Photostability of organic fluorophore influenced by adjacent amino acid residues.

Fluorescence microscopy represents a highly effective tool for examining the microscopic world. Modern microscopic techniques provide advanced temporal and spatial resolutions, while placing high demands on the photostability of fluorophores. Although it is well-known that the photostability of fluorophores is sensitive to their environment, the influence of nearby residues on the photostability of organic fluorophores attached to proteins is not yet fully understood. This study focuses on the influence of residues adjacent to the maleimide-derived fluorophore, specifically attached to cysteine residues in proteins. Under our experimental conditions, methionine, tryptophan, phenylalanine, valine, and leucine were all found to reduce the photostability, whereas glutamate was found to enhance the photostability. To put these experimental observations into perspective, we performed molecular dynamics simulations that offer insights into the mechanistic effects of adjacent residues.