A more recent report from Bellezza et al.40 suggests that the
interaction of Mb with phosphate-grafted zirconia nanoparticles
induces significant rearrangements in the Mb structure, particularly
loss of the secondary structure (α-helices). The amount of bound Mb
implies a monolayer of adsorbed molecules. Atomic force microscopy
(AFM) measurements indicate that the interaction also affects the morphology of the bound protein, inducing the nucleation of
prefibrillar-like aggregates at pH 4.7, whose appearance and height
(2–4 nm) are consistent with the prefibrillar-like assemblies previously
seen for Mb40. It is well known that Mb can nucleate fibrillar structures
only under destabilizing conditions, where it is has at least a partially
unfolded conformation41. In this case, the authors state that the
prefibrillar-like aggregates are always observed next to the ZrO2–P
nanoparticles, suggesting that the prefibrillar-like structures develop
from the bound protein.