2005 年 10 巻 1-2 号 p. 67-72
A kinetic analysis was done for the genetic transformation of Escherichia coil DH5 α with plasmid DNA. Transformation frequency, defined as a ratio of the number of transformants to the total number of viable cells, was correlated with temperature according to Arrhenius' equation, giving a kinetic parameter of energy change associated with the reaction, ΔU. The parameter YNT, 273, defined as the plasmid-based yield of transformation at 273 K, was also proposed to evaluate the transformation process in a quantitative manner. It was found that both the values of ΔU and YNT, 273 were smaller when plasmids with larger molecular weight were used as the DNA donors. This was attributed to the unstable state of large-size plasmid DNA in the periplasmic space of the recipient cells. The coexistence of chromosome DNA as an impurity mainly caused the reduction in the YNT, 273 value without a notable drop in the ΔU value, reflecting a competitive reaction between the plasmid and chromosome DNA molecules for receptor sites on the cell surfaces.
