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

Thomas P Burghardt, Mark Tidswell, Julian Borejdo

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

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 0.180 m there is little evidence for any preferred probe orientation, implying a high degree of crossbridge disorder. Below 0.160 m there is progressively more order with decreasing ionic strength down to 0.100 m, 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.

Original languageEnglish (US)
Pages (from-to)657-663
Number of pages7
JournalJournal of Muscle Research and Cell Motility
Volume5
Issue number6
DOIs
StatePublished - Dec 1984
Externally publishedYes

Fingerprint

Rhodamines
Myosins
Osmolar Concentration
Muscle
Labels
Ionic strength
Muscles
Fibers
Isometric Contraction
Sulfhydryl Compounds
Adenosine Diphosphate
Actins
Dichroism
Rabbits
Stretching
Light
Temperature
Polarization

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Clinical Biochemistry
  • Cell Biology

Cite this

Crossbridge order and orientation in resting single glycerinated muscle fibres studied by linear dichroism of bound rhodamine labels. / Burghardt, Thomas P; Tidswell, Mark; Borejdo, Julian.

In: Journal of Muscle Research and Cell Motility, Vol. 5, No. 6, 12.1984, p. 657-663.

Research output: Contribution to journalArticle

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