Continuous-wave (CW) EPR spectra were obtained at 9.48 GHz using an ELEXSYS E680 spectrometer (Bruker BioSpin GmbH) equipped with a standard TE102 cavity and an ESR900 Cryostat (Oxford Instruments). The measurements were performed at 20 K, modulation amplitude/frequency of 0.5 mT/100 kHz, time constant of 40 ms and microwave power of 0.16 mW.
Elexsys e680 spectrometer
Manufactured by Bruker
Sourced in Germany
The ELEXSYS E680 spectrometer is a high-performance electron paramagnetic resonance (EPR) spectrometer designed for advanced research applications. It features a versatile, modular design that allows for customization to meet specific experimental requirements. The core function of the ELEXSYS E680 is to detect and analyze the magnetic properties of unpaired electrons in a sample, providing valuable insights into the structure and behavior of materials at the molecular level.
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Lab products found in correlation
Cf935 cryostat, by Oxford Instruments (3 mentions)
Esr900 cryostat, by Oxford Instruments (1 mentions)
Emx epr spectrometer, by Bruker (1 mentions)
Emxplus epr spectrometer, by Bruker (1 mentions)
Helium gas flow cryostat, by Oxford Instruments (1 mentions)
Itc 502 temperature controller, by Oxford Instruments (1 mentions)
Elexsys e500 spectrometer, by Bruker (1 mentions)
Esr900 helium flow cryostat, by Oxford Instruments (1 mentions)
14 protocols using elexsys e680 spectrometer
1
Continuous-Wave EPR Spectroscopy at 20K
2
Pulsed EPR of Photoinduced Paramagnets
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Electron paramagnetic resonance (EPR) measurements were performed on a Bruker Elexsys E680 spectrometer (Karlsruhe, Germany) in pulsed mode using the Hahn sequence of the following: π/2 − τ—π − τ—(electron spin echo—ESE), where the duration of π/2 is equal to 64 ns and τ = 250 ns. Registration of EPR spectra was performed by detecting the ESE integral intensity dependance on the magnetic field. The choice of the high-frequency range of the experimental equipment (W-band, microwave frequency is of 94 GHz) was justified by the need to achieve a higher spectroscopic resolution (that allows identifying distinct EPR signals with close g-factors) and high sensitivity (to register weak EPR absorptions). A helium flow cryostat was used for measurements at low temperatures (T < 297 K). Stable photo-induced paramagnetic centers were formed under laser radiation in continuous-wave modes with a wavelength of λ = 266 nm (ultraviolet light—UV).
3
DEER Spectroscopy Methodology for Structural Analysis
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All DEER experiments were done at 9.7 GHz on an ELEXSYS E680 spectrometer (Bruker, Rheinstetten, Germany) using a 3 mm split-ring resonator (ER 4118XMS-3-W1). We performed the measurements at 40 K with a helium gas flow using a CF935 cryostat (Oxford Instruments, United Kingdom). The pump and observer frequencies were separated by 70 MHz and adjusted as reported before [33 (link)]. The power of the pump-pulse was adjusted to invert the echo maximally [24 (link),34 –36 (link)]. The length of the pump-pulse was set to 16 ns. The pulse lengths of the observer channel were 16 and 32 ns for π/2- and π—pulses, respectively. A phase cycle (+ x)—(- x) was applied to the first observer pulse. The complete pulse sequence is given by: The DEER time traces for ten different τ1 values spaced by 8 ns starting at τ1 = 200 ns were added to suppress proton modulations. Typical accumulation times per sample were 16–20 hours.
4
DEER Spectroscopy with Optimized Pulse Sequence
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All DEER experiments were done at X-band on an ELEXSYS E680 spectrometer (Bruker, Rheinstetten, Germany) using a 3 mm split-ring resonator (ER 4118XMS-3-W1). We performed the measurements at 40 K with a helium gas flow using a CF935 cryostat (Oxford Instruments, United Kingdom). The pump and observer frequencies were separated by 70 MHz and adjusted as reported before [26 (link)]. The pump-pulse power was adjusted to invert the echo maximally [42 (link)]. The pump- pulse length was set to 16 ns. The pulse lengths of the observer channel were 16 and 32 ns for π/2- and π - pulses, respectively. A phase cycle (+ x) -(- x) was applied to the first observer pulse. The complete pulse sequence is given by: The DEER time traces for ten different τ1 values spaced by 8 ns starting at τ1 = 200 ns were added to suppress proton modulations. Typical accumulation times per sample were 16 hours.
5
Probing Oxygen Exchange in Photosystem II
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PSII samples were thawed, and then concentrated to 4 to 5 mg Chl/mL (EDNMR set 1) or 8 to 9 mg/mL (EDNMR set 2) and loaded into the freeze quench system. Samples were mixed with 17O water (set 1: 77% enriched containing buffer with glycerol; set 2: 86%, no additions); see SI Appendix, Table S4 for the buffer composition during the exchange experiments. After freeze quenching, the frozen samples were packed into the EDNMR tubes. The S2 state was generated by illuminating the PSII samples for 3 s at 198 K (ethanol–dry ice bath) with two 250 W halogen lamps filtered by a 2 cm CuSO4 solution (5% w/v) and two filters each: Schott KG 3 (2 mm) and Schott GG 445 (2 mm). The final light intensity at the sample level was about 0.5 W/cm2.
