Zellwände von Bakterien eingebaut sind. [source]

Stereoselective Aldol Reactions Catalyzed by Acyclic Amino Acids in Aqueous Micelles

HELVETICA CHIMICA ACTA, Issue 1 2007
Dong-Sheng Deng
Abstract The catalytic properties of all proteinogenic, acyclic amino acids for direct aldol reaction in H2O, assisted by various surfactants, were investigated. The basic and neutral amino acids were shown to be efficient catalysts, giving rise to good-to-excellent yields of adducts (up to 95%), with moderate-to-good diastereoselectivities (up to 86%), L -arginine being the most-effective catalyst. The syn/anti diastereoisomer ratio could be readily tuned by proper choice of the amino acid used. Also, the range of substrates that underwent the reaction was extended to less-reactive aldehydes carrying electron-donating Br substituents. [source]

Characterization and astrocytic modulation of system L transporters in brain microvasculature endothelial cells

CELL BIOCHEMISTRY AND FUNCTION, Issue 3 2008
Yadollah Omidi
Abstract Brain trafficking of amino acids is mainly mediated by amino acids transport machineries of the blood,brain barrier (BBB), where astrocytes play a key maintenance role. However, little is known about astrocytes impacts on such transport systems, in particular system L that consists of large and small neutral amino acids (NAAs) transporters, that is, LAT1/4F2hc and LAT2/4F2hc, respectively. In the current investigation, functionality and expression of system L were studied in the immortalized mouse brain microvascular endothelial b.End3 cells cocultured with astrocytes or treated with astrocyte-conditioned media (ACM). LAT2/4F2hc mediated luminal uptake of L -phenylalanine and L -leucine resulted in significantly decreased affinity of system L in b.End3 cells treated with ACM, while LAT2/4F2hc mediated luminal uptake of L -alanine remained unchanged. Gene expression analysis revealed marked upregulation of LAT1 and 4F2hc, but downregulation of LAT2 in b.End3 cells cultured with ACM. The basal to apical transport of L -phenylalanine and L -alanine appeared to be significantly greater than that of the apical to basal direction in b.End3 cells indicating an efflux functionality of system L. No marked influence was observed for transport of L -phenylalanine in b.End3 cells cocultured with astrocytes, while a slight decrease was seen for L -alanine in the basal to apical direction. Based on our findings, we propose that system L functions as influx and/or efflux transport machinery displaying a greater propensity for the outward transport of large and small NAAs. Astrocytes appeared to modulate the transcriptic expression and uptake functionalities of system L, but not the transport activities. Copyright © 2008 John Wiley & Sons, Ltd. [source]