Effect of urea on fluorescence intensity of BCA II.

Dependence of fluorescence intensity I at 360 nm (A) and 320 nm (B) on urea concentration for wild-type BCA II (■ WT) and its two mutant forms ( L139A and A53C-A76C). Excitation at 280 nm. The vertical line at 7 M is a reference to compare the curves (see the text).