TABLE 3.

Conditions for the in vitro integration assay

Conditiona	Integration frequency (10−3)b
Standard	3.6
−Polyvinylalcohol	1.2
+Mg2+	1.6
+Spermidine	0.4
+ATP	2.7
+DMSO	2.6

^aThe standard reaction conditions are described in Materials and Methods. The E. coli host factor IHE was used in all of the reactions. Elimination of any component from the standard conditions is indicated with a “−” and addition of any component to the standard conditions is indicated with a “+”. The final concentrations for added components were as follows: Mg²⁺, 5 mM; spermidine, 2 mM; ATP, 2 mM; and DMSO, 10%.

^bThe integration frequency is expressed as the ratio of Ap^r Cm^r colonies to Ap^r colonies from the electroporation method (see Materials and Methods). Each value was the average of the results of four individual reactions.