Smith M G, Skalka A
J Gen Physiol. 1966 Jul;49(6):127-42. doi: 10.1085/jgp.49.6.127.
Replicating T5 or lambda phage DNA has been labeled by adding tritiated thymidine for short periods to cultures of phage-infected Escherichia coli before isolation of intracellular DNA. Two procedures are described for separating T5 replicating DNA from DNA of intracellular phage particles. Both T5 and lambda replicating DNA had the same bouyant density in cesium chloride as DNA from phage particles but sedimented faster when centrifuged in sucrose density gradients. The fast sedimentation did not appear to be caused by DNA protein or DNA-RNA complexes or by aggregation of DNA, but is probably due to DNA molecules of unusual structure. Experiments involving hydrodynamic shear and sucrose density gradient centrifugation at alkaline pH have suggested that with lambda the replicating form of DNA is a linear molecule considerably longer than the DNA molecules of lambda-phage particles. The constituent polynucleotide chains of lambda but not T5 replicating DNA also appear to be longer than those of phage DNA.
通过在分离细胞内DNA之前，短时间向噬菌体感染的大肠杆菌培养物中添加氚化胸腺嘧啶来标记复制的T5或λ噬菌体DNA。描述了两种从细胞内噬菌体颗粒的DNA中分离T5复制DNA的方法。T5和λ复制DNA在氯化铯中的浮力密度与噬菌体颗粒的DNA相同，但在蔗糖密度梯度中离心时沉降得更快。快速沉降似乎不是由DNA-蛋白质或DNA-RNA复合物或DNA聚集引起的，而可能是由于结构异常的DNA分子。涉及流体动力剪切和碱性pH下蔗糖密度梯度离心的实验表明，对于λ噬菌体，DNA的复制形式是一种线性分子，比λ噬菌体颗粒的DNA分子长得多。λ噬菌体复制DNA的组成多核苷酸链似乎也比噬菌体DNA的链长，而T5复制DNA则不然。
