New aspects of the photodegradation of iron(III) citrate: spectroscopic studies and plant-related factors

Abstract

Iron (Fe) is an essential cofactor for all livings. Although Fe membrane transport mechanisms often utilize FeII, uncoordinated or deliberated ferrous ions can initiate Fenton reactions. FeIII citrate complexes are among the most important complexed forms of FeIII especially in plants that, indeed, can undergo photoreduction. Since leaves as photosynthetic organs of higher plants are generally exposed to illumination in daytime, photoreaction of ferric species may have biological relevance in iron metabolism, the relevance of which is poorly understood. In present work FeIII citrate transformation during the photodegradation in solution and after foliar application on leaves was studied by Mössbauer analysis directly. To obtain irradiation time dependence of the speciation of iron in solutions, four model solutions of different pH values (1.5, 3.3, 5.5, and 7.0) with Fe to citrate molar ratio 1:1.1 were exposed to light. Highly acidic conditions led to a complete reduction of Fe together with the formation of FeII citrate and hexaaqua complexes in equal concentration. At higher pH, the only product of the photodegradation was FeII citrate, which was later reoxidized and polymerized, resulting in the formation of polynuclear stable ferric compound. To test biological relevance, leaves of cabbage were treated with FeIII citrate solution. X-ray fluorescence imaging indicated the accumulation of Fe in the treated leaf parts. Mössbauer analysis revealed the presence of several ferric species incorporated into the biological structure. The Fe speciation observed should be considered in biological systems where FeIII citrate has a ubiquitous role in Fe acquisition and homeostasis. Graphical abstract

Mechanism of Reduction of Aqueous U(V)-dpaea and Solid-Phase U(VI)-dpaea Complexes: The Role of Multiheme c-Type Cytochromes

“…The experimental procedures for ferrihydrite synthesis and cell incubations with both Fe substrates are described in Texts S5 and S6, respectively. In both experiments, a high Fe(II) starting concentration was measured, an observation we attribute to Fe(III) photoreduction 37 in the HCl-digested samples when stored unprotected from light. In the presence of Fe(III)-citrate, we observed rapid Fe(III) reduction in the incubations with the WT strain, with the reaction complete within 2 h ( Figure S1 A).…”

Alginate/xanthan gum hydrogels as forensic blood substitutes for bloodstain formation and analysis

“…Ferric citrate was desired due to its oxidative properties and resemblance to the colour changes in blood relating to the aging process ex vivo . 47,48 In addition, Tween 20 was incorporated into the materials to lower the surface tension to the relevant human range without affecting the viscosity 49,50 and improve spreading on surfaces. 34…”

“…This journal is © The Royal Society of Chemistry 2023 aging process ex vivo. 47,48 In addition, Tween 20 was incorporated into the materials to lower the surface tension to the relevant human range without affecting the viscosity 49,50 and improve spreading on surfaces. 34 Compared to the base material of alginate, XG, Allura Red, and CaCl 2 (AX5C2), the addition of a small amount of talc had little influence on the viscosity profile but did appear to lower the viscosity at high shear rates (Fig.…”

MCO1 and MCO3, two putative ascorbate oxidases with ferroxidase activity, new candidates for the regulation of apoplastic iron excess in Arabidopsis

“…Second, the exposure to light is prone to generate Fe 2+ by photoreduction. Indeed, photons have been shown to catalyze the reduction of Fe, both in vitro and in vivo in leaves (Bienfait & Scheffers, 1992; Gracheva et al, 2022). On the basis of these elements, it could be expected that mesophyll cells would require an efficient system to maintain a strict balance between Fe 2+ and Fe 3+ , through the action of apoplastic ferroxidases, to counteract the reducing effects of ascorbate and photons.…”