7 research outputs found
Crystal growth of calcite mediated by ovalbumin and lysozyme: Atomic force microscopy study
Dissolution of the calcite (104) face under specific calcite-aspartic acid interaction as revealed by in situ atomic force microscopy
Dissolution of the Calcite (104) Face under Specific Calcite–Aspartic Acid Interaction As Revealed by in Situ Atomic Force Microscopy
In the presence of aspartic acid (Asp), the calcite (104)
face
shows distinct dissolution pit morphology, presumably resulting from
the surface reaction between calcite and Asp. However, the specific
nature of this interaction and the influence of solution hydrodynamics
remain unclear. To this end, we have followed the calcite (104) surface
dissolution using in situ fluid cell atomic force microscopy (AFM).
The results showed that at pH 4.5 and in 100 mM Asp the surface reactions
were controlled by diffusion under static conditions and that trapezoidal
etch pits were formed. In contrast, elliptical etch pits were rapidly
developed upon flowing due to the increased transfer of Asp to the
[010] step edge and the dissolution of Asp-surface complexes away
from the step edge. The occurrence of the [010], [461̀…], and
[4̀…11] steps of trapezoidal etch pits was attributed to the
stabilization of the (001), (1̀…12), and (01̀…1) faces by
Asp through bridging between the two carboxyl groups and two adjacent
Ca atoms, with the α-NH<sub>3</sub><sup>+</sup> group forming
a hydrogen bond with the oxygen of the H<sub>2</sub>O from the bulk
solution and the surface CO<sub>3</sub> groups from the (1̀…12)
and (01̀…1) faces. The mirror images of the etch pits formed
in d-Asp and l-Asp solutions resulted from the enantio-specific
interaction, supporting the tripodal contact of Asp with the crystal
surface. Thus, the etch pit morphology is affected by Asp concentration,
mass transfer, and specific surface reaction
Crystal Growth of Calcite Mediated by Ovalbumin and Lysozyme: Atomic Force Microscopy Study
Ovalbumin and lysozyme are two major
egg white proteins and putatively
related to the formation of the mammillary layer of eggshells. In
this work, we have investigated their influences on the morphology
and growth kinetics of hillocks at the molecular scale using fluid-cell
atomic force microscopy. Our studies identified two roles for ovalbumin,
favoring the formation of amorphous calcium carbonate–protein
clusters on terrace surface and accelerating the step growth kinetics
via reduction of the energy barrier for ion attachment to crystal
steps. The two effects are intimately linked to the inherent characteristics
of ovalbumin, i.e., being acidic and amphiphilic. In contrast, lysozyme
as a basic protein did not induce the formation of any moldable transient
phases. Instead, it interacted with step edges and pinned them, leading
to step bunching and even step advancement stop at higher concentrations.
These roles and their associated interactions on the molecular scale
are related to the macroscopic features of eggshells and provide a
reliable basis for further investigation into their influences in
more complex systems mimicking native biological environment