Major difference of hn proteins lies in no . 18 - no . 75 amino acid residues on n - terminal which includes three active sites of hn protein . the influence on biological action , caused by the difference of hn protein , is needed to study further . hn gene has only four glycosylation sites , which is 1 or 2 less on amount than that of other strains . so , this difference can be take on as a natural mark of ndv b95 strain furthermore , the fragment encoding hn gene was excised from the positive clone pgem - hn with sail and saci enzyme , and purified by agrose gel fraction method . then the fragment was subcloned into the pet - 28c expressing vector digested by sail and saci restriction enzyme 作者将正确的重组克隆质粒pgem - hn用saii 、 saci双酶切，电泳回收目的片段，将其亚克隆到经saii 、 saci双酶切处理的pet - 28c中，转化大肠杆菌tgi感受态细胞，得到的转化子经pcr鉴定和酶切分析，筛选出符合阅读框的重组子，构建成重组表达质粒pet - hn ，并在大肠杆菌bl _ ( 21 ) ( de _ 3 )宿主菌中成功地表达了含目的蛋白的融合蛋白，融合蛋白的分子量约66kd ，加入iptg诱导8h后，蛋白表达几乎达到最高水平。
