玉米谷氨酰胺转胺酶基因的克隆及原核表达

从玉米嫩叶中提取总RNA,通过RT-PCR的方法扩增出玉米谷氨酰胺转胺酶(TGase)全长基因,回收目的片段并测序,该基因编码区全长1605bp,编码535个氨基酸残基,分子量为60.9kD,与GenBank(登录号：AJ421525)上已发表的序列同源性为100%。按正确的阅读框架将玉米TGase基因片段定向克隆到表达载体pET-28a上,将重组质粒转化到大肠杆菌Rosetta(DE3)菌株,1mmol/L IPTG诱导融合蛋白表达,经凝胶分析软件测得蛋白表达量约占总蛋白的15%,以His-Tag抗体作为一抗,采用Western-blot方法检测目的蛋白,结果证明所表达的特异蛋白是带有His-Tag的重组融合蛋白,利用Ni2+-NTA琼脂糖树脂亲和层析柱纯化目的蛋白,SDS-PAGE鉴定为单一条带,测得纯化后的TGase酶活力达到16U/mg。     

气相色谱法测定乳及乳制品中碘的影响因素

设计了双因素无重复实验和衍生因素的正交试验,得出在气相色谱法测定碘时,沉淀过程对结果影响不大,衍生过程中,对结果影响的次序依次是丁酮加入量、硫酸加入量和衍生时间,双氧水加入量对结果影响无统计学意义。提出碘测定时气相色谱条件优化的原则。     

In vitro gastrointestinal digestion of bovine αS1- and αS2-casein variants gives rise to different IgE-binding epitopes

The occurrence and differences of resistant regions containing IgE-binding epitopes of α_S1-casein (α_S1-CN) variants B and C, as well as α_S2-CN A and B, after in vitro gastrointestinal digestion was investigated using mass spectrometry. The amino acid substitutions characterising the genetic variants affected the peptide pattern arising from the caseins and thus modifications in their allergenic epitopes occurred. Peptides f174–193 in α_S1-CN B and f179–198 in α_S1-CN C correspond to the IgE-binding epitope f173–194, which has been reported as one of the major epitopes in α_S1-CN B. Within α_S2-CN, the two variant-specific peptides, f7–29 from variant A and f1–22 from variant B, contain the previously identified IgE-binding epitope f1–20. These peptides, and in consequence the protein variants, may exhibit different immunoreactions, which could be significant in the production of milk with improved nutritional properties, such as hypoallergenic quality, by selection and breeding of cows with particular milk protein genotypes.     

纳滤在乳品工业中纯化乳糖的应用

阐述了纳滤分离过程的特点和机理,与传统生产乳糖的方法相比,列出纳滤技术生产乳糖的特点及优势。纳滤技术污染少、能耗低、收率高,具有良好的开发前景,现已应用到食品工业、化学工业、纸浆工业、电子纺织品工业、水处理工业等。