Transfection of phage (Charon 4 ) DNA through E. coli membrane

Abstract

Uptake of free phage DNA by E. coli can only be achieved when the recipient cells have been "Competent" either by turning them into spheroplast or by heat shock in the presence of calcium ion. The degree of transfection was varied with the changes in the DNA concentration, cell concentration and cell condition. Transfection degree profile showed a saturation mode with varied concentration of challenging charon 4 phage DNA. It is supposed that DNA is transported through cell membrane by a carrier-mediated process. Calcium ion cuases the change of cell surface or structure of cell membrane; challenging DNA can bind the carrier which has been exposured by the change of cell membrane structure. Although the nature of the carrier is uncertain, it is obvious that a portion of charon 4 phage DNA might be involved in the binding with the E. coli membrane protein. The affinity constant for phage DNA was estimated to be about 0.263 nM. Energy requirement for the uptake of pahge DNA is still ambiguous, but it is supposed that the major driving force for the transfection of DNA will be provided by heat shock process.