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1.
Amino acid analysis by hydrophilic interaction chromatography coupled on-line to electrospray ionization mass spectrometry 总被引:1,自引:0,他引:1
Summary. Collagens form a common family of triple-helical proteins classified in 21 types. This unique structure is further stabilized
by specific hydroxylation of distinct lysyl and prolyl residues forming 5-hydroxylysine and hydroxyproline (Hyp) isomers,
mostly 4-trans and 3-trans-Hyp. The molecular distribution of the Hyp-isomers among the different collagen types is still
not well investigated, even though disturbances in the hydroxylation of collagens are likely to be involved in several diseases
such as osteoporosis and autoimmune diseases. Here, a new approach to analyze underivatized amino acids by hydrophilic interaction
chromatography (HILIC) coupled on-line to electrospray ionization mass spectrometry (ESI-MS) is reported. This method can
separate all three studied Hyp-isomers, Ile, and Leu, which are all isobaric, allowing a direct qualitative and quantitative
analysis of collagen hydrolysates. The sensitivity and specificity was increased by a neutral loss scan based on the loss
of formic acid (46 u). 相似文献
2.
Summary. Amino acids analysis in single wheat embryonic protoplast was performed using capillary electrophoresis equipped with laser-induced
fluorescence (CE-LIF), combination with tissue culture technique. Reagent fluorescein isothiocyanate (FITC) was introduced
into living protoplasts by electroporation for intracellular derivatization. A special osmotic buffer (0.6 mol/L mannitol,
5 mmol/L CaCl2) was used to keep the osmotic balance of embryonic protoplasts during the protoplasts derivatization. After completion of
the derivatization reaction in the protoplasts, a single protoplast was drawn into the capillary tip by electroosmotic flow.
Then a 0.1 M NaOH lysing solution was injected by diffusion. The derivatized amino acids were separated by capillary electrophoresis
and detected by laser-induced fluorescence detection after the protoplast was lysed Nine amino acids were quantitatively and
qualitatively determined and compared in lysate and single protoplast of wheat embryonic cells respectively, with mean concentrations
of amino acids ranging from 2.68×10−5 mol/L to 18.18×10−5 mol/L in single protoplast. 相似文献
3.
Summary. Despite the wide interest in using modified amino acids as putative biomarkers of oxidative stress, many issues remain as
to their overall reliability for early detection and diagnosis of diseases. In contrast to conventional single biomarker studies,
comprehensive analysis of biomarkers offers an unbiased strategy for global assessment of modified amino acid metabolism due
to reactive oxygen and nitrogen species. This review examines recent analytical techniques amenable for analysis of modified
amino acids in biological samples reported during 2003–2007. Particular attention is devoted to the need for validated methods
applicable to high-throughput analysis of multiple amino acid biomarkers, as well as consideration of sample pretreatment
protocols on artifact formation for improved clinical relevance. 相似文献
4.
Asechi M Kurauchi I Tomonaga S Yamane H Suenaga R Tsuneyoshi Y Denbow DM Furuse M 《Amino acids》2008,34(1):55-60
Summary. Intracerebroventricular (i.c.v.) injection of L-serine was shown to have sedative and hypnotic effects on neonatal chicks
under acute stressful conditions. To clarify the central mechanism of these effects of L-serine, two experiments were done.
First, we focused on the glycogenic pathway in which L-serine is converted into pyruvate and finally glucose. I.c.v. administration
of pyruvate (0.84 μmol) did not induce any behavioral and endocrinological changes, while L-serine and glucose triggered sedative
and hypnotic effects. Secondly, the relationship between the sedation by L-serine and the metabolism into other amino acids
which have sedative effects was investigated in the telencephalon and diencephalon. In both brain areas, a dose-dependent
increase was seen in L-serine, although other amino acids were not changed. In the present study, it was concluded that the
sedative action of L-serine was not due to the action of its metabolite pyruvate, or to the action of other amino acids.
Authors’ address: M. Furuse, PhD, Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and
Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan 相似文献
5.
6.
Pawelke B 《Amino acids》2005,29(4):377-388
Summary. Substances of various chemical structures can be labelled with appropriate positron emitting isotopes and applied as tracer
compounds in PET examinations. Using dynamic data acquisition protocols, time-activity curves of radioactivity uptake in organs
can be derived and the measurements of tissue tracer concentrations can be translated into quantitative values of tissue function.
