用日立835-50型氨基酸分析仪测定色氨酸方法的试验报告

<正> 色氨酸是蛋白质的重要成分,是人和各种动物生长发育不可缺少的必需氨基酸之一,在营养代谢中起着重要作用。因此,准确测定食品及饲料中的色氨酸含量有着重要意义。由于色氨酸在酸水解中破坏较大,所以酸水解法不适于色氨酸测定,须用碱水解法单独测定,因色氨酸在碱水解中比较稳定。但以往所采用的碱水解法是以淀粉作保护     

用6300型氨基酸自动分析仪对色氨酸快速测定

本文对色氨酸分析程序进行了研究,编制了快速、定量测定色氨酸的专用分析程序,分析周期仅30分钟。     

酶法水解鲜猪血制备氨基酸的研究

本文以鲜猪血为主要原料,酶法水解制备氨基酸。其复合氨基酸收得率为１３．０７％·Ｗ／Ｖ）,分析测定表明除色氨酸含量含微量外,八种必需氨基酸的含量占复合氨基酸总量的４６．５２％。     

灵芝氨基酸研究

采用日立８３５－５０型氨基酸自动分析仪,测定了泰山地区的五种灵芝成品的氨基酸含量。结果表明,除色氨酸被水解破坏而未检出外,其它１７种氨基酸含量丰富,其氨基酸的总含量最高为１２．８７％,低的为４．６７６％,并含有７种人体必需氨基酸,值得深度开发利用。     

微波高压水解罐的研制及在测定色氨酸方面的应用

<正> 测定食物蛋白中色氨酸含量需先将蛋白质水解,常用的水解方法有酶法和碱法,后者近来已被美国公职分析家协会定为正式分析方法。两种方法通常需耗时4～20小时。在先前的工作中,我们已成功地用微波—NaOH在5分钟内快速水解了纯蛋白溶菌酶以及3份食品标样,并准确地测定了     

保护性氧化盐酸水解法分析蛋白质水解氨基酸

本文介绍了在保护剂存在下,通过过甲酸氧化,再以盐酸水解,在50分钟的分析循环时间内准确地分析17种氨基酸及三种含硫氨基酸衍生物的分析方法。     

PT-C_(18)小柱在食物氨基酸分析中脱色效果观察

<正> 在进行食物样品的氨基酸组分和含量分析时,需用盐酸水解处理,在此过程中,由于色氨酸和碳水化合物的破坏,产生有颜色的分解产物,从而干扰了正常的氨基酸分析,尤其是当水解样品中颜色较深而氨基酸含量较低时,影响更为明显。因此,对水解样品脱色引起人们的十分关注,很多学者在     

应用磺酸水解法进行人血白蛋白氨基酸组成分析

磺酸对色氨酸无破坏作用,因此,磺酸水解蛋白质可以同时测定出色氨酸。但,磺酸溶液制备比较繁琐,因此,至今在我国尚无人使用。本文用对甲苯磺酸法水解人血白蛋白,用氨基酸自动分析仪进行其氨基酸组成分析,其结果与理论值基本相符。     

日立835-50氨基酸分析仪色氨酸短程序分析

<正> 使用氨基酸分析仪分析色氨酸是一种常用的方法。张喻等人曾报道在日立835 50氨基酸分析仪上用短程序分析色氨酸,即在原机内1-pH-4缓冲液中加入14克柠檬酸钠使色氨酸色谱峰处于精氨酸之后。由于色氨酸吲哚基团与阳离子交换剂之间的非极性亲合力,在廷长保留时间的情况下,峰形变劣。由其在分析谷物、饲料等色氨酸含量较低(1nM/50μl)时,峰形扁平;在定量分析时由于检测信号变化缓慢,不利于检出峰的起始点和终点,影响了准确度和精确度。     

快速水解法对氨基酸收率的影响

<正> 采用氨基酸自动分析仪,分析蛋白质水解液的氨基酸组成与含量,水解条件往往是取得可靠结果的关键。目前多采用标准水解法,但因该法水解时间长,对于有些实验,如多肽合成过程中氨基酸的监测需快速分析,带来许多不便。当前,国内外介绍了一些快速水解     

