1
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Sension RJ, McClain TP, Michocki LB, Miller NA, Alonso-Mori R, Lima FA, Ardana-Lamas F, Biednov M, Chung T, Deb A, Jiang Y, Kaneshiro AK, Khakhulin D, Kubarych KJ, Lamb RM, Meadows JH, Otte F, Sofferman DL, Song S, Uemura Y, van Driel TB, Penner-Hahn JE. Structural Evolution of Photoexcited Methylcobalamin toward a CarH-like Metastable State: Evidence from Time-Resolved X-ray Absorption and X-ray Emission. J Phys Chem B 2024. [PMID: 39150518 DOI: 10.1021/acs.jpcb.4c03729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
CarH is a protein photoreceptor that uses a form of B12, adenosylcobalamin (AdoCbl), to sense light via formation of a metastable excited state. Aside from AdoCbl bound to CarH, methylcobalamin (MeCbl) is the only other example─to date─of photoexcited cobalamins forming metastable excited states with lifetimes of nanoseconds or longer. The UV-visible spectra of the excited states of MeCbl and AdoCbl bound to CarH are similar. We have used transient Co K-edge X-ray absorption and X-ray emission spectroscopies in conjunction with transient absorption spectroscopy in the UV-visible region to characterize the excited states of MeCbl. These data show that the metastable excited state of MeCbl has a slightly expanded corrin ring and increased electron density on the cobalt, but only small changes in the axial bond lengths.
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Affiliation(s)
- Roseanne J Sension
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Taylor P McClain
- Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Lindsay B Michocki
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Nicholas A Miller
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Frederico Alves Lima
- Femtosecond X-ray Experiments Group, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Fernando Ardana-Lamas
- Femtosecond X-ray Experiments Group, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Mykola Biednov
- Femtosecond X-ray Experiments Group, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Taewon Chung
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Aniruddha Deb
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Yifeng Jiang
- Femtosecond X-ray Experiments Group, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - April K Kaneshiro
- Department of Biological Chemistry, 1150 W. Medical Center Dr., Ann Arbor, Michigan 48109-0600, United States
| | - Dmitry Khakhulin
- Femtosecond X-ray Experiments Group, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Kevin J Kubarych
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Ryan M Lamb
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Joseph H Meadows
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Florian Otte
- Femtosecond X-ray Experiments Group, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Danielle L Sofferman
- Program in Applied Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Sanghoon Song
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Yohei Uemura
- Femtosecond X-ray Experiments Group, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - James E Penner-Hahn
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
- Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
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2
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Chung T, McClain TP, Alonso-Mori R, Chollet M, Deb A, Garcia-Esparza AT, Huang Ze En J, Lamb RM, Michocki LB, Reinhard M, van Driel TB, Penner-Hahn JE, Sension RJ. Ultrafast X-ray Absorption Spectroscopy Reveals Excited-State Dynamics of B 12 Coenzymes Controlled by the Axial Base. J Phys Chem B 2024; 128:1428-1437. [PMID: 38301132 DOI: 10.1021/acs.jpcb.3c07779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
Polarized time-resolved X-ray absorption spectroscopy at the Co K-edge is used to probe the excited-state dynamics and photolysis of base-off methylcobalamin and the excited-state structure of base-off adenosylcobalamin. For both molecules, the final excited-state minimum shows evidence for an expansion of the cavity around the Co ion by ca. 0.04 to 0.05 Å. The 5-coordinate base-off cob(II)alamin that is formed following photodissociation has a structure similar to that of the 5-coordinate base-on cob(II)alamin, with a ring expansion of 0.03 to 0.04 Å and a contraction of the lower axial bond length relative to that in the 6-coordinate ground state. These data provide insights into the role of the lower axial ligand in modulating the reactivity of B12 coenzymes.
