Structural analysis of proteinaceous components in Byssal threads of the mussel Mytilus galloprovincialis.
The mussel byssus is a unique holdfast structure employed by marine mussels to colonize diverse substrates. The byssus consists of extracellular threads with mainly proteinaceous components. Individual threads reveal high tensile strength at their distal end and high elasticity in their proximal portion. Our studies show that proteins of the distal part are oriented along the thread axis and are well-ordered with a high beta-structural content. In contrast, proteins of the proximal part are less ordered and are not as well-oriented with primarily alpha-helical structure. The detected differences in the structural features of the proteins along a byssus thread are likely an important basis for its gradual mechanical properties.
Impact tolerance in mussel thread networks by heterogeneous material distribution.
The Mytilidae, generally known as marine mussels, are known to attach to most substrates including stone, wood, concrete and iron by using a network of byssus threads. Mussels are subjected to severe mechanical impacts caused by waves. However, how the network of byssus threads keeps the mussel attached in this challenging mechanical environment is puzzling, as the dynamical forces far exceed the measured strength of byssus threads and their attachment to the environment. Here we combine experiment and simulation, and show that the heterogeneous material distribution in byssus threads has a critical role in decreasing the effect of impact loading. We find that a combination of stiff and soft materials at an 80:20 ratio enables mussels to rapidly and effectively dissipate impact energy. Notably, this facilitates a significantly enhanced strength under dynamical loading over 900% that of the strength under static loading.
Refinement of crystal structure parameters using convergent‐beam electron diffraction: the low‐temperature phase of SrTiO3
The method to refine crystal structure parameters (atom positions and Debye–Waller factors) using convergent-beam electron diffraction (CBED), which is applicable to crystal structure analysis of a small specimen area down to a few nm in diameter, is studied. The line profiles of higher-order Laue-zone reflections are recorded using imaging plates. Theoretical intensities are calculated based on the dynamical theory of electron diffraction with the aid of the generalized Bethe approximation to shorten calculation time. The structural parameters are determined by fitting the experimental profiles with the theoretical ones using a nonlinear least-squares method. The present method has been applied to the low-temperature phase of SrTiO3. The structural parameter or the rotation angle of the oxygen octahedron has been determined to be \varphi = 1.12 (4)°, which shows good agreement with that obtained from electron spin resonance experiments.