X-ray evidence that in contracting live frog muscles there exist two distinct populations of myosin heads.


Journal Article

Using synchrotron radiation and whole muscles, 2 ms time-resolved x-ray diffraction patterns were recorded at 8 degrees C. The results show that in both isotonic and isometric contractions, as well as in length changes imposed at maximum tension [Po], the meridional third myosin layer line consists of two distinct reflections with different intensities and spacings that measure approximately 14,623 and 14,412 nm at Po. Although the intensity behavior of the two reflections is strikingly different during quick releases, it is very similar during stretches. Study of the time courses indicates that myosin heads diffracting at Po with the approximately 14.623 nm periodicity are actively involved in tension production. Those diffracting at Po with the periodicity of approximately 14.412 nm appear not be associated with tension production during isometric contraction and releases, but the results suggest that they are recruited during stretches and here contribute to tension production. Our most important conclusion is that under all conditions of contraction we have investigated there exist two populations of myosin heads, each with a well defined axial disposition and configuration.

Full Text

Cited Authors

  • Bordas, J; Lowy, J; Svensson, A; Harries, JE; Diakun, GP; Gandy, J; Miles, C; Mant, GR; Towns-Andrews, E

Published Date

  • April 1995

Published In

Volume / Issue

  • 68 / 4 Suppl

Start / End Page

  • 99S - 104S

PubMed ID

  • 7787116

Pubmed Central ID

  • 7787116

International Standard Serial Number (ISSN)

  • 0006-3495


  • eng

Conference Location

  • United States