X-ray diffraction study of oriented gels of titin

The structural principles of multidomain organization of the giant polypeptide chain of the muscle titin protein: SAXS/WAXS studies during the stretching of oriented titin fibres

“…This suggestion is in contrast to our previous conclusions (Vazina et al, 2005). All earlier linear and zig-zag-like model structures, including our ones, are incorrect since all of them have an axial translation s c and would give rise to both equatorial and meridional reflections (Erickson, 1994;Leahy et al, 1992;Nakauchi et al, 1993. Let us now consider changes in the domain packing of an aperiodic structure during unidirectional stretching.…”

“…Until now titin fibres have shown no directionality (no texture). However, we have succeeded in preparing oriented fibres of purified titin and report here the first small-angle diffraction patterns (Soteriou et al, 1994, Vazina et al, 2005. They are similar to many semi-crystalline synthetic polymers that display only equatorial reflections in the form of blurred arcs and spots.…”

“…It should be emphasized that the diffraction patterns with the reflections in the form of diffuse arcs and spots characteristic of titin are also typical of most semi-crystalline polymers. The similarity of titin to semicrystalline polymers is also revealed in the studies of the mechanical properties of oriented titin fibres on stretching (Li et al, 1996;Vazina et al, 2005). The characteristic features of our morphological model make it possible to consider the molecular mechanism of the high elasticity of titin in the framework of the physics of structural transitions in semi-crystalline polymers (Flory, 1956a,b).…”

“…In particular, three stages of the stress-strain curves were observed. Stretching produces noticeable changes in the small-angle diffraction patterns (Li et al, 1996;Soteriou et al, 1994;Vazina et al, 2005) consistent with the concept of orientation-dependent melting i.e., the melting temperature of crystallites (b-barrels) aligned along the stretching direction was higher than of those aligned across. Below we address a question-why does stretching unfold one set of domains but stabilizes another?…”

“…The stretching forces are more manifest in SAXS than in WAXS diffraction patterns (Vazina et al, 2005). It should be emphasized that the diffraction patterns with the reflections in the form of diffuse arcs and spots characteristic of titin are also typical of most semi-crystalline polymers.…”