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A B S T R A C THydrolysis of ferric solutions leads initially to mono-and dinuclear species which interact to produce further species of higher nuclearity. These polynuclear species age eventually to either crystalline compounds or to an amorphous precipitate (amorphous iron(l1 I ) hydroxide hydrate).Amorphous iron(lI1) hydroxide hydrate is thermodynamically unstable and gradually transforms to a-FeO(0H) and a-Fe203. These crystalline products form by competing mechanisms and the proportion of each in the final product depends on the relative rates of formation. The master variable governing the rates at which these compounds form is pH. Other important factors are temperature and the presence of additives.Most additives retard the transformation and by suppressing formation of a-FeO(0H) lead to an increase in the amount of a-Fe,03 in the product; some additives also directly promote formation of the latter compound. Metal ions can o f e n replace a proportion of Fe in the a-FeO(0H) and a-Fe,O, lattices. At high enough concentrations they can induce formation of additional phases. Additives may also modify the morphology of the crystalline products.

The reductive mobilisation of iron from ferritin, the principal protein of iron storage, was studied. The kinetic characteristics of iron release by dithionite, thioglycollate, and dihydroriboflavin 5'-phosphate (FMNH,) were found to differ widely. The dependence on pH is most pronounced for the dithionite reduction which proceeds 100 times faster at pH 4 than at pH 7. The experimental data can be consistently explained in terms of specific interactions of products or educts with interfacial iron(II1) hydroxide of the ferritin core. Surface complexes with the product sulfite are postulated in the dithionite reaction, and with the educt in the thioglycollate reaction. Iron(I1) complexes with the radical anion FMN' are suggested to be involved in the iron release by FMNH?. The mobilisation of iron by a series of thiols of different size and coordinative properties confirmed the importance of surface complex formation. N o evidence was found for predominant effects of hindered shell penetration.Ferritin, as an iron storage protein, is a key molecule in iron metabolism. It maintains iron in a form from which it can easily be mobilised as and where it is required. Although the amino acid sequences of many ferritins are known [ I -51 and the three-dimensional structure of horse spleen ferritin has bccn solved at 0.28-nm resolution [6], the mechanisms of ferritin iron deposition and mobilisation are not yet really understood.

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1,3,5-Trideoxy-l,3,5-tris(dimethylamino)-cis-inositol (TDCI) and 1,3,5-trideoxy-l,3,5-tris(trimethylammonio)-cis-inositol (TTCI) were prepared by methylation of 1,3,5-triamino-l,3,5-trideoxy-cis-inositol (TACI). The ability of TDCI to form both intermolecular and intramolecular H-bonds, as demonstrated by X-ray diffraction, is probably responsible for the good solubility of TDCI in almost every common solvent. TTCI was found to be a polyol of unusual high acidity (pK, = 8.14 f 0.02, pK2 = 13.0 i 0.2). This phenomenon could be explained by electrostatic interactions between the charged substituents of the cyclohexane residue.Introduction. -Aliphatic and alicyclic polyhydroxy compounds are wide spread in nature and have, therefore, been extensively investigated. They are generally considered to be highly hydrophilic and insoluble in non-polar solvents. The acidity of the OH groups is usally only slightly enhanced, compared to aliphatic monohydroxy compounds or H20, and interactions with metal ions are known to be weak or even negligible. Metal-complex formation of sugars and cyclitols was investigated by Angyal [l]. He found that cis-inositol has some enhanced affinity to metal ions due to the unique configuration with three axial OH groups on the same side of the molecule in either of its two chair conformations. A similar conformation of either three OH or three NH, groups is found in 1,3,5-triamino-l,3,5-trideoxy-cis-inositol (TACI), and metal binding is possible by the OH or the NH, groups, depending on the nature of the metal. Developing new chelating agents for Fe(III), we found that TACI has a very high affinity for this cation. The complexes decay, however, probably due to the oxidation of the NH, groups catalyzed by Fe(II1). Using the two methylated derivatives, 1,3,5-trideoxy-l,3,5-tris-(dimethylamino)-cis-inositol (TDCI) and 1,3,5-trideoxy-1,3,5-tris(trimethylammonio)-cis-inositol (TTCI), this oxidation could be prevented, and very stable complexes of Fe(II1) could be observed. The more bulky dimethylamino and trimethylammonio groups also stabilize the conformation of three axial OH groups, as required for the coordination with Fe(II1). Both, TDCI and TTCI are unusual polyalcohols with regard to the qualities mentioned above. We report here the syntheses, structure, and some remarkable properties of these two new ligands. The equilibrium data of the metal complexes will be published separately.

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