Experimental Observation
of Double-Walled Peptide
Nanotubes and Monodispersity Modeling of the Number of Walls
- Publication date
- Publisher
Abstract
Self-assembled nanoarchitectures based on biological
molecules
are attractive because of the simplicity and versatility of the building
blocks. However, size control is still a challenge. This control is
only possible when a given system is deeply understood. Such is the
case with the lanreotide acetate, an octapeptide salt that spontaneously
forms monodisperse nanotubes when dissolved into pure water. Following
a structural approach, we have in the past demonstrated the possibility
to tune the diameter of these nanotubes while keeping a strict monodispersity,
either by chemical modification of one precise amino acid on the peptide
sequence or by changing the size of the counterions. On the basis
of these previous studies, we replaced monovalent counterions by divalent
ones to vary the number of walls. Indeed, in the present work, we
show that lanreotide associated with a divalent counterion forms double-walled
nanotubes while keeping the average diameter constant. However, the
strict monodispersity of the number of walls was unexpected. We propose
that the divalent counterions create an adhesion force that can drive
the wall packing. This adhesion force is counterbalanced by a mechanical
one that is related to the stiffness of the peptide wall. By taking
into account these two opposite forces, we have built a general model
that fully explains why the lanreotide nanotubes formed with divalent
counterions possess two walls and not more