Practice question

Native folded proteins frequently sequester tryptophan side chains within nonpolar interior, where low dielectric and restricted solvent mobility limit stabilization of excited state, producing emission around 320-335 nm. Chemical denaturation using urea, guanidinium chloride or thermal unfolding disrupts tertiary structure, unwinding polypeptide chain and exposing indole groups to bulk aqueous environment. Water molecules reorient around enlarged excited state dipole, a process termed solvent relaxation, lowering excited state energy via nonradiative losses. Resulting fluorescence shifts to longer wavelength near 350-355 nm, defined as red shift, accompanied by intensity changes reflecting unfolding.