Practice question

Cytochrome c model illustrates tryptophan fluorescence quenching by prosthetic group. Native state buries tryptophan 59 adjacent to heme, enabling efficient Förster resonance energy transfer and electron transfer that quenches emission, leaving weak signal near 325 nm if detectable. Chemical denaturation with guanidinium chloride disrupts tertiary fold, distances exceeding Förster radius, abolishes quenching and exposes indole to aqueous solvent. Solvent dipolar relaxation stabilizes excited state, increasing quantum yield and red shifting emission maximum to characteristic water-exposed value near 350-355 nm. This dequenching monitors unfolding thermodynamics and folding kinetics experimentally.