Color reaction for certain amino acids,amines, and proteins

Proteins, certain amino acids, and amines undergo a potentially useful color reaction. The reaction involves the apparent formation of pyrroles when the compounds are allowed to react with acetonylacetone. The pyrroles yield colored complexes on coupling with p-dimethylaminobenzaldehyde. This report describes the specificity and possible uses of this reaction in colorimetric measurements and in paper chromatographic detection of these compounds.     

Norepinephrine and dopamine: assay by mass fragmentography in the picomole range

Gas chromatography-mass spectrometry makes possible the simultaneous measurement of norepinephrine and dopamine in concentrations of 0.1-milligram tissue samples. Specificity of the assay is confirmed both by the retention time of the compound and by the mass to charge ratio of the fragments recorded. The sensitivity is of the order of 0.5 picomole, and linearity of the response is maintained up to at least 200 picomoles.     

A general method for site-specific incorporation of unnatural amino acids into proteins

A new method has been developed that makes it possible to site-specifically incorporate unnatural amino acids into proteins. Synthetic amino acids were incorporated into the enzyme beta-lactamase by the use of a chemically acylated suppressor transfer RNA that inserted the amino acid in response to a stop codon substituted for the codon encoding residue of interest. Peptide mapping localized the inserted amino acid to a single peptide, and enough enzyme could be generated for purification to homogeneity. The catalytic properties of several mutants at the conserved Phe66 were characterized. The ability to selectively replace amino acids in a protein with a wide variety of structural and electronic variants should provide a more detailed understanding of protein structure and function.     

Transport of sugars and amino acids in the intestine: evidence for a common carrier

D-Galactose, L-arginine, and their respective actively transported analogs are partially competitive inhibitors of the active transport of neutral amino acids in the small intestine of hamsters. Since the aforesaid classes of compounds are all transported by similar, sodium-ion-dependent mechanisms and elicit countertransport of each other, all may share a common, polyfunctional carrier in which a series of separate binding sites, namely, one each for sugars, neutral amino acids, basic amino acids, and Na(+) are joined together, as in a mosaic.     

十二指肠灌注饲料寡肽对鸡肠道氨基酸吸收的影响

用十二指肠灌注法在不麻醉状态下研究饲料寡肽对鸡肠道氨基酸吸收的影响。灌注用寡肽分别是 4种常规饲料 (鱼粉、豆粕、棉粕、菜粕 )体外酶水解产物的 2组低分子量组分 ( <3kD和 <1kD)。试验 1:十二指肠灌注豆粕 <3kD寡肽 (S3)后 ,测定不同时间肝门静脉血浆游离氨基酸 (FAA)浓度 ,结果表明 ,灌注后总FAA浓度迅速上升 ,2 0min时最高。试验 2 :采用吸收强度和吸收平衡系数作为评价肠道氨基酸吸收效率的指标 ,比较十二指肠灌注 8种饲料寡肽后 2 0min时的氨基酸吸收效率。结果表明 ,各种饲料 <3kD寡肽组的氨基酸吸收效率均显著高于其 <1kD组 (P <0 0 5 ) ;在同一种分子量寡肽组中鱼粉、豆粕寡肽组显著高于棉粕和菜粕寡肽组 (P <0 0 5 ) ;氨基酸吸收效率与灌注底物的寡肽含量 (PAA/TAA)存在显著正相关 (P <0 0 5 )。本研究结果显示 ,鱼粉、豆粕等优质蛋白质在动物胃肠道中产生较多寡肽 ,因而具有较高的氨基酸吸收效率     

不同品种精白米必需氨基酸、总氨基酸和蛋白质含量的相关分析

测定了28个精白米样品的必需氨基酸、总氨基酸、蛋白质含量,分析了不同精白样品各成分的相关性。结果表明,28个精白米样品蛋白质含量与总氨基酸含量、蛋白质含量与必需氨基酸含量、总氨基酸含量与必需氨基酸含量的相关系数分别达到0.940、0.950、0.995,均呈极显著正相关。精白米主要营养成分蛋白质的营养价值主要在于氨基酸含量的高低,必需氨基酸含量可作为判定稻米营养价值的重要指标。     

Gamma-glutamyl transpeptidase in brain capillaries: possible site of a blood-brain barrier for amino acids

A fraction containing capillaries and rich in gamma-glutamyl transpeptidase was isolated from homogenates of bovine brain cortex by density gradient centrifugation. The enzyme was localized in the endothelial cells by a histochemical procedure. gamma-Glutantyl transpeptidase may function in the transfer of some amino acids across the blood-brain barrier.     

