Calculate axial rising of actin monomer from ALL6 and ALL7 spacings

The arrangement of the actin subunits in the thin filaments can be described as two families of “genetic helices”, one set of left-handed helices based on a helical pitch of 5.9 nm and another set of right-handed helices based on a pitch of 5.1 nm with the axial rise of actin monomers at ~2.73 nm.

Ma, W.; Irving, T.C. Small Angle X-ray Diffraction as a Tool for Structural Characterization of Muscle Disease. Int. J. Mol. Sci. 2022, 23, 3052. https://doi.org/10.3390/ijms23063052

The 2.73 nm spacing is very useful information to assess the stiffness/compliance of thin filaments, but sometimes it is hard to access it due to multiple reasons. It, however, can be deduced from the ALL6 and ALL7 spacings. See the equation below:

How to cite

Gong, H. M., Ma, W., Regnier, M., & Irving, T. C. (2022). Thick filament activation is different in fast- and slow-twitch skeletal muscle. The Journal of physiology, 600(24), 5247–5266. https://doi.org/10.1113/JP283574