【摘要】 本文以质粒pBR322及噬菌体λcI857S7DNA 为底物研究了Mn⁺⁺及DMSO 对限制酶Hind Ⅲ对底物DNA 识别顺序的影响.在10mMTris-HClpH8.4,10mM MgCl₂,60mMNaCl 及7mM 巯基乙醇的正常反应条件下,HindⅢ在pBR322DNA 上只有一个切点,酶切后在凝胶电泳上可看到一条带.用10mM Mn⁺⁺代替Mg⁺⁺或在反应液中加入DMSO 进行酶切,在电泳上出现许多新的带.以λcI857S7DNA 为底物也得到类似的结果.新产生的片段可以用DNA 连接酶重新连接成线状分子.Mn⁺⁺及DMSO还能使Hind Ⅲ切割细菌本身的DNA.这些数据表明:Mn⁺⁺及DMSO 确实能降低Hind Ⅲ对底物的专一性,放松对识别顺序的要求.讨论了专一性降低的机制及其在核酸研究及基因工程中的意义。更多还原

【Abstract】 The effect of Mn⁺⁺ and DMSO on the sequence recognition of the restrictionendonuclease Hind Ⅲ was investigated.Under the normal reaction condition of10mM Tris-HCl,pH8.0,10mM MgCl₂,60mM NaCl and 7mM 2-ME,there is onlyone cutting site of Hind Ⅲ on pBR322 and only one band appears on gel electro-phoresis.But multiple bands can be seen on electrophoresis gel when Mg⁺⁺ isreplaced by Mn⁺⁺ or when DMSO is added.The DNA fragments generated inthe Hind Ⅲ-DMSO reaction are converted to linear DNA molecules.In theseconditions,the cellular DNA of the host（Haemophilus influenzac）is alsodigested by Hind Ⅲ.These data show that the specificity of cleavage of HindⅢ is relaxed and cleavages occur at many other sites in the presence of Mn⁺⁺and DMSO.更多还原