Ferritin analogs

DETAILED DESCRIPTION Despite the fact that ferritin is extremely selective in accumulating, storing and dispensing iron in living things, I have discovered that the forgoing objectives can be realized by inserting any of a variety of compositions into apoferritin at unexpectedly high purity and concentration to provide ferritin analogs.
Such ferritin analogs comprise a core which is substantially devoid of ferrihydrite, the natural core of ferritin.
For some applications the protein shell of the ferritin analog serves as an advantageous encapsulant for the core material, e.
g.
an organic or inorganic spherule, concentrated solution or other material.
For other applications it may be desirable to remove the protein shell from the ferritin analog to recover the core material as a spherule.
I have discovered that the protein shell can be advantageously removed, e.
g.
by partial or complete pyrolysis in the case of inorganic spherules or by subjecting the ferritin analog to an environment which causes disassembly of the protein shell, e.
g.
low or high pH.
Partial pyrolysis can provide carbon-coated spherules useful, e.
g.
for ceramic applications.
Such spherules have a substantially monomodal, nominal diameter typically in the range of about 4.
5-9 nanometers (45 to 90 Angstroms); such monomodal spherules can be advantageously grown substantially monomodally to even larger spherules or agglomerates of spherules, e.
g.
up to about 20 nanometers (200 Angstroms) or larger, say about 300 nanometers (3000 Angstroms).
I have also surprisingly discovered that monolithic articles prepared from inorganic spherules have unique properties, e.
g.
ceramics can be prepared at substantially lower sintering temperature, with substantially uniform shrinkage and with smaller surface flaws.