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. Author manuscript; available in PMC: 2009 Oct 5.
Published in final edited form as: Nat Protoc. 2007;2(8):1849–1861. doi: 10.1038/nprot.2007.249

Figure 1. Titration of a 214 bp lac promoter DNA fragment with E. coli CAP protein.

Figure 1

Sample compositions are given in Table 4. The complex consists of a single molecule of CAP bound predominantly to the highest affinity CAP site in the lac promoter (CAP site 149, 66). Electrophoresis was carried out with a 10% w/v polyacrylamide (75:1 acrylamide:bisacrylamide) gel, cast and run in the Tris-acetate EDTA buffer described in the protocol shown in Table 5. Cyclic AMP (final concentration 20 μM) was added to the electrophoresis running buffer. Pre-electrophoresis ensured that the cAMP was distributed throughout the gel before the samples were loaded. Band designations: F, free DNA; B, bound DNA (i.e., protein-DNA complex).