RT Journal Article SR Electronic T1 A general method to fine-tune fluorophores for live-cell and in vivo imaging JF bioRxiv FD Cold Spring Harbor Laboratory SP 127613 DO 10.1101/127613 A1 Jonathan B. Grimm A1 Anand K. Muthusamy A1 Yajie Liang A1 Timothy A. Brown A1 William C. Lemon A1 Ronak Patel A1 Rongwen Lu A1 John J. Macklin A1 Phillip J. Keller A1 Na Ji A1 Luke D. Lavis YR 2017 UL http://biorxiv.org/content/early/2017/04/14/127613.abstract AB Pushing the frontier of fluorescence microscopy requires the design of enhanced fluorophores with finely tuned properties. We recently discovered that incorporation of four-membered azetidine rings into classic fluorophore structures elicits substantial increases in brightness and photostability, resulting in the ‘Janelia Fluor’ (JF) series of dyes. Here, we refine and extend this strategy, showing that incorporation of 3-substituted azetidine groups allows rational tuning of the spectral and chemical properties with unprecedented precision. This strategy yields a palette of new fluorescent and fluorogenic labels with excitation ranging from blue to the far-red with utility in live cells, tissue, and animals.