Synthesis and Optical Properties of the Conformationally Locked Indole and Indoline Derivatives of the GFP Chromophore

We report novel conformationally locked GFP chromophore amino-derivatives containing indole and indoline moieties. Optical properties of these compounds were studied. The introduction of the indoline group produces a shift in the absorption and emission maxima to the long-wavelength region and stabilizes the quantum yield of fluorescence. The introduce of the indole group leads to a hypsochromic shift and a noticeable decrease of fluorescence intensity.