Biomedical Engineering Reference
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etc., and mixed modules. This classification is based on the hydrophilic surface
of the molecules that have alternating + and − charged amino acid residues,
either alternating by 1, 2, 3, 4 and so on. For example, charge arrangements for
the different modules are as follows: module I, − + − + − + − +; module II,
− − + + − − + +; module III, − − − + + +; and module IV, − − − − + + + +. The
charge orientation can also be designed in reverse orientations that yield entirely
different molecules with distinct molecular behaviors. These well-defined
sequences allow them to undergo ordered self-assembly, resembling some
situations found in well-studied polymer assemblies
[3, 4]
.
3. Dynamic Behavior of the Peptide Re-assemblies
The self-assembly process is reversible and dynamic since these peptides are
short and simple
[5]
, thus numerous individual peptides can be readily self-
organized through weak interactions that include hydrogen bonds, ionic bonds,
hydrophobic and
van der Waals
interactions, as well as water-mediated
hydrogen-bond formation. These nanofibers can be broken mechanically with
sonication. However, they can undergo dynamic re-assembly repeatedly, which
Fig. 3. AFM images of RADA16-I nanofiber at various time points before sonication (
A
) and after
sonication (
B-F
). Sample time points, 2 min (
B
), 30 min (
C
), 2h (
D
), 4h (
E
) and 24h (
F
), were
taken after sonication. Note the elongation and reassembly of the peptide nanofibers over time.
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