温度对普通玉米和高油玉米挤压产品品质的影响

以膨化率、淀粉糊化度、蛋白溶解度和有效赖氨酸为指标评价了挤压膨化过程中温度对普通玉米和高油玉米营养价值的影响．试验结果表明：与普通玉米相比，膨化高油玉米能够得到更高的膨化率，其更容易进行膨化加工；温度升高，提高了两种玉米的淀粉糊化度水平，要得到相似的淀粉糊化度，高油玉米需要更高的膨化温度，高温膨化对高油玉米蛋白质溶解性的不利影响要小于普通玉米，而对氨基酸品质的不利影响则刚好相反。综合考虑以上几个评价指标，结合膨化加工过程中的能量消耗，建议膨化腔内达到90℃来膨化普通玉米，用135℃温度膨化高油玉米。     

L-赖氨酸-L-天冬氨酸盐在小麦粉及馒头和面条中的应用研究

在小麦粉中分别强化764.55、1529.10和2293.65 mg/kg的L-赖氨酸-L-天冬氨酸盐(赖氨酸复合盐,简称LA),与对照组比较,作了基础分析,并制作了馒头和面条。研究表明:在本试验范围内,适度强化LA对面团的拉伸特性有一定的改善作用;不会对馒头感官品质产生不良影响;对面条的感官品质会产生良好作用。     

Prediction of lysine ubiquitylation with ensemble classifier and feature selection

Ubiquitylation is an important process of post-translational modification. Correct identification of protein lysine ubiquitylation sites is of fundamental importance to understand the molecular mechanism of lysine ubiquitylation in biological systems. This paper develops a novel computational method to effectively identify the lysine ubiquitylation sites based on the ensemble approach. In the proposed method, 468 ubiquitylation sites from 323 proteins retrieved from the Swiss-Prot database were encoded into feature vectors by using four kinds of protein sequences information. An effective feature selection method was then applied to extract informative feature subsets. After different feature subsets were obtained by setting different starting points in the search procedure, they were used to train multiple random forests classifiers and then aggregated into a consensus classifier by majority voting. Evaluated by jackknife tests and independent tests respectively, the accuracy of the proposed predictor reached 76.82% for the training dataset and 79.16% for the test dataset, indicating that this predictor is a useful tool to predict lysine ubiquitylation sites. Furthermore, site-specific feature analysis was performed and it was shown that ubiquitylation is intimately correlated with the features of its surrounding sites in addition to features derived from the lysine site itself. The feature selection method is available upon request.     

Nutritional assessment of transgenic lysine‐rich maize compared with conventional quality protein maize

BACKGROUND: The gene sb401 encoding a lysine‐rich protein has been successfully integrated into the genome of maize (Zea mays), its expression showing as increased levels of lysine and total protein in maize seeds. As part of a nutritional assessment of transgenic maize, nutritional composition, especially unintended changes in key nutrients such as proximates, amino acids, minerals and vitamins as well as in antinutrient (phytate phosphorus), and protein nutritional quality were compared between transgenic maize (inbred line 642 and hybrid line Y642) and conventional quality protein maize (QPM) Nongda 108. RESULTS: The contents of total protein, lysine, some other amino acids, several minerals and vitamin B₂ in transgenic inbred line 642 and hybrid line Y642 were significantly higher than those in conventional QPM. Water‐soluble protein and G2‐glutelin were significantly promoted in transgenic maize Y642. CONCLUSION: Insertion of the lysine‐rich sb401 gene increased the total protein and lysine content of transgenic maize varieties, leading to an improved amino acid score and therefore an improvement in the nutritive value of maize. © 2013 Society of Chemical Industry     

氨基酸的合成及其在食品中的应用

介绍了国内外氨基酸的生产状况,赖氨酸、复合氨基酸的性质、用途及开发前景。     

L-赖氨酸高产菌选育的研究

以黄色短杆菌ATCC140 6 7为出发菌株 ,经亚硝基胍 (NTG)、硫酸二乙酯 (DES)逐级诱变处理 ,S 2 氨基乙基 L 半胱氨酸 (AEC)、磺胺胍 (SG)等氨基酸结构类似物及琥珀酸为唯一碳源平板定向育种 ,获得 1株L 赖氨酸高产菌XQ 8(AECrSucgThr- SGr)。在含有 16 0 g/L葡萄糖的培养基中 ,摇瓶发酵 72h ,L 赖氨酸积累可达 77～ 82 g/L。     

Advances and Opportunities in Epigenetic Chemical Biology

The study of epigenetics has greatly benefited from the development and application of various chemical biology approaches. In this review, we highlight the key targets for modulation and recent methods developed to enact such modulation. We discuss various chemical biology techniques to study DNA methylation and the post-translational modification of histones as well as their effect on gene expression. Additionally, we address the wealth of protein synthesis approaches to yield histones and nucleosomes bearing epigenetic modifications. Throughout, we highlight targets that present opportunities for the chemical biology community, as well as exciting new approaches that will provide additional insight into the roles of epigenetic marks.     

Yeast sequencing reports. CAN1, a gene encoding a permease for basic amino acids in Candida albicans

The first gene coding for an amino-acid permease of Candida albicans was sequenced. The DNA fragment complementing the lysine-permease deficiency was 3385 bp long. An open reading frame of 1713 nucleotides was found encoding a protein of 571 amino acids, with a calculated molecular weight of 63 343. Analysis of the deduced primary structure revealed ten membrane spanning regions and three potential N-glycosylation sites. The protein sequence is strongly homologous to both permeases for basic amino acids (Can1 and Lyp1) of Saccharomyces cerevisiae. C-terminal part of another ORF (105 aa), highly homologous to the gene HAL2 of S. cerevisiae, was found 133 bp downstream, and in tail-to-tail orientation to the permease gene. The sequence data will appear in the EMBL/GenBank/DDBJ Nucleotide Sequence Data Libraries under the accession number X76689.     

L-(β,γ-~3H)赖氨酸的研制

氚标记的赖氨酸用来测定蛋白中赖氨酸的分布及人体内赖氨酸的代谢过程,因此,它是一种重要的示踪剂。我们以L-赖氨酸盐酸盐为起始原料,在浓盐酸中,在紫外光照下与氯反应,制得氯代赖氨酸,再经催化卤氚置换反应,制得(β,γ-~3H)赖氨酸,其放射性比度为16Ci/mmol,放化纯度大于95％。