351
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Costentin C, Robert M, Savéant JM, Tard C. Inserting a Hydrogen-Bond Relay between Proton Exchanging Sites in Proton-Coupled Electron Transfers. Angew Chem Int Ed Engl 2010; 49:3803-6. [DOI: 10.1002/anie.200907192] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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352
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Costentin C, Robert M, Savéant JM, Tard C. Inserting a Hydrogen-Bond Relay between Proton Exchanging Sites in Proton-Coupled Electron Transfers. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200907192] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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353
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Yates Z, Gunasekaran K, Zhou H, Hu Z, Liu Z, Ketchem RR, Yan B. Histidine residue mediates radical-induced hinge cleavage of human IgG1. J Biol Chem 2010; 285:18662-71. [PMID: 20304919 DOI: 10.1074/jbc.m110.108597] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hydroxyl radicals induce hinge cleavage in a human IgG1 molecule via initial radical formation at the first hinge Cys(231) followed by electron transfer to the upper hinge residues. To enable engineering of a stable monoclonal antibody hinge, we investigated the role of the hinge His(229) residue using structure modeling and site-directed mutagenesis. Direct involvement of His(229) in the reaction mechanism is suggested by a 75-85% reduction of the hinge cleavage for variants in which His(229) was substituted with either Gln, Ser, or Ala. In contrast, mutation of Lys(227) to Gln, Ser, or Ala increased hinge cleavage. However, the H229S/K227S double mutant shows hinge cleavage levels similar to that of the single H229S variant, further revealing the importance of His(229). Examination of the hinge structure shows that His(229) is capable of forming hydrogen bonds with surrounding residues. These observations led us to hypothesize that the imidazole ring of His(229) may function to facilitate the cleavage by forming a transient radical center that is capable of extracting a proton from neighboring residues. The work presented here suggests the feasibility of engineering a new generation of monoclonal antibodies capable of resisting hinge cleavage to improve product stability and efficacy.
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Affiliation(s)
- Zac Yates
- Department of Analytical and Formulation Science, Amgen Inc., Seattle, Washington 98119, USA
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354
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Sajenko I, Pilepić V, Jakobušić Brala C, Uršić S. Solvent Dependence of the Kinetic Isotope Effect in the Reaction of Ascorbate with the 2,2,6,6-Tetramethylpiperidine-1-oxyl Radical: Tunnelling in a Small Molecule Reaction. J Phys Chem A 2010; 114:3423-30. [DOI: 10.1021/jp911086n] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Ivana Sajenko
- Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1. Zagreb, Croatia
| | - Viktor Pilepić
- Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1. Zagreb, Croatia
| | | | - Stanko Uršić
- Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1. Zagreb, Croatia
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355
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Dogutan DK, Bediako DK, Teets TS, Schwalbe M, Nocera DG. Efficient Synthesis of Hangman Porphyrins. Org Lett 2010; 12:1036-9. [DOI: 10.1021/ol902947h] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Dilek K. Dogutan
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
| | - D. Kwabena Bediako
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
| | - Thomas S. Teets
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
| | - Matthias Schwalbe
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
| | - Daniel G. Nocera
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
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356
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Yago T, Gohdo M, Wakasa M. Hydrogen Bonding Effects on the Reorganization Energy for Photoinduced Charge Separation Reaction between Porphyrin and Quinone Studied by Nanosecond Laser Flash Photolysis. J Phys Chem B 2010; 114:2476-83. [DOI: 10.1021/jp909927w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Tomoaki Yago
- Department of Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Masao Gohdo
- Department of Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Masanobu Wakasa
- Department of Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan
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357
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Abstract
Personalized energy (PE) is a transformative idea that provides a new modality for the planet's energy future. By providing solar energy to the individual, an energy supply becomes secure and available to people of both legacy and nonlegacy worlds and minimally contributes to an increase in the anthropogenic level of carbon dioxide. Because PE will be possible only if solar energy is available 24 h a day, 7 days a week, the key enabler for solar PE is an inexpensive storage mechanism. HY (Y = halide or OH(-)) splitting is a fuel-forming reaction of sufficient energy density for large-scale solar storage, but the reaction relies on chemical transformations that are not understood at the most basic science level. Critical among these are multielectron transfers that are proton-coupled and involve the activation of bonds in energy-poor substrates. The chemistry of these three italicized areas is developed, and from this platform, discovery paths leading to new hydrohalic acid- and water-splitting catalysts are delineated. The latter water-splitting catalyst captures many of the functional elements of photosynthesis. In doing so, a highly manufacturable and inexpensive method for solar PE storage has been discovered.
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Affiliation(s)
- Daniel G Nocera
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA.
