Table 1.

Absorption maxima (λ_max), extinction coefficients (ε), fluorescence excitation (λ_exc) and emission (λ_em) maxima in the presence and absence of DNA for HPr⁺ and its oxidation products

Compound	UV-Vis absorption		Fluorescence

	λ_max [nm]	ε [M⁻¹cm⁻¹]	without DNA		with DNA

			λ_exc [nm]	λ_em [nm]	λ_exc [nm]	λ_em [nm]
HPr⁺	264		258	403
HPr⁺	350	1.15×10⁴	350	403
2-OH-Pr⁺⁺	269		479	597	391	575
2-OH-Pr⁺⁺	483	1.1×10⁴	479	597	508	575
Pr⁺⁺	288		485	614	533	605
Pr⁺⁺	495	5.2×10³	485	614	533	605
Pr⁺⁺-Pr⁺⁺	290		480^a	618^a	529^a	607^a
Pr⁺⁺-Pr⁺⁺	513	~1.2×10⁴	480^a	618^a	529^a	607^a

The fluorescence intensity of Pr⁺⁺-Pr⁺⁺ is at least 10× lower than that of Pr⁺⁺ and 2-OH-Pr⁺⁺