Toward Intelligent Materials - Molecular Self-Assembly: Advances and Applications - page 9

that rhodamine (Rh110) could be attached to the peptide through
solid phase synthesis to generate the fluorescent monomer Rh17-
22. This labeled peptide was employed as a probe and shown to
co-assemble with A

β

(16-22) to give homogeneously florescent
nanotubes (Fig. 1.4A). More significantly, the time-lapsed images
of the assembly identified an initial globular phase, fluid particle-
like aggregates of the mixed Rh17-22/A

β

(16-22) peptides, and
conclusively established that these intermediate disordered phases
serve as nucleation centers for the transition to crystalline phases
[67]. Propagation occurs in the solution, as the crystalline template
emerges from the disordered phase, documenting the dynamic
equilibrium that exists between the free peptide in the solution
and the particles (Fig. 1.4B). The phase behavior accessible to these
simple peptides is proving to be both diverse and acutely responsive
to many different physical and chemical conditional inputs. We
maintain that such dynamic diversity will be critical in realizing the
self-organizing behaviors, and transitioning to intelligent materials
for chemical evolution.

A

0 min

0 min 5 min 10 min 15 min 20 min 25 min

1 µ m

B

addition
of solution
monomers
to template

fluid-
crystalline
transition

crystalline
aggregates

solution
monomers

fluid
oligomers

Figure 1.4 ( ) Amyloid nucleation and propagation followed by

fluorescence microscopy in which Aβ(16-22)/Rhodamine17-
22 (0.6 mM/4 μM) aggregates were followed at early time
points to capture the self-assembly pathway. The elongating
amyloids were photobleached within the red square and the
growing end was followed as a function of time (adapted
from ref [67]). (

A

) Model of amyloid nucleation and
propagation in which peptides collapse into a fluid oligomer
that serves as amyloid nucleation sites. Propagation occurs
by addition of solution monomers (red) onto the ordered
β-sheet templates (blue).

B