(+)-Blebbistatin is the inactive enantiomer of (-)-blebbistatin (Item No. 13013), which is a selective inhibitor of non-muscle myosin II ATPases.{16452,17037} Prolonged exposure to blue light (450-490 nm) results in degradation of blebbistatin to an inactive product via cytotoxic intermediates, which may be problematic for its use in fluorescent live cell imaging applications.{17038,24037} (R)-nitro-Blebbistatin (Item No. 9001935) is a more stable form of (+)-blebbistatin.{16725} The addition of a nitro group stabilizes the molecule to circumvent its degradation by prolonged blue light exposure. (R)-nitro-Blebbistatin has the same stereochemistry as the inactive (+)-blebbistatin enantiomer.