1 research outputs found
Tuning Chelation by the Surfactant-Like Peptide A<sub>6</sub>H Using Predetermined pH Values
We examine the self-assembly of a
peptide A<sub>6</sub>H comprising
a hexa-alanine sequence A<sub>6</sub> with a histidine (H) “head
group”, which chelates Zn<sup>2+</sup> cations. We study the
self-assembly of A<sub>6</sub>H and binding of Zn<sup>2+</sup> ions
in ZnCl<sub>2</sub> solutions, under acidic and neutral conditions.
A<sub>6</sub>H self-assembles into nanotapes held together by a β-sheet
structure in acidic aqueous solutions. By dissolving A<sub>6</sub>H in acidic ZnCl<sub>2</sub> solutions, the carbonyl oxygen atoms
in A<sub>6</sub>H chelate the Zn<sup>2+</sup> ions and allow for β-sheet
formation at lower concentrations, consequently reducing the onset
concentration for nanotape formation. A<sub>6</sub>H mixed with water
or ZnCl<sub>2</sub> solutions under neutral conditions produces short
sheets or pseudocrystalline tapes, respectively. The imidazole ring
of A<sub>6</sub>H chelates Zn<sup>2+</sup> ions in neutral solutions.
The internal structure of nanosheets and pseudocrystalline sheets
in neutral solutions is similar to the internal structure of A<sub>6</sub>H nanotapes in acidic solutions. Our results show that it
is possible to induce dramatic changes in the self-assembly and chelation
sites of A<sub>6</sub>H by changing the pH of the solution. However,
it is likely that the amphiphilic nature of A<sub>6</sub>H determines
the internal structure of the self-assembled aggregates independent
from changes in chelation