Skoog L, Nordenskjöld B A, Lindberg U
J Virol. 1970 Jul;6(1):28-32. doi: 10.1128/JVI.6.1.28-32.1970.
Polyoma virus particles were purified by equilibrium centrifugation in CsCl. Particles from three regions of the density gradient were examined for infectivity, for their ability to induce expanded pools of deoxyribonucleic acid (DNA) precursors, and for their ability to stimulate the synthesis of DNA. The most infectious population of particles, the virions, having a buoyant density of 1.33 g/ml, gave the greatest stimulation of the DNA-synthesizing apparatus of mouse embryo cells. Empty particles at density 1.29 g/ml had no DNA stimulatory activity. A population of particles of intermediate density, referred to as pseudovirions, was also much less active than virions in stimulating DNA synthesis, and the limited stimulatory activity of the latter fraction may be accounted for by its measured contamination with infective particles.
多瘤病毒颗粒通过在氯化铯中进行平衡离心来纯化。对密度梯度三个区域的颗粒进行了感染性检测、诱导脱氧核糖核酸（DNA）前体池扩大的能力检测以及刺激DNA合成的能力检测。颗粒中最具感染性的群体，即浮力密度为1.33 g/ml的病毒粒子，对小鼠胚胎细胞的DNA合成装置刺激作用最大。密度为1.29 g/ml的空颗粒没有DNA刺激活性。一种中等密度的颗粒群体，称为假病毒粒子，在刺激DNA合成方面也比病毒粒子活性低得多，而后一部分有限的刺激活性可能是由于其检测到的感染性颗粒污染所致。
