Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Crossbridge order and orientation in resting single glycerinated muscle fibres studied by linear dichroism of bound rhodamine labels

  • 22 Accesses

  • 11 Citations


Linear dichroism of iodoacetyl-rhodamine labels attached to the highly reactive thiol of the myosin heads was measured in order to infer the spatial orientation and the degree of order in myosin crossbridges in single glycerinated rabbit psoas fibres at rest. We have previously shown that in rigor the chromophoric labels are well ordered and that in the presence of MgADP and during isometric contraction a large fraction of probes is also ordered but at an attitude different from that of rigor. Here we show that in relaxed muscle the probe order is dependent on total ionic strength: at and above 0.180m there is little evidence for any preferred probe orientation, implying a high degree of crossbridge disorder. Below 0.160m there is progressively more order with decreasing ionic strength down to 0.100m, below which no measurements could be taken at room temperature (because the fibres would not relax). The dichroism observed under these conditions resembles that of the rigor state in that the dichroism peaks at the same polarization of excitation light, implying that the average probe attitude relative to the fibre axis is larger than 54.7°. Stretching the muscle beyond the point of overlap between actin- and myosin-containing filaments does not affect the ionic strength dependence of the amount of order present in relaxed muscle, suggesting that the observed order is due to ionic interactions of crossbridges with the thick filament surface.

This is a preview of subscription content, log in to check access.


  1. ARONSON, J. F. & MORALES, M. F. (1969) Polarization of tryptophan fluorescence in muscle.Biochemistry 8, 4517–22.

  2. BOREJDO, J. & PUTNAM, S. (1977) Polarization of fluorescence from single skinned glycerinated rabbit psoas fibers in rigor and relaxation.Biochim. Biophys. Acta 459, 578–95.

  3. BOREJDO, J., ASSULIN, O., ANDO, T. & PUTNAM, S. (1982) Cross-bridge orientation in skeletal muscle measured by linear dichroism of an extrinsic chromophore.J. molec. Biol. 158, 391–414.

  4. BRENNER, B., SHOENBERG, M., CHALOVICH, J. M., GREENE, L. E. & EISENBERG, E. (1982) Evidence for cross-bridge attachment in relaxed muscle at low ionic strength.Proc. natn. Acad. Sci. USA 79, 7288–91.

  5. BURGHARDT, T. P., ANDO, T. & BOREJDO, J. (1983) Evidence for cross-bridge order in contraction of glycerinated skeletal muscle.Proc. natn. Acad. Sci. USA 80, 7515–9.

  6. GORDON, A. M., GODT, R. E., DONALDSON, S. K. B. & HARRIS, E. J. (1973) Tension in skinned frog muscle fibers in solutions of varying ionic strength and neutral salt composition.J. gen. Physiol. 62, 550–74.

  7. GULATI, J. (1983) Mg-ion dependent contraction of skinned frog muscle fibers in Ca-free solution.Biophys. J. 44, 113–21.

  8. HUXLEY, H. E. & BROWN, W. (1967) The low angle X-ray diagram of vertebrate striated muscle and its behavior during contraction and rigor.J. molec. Biol. 30, 383–434.

  9. LOXDALE, H. & TREGEAR, R. T. (1983) Generation of tension by glycerol-extracted vertebrate skeletal muscle fibre in the absence of calcium.J. Musc. Res. Cell Motility 4, 543–56.

  10. NIHEI, T., MENDELSON, R. & BOTTS, J. (1974) The site of force generation in muscle contraction as deduced from fluorescence polarization studies.Proc. natn. Acad. Sci. USA 71, 274–7.

  11. POULSEN, F. R. & LOWY, J. (1983) Small angle X-ray scattering from myosin heads in relaxed and rigor frog skeletal muscles.Nature 303, 148–52.

  12. REEDY, M. K., HOLMES, K. C. & TREGEAR, R. T. (1965) Induced changes in orientation of the cross-bridge of glycerinated insect flight muscle.Nature 207, 1275–80.

  13. THOMAS, D. D. & COOKE, R. (1980) Orientation of spin labeled myosin heads in glycerinated muscle fibers.Biophys. J. 32, 891–906.

  14. WILSON, M. G. A. & MENDELSON, R. A. (1983) A comparison of order and orientation of cross-bridges in rigor and relaxed muscle fibers using fluorescence polarization.J. Musc. Res. Cell Motility 4, 671–93.

  15. YANAGIDA, T. (1981) Angles of nucleotides bound to crossbridges in glycerinated muscle fibers at various concentrations of ε-ATP, ε-ADP and ε-AMPPNP detected by polarized fluorescence.J. molec. Biol. 146, 539–60.

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Burghardt, T.P., Tidswell, M. & Borejdo, J. Crossbridge order and orientation in resting single glycerinated muscle fibres studied by linear dichroism of bound rhodamine labels. J Muscle Res Cell Motil 5, 657–663 (1984). https://doi.org/10.1007/BF00713924

Download citation


  • Ionic Strength
  • Rhodamine
  • Isometric Contraction
  • Fibre Axis
  • Probe Attitude