The binding of fluorophores to proteins depends on the cellular environment.

Lighten up! To investigate intracellular binders of myotube-specific probes, a thiol-reactive derivative, CDy2, was prepared. In live cells, the derivative selectively localizes in mitochondria and covalently labels its binding partners. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.