Heat-stable proteins and abscisic Acid action in barley aleurone cells

[³⁵S]Methionine labeling experiments showed that abscisic acid (ABA) induced the synthesis of at least 25 polypeptides in mature barley (Hordeum vulgare) aleurone cells. The polypeptides were not secreted. Whereas most of the proteins extracted from aleurone cells were coagulated by heating to 100°C for 10 minutes, most of the ABA-induced polypeptides remained in solution (heat-stable). ABA had little effect on the spectrum of polypeptides that were synthesized and secreted by aleurone cells, and most of these secreted polypeptides were also heatstable. Coomassie blue staining of sodium dodecyl sulfate polyacrylamide gels indicated that ABA-induced polypeptides already occurred in high amounts in mature aleurone layers having accumulated during grain development. About 60% of the total protein extracted from mature aleurone was heat stable. Amino acid analyses of total preparations of heat-stable and heat-labile proteins showed that, compared to heat-labile proteins, heat-stable intracellular proteins were characterized by higher glutamic acid/glutamine (Glx) and glycine levels and lower levels of neutral amino acids. Secreted heat-stable proteins were rich in Glx and proline. The possibilities that the accumulation of the heat-stable polypeptides during grain development is controlled by ABA and that the function of these polypeptides is related to their abundance and extraordinary heat stability are considered.     

Amino Acid Composition of Bulk Protein of Euglena Grown in Waste Water

The amino acid content of bulk protein in a sewage-grown Euglena sp. was examined. Concentrations of the essential amino acids, threonine, histidine, tryptophan, and valine, were similar to those found in other algae. The concentration of alanine was much higher. Methionine was not found at all, proline only in traces, and other amino acids at low concentrations. These results indicate that the amino acid content of bulk protein of the species of Euglena studied resembles that of plants far more closely than that of animals.     

Continued Expression of the Ribonucleic Acid Control Gene During Inhibition of Escherichia coli Ribonucleic Acid and Protein Synthesis

The effect of the ribonucleic acid (RNA) control (RC) gene on the biosynthesis of viral RNA has been examined in an RC(str) and an RC(rel) host infected with R17 RNA bacteriophage under conditions in which host RNA and protein synthesis were inhibited by the addition of rifampicin. Methionine and isoleucine starvation depressed viral RNA biosynthesis in an RC(str) host but not in an RC(rel) host. However, histidine starvation had little effect on viral RNA and protein synthesis in both RC(str) and RC(rel) cells, although it had a marked effect on host protein and RNA synthesis in an RC(str) host. Chloramphenicol relieved the effect of amino acid starvation on viral RNA synthesis in an RC(str) host. It is concluded that stringent control of viral RNA biosynthesis does not require the continued biosynthesis of the RC gene product (RNA or protein) and that a preformed RC gene product can regulate the biosynthesis of the exogenous RNA. It is suggested that the amino acid dependence of viral RNA biosynthesis is due to its obligatory coupling with the translation of the viral coat protein which lacks histidine. It may be inferred that the amino acid requirement of bacterial RNA is due to its coupling with the translation of a host-specific protein (other than the RC gene product) which requires a full complement of amino acids. Since chloramphenicol is known to permit ribosome movement in the absence of protein synthesis, it is suggested that ribosome movement along the nascent RNA chain is a sufficient condition for the continuation of RNA synthesis.     

Tryptophan metabolism, from nutrition to potential therapeutic applications

Tryptophan is an indispensable amino acid that should to be supplied by dietary protein. Apart from its incorporation into body proteins, tryptophan is the precursor for serotonin, an important neuromediator, and for kynurenine, an intermediary metabolite of a complex metabolic pathway ending with niacin, CO₂, and kynurenic and xanthurenic acids. Tryptophan metabolism within different tissues is associated with numerous physiological functions. The liver regulates tryptophan homeostasis through degrading tryptophan in excess. Tryptophan degradation into kynurenine by immune cells plays a crucial role in the regulation of immune response during infections, inflammations and pregnancy. Serotonin is synthesized from tryptophan in the gut and also in the brain, where tryptophan availability is known to influence the sensitivity to mood disorders. In the present review, we discuss the major functions of tryptophan and its role in the regulation of growth, mood, behavior and immune responses with regard to the low availability of this amino acid and the competition between tissues and metabolic pathways for tryptophan utilization.     

L-Tryptophan: Biochemical,nutritional and pharmacological aspects

Summary Tryptophan is important both for protein synthesis and as a precursor of niacin, serotonin and other metabolites. Tryptophan is an unusual amino acid because of the complexity of its metabolism, the variety and importance of its metabolites, the number and diversity of the diseases it is involved in, and because of its use in purified form as a pharmacological agent. This review covers the metabolism of tryptophan, its presence in the diet, the disorders associated with low tryptophan levels due to low dietary intake, malabsorption, or high rates of metabolism, the therapeutic effects of tryptophan and the side effects of tryptophan when it is used as a drug including eosinophilia myalgia syndrome.     