EDNMR measurements at W-band were performed on these samples using a Bruker ELEXSYS E680 spectrometer at T =4 .8 K. Electron spin echo detected field-swept EPR spectra were measured using the pulse sequence: tp -τ-2 tp -τ- echo, with tp = 20 ns and τ = 600 ns. EDNMR spectra were collected using the pulse sequence: tHTA -T- tp -τ- tp -τ- echo, with tHTA = 6 μs, tp = 80 ns, τ = 600 ns, and T = 1 μs. Simulations of the EPR and EDNMR spectra were performed using the EasySpin package (79 (link)). SeeSI Appendix, Texts S2 and S3 for further details.
EDNMR measurements at W-band were performed on these samples using a Bruker ELEXSYS E680 spectrometer at T =4 .8 K. Electron spin echo detected field-swept EPR spectra were measured using the pulse sequence: tp -τ-2 tp -τ- echo, with tp = 20 ns and τ = 600 ns. EDNMR spectra were collected using the pulse sequence: tHTA -T- tp -τ- tp -τ- echo, with tHTA = 6 μs, tp = 80 ns, τ = 600 ns, and T = 1 μs. Simulations of the EPR and EDNMR spectra were performed using the EasySpin package (79 (link)). See
6
Electron Paramagnetic Resonance of Cobalt Complexes
7
EPR Spectroscopy of Protein Samples
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The 9 GHz, continuous-wave EPR spectra were recorded using an ELEXSYS E680 spectrometer (Bruker, Rheinstetten, Germany). The measurements were done under the following conditions: room temperature, a microwave power of 0.63 mW and a modulation amplitude of 0.25 mT at a modulation frequency of 100 kHz. The time expended on each measurement was adapted according to the spectral lineshape, i.e., the aggregation time, and they could last from 3 to 8 hours. At long aggregation times the spectral amplitude decreases due to line broadening, and therefore, to obtain the desired signal-to-noise ratio, a longer accumulation time is needed. In practice, we inspected the signal-to-noise ratio of each EPR spectrum after a given accumulation time and increased the measurement time if the spectral quality was not yet sufficient. Glass micropipettes of a volume of 50 μL (Blaubrand Intramark, Wertheim, Germany) were filled with 20 μL of the sample for each measurement. The spin concentration was determined by comparing the double integral of the EPR spectra with the double integral of a reference sample (MTSL, 100 μM). The spin concentrations were ≈ 10 μM for a total protein concentration of 100 μM.
8
Continuous-Wave EPR Spectroscopy of Peptides
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The X-band continuous wave (cw) EPR measurements have been performed at room temperature (20°C) using an ELEXSYS E680 spectrometer (Bruker, Rheinstetten, Germany) equipped with a rectangular cavity. Samples of 10–15 μl peptide solution were drawn into Blaubrand 50- μl capillaries. Often, a white precipitate was observed. In cases where a white precipitate was observed, the sample height was carefully adjusted in order to be sensitive to that part of the solution. Measurements were performed using the following parameters: 6.31 mW of microwave power, a modulation amplitude of 1.4 G, and a modulation frequency of 100 kHz. The large modulation amplitude helps to obtain a better signal-to-noise ratio for broad lines. The accumulation time for the spectra was 40 min per spectrum.
9
EPR Spectroscopy of Biomolecular Samples
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The X‐band continuous‐wave EPR measurements were performed using an ELEXSYS E680 spectrometer (Bruker, Rheinstetten, Germany) with a super high Q cavity (ER 4122 SHQE‐W1/1108). Measurements were performed at 20 °C, using 0.63 mW of microwave power, 100 kHz modulation frequency, and a modulation amplitude of 1.0 G. Total acquisition time for the EPR spectra was 20 minutes.
10
EPR Spectroscopy of Magnetic Samples
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The X-band continuous wave (cw) EPR measurements have been performed using a. an EMX PLUS EPR spectrometer (Bruker, Rheinstetten, Germany) with a super high Q cavity (ER 4119 HS-W1) for room temperature measurements and b. an ELEXSYS E680 spectrometer (Bruker, Rheinstetten, Germany) with a rectangular cavity (ER 4102 ST) for low temperature measurements. The room temperature measurements were done at 20°C, using 0.6315 mW of microwave power, 100 kHz modulation frequency and a modulation amplitude of 1.0 G. Total time to acquire EPR spectra was 20 min. The low-temperature measurements were done at 120 K using a helium gas-flow cryostat (Oxford Instruments, United Kingdom) with an ITC502 temperature controller (Oxford Instruments). The EPR spectra were acquired using a modulation amplitude of 2.5 G and a microwave power of 0.6315 mW.
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