Iron Interactions

Let us first consider data from [2Fe2S] clusters. The experimental values (isotropic couplings) obtained from plant-type and vertebrate ferredoxins yield about 48.2 MHz for the Fe(III) ion and 22.1 MHz for the Fe(II) ion (tabulated in. [35]). Since for both ions the value is much larger than the nuclear Zeeman 

In the group of molybdopterin hydroxylases, there is the complication in terms of spectral overlap of two different [2Fe2S] clusters, FeSI and FeSII, which was already discussed for the proton interactions above. The main question involved with the study of Fe interactions is whether the two sites can be distinguished, i.e.. 

REINHARD KAPPL, GERHARD BRACIC, AND JURGEN HUTTERMANN 

Proton and Fe hyperfme interactions give insight into the spin density (sometimes denoted spin population) and its distribution, in the present context, over the iron ions and other nuelei of iron sulfur clusters. For protons, the dipolar part of the tensor is direetly eonneeted, apart from distanee to the spin center (iron) in the straeture, with the spin density at the center in the point-dipole approximation. This type of spin density is therefore not assoeiated with any iron orbital. The iso-tropie part that we have eonsidered only for the eysteine P-protons is connected with the 2 i-orbital spin density on the sulfur and the dihedral angle as typical P-protons [40]. The latter spin density is usually not more than about 3-5%. The Fe hyperfine interaetion is also associated with the iron spin density, and there have been several approaehes to its description. 

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G. C. Elliott and A. Liiuchli, Phosphorus efficiency and phosphate-iron interaction in maize. Agron J. 77 399 (1985). 

Phosphine ligands based on the ferrocene backbone are very efficient in many palladium-catalyzed reactions, e.g., cross-coupling reactions,248 Heck reaction,249 amination reaction,250 and enantioselective synthesis.251 A particularly interesting example of an unusual coordination mode of the l,l -bis(diphenylphosphino)ferrocene (dppf) ligand has been reported. Dicationic palladium(II) complexes, such as [(dppf)Pd(PPh3)]2+[BF4 ]2, were shown to contain a palladium-iron bond.252,253 Palladium-iron bonds occur also in monocationic methyl and acylpalladium(II) complexes.254 A palladium-iron interaction is favored by bulky alkyl substituents on phosphorus and a lower electron density at palladium. 

Pollitt E Univ of California, Administration, Davis, CA The effects of lead and iron interaction on behavioral development the effects of iron treatment on iron status, blood lead level, and behavioral development in children with elevated lead levels and iron deficiency U. S. Department of Agriculture, Competitive Research... 

Ceruloplasmin is a protein for which many functions have been proposed - somewhat akin to Pirandello s Six Characters in Search of an Author, ceruloplasmin has long been a protein in search of a function. However, its importance in iron metabolism has been underlined by the observation of systemic iron loading in the tissues of patients with aceruloplasminaemia and other mutations in the ceruloplasmin gene. For further information on copper and iron interactions, see Chapter 12. 

To explain how H+ transfer occurred across the membrane Mitchell suggested the protons were translocated by redox loops with different reducing equivalents in their two arms. The first loop would be associated with flavoprotein/non-heme iron interaction and the second, more controversially, with CoQ. Redox loops required an ordered arrangement of the components of the electron transport system across the inner mitochondrial membrane, which was substantiated from immunochemical studies with submitochondrial particles. Cytochrome c, for example, was located at the intermembranal face of the inner membrane and cytochrome oxidase was transmembranal. The alternative to redox loops, proton pumping, is now known to be a property of cytochrome oxidase. 

Waite, T. D., and F. M. M. Morel. 1984b. Ligand exchange and fluorescence quenching studies of the fulvic acid-iron interaction. Analytica Chemica Acta 162 263-274. 

It is well known that starch-iron complexes are suitable for fortifying bread and flour with iron. The state of iron in flour, dough, and bread was investigated by Leichter and Joslyn.643 Iron salts influence the whiteness of sweet-potato starch, but this effect is variable.644 It was also reported645 that colloidal iron interacts with starch, a process which is used to fractionate starch into three portions The first portion (80% of the total amount) is formed by colloidal iron itself, the second (9% of the total) is formed by iron and electrolytes, and the third portion (11% of the total) is not precipitated at all. 

Powers HJ (1995) Riboflavin-iron interactions with particular emphasis on the gastrointestinal tract. Proceedings of the Nutrition Society 54, 509-17. 

Keys, J. D., J. L. Horwood, T. M. Baleshta, L. J. Cabri, and D. C. Harris (1968). Iron-iron interaction in iron-containing zinc sulfide. Canad. Mineral. 9, 453-67. 

A dimeric dilithioferrocene compound 70 (95) involves terminally bonded lithium atoms analogous to structures 1-4 (type II, A) and bridging lithium atoms analogous to compounds 7-9 (type n, B structures the bridging lithium atoms are not solvent coordinated, however). Lithium-lithium as well as lithium-iron interactions may be important in the structure of this complex. 

Iron interactions with N sources are not limited to phytoplankton. Kirchman et al. (2003) found that the growth rate, respiratory electron transport system activity, and growth efficiency of a marine gamma proteobacterium (Vibrio hatveyi) were much lower in Fe-limited cultures grown with NOs" than when NH4+ or amino acids were suppHed as N sources. They suggested that these results may help to explain why natural bacterial communities in nitrate-rich, iron-poor HNLC areas also typically exhibit reduced growth rates and efficiencies. 

Mechanistic Aspects of the Ascorbic Acid—Iron Interaction in the Intestine. Studies of the mechanism of the interaction of ascorbic acid and iron at the molecular and cellular levels have yielded a variety of theories. An acidic pH in the lumen of the intestine favors the absorption... 

The 2,3-diethyl-1,4-dihydro-1,4-dimethyl-1,4-diboranaphthalene (2) (38) reacts with (CO)1Fe(C8H14)2 to give the orange anti-dinuclear complex 15 and the cherry-red syn-complex 16 (39). Its formation occurs via the mononuclear complex (2)Fe(CO)3, which is attacked by the second Fe(CO)3 moiety at the diene of the tj2-complexed benzo-ring. Obviously the anti-complex 15 (43%) is favored over the syn-product 16 (14%). In 16 a weak iron-iron interaction (2.98 A) is present. On the basis of the 18 VE... 

Hamilton DL, Bellamy JEC, Valberg JD, et al. 1978. Zinc, cadmium, and iron interactions during intestinal absorption in iron-deficient mice. Can J Physiol Pharmacol 56 384-389. 

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