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Affiliation(s)
- Taewon Chung
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 481091055, United States
| | - Taylor P McClain
- Biophysics, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Matthieu Chollet
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Aniruddha Deb
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 481091055, United States
| | - Angel T Garcia-Esparza
- Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025-7015, United States
| | - Joel Huang Ze En
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 481091055, United States
| | - Ryan M Lamb
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 481091055, United States
| | - Lindsay B Michocki
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 481091055, United States
| | - Marco Reinhard
- Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025-7015, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - James E Penner-Hahn
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 481091055, United States
- Biophysics, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Roseanne J Sension
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 481091055, United States
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
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3
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Elmendorf LD, Brunold TC. Vibronic Coupling in Vitamin B 12: A Combined Spectroscopic and Computational Study. Inorg Chem 2023; 62:12762-12772. [PMID: 37463115 DOI: 10.1021/acs.inorgchem.3c01305] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
Understanding the diverse reactivities of vitamin B12 and its derivatives, collectively called cobalamins, requires detailed knowledge of their geometric and electronic structures. Electronic absorption (Abs) and resonance Raman (rR) spectroscopies have proven invaluable in this area, particularly when used in concert with computational techniques such as density functional theory (DFT). There remain, however, lingering uncertainties in the computational description of electronic excited states of cobalamins, particularly surrounding the vibronic coupling that impacts the Abs bandshapes and gives rise to rR enhancement of vibrational modes. Past computational analyses of the vibrational spectra of cobalamins have either neglected rR enhancement or calculated rR enhancement for only a small number of modes. In the present study, we used the recently developed ORCA_ASA computational tool in conjunction with the popular B3LYP and BP86 functionals to predict Abs bandshapes and rR spectra for vitamin B12. The ORCA_ASA/B3LYP-computed Abs envelope in the visible spectral region and rR spectra of vitamin B12 agree remarkably well with our experimental data, while BP86 fails to reproduce both. This finding represents a significant advance in our understanding of how these two commonly used density functionals differently model the electronic properties of cobalamins. Guided by the computed frequencies for the Co-C stretching and Co-C-N bending modes, we identified, for the first time, isotope-sensitive features in our rR spectra of 12CNCbl and 13CNCbl that can be assigned to these modes. A normal coordinate analysis of the experimentally determined Co-C stretching and Co-C-N bending frequencies indicates that the Co-C force constant for vitamin B12 is 2.67 mdyn/Å, considerably larger than the Co-C force constants reported for alkylcobalamins.
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Affiliation(s)
- Laura D Elmendorf
- Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States
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4
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Marques HM. The inorganic chemistry of the cobalt corrinoids - an update. J Inorg Biochem 2023; 242:112154. [PMID: 36871417 DOI: 10.1016/j.jinorgbio.2023.112154] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 01/23/2023] [Accepted: 01/26/2023] [Indexed: 02/05/2023]
Abstract
The inorganic chemistry of the cobalt corrinoids, derivatives of vitamin B12, is reviewed, with particular emphasis on equilibrium constants for, and kinetics of, their axial ligand substitution reactions. The role the corrin ligand plays in controlling and modifying the properties of the metal ion is emphasised. Other aspects of the chemistry of these compounds, including their structure, corrinoid complexes with metals other than cobalt, the redox chemistry of the cobalt corrinoids and their chemical redox reactions, and their photochemistry are discussed. Their role as catalysts in non-biological reactions and aspects of their organometallic chemistry are briefly mentioned. Particular mention is made of the role that computational methods - and especially DFT calculations - have played in developing our understanding of the inorganic chemistry of these compounds. A brief overview of the biological chemistry of the B12-dependent enzymes is also given for the reader's convenience.
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Affiliation(s)
- Helder M Marques
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa.
