Fluoride nanoparticles
(NPs) are materials utilized in the biomedical
field for applications including imaging of the brain. Their interactions
with biological systems and molecules are being investigated, but
the mechanism underlying these interactions remains unclear. We focused
on possible changes in the secondary structure and aggregation state
of proteins on the surface of NPs and investigated the principle underlying
the changes using the amyloid β peptide (Aβ
16–20
) based on infrared spectrometry. CeF
3
NPs (diameter 80
nm) were synthesized via thermal decomposition. Infrared spectrometry
showed that the presence of CeF
3
NPs promotes the formation
of the β-sheet structure of Aβ
16–20
.
This phenomenon was attributed to the hydrophobic interaction between
NPs and Aβ peptides in aqueous environments, which causes the
Aβ peptides to approach each other on the NP surface and form
ordered hydrogen bonds. Because of the coexisting salts on the secondary
structure and assembly of Aβ peptides, the formation of the
β-sheet structure of Aβ peptides on the NP surface was
suppressed in the presence of NH
4
+
and NO
3
–
ions, suggesting the possibility that
Aβ peptides were adsorbed and bound to the NP surface. The formation
of the β-sheet structure of Aβ peptides was promoted in
the presence of NH
4
+
, whereas it was suppressed
in the presence of NO
3
–
because of the
electrostatic interaction between the lysine residue of the Aβ
peptide and the ions. Our findings will contribute to comparative
studies on the effect of different NPs with different physicochemical
properties on the molecular state of proteins.
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