title: Experimental Determination of Zinc Isotope Fractionation in Complexes with the Phytosiderophore 2'-Deoxymugeneic Acid (DMA) and Its Structural Analogues, and Implications for Plant Uptake Mechanisms.
abstract: The stable isotope signatures of zinc and other metals are increasingly used to study plant and soil processes. Complexation with phytosiderophores is a key reaction and understanding the controls of isotope fractionation is central to such studies. Here, we investigated isotope fractionation during complexation of Zn2+with the phytosiderophore 2'-deoxymugeneic acid (DMA), and with three commercially available structural analogues of DMA: EDTA, TmDTA, and CyDTA. We used ion exchange chromatography to separate free and complexed zinc, and identified appropriate cation exchange resins for the individual systems. These were Chelex-100 for EDTA and CyDTA, Amberlite CG50 for TmDTA and Amberlite IR120 for DMA. With all the ligands we found preferential partitioning of isotopically heavy zinc in the complexed form, and the extent of fractionation was independent of the Zn:ligand ratio used, indicating isotopic equilibrium and that the results were not significantly affected by artifacts during separation. The fractionations (in ‰) were +0.33 ± 0.07 (1σ, n = 3), + 0.45 ± 0.02 (1σ, n = 2), + 0.62 ± 0.05 (1σ, n = 3) and +0.30 ± 0.07 (1σ, n = 4) for EDTA, TmDTA, CyDTA, and DMA, respectively. Despite the similarity in Zn-coordinating donor groups, the fractionation factors are significantly different and extent of fractionation seems proportional to the complexation stability constant. The extent of fractionation with DMA agreed with observed fractionations in zinc uptake by paddy rice in field experiments, supporting the possible involvement of DMA in zinc uptake by rice.
authors.affiliation: Department of Earth Science and Engineering, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Tamara
authors.initials: T
authors.lastname: Marković
authors.affiliation: Department of Earth Science and Engineering, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Saba
authors.initials: S
authors.lastname: Manzoor
authors.affiliation: Core Research Laboratory, Natural History Museum London, SW7 5BD, London, United Kingdom.
authors.forename: Emma
authors.initials: E
authors.lastname: Humphreys-Williams
authors.affiliation: School of Water, Energy & Environment, Cranfield University , Cranfield, Bedford MK43 0AL, United Kingdom.
authors.forename: Guy Jd
authors.initials: GJ
authors.lastname: Kirk
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Ramon
authors.initials: R
authors.lastname: Vilar
authors.affiliation: Department of Earth Science and Engineering, Imperial College London , London SW7 2AZ, United Kingdom.|Stanford School for Earth, Energy and Environmental Sciences, Stanford University , Stanford California 94305, United States.
authors.forename: Dominik J
authors.initials: DJ
authors.lastname: Weiss
mesh_terms: D005591:Chemical Fractionation; D007554:Isotopes; D012987:Soil; D015032:Zinc / Q000737:chemistry*; D015033:Zinc Isotopes / Q000737:chemistry*
chemical_list: D007554:Isotopes; D012987:Soil; D015033:Zinc Isotopes; D015032:Zinc