Electron Paramagnetic Resonance Instrumentation

Reijerse, Edward J.; Savitsky, Anton

doi:10.1002/9780470034590.emrstm1511

Cited by 12 publications

(9 citation statements)

References 58 publications

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“…Q-band Echo detected experiments were conducted on a Bruker Elexsys 580 Q-band pulsed EPR spectrometer using a homebuilt Q-band resonator [ 37 ]. Low temperatures were reached using a closed cycle Helium cryostat from Cryogenic Ltd [ 38 ].…”

Section: Methodsmentioning

confidence: 99%

Spectroscopic investigations of a semi-synthetic [FeFe] hydrogenase with propane di-selenol as bridging ligand in the binuclear subsite: comparison to the wild type and propane di-thiol variants

et al. 2018

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[FeFe] Hydrogenases catalyze the reversible conversion of H2 into electrons and protons. Their catalytic site, the H-cluster, contains a generic [4Fe–4S]H cluster coupled to a [2Fe]H subsite [Fe2(ADT)(CO)3(CN)2]2−, ADT = µ(SCH2)2NH. Heterologously expressed [FeFe] hydrogenases (apo-hydrogenase) lack the [2Fe]H unit, but this can be incorporated through artificial maturation with a synthetic precursor [Fe2(ADT)(CO)4(CN)2]2−. Maturation with a [2Fe] complex in which the essential ADT amine moiety has been replaced by CH2 (PDT = propane-dithiolate) results in a low activity enzyme with structural and spectroscopic properties similar to those of the native enzyme, but with simplified redox behavior. Here, we study the effect of sulfur-to-selenium (S-to-Se) substitution in the bridging PDT ligand incorporated in the [FeFe] hydrogenase HydA1 from Chlamydomonas reinhardtii using magnetic resonance (EPR, NMR), FTIR and spectroelectrochemistry. The resulting HydA1-PDSe enzyme shows the same redox behavior as the parent HydA1-PDT. In addition, a state is observed in which extraneous CO is bound to the open coordination site of the [2Fe]H unit. This state was previously observed only in the native enzyme HydA1-ADT and not in HydA1-PDT. The spectroscopic features and redox behavior of HydA1-PDSe, resulting from maturation with [Fe2(PDSe)(CO)4(CN)2]2−, are discussed in terms of spin and charge density shifts and provide interesting insight into the electronic structure of the H-cluster. We also studied the effect of S-to-Se substitution in the [4Fe–4S] subcluster. The reduced form of HydA1 containing only the [4Fe–4Se]H cluster shows a characteristic S = 7/2 spin state which converts back into the S = 1/2 spin state upon maturation with a [2Fe]–PDT/ADT complex.Electronic supplementary materialThe online version of this article (10.1007/s00775-018-1558-4) contains supplementary material, which is available to authorized users.

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Section: Methodsmentioning

confidence: 99%

Spectroscopic investigations of a semi-synthetic [FeFe] hydrogenase with propane di-selenol as bridging ligand in the binuclear subsite: comparison to the wild type and propane di-thiol variants

et al. 2018

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“…In X-band continuous-wave EPR spectrometers rectangular cavities are most widespread and applicable for a wide range of samples whilst cylindrical ones are more suitable for aqueous and high-dielectric samples. [13] The choice of cavity thus depending on the nature of the sample. Analysis of aqueous samples at room temperature in a rectangular cavity is preferably done in a flat cell with sample layer thickness of approximately 0.3 mm because the electric dipole of water interacts with the electric field of the microwaves resulting in a large amount of electromagnetic radiation being absorbed by the sample and consequentially a lower Q-factor.…”

Section: Introductionmentioning

confidence: 99%

“…[14] The sample has to be located at the position in the cavity with minimum of the electric field component and the maximum of magnetic field component of the microwave which is facilitated by the use of a flat cell for a standard rectangular cavity operating in the TE 102 mode. [13] In cylindrical cavities, a capillary needs to be used for the measurements of lossy samples.…”

Section: Introductionmentioning

confidence: 99%

A Versatile In‐Situ Electron Paramagnetic Resonance Spectro‐electrochemical Approach for Electrocatalyst Research

et al. 2020

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Empirical electrocatalyst research generally consists of the synthesis and experimental characterization of catalysts and the analysis of electrolysis products by conventional analytical techniques. In‐situ electron paramagnetic resonance spectro‐electrochemistry provides an evidence‐based in‐depth understanding of the formed intermediates and the reaction mechanism enabling the desired tuning of electrocatalysts. The use of this technique has been underexploited because of the opposite requirements they impose on the conventional setup. In this work, a versatile electrode with commercially available indium tin oxide on polyethylene terephthalate (PET) was constructed for the first time which can fit inside commonly used flat cells. It allows reproducible electrodeposition of catalytic material combined with sensitive radical detection, owing to its large surface area and minimal disruption to the resonator's Q‐factor. Moreover, with a resistivity of 8–10 Ω sq−1, the surface potential of the thin semiconductor electrode within the resonator was well‐controlled, allowing targeted radical production.

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“…The phases and amplitudes of B 1 and E 1 depend on the particular experimental implementation (see ref. 20 for examples). If the electronic relaxation time is long in comparison with the p=2 ð Þ I y pulse, one can presume that the case II, i.e., q 2 (0) p Ŝ y Î x , represents a promising initial state.…”

Section: Effects P Cmentioning

confidence: 99%