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Gracheva M, Klencsár Z, Homonnay Z, Solti Á, Péter L, Machala L, Novak P, Kovács K. Revealing the nuclearity of iron citrate complexes at biologically relevant conditions. Biometals 2024; 37:461-475. [PMID: 38110781 PMCID: PMC11006783 DOI: 10.1007/s10534-023-00562-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 11/09/2023] [Indexed: 12/20/2023]
Abstract
Citric acid plays an ubiquitous role in the complexation of essential metals like iron and thus it has a key function making them biologically available. For this, iron(III) citrate complexes are considered among the most significant coordinated forms of ferric iron that take place in biochemical processes of all living organisms. Although these systems hold great biological relevance, their coordination chemistry has not been fully elucidated yet. The current study aimed to investigate the speciation of iron(III) citrate using Mössbauer and electron paramagnetic resonance spectroscopies. Our aim was to gain insights into the structure and nuclearity of the complexes depending on the pH and iron to citrate ratio. By applying the frozen solution technique, the results obtained directly reflect the iron speciation present in the aqueous solution. At 1:1 iron:citrate molar ratio, polynuclear species prevailed forming most probably a trinuclear structure. In the case of citrate excess, the coexistence of several monoiron species with different coordination environments was confirmed. The stability of the polynuclear complexes was checked in the presence of organic solvents.
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Affiliation(s)
- Maria Gracheva
- Department of Analytical Chemistry, Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány P. s. 1/A, 1117, Budapest, Hungary
- Nuclear Analysis and Radiography Department, Centre for Energy Research, Konkoly-Thege Miklós út. 29-33, 1121, Budapest, Hungary
| | - Zoltán Klencsár
- Nuclear Analysis and Radiography Department, Centre for Energy Research, Konkoly-Thege Miklós út. 29-33, 1121, Budapest, Hungary
| | - Zoltán Homonnay
- Department of Analytical Chemistry, Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány P. s. 1/A, 1117, Budapest, Hungary
| | - Ádám Solti
- Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, ELTE Eötvös Loránd University, Pázmány Péter s. 1/C, 1117, Budapest, Hungary
| | - László Péter
- Department of Complex Fluids, Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Konkoly-Thege Miklós út 29-33, 1121, Budapest, Hungary
| | - Libor Machala
- Department of Experimental Physics, Faculty of Science, Palacký University Olomouc, 17. listopadu 1192/12, 771 46, Olomouc, Czech Republic
| | - Petr Novak
- Department of Experimental Physics, Faculty of Science, Palacký University Olomouc, 17. listopadu 1192/12, 771 46, Olomouc, Czech Republic
| | - Krisztina Kovács
- Department of Analytical Chemistry, Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány P. s. 1/A, 1117, Budapest, Hungary.
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Joe-Wong C, Schaller RD, Gilbert B. Common Photo-oxidative Decarboxylation Mechanism in Iron Hydroxy Carboxylate Complexes. J Phys Chem A 2023. [PMID: 37471523 DOI: 10.1021/acs.jpca.3c02656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/22/2023]
Abstract
Photochemical oxidation of dissolved organic matter is a crucial component of carbon cycling in surface waters. Photo-oxidation of iron(III)-carboxylate complexes is of particular interest because complexation with iron(III) can sensitize this functional group to photodecarboxylation. The photo-oxidation mechanism of ferrioxalate has been extensively characterized, but it is unclear whether the mechanism or timing is similar for other more complex carboxylates. In this study, we use time-resolved infrared spectroscopy to demonstrate that Fe(III)-citrate, an aliphatic carboxylate, and Fe(III)-salicylate, an aromatic carboxylate, follow the same photo-oxidation kinetics as ferrioxalate. Hence the data suggest a common mechanism for decarboxylation of iron hydroxy carbonates. Differences in the CO2 yield within 50 ps are qualitatively similar to the long-time-scale quantum yield for Fe(II) production.
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Affiliation(s)
- Claresta Joe-Wong
- Energy Geoscience Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
| | - Richard D Schaller
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Building 440, Argonne, Illinois 60439, United States
| | - Benjamin Gilbert
- Energy Geoscience Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
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West CP, Mesa Sanchez D, Morales AC, Hsu YJ, Ryan J, Darmody A, Slipchenko LV, Laskin J, Laskin A. Molecular and Structural Characterization of Isomeric Compounds in Atmospheric Organic Aerosol Using Ion Mobility-Mass Spectrometry. J Phys Chem A 2023; 127:1656-1674. [PMID: 36763810 DOI: 10.1021/acs.jpca.2c06459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Secondary organic aerosol (SOA) formed through multiphase atmospheric chemistry makes up a large fraction of airborne particles. The chemical composition and molecular structures of SOA constituents vary between different emission sources and aging processes in the atmosphere, which complicates their identification. In this work, we employ drift tube ion mobility spectrometry with quadrupole time-of-flight mass spectrometry (IM-MS) detection for rapid gas-phase separation and multidimensional characterization of isomers in two biogenic SOAs produced from ozonolysis of isomeric monoterpenes, d-limonene (LSOA) and α-pinene (PSOA). SOA samples were ionized using electrospray ionization (ESI) and characterized using IM-MS in both positive and negative ionization modes. The IM-derived collision cross sections in nitrogen gas (DTCCSN2 ) for individual SOA components were obtained using multifield and single-field measurements. A novel application of IM multiplexing/high-resolution demultiplexing methodology was employed to increase sensitivity, improve peak shapes, and augment mobility baseline resolution, which revealed several isomeric structures for the measured ions. For LSOA and PSOA samples, we report significant structural differences of the isomer structures. Molecular structural calculations using density functional theory combined with the theoretical modeling of CCS values provide insights into the structural differences between LSOA and PSOA constituents. The average DTCCSN2 values for monomeric SOA components observed as [M + Na]+ ions are 3-6% higher than those of their [M - H]- counterparts. Meanwhile, dimeric and trimeric isomer components in both samples showed an inverse trend with the relevant values of [M - H]- ions being 3-7% higher than their [M + Na]+ counterparts, respectively. The results indicate that the structures of Na+-coordinated oligomeric ions are more compact than those of the corresponding deprotonated species. The coordination with Na+ occurs on the oxygen atoms of the carbonyl groups leading to a compact configuration. Meanwhile, deprotonated molecules have higher DTCCSN2 values due to their elongated structures in the gas phase. Therefore, DTCCSN2 values of isomers in SOA mixtures depend strongly on the mode of ionization in ESI. Additionally, PSOA monomers and dimers exhibit larger DTCCSN2 values (1-4%) than their LSOA counterparts owing to more rigid structures. A cyclobutane ring is present with functional groups pointing in opposite directions in PSOA compounds, as compared to noncyclic flexible LSOA structures, forming more compact ions in the gas phase. Lastly, we investigated the effects of direct photolysis on the chemical transformations of selected individual PSOA components. We use IM-MS to reveal structural changes associated with aerosol aging by photolysis. This study illustrates the detailed molecular and structural descriptors for the detection and annotation of structural isomers in complex SOA mixtures.
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Affiliation(s)
- Christopher P West
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Daniela Mesa Sanchez
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Ana C Morales
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Yun-Jung Hsu
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jackson Ryan
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Andrew Darmody
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States.,Department of Aeronautics and Aerospace Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Lyudmila V Slipchenko
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Julia Laskin
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Alexander Laskin
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States.,Department of Earth, Atmospheric & Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, United States
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