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13 Pags.- 1 Tabl.- 7 Figs., Main conclusion Fe uptake machinery of chloroplasts prefers to utilise Fe(III)–citrate over Fe–nicotianamine complexes., Iron uptake in chloroplasts is a process of prime importance. Although a few members of their iron transport machinery were identifed, the substrate preference of the system is still unknown. Intact chloroplasts of oilseed rape (Brassica napus) were purifed and subjected to iron uptake studies using natural and artifcial iron complexes. Fe–nicotianamine (NA) complexes were characterised by 5 K, 5 T Mössbauer spectrometry. Expression of components of the chloroplast Fe uptake machinery was also studied. Fe(III)–NA contained a minor paramagnetic Fe(II) component (ca. 9%), a paramagnetic Fe(III) component exhibiting dimeric or oligomeric structure (ca. 20%), and a Fe(III) complex, likely being a monomeric structure, which undergoes slow electronic relaxation at 5 K (ca. 61%). Fe(II)–NA contained more than one similar chemical Fe(II) environment with no sign of Fe(III) components. Chloroplasts preferred Fe(III)–citrate compared to Fe(III)–NA and Fe(II)–NA, but also to Fe(III)–EDTA and Fe(III)–o,o′EDDHA, and the Km value was lower for Fe(III)-citrate than for the Fe–NA complexes. Only the uptake of Fe(III)–citrate was light-dependent. Regarding the components of the chloroplast Fe uptake system, only genes of the reduction-based Fe uptake system showed high expression. Chloroplasts more efectively utilize Fe(III)–citrate, but hardly Fe–NA complexes in Fe uptake., This work was supported by the grants fnanced by the National Research, Development and Innovation Ofce, Hungary (NKFIH PD-112047, PD-111979 and K-124159), VEKOP2.3.3-15-2016-00008 and the Spanish Ministry of Economy and Competitiveness (MINECO; project AGL2016-75226-R, co-fnanced with FEDER). Á.S. was also supported by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences (BO/00207/15/4). The authors (JP, LM, and RZ) gratefully acknowledge the fnancial support provided by the project LO1305 of the Ministry of Education, Youth and Sports of the Czech Republic.

A simple visual method for determining the total iron in human serum is proposed based on color development in the nanospace of mesoporous silica MCM-41 and a chromogenic ligand bathophenathroline disulfonate (BPS). Observing the color intensity of a complex between iron(II) and BPS devloped on the MCM-41 material by the naked eye enabled us to quntify iron(II) with a detection limit of 0.5 μM. The BPS-loaded MCM-41 was successfully applied for quantifying the total iron in human serum.

International audience; Fluorescent detection of proteins is a popular method of detection allying sensitivity, linearity and compatibility with mass spectrometry. Among the numerous methods described in the literature, staining with ruthenium II tris(bathophenanthroline disulfonate) is particularly cost-effective, but slightly cumbersome owing to difficulties in the preparation of the complex and complexity of staining protocols. We describe here the modifications on both aspects that allow to perform a higher contrast staining and offer a more robust method of complex preparation, thereby maximizing the advantages of the method.

In order to clarify the mechanism of growth of musty-odor producing cyanobacteria, the effect of seven chelating agentssuch as EDTA (Ethylenediaminetetraacetic acid), CyDTA (Trans-1, 2-cyclohexanediamine-N, N, N′, N′-tetraacetic acid), DTPA (Diethylenetriamine-N, N, N′, N″, N″-pentaacetic acid), EDDHA {Ethylenediaminedi (o-hydroxyphenylacetic acid) }, HBED {N, N′-di (2-hydroxylbenzyl) -ethylenediamine-N, N′-diacetic acid}, DESF (Desferrioxamine B), BPDS (Bathophenanthroline disulfonate) on the growth ofPhormidium tenuewere studied using laboratory cultures.P.tenuegrew well in the pfesence of 1: 1 chelates (molar ratio of chelator to Fe) of CyDTA, DTPA, EDDHA and HBED as wellas EDTA as the iron sources.P. tenuegrew well in the presenceof CyDTA up to 17-fold for Fe (molar ratio) . However, the growth ofP.tenuewas suppressed in the presence of DTPA of 7-fold, EDDHA of 3-fold and HBED of 3-fold for Fe (molar ratio), respectively.P.tenuealso could utilize FeII (BPDS) 3chelate as the iron source. In addition, it could utilize FeII (BPDS) 3in the presence of HBED. However, it could not utilize FeII (BPDS) 3in the presence of DTPA, DESF or EDDHA.The present results indicate thatP.tenuecan utilize a wide variety of iron chelates as the iron sources and has a stronger ability of chelating functions on the cell surfaces compared withO.tenuisandA. macrospora. However, the addition of excess of chelating agents (DTPA, DESF, EDDHA and HBED) having higher stability constants of Fe (III) chelates affected the growth ofP.tenue. Furthermore, the results show that the absorption of iron byP.tenuedoes not only depend on the stability constants of Fe chelates and that it also depends on the chemical structure or characteristics of chelators.

In order to clarify the mechanism of growth of a musty-odor producing cyanobacterium Oscillatoria brevis isolated in Norway, the effects of iron forms on the growth and geosmin production of O.brevis were studied using laboratory cultures.O.brevis grew well and produced geosmin in the EDTA-free CT medium as well as in the presence of EDTA.Thus, O.brevis showed an ability to utilize colloidal iron and even iron oxides for its growth. This suggests that O.brevis would be expected to produce a specific high affinity iron chelator (siderophore) in the chelator-free medium.In the presence of bathophenanthroline disulfonate (BPDS), a strong Fe (II) chelating agent, O.brevis was able to grow.Furthermore, O.brevis was capable of growing in the medium containing a microbial siderophore, desferrioxamine B (DESF), instead ofEDTA.These results show that O.brevis has an excellent ability to utilize a variety of iron forms including Fe (III) -EDTA, Fe (II) -BPDS, Fe (III) -DESF chelates, colloidal ferric hydroxide and more thermodynamically stable crystalline iron oxides (Fe2O3, Fe3O4) in comparison with musty-odor producing cyanobacteria such as Anabaena macrospora, Phormidium tenue and Oscillatoria tenuis isolated from Lake Biwa

This study presents information on the dynamics of sugar beet (Beta vulgaris L.) root metabolic responses to Fe deficiency. Four days after Fe withdrawal from the nutrient solution, the concentration of reduced glutathione (GSH) and the activities of ferric chelate reductase (FC-R, E.C. 1.6.99.13) and ascorbate peroxidase (APX, E.C. 1.11.1.11) showed marked differences with the control values. The differences in root fresh weight, the concentrations of ascorbate (Asc) and soluble proteins, and proton release rates by roots became more prominent after the first week. Time course kinetics of FC-R activity and proton extrusion showed induction maxima, followed by rapid declines with the progress of Fe deficiency. The time courses of root Asc and GSH concentrations showed gradual increases with the advancement of Fe deficiency suggesting that plant responses to Fe deficiency stress may include a shift in the redox balance inside the root cells towards more reduced state. Data imply that an alternative Asc-dependent Fe reduction may become important with the advancement of Fe deficiency stress, when FC-R activity is declining. The time course of APX activity reveals that it could be a sensitive indicator of the initial changes in the plant Fe nutritional status., Work supported by grant BOS2001-2343 from the Spanish Ministry of Science and Technology to J.A. T.Z. was supported by a sabbatical grant (SAB95-0551) from the Spanish Ministry of Science and Education.