★ PEG is a minimal requirement for the binding of DNA to yeast cell surfaces
★ Li⁺ only has an effect on yeast cell wall instead of the cell membrane

Effect of PEG and Li⁺ on yeast transformation

Binding of pUC18 plasmid DNA labeled with YOYO-1 to the surfaces of living yeast protoplasts.

A: Yeast cells only; B: 0.1 M Li+ was added; C: 40% PEG was added; D: 0.1 M Li⁺ and 40% PEG were added 　

Surface topography changes of yeast cells with treatment of Li⁺ and PEG

SEM images of intact yeast cells.
A : Intact yeast cells without treatment of Li⁺; B : Intact yeast cells after 30min incubation with Li⁺

AFM images of intact yeast cells (A); Li⁺-treated yeast cells (B); and the cell wall of a Li⁺-treated single yeast cell (C)

H.Z. Zheng et al. Bioconjugate Chem., 16 (2005) 250