不同浓度氨基酸对仔猪原代肝细胞尿素循环的影响

【目的】研究不同浓度的氨基酸对仔猪原代肝细胞尿素循环的影响及其机理。【方法】5日龄仔猪门静脉灌流后从中分离纯化出肝细胞并进行培养,在培养基中添加不同浓度的氨基酸(分别为猪血液中氨基酸生理浓度的1、2和4倍),24 h后收集上清和细胞。用比色法检测上清中尿素、底物氨和细胞中氨的浓度以及谷氨酰胺酶(Glutaminase,GLS)和谷氨酰胺合成酶(Glutamine synthetase,GS)的活性,实时荧光定量PCR法检测细胞中氨甲酰磷酸合成酶1(Carbamyl phosphate synthetase 1,CPS1)、精氨基琥珀酸合成酶(Argininosuccinate synthetase,ASS)、精氨琥珀酸裂解酶(Argininosuccinate lyase,ASL)、鸟氨酸氨甲酰转移酶(Omithine transcarbamylase,OTC)和精氨酸酶(Arginase,ARG)等尿素循环相关酶基因m RNA的表达。【结果】4倍氨基酸组显著提高了仔猪原代肝细胞培养上清中氨和尿素的浓度,增强了细胞中GLS的活性。荧光定量PCR结果表明,4倍氨基酸组显著提高了细胞中CPS1、ASS和ASL等基因m RNA的表达。1.0和2.0 mmol·L~(-1)的NH4Cl显著促进细胞尿素的合成。【结论】在仔猪原代肝细胞中,高浓度氨基酸可以通过提高GLS的活性等途径加速氨的积累,促进CPS1、ASS、ASL等尿素循环相关酶基因m RNA的表达,从而促进尿素的生成。     

Structure of the GDP domain of EF-Tu and location of the amino acids homologous to ras oncogene proteins

A 2.7 angstrom resolution x-ray diffraction analysis of a trypsin-modified form of the Escherichia coli elongation factor Tu reveals that the GDP-binding domain has a structure similar to that of other nucleotide-binding proteins. The GDP ligand is located at the COOH-terminal end of the beta sheet and is linked to the protein via a Mg2+ ion salt bridge. The location of the guanine ring is unusual; the purine ring is located on the outer edge of the domain, not deep within a hydrophobic pocket. The amino acids from Pro10 to Arg44 and from Gly59 to Glu190 have been assigned to the electron density with computer graphic techniques, and the resulting model is consistent with all known biochemical data. An analysis of the structure reveals that four regions of the amino acid sequence that are homologous with the family of ras oncogene proteins, termed p21, are located in the vicinity of the GDP-binding site, and most of the invariant amino acids shared by the proteins interact directly with the GDP ligand.     

Absorption of proteins and peptides in the far ultraviolet

An absorption peak for the peptide bond at 187 nanometers has been confirmed; a protein assay at this wavelength allows quantitation of proteins in aqueous solution at concentrations between 0.1 and 25 micrograms per milliliter. Assays are conducted at 6 degrees C to take advantage of the reduction of end-absorption of water with temperature.     

Isoleucine epimerization in peptides and proteins: kinetic factors and application to fossil proteins

The observed rate of isoleucine epimerization in peptides and proteins is dependent on (in addition to time and temperature) (i) the position of isoleucine in the peptide chain, (ii) the nature of adjacent amino acids, and (iii) the stability of the isoleucine peptide bonds. The relative rate is: NH(2)-terminal > COOH-terminal > interior >/= free amino acid. The gradual hydrolysis of peptides and proteins to the more slowly epimerizing free amino acid causes a decrease in the apparent first-order rate constant with time. These results explain the isoleucine kinetics observed in fossil shells.     

