Oscillations, Waves, and Interactions - GWDG

442 S. Lakämper and C. F. Schmidt
Figure 4. Finite-element simulations of MTs with bound tau. On top, the cross-sections of
the models with their dimensions in nm are given. Left, MT in the absence of tau. Center,
tau is added as a 0.5 nm thick layer between the protofilaments. Right, tau is added as 1 nm
thick filaments on the ridges of the protofilaments. For all models the elastic modulus of the
added material was set to 0.6 GPa, which is equal to that of the MT. The graph shows the
computed deformation of the tube when indented with a parabolic tip with a 20 nm radius.
The addition of tau as 1 nm filaments on top of the proto-filaments adds very little to the
probed stiffness, but when tau is added as a 0.5 nm layer between the protofilaments, the
stiffness increases by more than 60 %. The inset shows the MT with tau on top of the protofilaments.
The strain (indicated by brighter colors) is concentrated at the loading point and
between the proto-filaments. (From Ref. [3]).
the expanded state they become super-elastic and can be reversibly compressed until
the opposing walls touch [5–7].
2.5 Self-assembled DNA-tetrahedra
The smallest structures we have studied are nanometre-sized cages of DNA the mechanics
of which are similar to those of the shells described above. DNA is an interesting
material for the construction of nanomaterials because its self-assembly can
be pre-programmed by the sequence of bases. With the tools of current molecular
biology DNA oligomers can be generated with any desired sequence. Together with a
group in Oxford, we have studied a family of DNA nanostructures that were designed
to self-assemble to tetrahedra with double-stranded edges in a single step in only a