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5
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Hannibal L, Jacobsen DW. Intracellular processing of vitamin B 12 by MMACHC (CblC). VITAMINS AND HORMONES 2022; 119:275-298. [PMID: 35337623 DOI: 10.1016/bs.vh.2022.02.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Vitamin B12 (cobalamin, Cbl, B12) is a water-soluble micronutrient synthesized exclusively by a group of microorganisms. Human beings are unable to make B12 and thus obtain the vitamin via intake of animal products, fermented plant-based foods or supplements. Vitamin B12 obtained from the diet comprises three major chemical forms, namely hydroxocobalamin (HOCbl), methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl). The most common form of B12 present in supplements is cyanocobalamin (CNCbl). Yet, these chemical forms cannot be utilized directly as they come, but instead, they undergo chemical processing by the MMACHC protein, also known as CblC. Processing of dietary B12 by CblC involves removal of the upper-axial ligand (beta-ligand) yielding the one-electron reduced intermediate cob(II)alamin. Newly formed cob(II)alamin undergoes trafficking and delivery to the two B12-dependent enzymes, cytosolic methionine synthase (MS) and mitochondrial methylmalonyl-CoA mutase (MUT). The catalytic cycles of MS and MUT incorporate cob(II)alamin as a precursor to regenerate the coenzyme forms MeCbl and AdoCbl, respectively. Mutations and epimutations in the MMACHC gene result in cblC disease, the most common inborn error of B12 metabolism, which manifests with combined homocystinuria and methylmalonic aciduria. Elevation of metabolites homocysteine and methylmalonic acid occurs because the lack of an active CblC blocks formation of the indispensable precursor cob(II)alamin that is necessary to activate MS and MUT. Thus, in patients with cblC disease, vitamin B12 is absorbed and present in circulation in normal to high concentrations, yet, cells are unable to make use of it. Mutations in seemingly unrelated genes that modify MMACHC gene expression also result in clinical phenotypes that resemble cblC disease. We review current knowledge on structural and functional aspects of intracellular processing of vitamin B12 by the versatile protein CblC, its partners and possible regulators.
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Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany.
| | - Donald W Jacobsen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
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6
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Sension RJ, Chung T, Dewan P, McClain TP, Lamb RM, Penner-Hahn JE. Time-resolved spectroscopy: Advances in understanding the electronic structure and dynamics of cobalamins. Methods Enzymol 2022; 669:303-331. [DOI: 10.1016/bs.mie.2022.01.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Greenhalgh ED, Kunze C, Schubert T, Diekert G, Brunold TC. A Spectroscopically Validated Computational Investigation of Viable Reaction Intermediates in the Catalytic Cycle of the Reductive Dehalogenase PceA. Biochemistry 2021; 60:2022-2032. [PMID: 34132518 DOI: 10.1021/acs.biochem.1c00271] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Organisms that produce reductive dehalogenases utilize halogenated aromatic and aliphatic substances as terminal electron acceptors in a process termed organohalide respiration. These organisms can couple the reduction of halogenated substances with the production of ATP. Tetrachloroethylene reductive dehalogenase (PceA) catalyzes the reductive dehalogenation of per- and trichloroethylenes (PCE and TCE, respectively) to primarily cis-dichloroethylene (DCE). The enzymatic conversion of PCE to TCE (and subsequently DCE) could potentially proceed via a mechanism in which the first step involves a single-electron transfer, nucleophilic addition followed by chloride elimination or protonation, or direct attack at the halogen. Difficulties with producing adequate quantities of PceA have greatly hampered direct experimental studies of the reaction mechanism. To overcome these challenges, we have generated computational models of resting and TCE-bound PceA using quantum mechanics/molecular mechanics (QM/MM) calculations and validated these models on the basis of experimental data. Notably, the norpseudo-cob(II)alamin [Co(II)Cbl*] cofactor remains five-coordinate upon binding of the substrate to the enzyme, retaining a loosely bound water on the lower face. Thus, the mechanism for the thermodynamically challenging Co(II) → Co(I)Cbl* reduction used by PceA differs fundamentally from that utilized by adenosyltransferases, which generate four-coordinate Co(II)Cbl species to facilitate access to the Co(I) oxidation state. The same QM/MM computational methodology was then applied to viable reaction intermediates in the catalytic cycle of PceA. The intermediate predicted to possess the lowest energy is that resulting from electron transfer from Co(I)Cbl* to the substrate to yield Co(II)Cbl*, a chloride ion, and a vinylic radical.
