Actin filaments illustration

Selective two-photon excitation can provide additional contrast for single-cell imaging. It might be particularly useful for co-localization studies. In Figure 8.8, it is illustrated on HeLa cells. The cells were co-stained with Phalloidin-350 (actin filaments) and with MitoTracker 488 (mitochondria). An amplitude shaping was used... 

Figure 19-9 Stereoscopic ribbon drawing of the proposed structure of a thin actin filament with tropomyosin coiled-coils bound on opposing sides.124 Five actin nomomers are assembled in the structure as is also illustrated in Fig. 7-10. From Lorenz et al.125 Courtesy of Michael Lorenz.

Figure 19-19 Schematic drawing (not to scale) illustrating the use of two optical traps that are focused on beads attached to a single actin filament.

Digitalis and the other cardiac glycosides increase the heart s mechanical pumping ability by bringing about an increase in intracellular calcium concentration. Increased intracellular calcium enhances contractility by facilitating the interaction between thick (myosin) and thin (actin) filaments in the myocardial cell.60,66 Digitalis probably increases intracellular calcium concentration by a complex mechanism, which is illustrated in Figure 24—3. Details of this mechanism are also briefly outlined below. 

Not all actin filaments have 13/6 helical symmetry. For example, in insect flight muscle, as exemplified by Lethocerus, the actin filaments form a 28/13 helix. This also occurs in the vertebrate striated muscle Z-band (Squire et al., this volume. Section III.E Luther and Squire, 2002). The differences between the diffraction patterns from helices with 13/6 and 28/13 symmetry are illustrated in Fig. 10. The diffraction patterns were generated by the program HELIX (Knupp and Squire, 2004), but the program MusLabel can also be used (Squire and Knupp, 2004). Another... 

Fig. 9. Representation of a 13/6 actin filament together with its illustration by means of a radial net. In (A) an imaginary piece of paper is wrapped round the filament and on it are marked all the positions of the actin monomers. The paper is then unwrapped as in (B) and the helical tracks in (A) become straight lines. The final result in (C) is the radial projection or radial net. The 59 A pitch length (P) and 27.5 A subunit axial translation (h) are indicated in (C).

Fig. 15.1. Schematic illustration of the muscle. The force generating unit is the sarcomere with a length of about 2 tm. Contraction is caused by the myosin and actin filaments. Titin spans the whole half-sarcomere, keeps the myosin filaments in place and provides the muscle with its passive elasticity. At the M-line, where titin is cross-linked, the titin kinase is integrated with its surrounding and globular Ig and Fn domains. This position is ideal to detect the imbalances between neighboring filaments...

To further illustrate the properties of motor proteins, we consider myosin II, which moves along actln filaments in muscle cells during contraction. Other types of myosin can transport vesicles along actin filaments in the cytoskeleton. Myosin II and other members of the myosin superfamily are composed of one or two heavy chains and several light chains. The heavy chains are organized into three structurally and functionally different types of domains (Figure 3-24a). 

Figure 4.26 Intracellular structure, (a) Illustration of the internal structure of a typical human cell, (b) Fluorescence micrograph showing the organized actin filaments in a surface-attached fibroblast.

Fig. 6. Organization of structural elements within the smooth muscle cell. For purposes of simplicity, the contractile filaments are illustrated on the left side of the cell, whereas the cytoskeletal filaments are illustrated on the right side. Thin filaments composed of contractile actin (a or y isoforms) are proposed to associate with thick filaments. Thin filaments composed of cytoskeletal actin do not associate with myosin (as reviewed by Small (1995)). Actin filaments anchor at dense bodies in the cytosol and dense plaques at the cell membrane via linker proteins. Intermediate filaments link chains of dense bodies. Intermediate filaments are also linked to the cell surface at dense plaques...

A common perspective of the contraction/ relaxation cycle comes from the text of Voet et al., as shown in Figure 8.46. An illustration at the top of Figure 8.46 shows the thick myosin filament between thin actin filaments with globular (3 oss-bridges directed from the myosin filament toward the thin actin filaments. The sliding filament model has the cyclic attach-ment-contraction/detachment-relaxation action of the ca oss-bridges driving the thick... 

Figure 8.4 Schematic illustrating the molecular structure of filopodium, where bundles of actin filaments (connected by various cross-finking proteins) are wrapped around by the cell membrane.

FIGURE 34.2 Illustration of cadherin receptors associated with actin cytoskeleton. Cadherin dimers are shown in a linear zipper structure with antiparallel binding of the ECl domains. Cytopiasmic taiis of cadherins interact with actin filaments through structural proteins -catenin, pl20 catenin, plakoglobin, and a-catenin. 

Figure 4 Illustration of the assembly and disassembly of microtubules and actin filaments.

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