Table 2.

Lifetimes of spectrin tryptophans, NATA, and PRODAN

System	α1	τ1 (ns)	α2	τ2 (ns)
Spectrina (native)	0.73	1.48	0.27	4.98
Spectrina (denatured)	0.82	2.85	0.18	6.91
NATAb (water)	1.00	3.00
NATAb (8 M Urea)	1.00	4.03
PRODANc (water)	1.00	1.54
PRODANd (bound to spectrin)	0.77	4.41	0.23	8.08

The concentration of native and denatured spectrin was 0.6 and 0.4 μM, respectively. The concentration of NATA was 100 μM. PRODAN in water was used at a concentration of 1 μM. The concentration of PRODAN was 0.5 μM and spectrin was 1.5 μM for PRODAN bound to spectrin.

^a Excitation at 297 nm; emission monitored at 340 nm.

^b Excitation at 297 nm; emission monitored at 330 nm.

^c Excitation at 360 nm; emission monitored at 520 nm.

^d Excitation at 360 nm; emission monitored at 430 nm.