Patricia C. Wilkins

The coordination chemistry of the binuclear iron site in hemerythrin

A. Introduction 195 B. Methemerythrin 197 (i) The Fe(III)Fe(III) site 197 (ii) The reactions 198 (a) Anations 198 (b) Reductions. 199 C. Deoxyhemerythrin 201 (i) The Fe(II)Fe(II)site 201 (ii) The reactions 202 (a) With oxygen. 202 (b) Oxidations 203 (c) Ligand interactions 204 D Semi-methemerythrin 205 (i) The Fe(II)Fe(III)site 205 (ii) The reactions 206 (a) Anations 206 (b) Redox reactions 207 E. Conformationally controlled reactions 208 F. The last ten years 209 Acknowledgements 211 References 211

Vanadium(IV) and vanadium(V) complexes of dipicolinic acid and derivatives. Synthesis, X-ray structure, solution state properties: and effects in rats with STZ-induced diabetes

Abstract Preparation and characterization of new vanadium compounds with insulin mimetic properties is important for investigations into the mechanism of action of these complexes. In this work, we report the synthesis of three new compounds related to the (dipicolinato)dioxovanadium(V) complex: (4-hydroxy-2,6-pyridinedicarboxylato)dioxovanadium(V), (diaqua)(4-hydroxy-2,6-pyridinedicarboxylato)oxovanadium(IV) and (4-amino-2,6-pyridinedicarboxylato)dioxovanadium(V), and present the first preliminary kinetic study of a vanadium dipicolinate system. One of these complexes, (4-hydroxy-2,6-pyridinedicarboxylato)oxovanadium(V), is investigated in greater detail with regard to chemistry, structure, kinetics and insulin-like properties in rats with streptozotocin-induced diabetes. Oral administration of [VO 2 (dipic-OH)] − was found to be effective in lowering both the hyperglycemia and hyperlipidemia of diabetes. This is the first report of the effective lowering of diabetic hyperlipidemia by a vanadium(V) coordination complex.

Switching Off Electron Transfer Reactions in Confined Media: Reduction of [Co(dipic)2]− and [Co(edta)]− by Hexacyanoferrate(II)

The kinetics of reduction of two cobalt(III) complexes with similar redox potentials by hexacyanoferrate(II) were investigated in water and in reverse micelle (RM) microemulsions. The RMs were composed of water, surfactant [(sodium(bis(2-ethylhexylsulfosuccinate)), NaAOT], and isooctane. Compared to the reaction in water, the reduction rates of (ethylenediaminetetraacetato)cobaltate(III) by hexacyanoferrate(II) were dramatically suppressed in RM microemulsions whereas a slight rate increase was observed for reduction of bis-(2,6-dipicolinato)cobaltate(III). For example, the ferrocyanide reduction of [Co(dipic)(2)](-) increased from 55 M(-1) s(-1)in aqueous media to 85 M(-1) s(-1) in a w(o) = 20 RM. The one-dimensional (1-D) and two-dimensional (2-D) (1)H NMR and FT-IR studies are consistent with the reduction rate constants of these two complexes being affected by their location within the RM. Since reduction of [Co(edta)](-) is switched off, in contrast to [Co(dipic)(2)](-), these observations are attributed to the penetration of the [Co(edta)](-) into the interfacial region of the RM whereas [Co(dipic)(2)](-) is in a region highly accessible to the water pool and thus hexacyanoferrate(II). These results demonstrated that compartmentalization completely turns off a redox reaction in a dynamic microemulsion system by either reactant separation or alteration of the redox potentials of the reactants.

Acid-assisted anion interaction with deoxyhemerythrin.

The interaction of N3-, CNO- and F- with deoxyhemerythrin was monitored from pH 6 to 9 and 3 degrees C to 25 degrees C at an ionic strength 0.5 M (Na2SO4) by using competition with O2. A proton is involved in forming the adduct and is not lost from the protein even at pH values as high as 9. Thermodynamic and kinetic parameters for the interaction of each anion are obtained. It is considered that the proton is introduced as the acid HX and the corresponding parameters for the reaction of HX with deoxyhemerythrin are calculated. These are compared with those for the O2 reaction with deoxyhemerythrin. The adducts are remarkably inert and have dissociation half-lives ranging from 7 s (N3-) to 70 s (CNO- and F-) at 25 degrees C. This stability is ascribed to protonation of a bridged hydroxy group or even bridge-breakage.

The role of calcium and comparable cations in animal behaviour.

The Ions Biological Roles Moving Ions Through Membranes Intracellular Signalling Intercellular Signalling Muscle Senses Biomineralization Subject Index.