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Affiliation(s)
- Elizabeth D Greenhalgh
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Cindy Kunze
- Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University, 07743 Jena, Germany
| | - Torsten Schubert
- Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University, 07743 Jena, Germany
| | - Gabriele Diekert
- Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University, 07743 Jena, Germany
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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8
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Probing the nature of the Co(III) ion in cobalamins: The ligand substitution reactions of aquacyanocobester, aquacyano(10-nitro)cobester and aquacyano(10-amino)cobester. Inorganica Chim Acta 2016. [DOI: 10.1016/j.ica.2016.06.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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9
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Morita Y, Oohora K, Mizohata E, Sawada A, Kamachi T, Yoshizawa K, Inoue T, Hayashi T. Crystal Structures and Coordination Behavior of Aqua- and Cyano-Co(III) Tetradehydrocorrins in the Heme Pocket of Myoglobin. Inorg Chem 2016; 55:1287-95. [DOI: 10.1021/acs.inorgchem.5b02598] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yoshitsugu Morita
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Koji Oohora
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
- Frontier Research Base for Global Young
Researchers, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Eiichi Mizohata
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Akiyoshi Sawada
- Institute
for Materials Chemistry and Engineering and International Research
Center for Molecular Systems, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - Takashi Kamachi
- Institute
for Materials Chemistry and Engineering and International Research
Center for Molecular Systems, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute
for Materials Chemistry and Engineering and International Research
Center for Molecular Systems, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
- Elements
Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Nishikyo-ku, Kyoto 615-8520, Japan
| | - Tsuyoshi Inoue
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
| | - Takashi Hayashi
- Department of Applied Chemistry, Graduate
School of Engineering, Osaka University, Suita 565-0871, Japan
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10
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Synthesis, X-ray structure analysis and density functional study of an unusual anhydrous 5,6-dimethylbenzo-1,3-imidazolium(H3) chloride. J Mol Struct 2015. [DOI: 10.1016/j.molstruc.2014.09.054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Randaccio L, Brancatelli G, Demitri N, Dreos R, Hickey N, Siega P, Geremia S. Trans and Cis Effects of Axial Fluoroalkyl Ligands in Vitamin B12 Analogues: Relationship between Alkyl- and Fluoroalkyl-Cobalamins. Inorg Chem 2013; 52:13392-401. [DOI: 10.1021/ic401715e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Lucio Randaccio
- Department of Chemical
and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
| | - Giovanna Brancatelli
- Department of Chemical
and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
| | - Nicola Demitri
- Department of Chemical
and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
| | - Renata Dreos
- Department of Chemical
and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
| | - Neal Hickey
- Department of Chemical
and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
| | - Patrizia Siega
- Department of Chemical
and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
| | - Silvano Geremia
- Department of Chemical
and Pharmaceutical Sciences, University of Trieste, 34127 Trieste, Italy
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12
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Ruetz M, Salchner R, Wurst K, Fedosov S, Kräutler B. Phenylethinylcobalamin: ein radikalsynthetisch hergestelltes, lichtstabiles und hitzeresistentes metallorganisches B12-Derivat. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201305206] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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13
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Ruetz M, Salchner R, Wurst K, Fedosov S, Kräutler B. Phenylethynylcobalamin: A Light-Stable and Thermolysis-Resistant Organometallic Vitamin B12Derivative Prepared by Radical Synthesis. Angew Chem Int Ed Engl 2013; 52:11406-9. [DOI: 10.1002/anie.201305206] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Indexed: 11/10/2022]
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14