Studies on Amino Acid Contents of Processed Soybean

The influence of sugars on the heat destruction of the basic and sulphur containing amino acids of soybean products, soybean protein and also pure amino acids has been investigated.

Amino acids were estimated by microbiological assay procedure. Cystine was also determined chromatographically.

Lysine, arginine and histidine were destroyed in different ways behaved when soybean products, soybean protein or pure amino acids mixed with and without sugars were autoclaved; and the condition of added sugars tended to influence the way of destruction.

Cystine was the most heat-labile amino acid. But the destruction did not appear to be ascribed to added sugars except 50% ethyl alcohol-soluble sugar solution of defatted soybean flour. This finding was also substantiated by the chromatographic analysis.

Methionine, in soybean products and soybean protein or as pure amino acid with and without the addition of sugars, was not influenced by autoclaving.     

Effect of cycloheximide on the induction of tryptophan oxygenase mRNA by hydrocortisone invivo

Hydrocortisone increases rat liver tryptophan oxygenase mRNA activity as measured by a translational assay. Pretreatment of rats with cycloheximide thirty minutes before hydrocortisone administration largely prevents the hormonal induction of tryptophan oxygenase mRNA. Tryptophan oxygenase mRNA activity begins to increase after a lag of at least 30 to 60 minutes after hydrocortisone injection. These results suggest that the synthesis of intermediary protein(s) is required for the induction of tryptophan oxygenase mRNA by glucocorticoids.     

Oxidation of tryptophan to oxindolylalanine by dimethyl sulfoxide-hydrochloric acid. Selective modification of tryptophan containing peptides

Tryptophan is readily oxidized to oxindolylalanine (2-hydroxytryptophan) in good yield on treatment in acetic acid solution with a mixture of dimethyl sulfoxide (DMSO) and concentrated aqueous HCl at room temperature. Other sulfoxides can be used in combination with HCl; for example, methionine sulfoxide reacts with an equimolar amount of tryptophan to give high yields of methionine and oxindolylalanine. Methionine and cysteine are quantitatively oxidized by DMSO/HCl to methionine sulfoxide and cystine, respectively. The tryptophan containing peptides LRF (luteinizing hormone-releasing factor), somatostatin, valine-gramicidin A and ACTH 1-24 were each treated with the DMSO/HCl reagent in acetic acid solution and the corresponding oxindolylalanine-derivatives isolated in over 90% yield after chromatography. The identity and purity of the derivatives were established on the basis of ultraviolet spectral characteristics and quantitative amino acid analysis of the oxindolylalanine content of acid hydrolyzates of the oxidized peptides with 3N-p-toluenesulfonic acid at 110 degrees for 24 h. The results indicate that modification of tryptophan peptides with DMSO/HCl provides a useful procedure, which seems superior to previously used reagents. In addition, the method could be well applied to other indoles of biological and pharmacological interest.     

Studies on the Destruction of Indole-3-acetic Acid by a Species of Arthrobacter. V. Indole-3-acetic Acid Production from Tryptophan

Tryptophan (Try) metabolism of Arthrobacter sp. was examined. The inducibility of the Try oxidizing enzyme system seems to be correlated with that of the indole-3-acetic acid (IAA) oxidizing enzyme system. Try is metabolized to IAA via indole-3-pyruvic acid (Ip) and indole-3-acetaldehyde (IAAId). Indole-3-acetamide (IAm) is formed as a product of Try oxidation. Exogenous IAm, indole-3-acetonitrile (IAN) and tryptamine are not oxidized by Try-induced cells.     

Status of Mungbean Protein Fractions Under Changing Nutrient Regime

Effect of nutrient supply on mungbean protein fractions was studied with respect to four concentration levels (0.0, 25, 50 and 100 mM) each of sulphur, potassium and phosphorus. Whereas amount (mg/g seed meal) of globulins increased under the increasing concentrations of all the three minerals, albumins increased under sulphur and potassium and glutelins under sulphur and phosphorus only. Tryptophan contribution due to albumins and globulins was found to increase while that due to glutelins decreased under increasing supplies of sulphur and phosphorus. However, under higher supply levels of potassium, tryptophan contribution due to all the fractions was found to increase. Methionine contribution due to albumin and globulin fractions increased under sulphur and potassium and that due to glutelins decreased as the concentration levels of potassium and phosphorus increased.