However, analysis of metabolites of these tracers regarding their nature and distribution in the living organism is an essential
need for the quantitative analysis of PET measurements. In addition, metabolite analysis contributes to the interpretation
of the images obtained as well as to the identification of pathological changes in metabolic pathways. This paper reports
on representative examples of radiolabelled compounds which might be of importance in food science (e.g., amino acids, polyphenols,
and model compounds for advanced glycation end products (AGEs)). Typical procedures of analysis (radio-HPLC, radio-TLC) including
pre-analytical sample preparation are described. Specific challenges of the method, e.g., trace amounts of radiolabelled compounds
and the influence of the often very short half-lives of positron-emitting nuclides used are highlighted. Representative results
of analyses of plasma, urine, and tissue samples are presented and discussed in terms of the metabolic fate of the tracers. 相似文献
7.
Summary. A fluorescent electrophilic reagent, 9-fluorenone-4-carbonyl chloride (FCC), is chosen to functionalize amino acids in alkaline
medium before their HPLC resolution. FCC reacts with both primary and secondary amino acids to produce stable and highly fluorescent
derivatives suitable for sensitive and efficient chromatographic determination and resolution on a teicoplanin chiral stationary
phase (CSP) using the methanol-based solvent mixture as the mobile phase. The detection limit is in the picomole range and
approximately 0.01% of the d-enantiomer in an excess of the l-enantiomer is detectable. However, the resolution is not reproducible under the elution of either the water- or the acetonitrile-based
mobile phase. The increase in solubility of analyte in the mobile phase seems to be responsible. Upon comparison under the
optimal chromatographic conditions, the resolution is better than that for the 9-fluorenylmethyl chloroformate (FMOC) or 6-aminoquinolyl-N-hydroxysuccinimidyl
carbamate (AQC) derivatives reported previously. 相似文献
8.
Summary. The premise that free amino acid or dipeptide based diets will resolve the nutritional inadequacy of formulated feeds for
larval and juvenile fish and improve utilization of nitrogen in comparison to protein-based diets was tested in stomachless
fish, common carp (Cyprinus carpio L.) larvae. We examined the postprandial whole body free amino acid (FAA) pool in fish that were offered a FAA mixture based
diet for the duration of 2 or 4 weeks. We found that the total amount and all indispensable amino acids concentrations in
the whole body decreased after a meal. We then fed juvenile carp with dietary amino acids provided in the FAA, dipeptide (PP),
or protein (live feed organisms; brine shrimp Artemia salina nauplii, AS) forms. Histidine concentrations in the whole fish body increased in all dietary groups after feeding whereas
all other indispensable amino acids decreased in FAA and PP groups in comparison to the AS group. Taurine appears to be the
major osmotic pressure balancing free amino acid in larval freshwater fish which may indicate a conditional requirement. We
present the first evidence in larval fish that in response to synthetic FAA and PP diets, the whole body indispensable free
AA concentrations decreased after feeding. This study shows that amino acids given entirely as FAA or PP cannot sustain stomachless
larval fish growth, and may result in depletion of body indispensable AA and most of dispensable AA. The understanding of
these responses will determine necessary changes in diet formulations that prevent accelerated excretion of amino acids without
protein synthesis. 相似文献
9.
Summary. The purpose of the present study was to determine whether the regulation of brain protein synthesis was mediated through changes
in the plasma concentrations of insulin and growth hormone (GH), and whether the concentrations of amino acids in the brain
and plasma regulate the brain protein synthesis when the quantity and quality of dietary protein is manipulated. Two experiments
were done on three groups of aged rats given diets containing 20% casein, 5% casein or 0% casein (Experiment 1), and 20% casein,
20% gluten, or 20% gelatin (Experiment 2) for 1 d (only one 5-h period) after all rats were fed the 20% casein diet for 10
d (only 5-h feeding per day). The aggregation of brain ribosomes, the concentration in plasma GH, and the branched chain amino
acids in the plasma and cerebral cortex declined with a decrease of quantity and quality of dietary protein. The concentration
of plasma insulin did not differ among groups. The results suggest that the ingestion of a higher quantity and quality of
dietary protein increases the concentrations of GH and several amino acids in aged rats, and that the concentrations of GH
and amino acids are at least partly related to the mechanism by which the dietary protein affects brain protein synthesis
in aged rats. 相似文献
10.
Summary. Glucocorticoid hormones enhance the reabsorptive capacity of filtered amino acids in rat kidney, as it was shown in previous
in vivo clearance experiments. In the present study, the site of glucocorticoid action on neutral amino acid transport in superficial
nephrons of rat kidney was investigated using in vivo micropuncture technique. Adult female Wistar rats were treated with dexamethasone (DEX), and fractional excretion of L-glutamine
(L-Gln) and L-leucine (L-Leu) were determined and related to inulin after microinfusion into different nephron segments. DEX
reduced fractional excretion of both neutral amino acids as a sign of enhanced reabsorptive capacity. The site of main DEX
action on L-Leu reabsorption has been localized in the proximal straight tubule. However, in the case of L-Gln, the inhibition
of γ-glutamyltranspeptidase (γ-GT) by administration of acivicin indicated the importance of this brush border enzyme in reduced L-Gln excretion. DEX enhanced
γ-GT activity by tubular acidification. It can be presumed a DEX-inducible transport system for neutral amino acids mainly
localized in proximal straight tubules of rat kidney.
