Figure 5.

Oligo(dT) E-DNA sensors distinguish between cooperative binding of full-length g32p and noncooperative binding of the core domain (*III) fragment. Sensors modified with (dT)₇, (dT)₁₄, (dT)₂₁, and (dT)₈₀ DNA probes are utilized to differentiate between cooperative and noncooperative binding, with the full-length g32p and truncated core domain (*III) protein used as targets. At high ionic strength, the full-length g32p cooperatively binds single-strand DNA in a probe-length-dependent manner (black lines), while the *III protein binds tightly and noncooperatively to DNA (gray lines). As seen in the binding curves, the full-length g32p generally exhibits weaker DNA–protein binding interactions relative to *III protein, which is characteristic of cooperativity between protein molecules. Except in the plots showing binding to (dT)₇, which is fit to the Langmuir expression, lines are drawn to guide the reader’s eye.