Figure 1.

Dye structures and their emission spectra in various solvents

(A–D) Changes of the emission fluorescence spectra for free DyeA (A), DyeB (B), DyeC (C), and DyeD (D) in solvents with different polarity and viscosity. The excitation wavelengths were 410 nm (DyeA), 430 nm (DyeB), 380 nm (DyeC), and 420 nm (DyeD). Complete results and additional information for the tested dyes are provided in Table S1.

(E) The HBDI fluorescent core is shown in the center and four dyes as its derivatives; the maleimide groups, responsible for cysteine interaction, are colored in blue; the fluorescent core modifications are colored in red.