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358
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Meylemans HA, Damrauer NH. Controlling Electron Transfer through the Manipulation of Structure and Ligand-Based Torsional Motions: A Computational Exploration of Ruthenium Donor−Acceptor Systems using Density Functional Theory. Inorg Chem 2009; 48:11161-75. [DOI: 10.1021/ic901637b] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Heather A. Meylemans
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
| | - Niels H. Damrauer
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
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359
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Brenner S, Heyes DJ, Hay S, Hough MA, Eady RR, Hasnain SS, Scrutton NS. Demonstration of proton-coupled electron transfer in the copper-containing nitrite reductases. J Biol Chem 2009; 284:25973-83. [PMID: 19586913 DOI: 10.1074/jbc.m109.012245] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The reduction of nitrite (NO2-) into nitric oxide (NO), catalyzed by nitrite reductase, is an important reaction in the denitrification pathway. In this study, the catalytic mechanism of the copper-containing nitrite reductase from Alcaligenes xylosoxidans (AxNiR) has been studied using single and multiple turnover experiments at pH 7.0 and is shown to involve two protons. A novel steady-state assay was developed, in which deoxyhemoglobin was employed as an NO scavenger. A moderate solvent kinetic isotope effect (SKIE) of 1.3 +/- 0.1 indicated the involvement of one protonation to the rate-limiting catalytic step. Laser photoexcitation experiments have been used to obtain single turnover data in H2O and D2O, which report on steps kinetically linked to inter-copper electron transfer (ET). In the absence of nitrite, a normal SKIE of approximately 1.33 +/- 0.05 was obtained, suggesting a protonation event that is kinetically linked to ET in substrate-free AxNiR. A nitrite titration gave a normal hyperbolic behavior for the deuterated sample. However, in H2O an unusual decrease in rate was observed at low nitrite concentrations followed by a subsequent acceleration in rate at nitrite concentrations of >10 mM. As a consequence, the observed ET process was faster in D2O than in H2O above 0.1 mM nitrite, resulting in an inverted SKIE, which featured a significant dependence on the substrate concentration with a minimum value of approximately 0.61 +/- 0.02 between 3 and 10 mM. Our work provides the first experimental demonstration of proton-coupled electron transfer in both the resting and substrate-bound AxNiR, and two protons were found to be involved in turnover.
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Affiliation(s)
- Sibylle Brenner
- Manchester Interdisciplinary Biocentre and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
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360
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Reece SY, Lutterman DA, Seyedsayamdost MR, Stubbe J, Nocera DG. Re(bpy)(CO)3CN as a probe of conformational flexibility in a photochemical ribonucleotide reductase. Biochemistry 2009; 48:5832-8. [PMID: 19402704 PMCID: PMC3340421 DOI: 10.1021/bi9005804] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photochemical ribonucleotide reductases (photoRNRs) have been developed to study the proton-coupled electron transfer (PCET) mechanism of radical transport in Escherichia coli class I ribonucleotide reductase (RNR). The transport of the effective radical occurs along several conserved aromatic residues across two subunits: beta2((*)Y122 --> W48 --> Y356) --> alpha2(Y731 --> Y730 --> C439). The current model for RNR activity suggests that radical transport is strongly controlled by conformational gating. The C-terminal tail peptide (Y-betaC19) of beta2 is the binding determinant of beta2 to alpha2 and contains the redox active Y356 residue. A photoRNR has been generated synthetically by appending a Re(bpy)(CO)(3)CN ([Re]) photo-oxidant next to Y356 of the 20-mer peptide. Emission from the [Re] center dramatically increases upon peptide binding, serving as a probe for conformational dynamics and the protonation state of Y356. The diffusion coefficient of [Re]-Y-betaC19 has been measured (k(d1) = 6.1 x 10(-7) cm(-1) s(-1)), along with the dissociation rate constant for the [Re]-Y-betaC19-alpha2 complex (7000 s(-1) > k(off) > 400 s(-1)). Results from detailed time-resolved emission and absorption spectroscopy reveal biexponential kinetics, suggesting a large degree of conformational flexibility in the [Re]-Y-betaC19-alpha2 complex that engenders partitioning of the N-terminus of the peptide into both bound and solvent-exposed fractions.
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Affiliation(s)
- Steven Y Reece
- Department of Chemistry, Massachusetts Institute of Technology,77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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361
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Affiliation(s)
- My Hang V Huynh
- DE-1: High Explosive Science and Technology Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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362
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Yeung KWK, Poon RWY, Liu XY, Ho JPY, Chung CY, Chu PK, Lu WW, Chan D, Cheung KMC. Investigation of nickel suppression and cytocompatibility of surface-treated nickel-titanium shape memory alloys by using plasma immersion ion implantation. J Biomed Mater Res A 2005. [PMID: 15662652 DOI: 10.1016/j.mattod.2018.04.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Nickel-titanium (NiTi) shape memory alloys are increasingly being used in orthopedic applications. However, there is a concern that Ni is harmful to the human body. We have recently investigated the use of nitrogen, or oxygen plasma immersion ion implantation to mitigate this deleterious effect. Our results reveal that the near-surface Ni concentration in all the treated samples is significantly suppressed. In addition, our in vitro tests show that the plasma-treated surfaces are cytologically compatible allowing the attachment and proliferation of osteoblasts. Among the two types of samples, the best biological effects are found on the samples with nitrogen implantation.
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Affiliation(s)
- K W K Yeung
- Department of Orthopaedics and Traumatology, Division of Spine Surgery, Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong
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