The Flp double cross system a simple efficient procedure for cloning DNA fragments

BMC Biotechnology

Table 2 Flp cloning using linear plasmid DNA*

Addition/reaction	1	2	3	4
Circular pBA128	+
Linear pBA128	-	+	+	+
Lac Z cassette	-	-	-	+
Flp	-	-	+	+
Colonies/μg	6 × 10⁷	1.8 × 10⁶	1.5 × 10⁴	3 × 10⁵
% blue colonies	0	0	0	56%

*The reactions (10 μl) contained 100 ng of the indicated plasmid DNA, and where indicated, 100 ng of the purified lacZ cassette and 130 ng of S300 fraction of Flp. The reactions were processed as described in the Methods and 1 μl aliquots were used to transform competent XL1-blue E. coli cells (Stratagene). Transformed cells were plated on LB agar plates containing ampicillin, IPTG and X-Gal as described in the Methods.

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