修饰作用导致大豆蛋白氨基酸低效化问题的研究进展

大豆蛋白是广泛应用的食品加工原料,是人体可摄入的优质氨基酸来源,工业生产中为提高大豆蛋白的加工功能特性,常对其进行修饰改性。然而修饰改性有时会导致氨基酸消化吸收低效化。综述了大豆蛋白的功能特性及营养价值、主要修饰作用及其对氨基酸有效性影响,并对现阶段国内外研究的动态进行了分析,并提出今后的研究方向和展望,较全面地呈现修饰导致的大豆蛋白氨基酸低效化问题的研究进展,进一步解释蛋白聚合体与氨基酸消化性的关系,为提高大豆蛋白利用率,创新加工生产提供参考。     

有机酸沉淀法分离牡蛎中的糖原和蛋白质

研究了有机酸对牡蛎匀浆中糖原和蛋白质分离效果的影响。采用有机酸溶液对牡蛎匀浆进行处理,离心后得到富含蛋白质的沉淀和糖原含量相对较高的上清液,以达到分离牡蛎中糖原和蛋白质目的。通过单因素实验和正交试验得到的优化工艺条件为:牡蛎匀浆与0.5mol/L的乙酸溶液的料(g)液(mL)比为1∶3,将pH值调至7.0,60℃下搅拌30min,最后5000r/min离心10min。在此优化条件下得到的沉淀中蛋白质质量比为62.1%,占总蛋白质的59.6%；糖原质量比为2.21%,占总糖原的5.5%。上清液中蛋白质质量比为19.4%,占总蛋白质的29.7%；糖原质量比为23.8%,占总糖原的93.5%。研究结果表明,乙酸沉淀法可有效分离牡蛎中的糖原和蛋白质。     

短期UVB辐照对抱茎风毛菊光合作用的影响

以抱茎风毛菊(Saussurea chingiana)为实验材料,利用短期中波紫外线(UVB,Ultraviolet B)辐照对比实验(CK:对照组,自然大气UVB强度;UVB:UVB辐照度为205μw·cm~(-2),短期辐照时间为4h)研究了光合色素含量、叶绿素荧光快速诱导动力学曲线(OJIP)和光合蛋白表达量的变化。结果显示:UVB辐照降低了抱茎风毛菊的叶绿素质量分数,增大了叶绿素a/b比值和类胡萝卜素质量分数;UVB辐照导致PSII反应中心蛋白(D1、D2)、捕光色素蛋白(CP43)、Cytb6f复合物和ATP酶复合体蛋白均发生降解,外周捕光色素蛋白(LHCII)的表达量升高;UVB辐照抑制了从QA-往下的电子传递,增加了热耗散能量,阻碍了光合作用的碳同化过程,进而降低光能利用率。叶绿素a/b比值、类胡萝卜素含量的增大虽然缓解了短期UVB辐照对抱茎风毛菊的伤害,但是UVB辐照对光合作用仍具有显著的负影响。     

基于T检验与支持向量机的蛋白质质谱数据分析

对蛋白质质谱数据进行模式识别成为癌症诊断的一种新方法,但质谱数据存在高维小样本问题,因而数据分析面临着巨大挑战.在对原始数据进行基线校正与标准化并用分箱法进行降维预处理的基础上,提出用T检验方法选取特征,对蛋白质质谱数据进行分析研究.实验对卵巢质谱数据集进行分类,用10-fold交叉验证法选择训练和测试样本,以支持向量...     

碱提酸沉法制备燕麦浓缩蛋白的工艺研究

燕麦蛋白具有高营养价值,可采用碱提酸沉工艺以脱脂燕麦粉为原料提取.以燕麦浓缩蛋白的提取率为目标函数,在通过单因素试验对提取的工艺条件进行初步探索的基础上,运用正交试验设计对碱提酸沉法的工艺条件予以优化,确定合适的提取条件为:浸提pH值9.5、液料比10:1、温度45～50℃、时间90min.在此条件下,燕麦浓缩蛋白的提...     

