Rodicio M R, Chater K F
J Bacteriol. 1982 Sep;151(3):1078-85. doi: 10.1128/jb.151.3.1078-1085.1982.
DNA of the bacteriophage phi C31 was rendered DNase resistant by entrapment in liposomes. Liposome-entrapped phi C31 DNA transfected Streptomyces protoplasts in the presence of 50% polyethylene glycol (PEG), providing a potential alternative route to conventional PEG-mediated transfection of protoplasts. However, probably partially because of low entrapment of DNA, this system did not result in an effective increase in transfection efficiency over the conventional transfection procedure. A more effective use of liposomes for stimulating transfection was provided by the discovery that supernatants obtained during the washing of DNA-free liposome preparations stimulated PEG-mediated transfection of protoplasts. This effect appeared to involve small (0.1- to 0.3-micrometer diameter) poorly sedimented liposomes. It was most effective (more than 100-fold stimulation) with positively charged liposome supernatants and high (about 50% [wt/vol]) PEG concentrations. Stimulation of transfection was also observed with cloning ligation mixtures containing phi C31 DNA as the vector. Transformation by plasmids (but not by chromosomal DNA fragments) was also significantly more efficient in these conditions than in conventional protoplast transformation.
噬菌体phi C31的DNA通过包裹在脂质体中而变得对DNA酶具有抗性。在50%聚乙二醇（PEG）存在的情况下，脂质体包裹的phi C31 DNA转染了链霉菌原生质体，为传统的PEG介导的原生质体转染提供了一条潜在的替代途径。然而，可能部分由于DNA的包裹率低，该系统与传统转染方法相比，并未有效提高转染效率。发现无DNA脂质体制备过程中获得的上清液能刺激PEG介导的原生质体转染，这为更有效地利用脂质体促进转染提供了方法。这种效应似乎涉及小的（直径0.1至0.3微米）沉降性差的脂质体。带正电荷的脂质体上清液和高浓度（约50%[重量/体积]）的PEG时最为有效（刺激超过100倍）。以phi C31 DNA为载体的克隆连接混合物也观察到了转染刺激。在这些条件下，质粒（而非染色体DNA片段）介导的转化也比传统原生质体转化显著更有效。
