Comparative Biomechanics of Thick Filaments and Thin Filaments with Functional Consequences for Muscle Contraction

Figure 1

Some approaches used to measure the biomechanical properties of muscle, from single molecules to a living organism. Scale bars are approximate and are based on the size of the preparations, not the equipment. (a) Measurement of axial forces produced when pulling individual myosin molecules [2, 3] (figure adapted from [3]). (b) The biomechanical characteristics of thick filaments and thin filaments have been measured with a variety of techniques. (b1) Measurement of elastic properties of thick filaments with cantilevers [4, 5] (figure adapted from [5]). Thin filament elastic properties also have been measured in this way [6]. (b2) Shearing and bending of thick filaments with an AFM probe [7] (figure modified from [7]). (b3) Young’s modulus and persistence length of thick filaments calculated from AFM images [8, 9] (figure modified from [9]). The persistence length of thin filaments has also been measured by monitoring their thermal fluctuations in shape [10–12]. (b4) Axial stiffness of thin filaments measured with a glass microneedle [13] (figure adapted from [13]). (b5) Flexural rigidity of thin filaments measured in an optical trap [14] (figure modified from [14]). (b6) Torsional rigidity of thin filaments [15, 16] (figure adapted from [16]). (c) Axial passive stiffness of myofibrils measured with cantilever force transducers [17–19] (adapted from [17]). (d) Elastic and viscous properties of skinned muscle fibers [20–22]. (e) Elastance of the heart [23, 24]. The scale bar here reflects a mouse heart. (f) X-ray diffraction of live Drosophila flight muscles [25].