The effect of a secretion-enhanced heavy chain on improving intein-based dual-vector co-delivery of a full-length factor VIII gene

Treatment of hemophilia A by gene therapy is adversely affected by inefficient FVIII secretion and the large FVIII gene, which is difficult to package in the promising adeno-associated virus (AAV) vectors. Inhibited secretion of FVIII is caused mainly by inefficient secretion of its heavy chain. Previously, we have employed a protein splicing-based dual-vector to co-transfer a B-domain-deleted FVIII (BDD-FVIII) gene, suggesting that the light chain, covalently ligated to a co-expressed heavy chain can improve the secretion of spliced BDD-FVIII. However, its level of secretion was affected by inefficient secretion the heavy chain. Here, we studied the effect of a mutant heavy chain with L303E/F309S substitutions, which enhance FVIII secretion on the heavy chain itself and spliced FVIII when using a protein splicing-based split-delivery of a full-length FVIII gene. Eukaryotic vectors expressing Ssp DnaB intein-fused mutant heavy and light chains were transiently co-transfected into cultured COS-7 cells. A spliced FVIII protein was seen in co-transfected cells by Western blot analysis. The heavy chain was secreted by cells transfected with the mutant heavy chain gene alone at (39±11) ng/mL and this secretion increased to (123±13) ng/mL when cells were co-transfected with the light chain gene, which was greater than the secretion of wild-type heavy chain. The amount of spliced FVIII in the culture supernatant of co-transfected cells was (86±14) ng/mL, with an activity of (0.61±0.08) IU/mL, which was greater than that of wild-type FVIII co-transfected cells. Spliced FVIII and bioactivity were also detected in the combined culture supernatant of cells individually transfected with mutant heavy and light chain gene at a higher level than that of combined wild-type heavy and light chain transfections. This suggested that the heavy chain with improved secretion markedly increased the efficacy of protein splicing-based split delivery of the full-length FVIII gene using a dual-vector. These results encourage the transfer of this technology to an animal model using a dual-AAV vector.     

A case study of 3D protein structure prediction with genetic algorithm and Tabu search

This paper describes a case study of 3D protein structure prediction of six sequences from protein data bank (PDB) by genetic algorithm and tabu search (GATS), where off-lattice AB model is considered as a simplified model of protein structure. The lowest-energy values required for forming the native conformation of proteins are searched by GATS, and then the coarse structures (i.e., simplified structure) of the proteins are obtained according to the multiple angle parameters corresponding to the lowest energies. All the coarse structures form single hydrophobic cores surrounded by hydrophilic residues, which stay on the right side of the actual characteristic of protein structure. It demonstrates that this approach can predict the 3D protein structure effectively.     

锌指蛋白Zbed3的表达与分离纯化

将编码小鼠锌指蛋白Zbed3的基因克隆到大肠杆菌表达载体pET28c,构建了含组氨酸标签的表达质粒pET28c-Zbed3,并将其转入大肠杆菌BL21-CodonPlus(DE3)-RP;在20℃条件下,采用100μmol/L的异丙基硫代--βD半乳糖苷(IPTG)诱导、培养20 h而获得含Zbed3的菌体;菌体裂解液经超滤浓缩后采用镍(螯合)柱分离纯化得到锌指蛋白Zbed3(浓度达60 mg/L);同时,采用30%醋酸溶解包涵体,用0.5 mol/L的Tris-HCl(pH=8.8)缓冲液中和而使Zbed3在生理pH环境中复性.结果表明,Zbed3复性后在离心上清液中的回收率达到80%,其复性蛋白质与表达产物为可溶性(天然态)Zbed3的圆二色性光谱特征相一致,以此验证了复性后Zbed3空间构象的正确性.     

我国西北地区12个不同硬质度优质蛋白玉米自交系的品质及配合力

以中国西北地区常用的12个优质蛋白玉米(QPM)自交系为试材,采用胚乳硬质度5级分类法,分别对籽粒的物理性状和营养品质进行测定分析;应用NCII设计,以硬质度1,2级3个QPM自交系为测验种与硬质度3,4,5级的9个QPM自交系配制27个测交组合,分析这些测交组合的产量配合力.结果表明:胚乳硬质度越高,籽粒的物理性状越...     

从高分子构象与动力学到蛋白质折叠

针对作用在聚合物刷上的键拉力研究表明作用在接枝基面上的力随着聚合物刷接枝密度的增大反而减小,然而尾端单体上的拉伸张力并没有消失.高分子的构象和动力学转变决定了其物性和多种多样的应用,而生物大分子蛋白质作为由二十种不同属性的氨基酸构成的序列,更是具有由其序列所决定的特别的三维自然结构.本文就聚合物刷、聚合物纳米复合材料、聚合物网络等几种高分子体系的构象与动力学过程,及蛋白质构象和其折叠与去折叠的动力学过程做了介绍.特别是蛋白质的折叠与去折叠速率在单分子操纵实验中受到拉力的调控,通过测量这种拉力依赖的动力学过程、蛋白质的自由能曲面和折叠去折叠路径可以得到系统全面的研究.本文以肌肉蛋白titin的免疫球蛋白结构域I27为例对蛋白质折叠研究进行了阐述.