What is the clinical evidence from this study?

Study design: Other. Intervention: Caged ATP photolysis via UV flash vs. Caged AMP. Primary outcome: Orientational order of myosin heads (P2 intensity).

What question did this study set out to answer?

To measure the real-time orientational distribution and structural order of myosin heads immediately following rapid photolytic release of ATP during isometric muscle contraction.

July 1, 1990Proceedings of the National Academy of SciencesOpen Access

Myosin heads have a broad orientational distribution during isometric muscle contraction: time-resolved EPR studies using caged ATP.

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Key result

In isometric contraction, most (88% +/- 4%) of the myosin heads are in a population characterized by a high degree of axial disorder, comparable to that observed for all heads in relaxation.

Population

Rabbit psoas muscle fibers labeled with maleimide spin label (modifying 60% of myosin heads)

Comparison

Laser flash photolysis of 5 mM caged ATP vs Caged AMP

Design

Preclinical

Authors

PFPiotr G. FajerFlorida State University EFElizabeth A. FajerFlorida State University DTDavid D. ThomasHeart Failure / Cardiomyopathy

Discussion

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Implication

Challenges ordered cross-bridge models in animal muscle; leaves open relevance to human cardiac force generation.

Key Points

To measure the real-time orientational distribution and structural order of myosin heads immediately following rapid photolytic release of ATP during isometric muscle contraction.
Rabbit psoas muscle bundles were labeled with maleimide spin label (modifying 60% of myosin heads) and incubated with 5 mM caged ATP.
An excimer laser flash photolyzed caged ATP to release 2–3 mM ATP, while time-resolved electron paramagnetic resonance (EPR) monitored the orientational order parameter (P2 intensity) in the presence or absence of Ca2+.
Photolysis of caged ATP triggered a rapid decrease in orientational order (P2 intensity) during both relaxation and isometric contraction, reverting to rigor order only upon ATP exhaustion.
During isometric contraction, 88% ± 4% of myosin heads exhibited high axial disorder, displaying an orientational spread comparable to heads in fully relaxed muscle.
Because fiber stiffness during isometric contraction remained at 80% of rigor stiffness, most actin-attached myosin heads during contraction belong to this highly disoriented population.

Structured PICO

Population

Rabbit psoas muscle fibers labeled with maleimide spin label (modifying 60% of myosin heads)

Intervention

Laser flash photolysis of 5 mM caged ATP (liberating 2-3 mM ATP)

Comparator

Caged AMP (to rule out nonspecific effects of UV flash)

Outcome

Orientation of spin-labeled myosin heads (measured by EPR intensity at spectral position P2)surrogate

Time-resolved EPR studies using caged ATP reveal that during isometric contraction, the majority of actin-attached myosin heads exhibit a high degree of axial disorder.

Cite This Study

Fajer et al. (1990) studied this question. Caged ATP photolysis via UV flash vs. Caged AMP was evaluated on Orientational order of myosin heads (P2 intensity). In isometric contraction, most (88% +/- 4%) of the myosin heads are in a population characterized by a high degree of axial disorder, comparable to that observed for all heads in relaxation.

synapsesocial.com/papers/6a8d8ae323326f78e47dd2fc https://doi.org/10.1073/pnas.87.14.5538

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Myosin heads have a broad orientational distribution during isometric muscle contraction: time-resolved EPR studies using caged ATP.

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Myosin heads have a broad orientational distribution during isometric muscle contraction: time-resolved EPR studies using caged ATP.

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Also Consider

Also Consider