Response to Bianco et al.: Interaction forces between F-actin and titin PEVK domain measured with optical tweezers.

A recent publication in Biophysical Journal by Bianco et al. ("Interaction forces between F-actin and titin PEVK domain measured with optical tweezers") shows that the PEVK domain of titin molecules interacts with F-actin. This newly discovered behavior could influence the mechanical properties of striated muscles, and Bianco et al. suggest that the interactions between actin and titin could modulate thixotropic behavior. In this Comment to the Editor, we suggest that the thixotropic properties of striated muscles in vivo are more likely to reflect dynamic changes in the proportion of myosin cross-bridges bound between the myofilaments.