Will the size of plasmid affect transformation efficiency? "

The size of plasmid affects the efficiency greatly. For instance, the efficiency for a supercoiled 2.7 Kb and a 10 Kb plasmid (using 1 minute protocol and DH5α-CD191) is 1.6~5.5 x 109 and 4.0~9.0 x 106 respectively. The difference is approximately 100 times. Transformation efficiency for large plasmids (especially > 6 Kb) can be increased by using the optional protocol as described in Q4.