添加氨基酸降低肉用仔鸡日粮中部分蛋白质水平可行性研究

试验设置对照、赖、蛋、赖＋蛋氨酸４个体系，除对照体系设置１个对照组外，根据氨基酸添加量，赖、蛋、赖＋蛋氨酸体系分别设置３、３、２个水平组，共９个组。试验各组均在对照组基础上取代２．０％日粮粗蛋白质。试验鸡为ＡＡ鸡商品代，分０－４、５－８周两期，根据增重、饲料报酬、成活率、经济效益等指标综合评定试验结果。结果表明：在本试验设置范围内，添加赖、蛋、赖＋蛋氨酸均可以替代日粮中部分粗蛋白，饲料报酬和经济效     

薄层色谱法测定蛋氨酸的含量

提出了薄层色谱法测定复合氨基酸中蛋氨酸的含量，该法以正丁醇：乙酸：水(4：1：1)的混合液为展开剂，在GF254硅胶板上展开后直接用薄层色谱法测定，其被测组份点样量在0．20μg—1．30μg范围内与相应的峰面积符合朗伯—比耳定律：相关系数为0．9987，回收率为98．0％一101．5％．该法操作简便、快速、准确．     

Early effects of copper accumulation on methionine metabolism

Wilson's disease is characterized by longterm hepatic accumulation of copper leading to liver disease with reduction of S-adenosylmethionine synthesis. However, the initial changes in this pathway remain unknown and constitute the objective of the present study. Using the Long Evans Cinnamon rat model, early alterations were detected in the mRNA and protein levels, as well as in the activities of several enzymes of the methionine cycle. Notably, the main change was a redox-mediated 80% decrease in the mRNA levels of the methionine adenosyltransferase regulatory subunit as compared to the control group. Moreover, changes in S-adenosylmethionine, S-adenosylhomocysteine, methionine and glutathione levels were also observed. In addition, in vitro experiments show that copper affects the activity and folding of methionine adenosyltransferase catalytic subunits. Taken together, these observations indicate that early copper accumulation alters methionine metabolism with a pattern distinct from that described previously for other liver diseases.     

硝酸铒与DL—α—蛋氨酸配合行为研究

测定了三元体系Er(NO_3)_3。—Met—H_2O在25℃时的溶度和饱和溶液的折光率,结果表明该体系可形成两种配合物,即Er(Met)(NO_3)_3·H_2O与E_r(Met).(NO_3)_3·6H_2O。用相平衡方法合成了 1:4型配合物,通过元素分析、IR、UV、X 粉末衍射、TG—DTG与DSC对其进行了物化性质表征,并讨论了配合行为。     

Structure-function relationships in methionine adenosyltransferases

Methionine adenosyltransferases (MATs) are the family of enzymes that synthesize the main biological methyl donor, S-adenosylmethionine. The high sequence conservation among catalytic subunits from bacteria and eukarya preserves key residues that control activity and oligomerization, which is reflected in the protein structure. However, structural differences among complexes with substrates and products have led to proposals of several reaction mechanisms. In parallel, folding studies begin to explain how the three intertwined domains of the catalytic subunit are produced, and to highlight the importance of certain intermediates in attaining the active final conformation. This review analyzes the available structural data and proposes a consensus interpretation that facilitates an understanding of the pathological problems derived from impairment of MAT function. In addition, new research opportunities directed toward clarification of aspects that remain obscure are also identified. Received 22 August 2008; received after revision 22 September 2008; accepted 26 September 2008     

人cDNA序列中二类甲硫氨酸密码子的区分

在人类cDNA序列确定全长基因的过程中，必须判断第一个ATG密码子是真正的起始密码子还是框内的非起始作用的甲硫氨酸密码子，在总结了这二类密码子上下文共有序列特征，周期性，密码子的碱基偏向性，以及编码的氨基酸的疏水性等方面差异的基础上，从模式识别的角度出发，将这二类密码子视为由此构成的多维特征空间中的二个模式类，应用费歇线性判别法进行分类器的设计，并对分类器的错误率进行估计，表明在这些特征下，这二类密码子可以区分，以此分类器的判断真正的起始密码子和非起始甲硫氨酸密码子，其准确率可达75％。     

Possible involvement of indolamines in the glycogenic effect of the convulsant methionine sulfoximine in rat brain

Summary The aim of the present investigation was to look for the mechanisms causing disturbances in carbohydrate metabolism during the action of the epileptogenic agent methionine sulfoximine The levels of glucose, glycogen, and indolamines were measured in seven different regions of rat brain. Methionine sulfoximine induced a decrease in serotonin level which was roughly dose-dependent. There were no obvious, changes in tryptophan and 5-hydroxyindoleacetic levels in any area. Methionine sulfoximine induced the known increase in glucose and glycogen levels. The direct precursor of serotonin, 5-hydroxytryptophan, and benserazide (a decarboxylase inhibitor) were then injected into rats in association with methionine sulfoximine. In this case, methionine sulfoximine failed to induce seizures. Moreover, the serotonin level was unchanged and the carbohydrate content did not significantly increase. There was only a rise in 5-hydroxyindoleacetic acid level. This work shows a striking parallelism between serotonin decrease and glycogen increase.