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Marino N, Rabideau AE, Doyle RP. Trifluoracetic acid-assisted crystallization of vitamin B12 results in protonation of the phosphate group of the nucleotide loop: insight into the influence of crystal packing forces on vitamin B12 structures. Inorg Chem 2010; 50:220-30. [PMID: 21128680 DOI: 10.1021/ic101810v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In the course of experiments concerning our ongoing project on the synthesis of vitamin B(12) (cyanocobalamin, CNCbl) bioconjugates for drug-delivery purposes, we observed the formation of well-shaped red parallelepipeds from a concentrated aqueous solution of the HPLC-purified vitamin. The X-ray structural investigation (MoK(α)) at 98 K on these crystals revealed a CNCbl-TFA salt of formula [CNCbl(H)](TFAc)·14H(2)O (1, where TFA = trifluoracetic acid; TFAc(-) = trifluoracetate anion), in which a proton transfer from the trifluoracetic acid to the phosphate-O4P oxygen atoms is observed. 1 crystallizes in the standard orthorhombic P2(1)2(1)2(1) space group, a = 16.069(2) Å, b = 20.818(2) Å, c = 24.081(2) Å, Z = 4. The final full-matrix least-squares refinements on F(2) converged with R(1) = 4.1% for the 18957 significant reflections, a very low crystallographic residual for cobalamins, which facilitated the analysis of the extensive network of hydrogen bonds within the lattice. To the best of our knowledge, this is the first cobalamin structure to show protonation of the phosphate group of the cobalamin nucleotide loop. In this work, the crystal structure of 1 is analyzed and compared to other CNCbls reported in the literature, namely, CNCbl·3PrOH·12H(2)O (2, PrOH = propyl alcohol), CNCbl·acetone·20H(2)O (3), CNCbl·2LiCl·10.2H(2)O (4), and CNCbl·2KCl·10.6H(2)O (5). The analysis confirmed that protonation of the phosphate leaves the major CNCbl structural parameters unaffected, so that 1 can be considered an "unmodified" Cbl solvate. However, comparison between 1-5 led to interesting findings. In fact, although the cobalt(III) coordination sphere in 1-5 is similar, significant differences could be noted in the upward fold angle of the corrin macrocycle, a parameter commonly related to the steric hindrance of the axial lower "α" nucleotide-base and the electronic trans influence of the upper "β" substituent. This suggests that crystal-packing forces may influence the corrin deformation as well. Herein we explore, on the basis of the newly acquired structure and reported crystallographic data, whether the incongruities among 1-5 have to be attributed to random crystal packing effects or if it is possible to associate them with specific crystal packing (clusters).
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Affiliation(s)
- Nadia Marino
- Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100, USA
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15
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Randaccio L, Geremia S, Demitri N, Wuerges J. Vitamin B12: unique metalorganic compounds and the most complex vitamins. Molecules 2010; 15:3228-59. [PMID: 20657474 PMCID: PMC6257451 DOI: 10.3390/molecules15053228] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 04/27/2010] [Accepted: 04/28/2010] [Indexed: 11/16/2022] Open
Abstract
The chemistry and biochemistry of the vitamin B(12) compounds (cobalamins, XCbl) are described, with particular emphasis on their structural aspects and their relationships with properties and function. A brief history of B(12), reveals how much the effort of chemists, biochemists and crystallographers have contributed in the past to understand the basic properties of this very complex vitamin. The properties of the two cobalamins, the two important B(12) cofactors Ado- and MeCbl are described, with particular emphasis on how the Co-C bond cleavage is involved in the enzymatic mechanisms. The main structural features of cobalamins are described, with particular reference to the axial fragment. The structure/property relationships in cobalamins are summarized. The recent studies on base-off/base-on equilibrium are emphasized for their relevance to the mode of binding of the cofactor to the protein scaffold. The absorption, transport and cellular uptake of cobalamins and the structure of the B(12) transport proteins, IF and TC, in mammals are reviewed. The B(12) transport in bacteria and the structure of the so far determined proteins are briefly described. The currently accepted mechanisms for the catalytic cycles of the AdoCbl and MeCbl enzymes are reported. The structure and function of B(12) enzymes, particularly the important mammalian enzymes methyltransferase (MetH) and methyl-malonyl-coenzyme A mutase (MMCM), are described and briefly discussed. Since fast proliferating cells require higher amount of vitamin B(12) than that required by normal cells, the study of B(12 )conjugates as targeting agents has recently gained importance. Bioconjugates have been studied as potential agents for delivering radioisotopes and NMR probes or as various cytotoxic agents towards cancer cells in humans and the most recent studies are described. Specifically, functionalized bioconjugates are used as "Trojan horses" to carry into the cell the appropriate antitumour or diagnostic label. Possible future developments of B(12) work are summarized.
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Affiliation(s)
- Lucio Randaccio
- Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy.
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