Table 2.

Effects of DNA binding on Trp lifetime and rotation

	Lifetime, ns		Rotational correlation time (θ), ns
	Center	Width	Average θ	θ1	f1*	θ2	f2*
E2c	1.70	0.85	4.4	9.2	0.14	0.18	0.16
E2c–DNA	2.26	1.62	15.8	36.9	0.13	0.32	0.17

Excitation wavelength was 295 nm and the emission was observed through a long-wavelength pass filter (WG335) with a cutoff at 335 nm. All measurements were performed in 50 mM Bis-Tris⋅HCl/1 mM DTT (pH 5.5), at 25°C. The protein and DNA concentrations were both 5 μM. The χ² values for the fittings of lifetime distribution and rotations were typically less than 2.0. 

^*f is the fraction of each rotational correlation time.