氨基酸胁迫对小麦种子幼苗生长和体内游离氨基酸水平的影响

摘 要：用赖氨酸、苏氨酸两种氨基酸单因子胁迫和两因子协同胁迫不同蛋白质含量小麦品种种子的发芽幼苗,发现5 mmol/l浓度可严重抑制根系生长,但对叶生长抑制较轻;两种氨基酸具有协同抑制作用。相比较,高蛋白含量基因型品种比低蛋白含量基因型品种可忍耐较高浓度氨基酸胁迫。HPLC方法测定胁迫植株体内游离氨基酸含量,发现胁迫氨基酸有比对照高3～10倍积累,同族氨基酸有比对照高2～3倍积累,相关氨基酸也有1～2倍积累。     

Alcohol, amines, and alkaloids: a possible biochemical basis for alcohol addiction

Tetrahydropapaveroline is a benzyltetrahydroisoquinoline alkaloidderivative of the biogenic amine, dopnmine. Alcohol, by way of its primary metabolite, acetaldehyde, competitively inhibits nicotinamide-adenine Sinucleotide-linked aldehyde dehydrogenase and augments the formation of tetrahydropapaveroline in vitro. The limited capacity of brain to oxidize aldehydes may be of pharmacological importance because it facilitates the production of tetrahydropapaveroline in the presence of drugs which inhibit this enzyme.     

Experimental allergic encephalomyelitis in the rat: response to encephalitogenic proteins and peptides

Lewis rats were used to determine the encephalitogenic activity of myelin basic protein of different species and of 45-residue fragments of basic protein. Basic protein from guinea pigs was more active than that from rats, and the fragments from the two species showed the same order of activity. Bovine basic protein was the least active of the intact proteins, and the respective fragment was inactive. Studies of serum-binding capacity did not support the hypothesis that blocking antibody played a role in this biological variation, whereas consideration of the amino acid sequences of the three fragments suggested that differences in primary structure, operating either at the sensitization or the effector phase of the immune response, could account for the variation.     

太湖水体溶解性氨基酸的空间分布特征

为探索氨基酸(DAAs)组分特征对生物可利用性溶解有机质(DOM)的示踪及定量表征可能性, 对太湖3个湖区(北太湖: 藻型湖区,东太湖: 草型湖区, 南太湖: 农业污染湖区)水体DAAs浓度、组分特征及其空间变化进行了调查研究,并对控制其量、质空间分布的因素加以讨论。结果表明夏季太湖水体DAAs的浓度范围为0.27-3.95 μmol/L,平均值为(1.38±1.17)μmol/L,与湖泊、海洋中研究中报道结果相近。北太湖、南太湖、东太湖3个湖区的DAAs浓度平均值分别为(2.59±0.71)μmol/L,(0.48±0.14)μmol/L,(0.48±0.16)μmol/L,北太湖DAAs浓度及对有机碳氮的贡献都明显高于其他湖区,DAAs组分中以苯丙氨酸和赖氨酸为主,而在南太湖和东太湖,赖氨酸都是最主要的DAAs组分。表明水体的DAAs组分特征能对湖泊营养状态及生态类型的变化做出响应,可以作为指示湖泊营养状态的生物标记物。DAAs也可以作为DOM 生物降解性的评价参数,反映湖泊水体中与生物活性相关的DOM 动态变化。根据氨基酸对有机碳的贡献估算出北太湖的活性溶解性有机碳相对含量为(17.65±17.84)%,显著高于南太湖和东太湖。但由于太湖高度的空间异质性,还需要在今后的研究工作中进行相关的室内实验,建立适用于太湖的经验公式。     

真代谢能法对饲料酵母粉之蛋白质、氨基酸营养价值的评定研究

选用肉仔鸡24只,分成两组,以Sibbald氏TME法研究了饲料酵母粉粗蛋白、氨基酸的营养价值。结果:饲料酵母粉的粗蛋白质含量达642.4g/kg,真代谢率为(66.6 3.2)％,必需氨基酸含量达257.4g/kg,真代谢率为85.0％。表明饲料酵母粉的营养价值近似鱼粉,在饲料酵母粉中添加蛋氨酸后,在肉鸡日粮中可以一定的比例替代鱼粉使用。