Related Experiment Video
Updated: Jun 9, 2026

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer
Published on: May 7, 2020
Extraction and replacement of the tropomyosin-troponin complex in isolated myofibrils
Beatrice Scellini1, Nicoletta Piroddi, Corrado Poggesi
1Dipartmento di Scienze Fisiologiche, Università di Firenze, Firenze, Italy.
Abstract:
Tropomyosin (Tm) is an essential component in the regulation of striated muscle contraction. Questions about Tm functional role have been difficult to study because sarcomere Tm content is not as easily manipulated as Troponin (Tn). Here we describe the method we recently developed to replace Tm-Tn of skeletal and cardiac myofibrils from animals and humans to generate an experimental model of homogeneous Tm composition and giving the possibility to measure a wide range of mechanical parameters of contraction (e.g. maximal force and kinetics of force generation). The success of the exchange was determined by SDS-PAGE and by mechanical measurements of calcium dependent force activation on the reconstituted myofibrils. In skeletal and cardiac myofibrils, the percentage of Tm replacement was higher than 90%. Maximal isometric tension was 30-35% lower in the reconstituted myofibrils than in control myofibrils but the rate of force activation (k(ACT)) and that of force redevelopment (k(TR)) were not significantly changed. Preliminary results show the effectiveness of Tm replacement in human cardiac myofibrils. This approach can be used to test the functional impact of Tm mutations responsible for human cardiomyopathies.
Related Concept Videos
Actin and Myosin in Muscle Contraction
Excitation-Contraction Coupling in Skeletal Muscles
When an action potential...
The Sarcomere
Each myosin...
Relaxation of Skeletal Muscles
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
Cross-bridge Cycle
Overview of Skeletal Muscle

