Final answer:
Actin filaments have been studied using various experimental methods to understand their structure and behavior. Electron microscopy and the decoration of actin filaments have provided valuable insights into the sliding filament model of muscle contraction and the interaction between actin and myosin during ATPase activity.
Step-by-step explanation:
Actin filaments play an essential role in cell division, muscle contraction, and cellular motion. The structure and behavior of actin filaments have been studied using various experimental methods. For example, electron microscopy of actinomyosin preparations spread on a water surface revealed the contraction of the film when ATP was added, providing evidence for the sliding filament model of muscle contraction. Similarly, the decoration of actin filaments with arrowheads by myosin S1 fragments demonstrated the interaction between actin and myosin during the maximum rate of ATPase activity during contraction.