Another fascinating article from Janelia Research Campus in the Current Issue of Nature Methods. Dr. Lavis and his team introduced a new group of red shifted dye called 'Janelia Fluor' (JF) group.  They outlined a general rubric that directly correlates the lactone–zwitterion equilibrium constant (K_L–Z) to performance in biological environments. They compared a series of JF rhodamines with different fluorophoric systems. They developed a rubric to relate the performance of simple rhodamine dyes to a single parameter, K_L–Z (Figure below), and discovered an inverse correlation between K_L–Z and λ_abs. They hope these new findings help us to design fine-tuned dyes for specific biological applications. Such a great study!

Source: https://www.nature.com/articles/s41592-020-0909-6

Phenomenological plot categorizing the properties of different dyes based on K_L–Z (left) and  plot of K_L–Z vs. λ_abs for JF dyes and general tuning strategies for dyes with short or long λ_abs.