Received July 8, 1999 相似文献
11.
Summary. A technique is described for the enantiomeric determination of L- and D-amino acids. It works on the principle that the separation
efficiency of high-performance liquid chromatography is coupled with the specificity of enzymes and the sensitivity of electrochemical
detection. After separation on a lithium cation-exchange column the amino acids are converted into keto acids and hydrogen
peroxide under catalyzation of L- or D-amino acid oxidase. Hydrogen peroxide is detected amperometrically. The method has
been tested by the analysis of beer, port, sherry, wine and fruit juice.
A main emphasis was put onto the determination of D-alanine which can serve as an indicator for bacterial contamination. It
is shown that a coupling of HPLC with enzyme reactors is a suitable technique for the rapid detection of this marker.
Received April 14, 1999, Accepted September 15, 1999 相似文献
12.
Summary. The cDNA encoding D-aspartate oxidase (DASPO) was cloned from mouse kidney RNA by RT–PCR. Sequence analysis showed that it
contained a 1023-bp open reading frame encoding a protein of 341 amino acid residues. The protein was expressed in Escherichia coli with or without an N-terminal His-tag and had functional DASPO activity that was highly specific for D-aspartate and N-methyl-D-aspartate. To investigate the roles of the Arg-216 and Arg-237 residues of the mouse DASPO (mDASPO), we generated
clones with several single amino acid substitutions of these residues in an N-terminally His-tagged mDASPO. These substitutions
significantly reduced the activity of the recombinant enzyme against acidic D-amino acids and did not confer any additional
specificity to other amino acids. These results suggest that the Arg-216 and Arg-237 residues of mDASPO are catalytically
important for full enzyme activity. 相似文献
13.
14.
Summary. The concentrations of free amino acids in plasma change coordinately and their profiles show distinctive features in various
physiological conditions; however, their behavior can not always be explained by the conventional flow-based metabolic pathway
network. In this study, we have revealed the interrelatedness of the plasma amino acids and inferred their network structure
with threshold-test analysis and multilevel-digraph analysis methods using the plasma samples of rats which are fed diet deficient
in single essential amino acid.
In the inferred network, we could draw some interesting interrelations between plasma amino acids as follows: 1) Lysine is
located at the top control level and has effects on almost all of the other plasma amino acids. 2) Threonine plays a role
in a hub in the network, which has direct links to the most number of other amino acids. 3) Threonine and methionine are interrelated
to each other and form a loop structure. 相似文献
15.
Garcia RF Gazola VA Barrena HC Hartmann EM Berti J Toyama MH Boschero AC Carneiro EM Manso FC Bazotte RB 《Amino acids》2007,33(1):151-155
Summary. Our purpose was to determine the blood amino acid concentration during insulin induced hypoglycemia (IIH) and examine if the
administration of alanine or glutamine could help glycemia recovery in fasted rats. IIH was obtained by an intraperitoneal
injection of regular insulin (1.0 U/kg). The blood levels of the majority of amino acids, including alanine and glutamine
were decreased (P < 0.05) during IIH and this change correlates well with the duration than the intensity of hypoglycemia. On the other hand,
the oral and intraperitoneal administration of alanine (100 mg/kg) or glutamine (100 mg/kg) accelerates glucose recovery.
This effect was partly at least consequence of the increased capacity of the livers from IIH group to produce glucose from
alanine and glutamine. It was concluded that the blood amino acids availability during IIH, particularly alanine and glutamine,
play a pivotal role in recovery from hypoglycemia. 相似文献
16.
Summary. Oxidative stress induces various post-translational modifications (PTM); some are reversible in vivo via enzymatic catalysis.
The present paper reviews specific procedures for the detection of oxidative PTM in proteins, most of them including electrophoresis.
Main topics are carbonylated and glutathionylated proteins as well as modification of selected amino acids (Cys, Tyr, Met,
Trp, Lys). 相似文献
17.
