From Kuru to Nucleation, Aggregation, Polymerization and Crystallization in Biology and Medicine - Molecules: Nucleation, Aggregation and Crystallization - page 3

Osmium shading in electron microscopy reveals details
of molecular structure at nanometric distances
There is no contribution from carbon atoms to the image of an osmium
or platinum shaded freeze-fracture electron microscopy photograph of
individual molecules.
Mineral nucleants for crystal growth in outer space
McPherson and Shlichta (1988) sent a series of proteins into outer space
to avoid the convection of fluids by the gravity of the Earth. They nucle-
ated them with a selection of ground minerals. A subset of minerals usu-
ally initiated crystal formation in one or another of the proteins, a different
set for each protein and differing forms of epitactic crystal growth for a
given protein with each mineral.
What makes a diamond hold together?
Two polished ancient Chinese copper mirrors applied face-to-face stick
together and require considerable force to separate them. A stack of newly
opened clean microscopic cover slips slide one upon the other, yet it
requires considerable force to separate them.
A diamond, the hardest of minerals, can scratch steel, yet it is still
only made of carbon, the same as carbon black, coal or graphite.
Sulfur may be pure yet malleable, ductile, fragile or clay-like and of
many colors depending how the S atoms are packed. Such is the nature of
the van der Waals' forces that are brought into play at atomic distances.
Twinning of minerals
There are at least 200 twinning possibilities for quartz (SiO 2 ). Most pos-
sible forms have been found in the over 30 000 years of searching for
them. When one new twin “form,” “strain” or “species” is found, it is usu-
ally named for the region where it has been found. It is common to find