谷氨酸棒杆菌代谢工程高效生产L-缬氨酸北大核心CSCD

L-缬氨酸作为一种支链氨基酸,广泛应用于医药和饲料等领域。本研究借助多种代谢工程策略相结合的方法,构建了生产L-缬氨酸的微生物细胞工厂,实现了L-缬氨酸的高效生产。首先,通过增强糖酵解途径、减弱副产物代谢途径相结合的方式,强化了L-缬氨酸合成前体丙酮酸的供给;其次,针对L-缬氨酸合成路径关键酶—乙酰羟酸合酶进行定点突变,提高了菌株的抗反馈抑制能力,并利用启动子工程策略,优化了路径关键酶的基因表达水平;最后,利用辅因子工程策略,改变了乙酰羟酸还原异构酶和支链氨基酸转氨酶的辅因子偏好性,由偏好NADPH转变为偏好NADH,从而提高了L-缬氨酸的合成能力。在5L发酵罐中,最优谷氨酸棒杆菌工程菌株Corynebacterium glutamicum K020的L-缬氨酸产量、得率和生产强度分别达到了110g/L、0.51g/g和2.29 g/(L·h)。     

计算机虚拟筛选技术在害虫行为调节剂研究中的应用

害虫行为调节剂是一种以嗅觉系统为靶标的绿色农药,在害虫的田间管理中发挥着重要的作用。然而,其先导化合物的发现通常依赖一系列生物测定的方法,不仅费时费力,且发现效率低。近年来,随着昆虫嗅觉功能数据的积累和结构生物学的飞速发展,以机器学习技术和分子对接为代表的2种基于计算机的药物虚拟筛选方法在害虫行为调节剂的先导化合物研究中发挥着重要的作用,极大地促进了先导化合物的发现效率,减少了筛选的盲目性。本文系统综述了2种虚拟筛选方法及其在害虫行为调节剂先导化合物研究中的应用,并对2种筛选策略在实际应用中存在的问题及应用前景进行了讨论。     

ent-Pimarane Diterpenes from the Aerial Parts of Siegesbeckia pubescens

Five new ent-pimarane diterpenes ( 1 – 5 ) and five known analogs ( 6 – 10 ) were isolated from the aerial parts of Siegesbeckia pubescens. Their structures, including absolute configurations, were determined by comprehensive spectroscopic methods especially 1D and 2D NMR and quantum chemical electronic circular dichroism calculations. All the isolated compounds were evaluated for their cytotoxicity against human BT549, A549 and H157 cancer cell lines. Among them, compounds 1 and 2 showed mild cytotoxicity against lung cancer cell lines H157 with IC₅₀ values of 16.35±2.59 and 18.86±4.83 μM, respectively.     

硒对培养人胚肝细胞Ⅲ型前胶原,羟脯氨酸合成的影响

原代培养人胚肝细胞经１．１５６×１０￣(－７）ｍｏｌ／Ｌ硒预处理４ｈ,加入２０ｍｍｏｌ／Ｌ四氟化碳作用２０ｈ,观察硒对其Ⅲ型前胶原（ＰＣⅢ）和羟脯氨酸（Ｈｙｐ）生成的影响。结果培养液中ＰＣⅢ水平、细胞内Ｈｙｐ含量及细胞内外丙二醛（ＭＤＡ）水平均降低,与未加硒对照组比较差别有显著性（Ｐ＜０．０１）。而硒谷腕甘肽过氧化物酶（Ｓｅ－ＧＳＨ－ＰＸ）活性则较对照组显著增高（Ｐ＜０．００１）,且ＰＣⅢ水平与Ｓｅ－ＧＳＨ－Ｐ＿Ｘ／ＭＤＡ比值呈负相关（ｒ＝－０．９１５６,Ｐ＜０．０１）。提示硒可提高Ｓｅ－ＧＳＨ－Ｐ＿Ｘ／ＭＤＡ比值,抑制脂质过氧化激发的肝细胞胶原合成。     

黄芪有效成分对氧自由基清除作用的ESR研究

用电子自旋共振技术研究了黄芪总黄酮(TFA)、黄芪总皂甙(TSA)和黄芪总多糖(TPA)对次黄嘌呤／黄嘌呤氧化酶体系产生的超氧阴离子自由基和H₂O₂－Fe²⁺体系产生的羟自由基的清除作用．结果表明,这3种成分均有清除氧自由基的作用;对超氧阴离子自由基的清除效能大于对羟自由基的清除作用;其作用强度依次为TFA＞TSA＞TPA．结果提示清除氧自由基可能是黄芪抗衰老的主要机理之一,TFA和TSA是黄芪抗氧化作用的主要药理活性成分．     

Human genes for glutathione S-transferases

The tissue distribution of different glutathione S-transferases (GST) is analysed by electrophoresis. The existence of GST"e" (erythrocyte), GST3, GST1, and GST2 is confirmed. GST"e" the fastest and most thermolabile of different GST analysed is observed only in erythrocyte cells. GST3 which migrates more slowly than GST"e" is present in all tissues and cells analysed, excepted for erythrocyte cells in which only GST"e" is observed. GST1 presents a polymorphism with four phenotypes, 1, 1/2, 2, and 0 controlled by three alleles 1, 2, and 0 (null). With the sample of 56 livers analysed the different frequencies obtained are 9%, 5%, 43%, 43% for the phenotypes 1, 1/2, 2, and 0 respectively and 0.074 (p), 0.279 (q), 0.647 (r) for the alleles, 1, 2, and 0 (null). GST2 presents variant patterns due probably, in the majority of cases, to post-synthetic modifications rather than allelic variation. Two new GST are described, GST4 and GST5. GST4 abundant in muscle tissue is a dimeric protein. GST4 forms with GST1 a heterodimeric band. GST5 is observed in brain homogenates. For the chromosome localization the results obtained by man (leucocytes)-mouse somatic cell hybrid analysis indicate that the gene for leucocytes GST is on chromosome 11. This gene is the structural GST3 gene.     

Assignment of the gene for uroporphyrinogen decarboxylase to human chromosome 1 by somatic cell hybridization and specific enzyme immunoassay

Summary A specific enzyme immunoassay of uroporphyrinogen decarboxylase was developed and applied to the detection of the human enzyme in man-rodent somatic cell hybrids. This method allowed to assign the gene for uroporphyrinogen decarboxylase to human chromosome 1.