Summary. The influence of the operation conditions (temperature and residence time) of a thermic treatment on the total amount (free
and protein-bound) of amino acid enantiomers of dry fullfat soya was investigated. Total amino acid content was determined
using conventional ion-exchange amino acid analysis of total hydrolysates and chiral amino acid analysis was performed by
HPLC after precolumn derivatization with o-phthaldialdehyde and 1-thio-β-D-glucose tetraacetate. Contrary to corn that was investigated previously, notable racemization
was detected even at lower temperatures. At 140 °C the ratio of the D-enantiomer was 0.87% for glutamic acid, 2.81% for serine,
and 1.92% for phenylalanine; at 220 °C the ratios of the D-enantiomer of the above amino acids were 1.43, 4.61, and 4.68%,
respectively. The concentration of several L-amino acids decreased. At 220 °C there was 10% less L-glutamic acid, 17% less
L-serine, 5% less L-phenylalanine, 6.6% less L-aspartic, acid and 21% less L-lysine than in the control; their loss can be
assigned to different degrees of L – D conversion. While nearly complete transformation of L-phenylalanine can be attributed
to racemization, the main cause of the loss of L-lysine is not racemization. The treatments in the same order of magnitude
resulted in the formation of more D-amino acids and greater extent of racemization of amino acids in fullfat soya than that
of maize.
Authors’ address: J. Csapó, Faculty of Animal Science, Institute of Chemistry, University of Kaposvár, Guba S. u. 40., H-7400
Kaposvár, Hungary 相似文献
18.
Summary. We have studied the enzymatic derivatization of amino acids by use of the polyphenol oxidase laccase. Derivatization of L-tryptophan
was achieved by enzymatic crosslinking with the laccase substrate 2,5-dihydroxy-N-(2-hydroxyethyl)-benzamide. The main product
(yield up to 70%) was identified as the quinoid compound 2-[2-(2-hydroxy-ethylcarbamoyl)-3,6-dioxo-cyclohexa-1,4-dienylamino]-3-(1H-indol-3-yl)-
propionic acid and demonstrates that laccase-catalyzed C–N-coupling occurred on the amino group of the aliphatic side chain.
These enzyme based reactions provide a simple and fast method for the derivatization of unprotected amino acids. 相似文献
19.
Bittner S 《Amino acids》2006,30(3):205-224
Summary. Quinones and amino acids are usually compartmentally separated in living systems, however there are several junctions in which
they meet, react and influence. It occurs mainly in wounded, cut or crushed plant material during harvest, ensiling or disintegrating
cells. Diffusing polyphenols are oxidized by polyphenol oxidases (PPOs) to quinonic compounds, which associate reversibly
or irreversibly with amino acids and proteins. The reaction takes place with the free nucleophilic functional groups such
as sulfhydryl, amine, amide, indole and imidazole substituents. It results in imine formation, in 1,4-Michael addition via
nitrogen or sulphur and in Strecker degradation forming aldehydes. The formation and activity of quinone–amino acids conjugates
influences the colour, taste, and aroma of foods. Physical and physiological phenomena such as browning of foods, discoloration
of plants during processing, alteration of solubility and digestibility, formation of humic substances, germicidal activity,
cytotoxicity and more occur when quinones from disintegrating cells meet amino acids. The mechanisms of toxicity and the pathways
by which PCBs may be activated and act as a cancer initiator include oxidation to the corresponding quinones and reaction
with amino acids or peptides. Sclerotization of insect cuticle is a biochemical process involving also the reaction between
quinones and amino acid derivatives. 相似文献
20.
Bio-available amino acids and mineral nitrogen forms in soil of moderately mown and abandoned mountain meadows 总被引:1,自引:0,他引:1
Summary. The abandonment of traditional mowing methods of mountain meadows in the Czech Republic at the end of the last century has
resulted in secondary re-colonization of these areas. Altered accumulation of plant biomass resulted in a deceleration of
N turnover. A mountain meadow may be regarded as a N-limited ecosystem in which plant nutrition is dependent on direct uptake
of soil amino acids. The composition and distribution of ammonium ions, nitrate ions and the 16 bio-available proteinaceuous
amino acids were investigated in the top 7 cm of the Ah horizon of a Gleyic Luvisol in a long-term moderately mown meadow
and an eleven year old, abandoned or uncut meadow. Ammonium N has a dominant role in both ecosystems. The moderately mown
meadow showed accelerated N-turnover and higher net ammonization. The plant community showed a dependence on this form. Plant
utilization of nitrates and amino acids appeared to be negligible. The uncut or abandoned meadow showed net ammonization from
May (start of the experiment) through August, after which plant N-uptake consisted only of amino acids due to microbial immobilization.
The release of bio-available nitrogen from spring until the beginning of summer in the Ah horizon was too low to explain total
plant N-uptake. Glutamic acid, arginine and aspartic acids had the highest concentrations of any of the amino acids analyzed.
Authors’ address: Pavel Formánek, Department of Geology and Pedology, Mendel University of Agriculture and Forestry, Zemedelska
3, 613 00 Brno, Czech Republic 相似文献