First-principles electronic structure study of rhizoferrin and its Fe(III) complexes
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First-principles electronic structure study of rhizoferrin and its Fe(III) complexes Archana Dubey • Olle Heinonen
Received: 8 August 2013 / Accepted: 14 September 2013 / Published online: 25 September 2013 Ó Springer Science+Business Media New York 2013
Abstract We have determined the structure and coordination chemistry of rhizoferrin (Rf), which is a particular type of siderophore, and its Fe(III) complexes using density functional theory calculations. Our results show that the Fe(III) ion binds in an octahedral coordination, with a low-spin (S = 1/2) charge-neutral chiral complex having the largest binding energy of the investigated complexes. We have also calculated nuclear magnetic resonance parameters, such as chemical shifts for 1H and 13C, and indirect nuclear spin–spin couplings for 1H–1H and 13C–1H in free Rf and in a low-spin neutral Rf metal complex, as well as nuclear quadrupole interaction parameters, such as asymmetry parameter and nuclear quadrupole coupling constants for 14N. Our calculated values for the chemical shifts for free Rf are
Electronic supplementary material The online version of this article (doi:10.1007/s10534-013-9677-4) contains supplementary material, which is available to authorized users. A. Dubey Department of Physics and Astronomy, University of Central Florida, Orlando, FL, USA O. Heinonen (&) Materials Science Division, Argonne National Laboratory, Chicago, IL, USA e-mail: [email protected] O. Heinonen Department of Physics and Astronomy, Northwestern University, Chicago, IL, USA
in excellent agreement with experimental data while the calculated NMR parameters for Fe(III) complexes are predictions for future experimental work. Keywords transport
Rhizoferrin Siderophore Iron
Introduction Siderophores are low-molecular-weight (500–1,500 Da) iron chelators (Hilder and Kong 2009) produced by bacteria and fungi to absorb Fe(III) ions under low-iron stress conditions (Neilands 1995). Chelation is the process by which a metallic ion is sequestered and bound to a molecule. An important and perhaps familiar chelation process is the one by which iron is sequestered, bound, transported, and subsequently released by hemoglobin in vertebrates. Iron chelation, as well more general types of chelation in which other metal ions are bound, transported, and delivered, is of great interest for drug delivery and chemotherapy (Mo¨llmann et al. 2009; Rivault et al. 2007; Han et al. 2010; Heinisch et al. 2003; Roosenberg et al. 2000; Liu et al. 2010; Esteves et al. 1995). For example, siderophores have found applications in medicine to remove excesses of iron accumulated at toxic levels during supportive therapy. The ironbinding functional groups of siderophores have also been introduced into the structure of common antibiotics to enhance their potency; they are also associated with the virulence of microbial pathogens infecting plants and
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Biometals (2013) 26:1003–1012
Fig. 1 Structure of free Rf. Carbon atoms are colored gray, oxygen red, nitrogen blue, and hydrogen white. The
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