Biomedical Engineering Reference
In-Depth Information
Fig. 2.20
Outlines of ice pyramidal faces (
h
0
l
) encountered in a broad range of pyramid-shaped
ice crystallites under the influence of (mostly) fish AFPs (absolute size is not to scale). [The
ice pyramid face labeled (101) resembles those triggered by the insect TmAFP.] Reprinted with
permission from ref. [
44
]. Copyright (2005) American Chemical Society
aspects. In the work of ref. [
90
], the addition of divalent ions changes the ice binding
surface of the AFP so radically as to transform the crystal shape from secondary to
primary facets and vice versa. Moreover, the report on the action of dimer, trimer,
and tetramer of type III AFP on ice crystals [
91
] states that each multimer “changes
the morphology of a single ice crystal into a unique shape that is similar but not
identical to the ordinary hexagonal bipyramid.” The ice binding surface of type
III AFP belongs to the irregular globular ice binding surface type. A significant
change in the ice binding surface was noted to cause a radical conversion between
pyramidal (Fig. 2.2a of ref. [
91
]) and prismatic (Fig. 2.2c of ref. [
91
]) forms, leading
to a strong, direct correlation between ice binding surface structure and morphology.
It has long been recognized in the literature [
5
] that the insect AFP's capacity to
suppress freezing is because of its capacity to grip firmly on the ice lattice via its
2D periodic binding intervals attuned to the ice lattice constants. Take the primary
prism (100) (cf. Fig.
2.21
) as an example, the spruce budworm AFP producing the
hexagonal disk type [
92
] morphology (Fig.
2.21
b) has regular binding intervals in
two directions equal to
4.5 and 7.5 A, matching the periods of the strong bonding
