The determination of the concentration of the radicals of 2 , 3 , 7, and 10 was performed by an X-band electron paramagnetic resonance (EPR) spectrometer (Elexsys 500, Bruker, Billerica, MA, USA) equipped with a variable temperature dewar placed in the resonant cavity. Suprasil quartz EPR tubes were filled with the pure oil samples (no dilution) up to 4 cm and thermostatted at 40 °C by nitrogen gas flowing in the dewar. The small quantity of oil ensured a homogeneous temperature inside the analyzed sample. Typical instrumental settings were: microwave power = 10 mW, amplitude = 2 G, 64 accumulations. The radical concentration was obtained from the double integration of the EPR signal multiplied by the inverse temperature in Kelvin degrees to correct for the Curie temperature dependence and calibrated with the signal of the strong-pitch standard from Bruker. The spectra were simulated with the software Winsim [19 (link)], freely available from the Public Electron paramagnetic resonance Software Tools (PEST) from NIEHS (National Institue of Environmental Health Sciences). The radicals were identified as the phenoxyl radicals of the investigated antioxidants from the agreement of their spectral parameters (hyperfine coupling constants, a, and g-factors) with those reported in the literature [20 (link),21 (link)] or with those expected from their structure [22 (link)].
Elexsys 500
Manufactured by Bruker
Sourced in United States
The ELEXSYS 500 is a high-performance electron paramagnetic resonance (EPR) spectrometer designed for advanced research applications. It provides precise and reliable measurements of the magnetic properties of materials and molecules with unpaired electrons.
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Lab products found in correlation
Cf400 cu 50, by Electron Microscopy Sciences (1 mentions)
Smartlab se, by Rigaku (1 mentions)
Microtof 2, by Bruker (1 mentions)
Alpha p, by Bruker (1 mentions)
Lightingcure lc8, by Hamamatsu Photonics (1 mentions)
Variable temperature unit, by Bruker (1 mentions)
Ftir 8400s spectrophotometer, by Shimadzu (1 mentions)
Ea3000 chns o analyzer, by Eurovector (1 mentions)
8 protocols using elexsys 500
1
Antioxidant Radicals Quantification by EPR
2
Comprehensive Characterization of Nanocrystals
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All measurements were collected at room-temperature unless specified otherwise. Electronic absorption spectra were collected on colloidal suspensions in air-tight quartz cuvettes with 1 cm pathlengths (Cary 50 Bio). EPR spectra were measured at X-band frequency (9.6 GHz) with a Bruker Elexsys-500 equipped with a Super High QE (ER4123SHQE) cavity. Transmission electron microscopy (TEM) images of NCs deposited onto copper grids (CF400-CU-50, Electron Microscopy Sciences) with a 3 nm carbon coating (JEOL TEM-2000FX). Powder X-ray diffraction patterns were collected in the Bragg–Brentano configuration with a Cu Kα source (Rigaku SmartLab SE). FTIR spectra were collected using Bruker Alpha-P equipped with a diamond attenuated total reflectance (ATR) crystal. High resolution electrospray ionization mass spectra (ESI-MS) were collected in negative ion mode with Bruker MicroTOF-II. In a typical sample preparation for ESI-MS, the aqueous reaction mixture from the hydrothermal synthesis was centrifuged to separate NCs from the rest of the water-soluble side-products. The aqueous supernatant was used for ESI-MS measurements with no further purification.
3
EPR Spectra of Hydrated Samples
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EPR spectra
were recorded with a Bruker ELEXSYS 500 spectrometer
operating at the X-band. The magnetic field was calibrated with an RMN test tube, and the frequency was measured into the cavity
with a microwave integrated counter. The temperature was stabilized
with an Oxford Instrument regulator (ITC4) at −150 °C.
Samples were analyzed in their hydrated form due to exposure to the
environment before the analysis.
were recorded with a Bruker ELEXSYS 500 spectrometer
operating at the X-band. The magnetic field was calibrated with an RMN test tube, and the frequency was measured into the cavity
with a microwave integrated counter. The temperature was stabilized
with an Oxford Instrument regulator (ITC4) at −150 °C.
Samples were analyzed in their hydrated form due to exposure to the
environment before the analysis.
4
EPR Spectroscopy of Radical Species
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The X‐band EPR spectra were collected in quartz tubes with Elexsys 500 (Bruker) and a MiniScope MS 5000 (Magnettech), both equipped with temperature control. UV irradiation in cavity was provided by an optical fiber from a mercury‐xenon lamp (Hamamatsu Lightingcure LC8, 240–400 nm). Solutions were deoxygenated by prolonged N2 bubbling in the tube. Radical cations and neutral radicals were generated by adding 10 % CF3COOH or 10 % tBuOOtBu, respectively, to a 3–10 mM sample solution in benzene. EPR equilibration experiments were performed by mixing the concentrated solutions of the investigated compounds and of the reference phenol (2,6‐di‐tert‐butyl‐4‐methylphenol) with the addition of 10 % tBuOOtBu inside a quartz tube, followed by N2 bubbling.[21 , 22a (link), 28 (link)] Spectra were analysed by the WinESR program. Measured g‐factors were corrected with respect of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) radical, g=2.0062,[30] and that of 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical in benzene, g=2.00364.[26b] (link)
5
EPR Spectroscopy of Radical-Labeled Compounds
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Electronic paramagnetic
resonance spectroscopy (EPR) spectra were
obtained with an X-Band (9.7 GHz) Bruker ELEXSYS 500 spectrometer
equipped with a ST8911 microwave cavity, a Bruker variable-temperature
unit, a field frequency lock system Bruker ER 033 M and equipped with
an NMR Gaussmeter Bruker ER 035 M. The modulation amplitude was kept
well below the line width, and the microwave power was well below
saturation. All liquid samples were previously degassed with Ar. A
quantitative EPR study was performed for G3-Tyr-PROXYL-ONa under the
same conditions and at the same concentration as for G0- to G3-Tyr-PROXYL-OLi,28 (link) comparing the corresponding double integration
value of the EPR spectrum with those of the former ones, resulting
in an area matching the full radical substitution. EPR spectra of
urine were carried out in a quartz flat cell, and the different organ
tissues were analyzed using a quartz tissue cell. Previously,
tissue organs were weighed in an analytical balance.
resonance spectroscopy (EPR) spectra were
obtained with an X-Band (9.7 GHz) Bruker ELEXSYS 500 spectrometer
equipped with a ST8911 microwave cavity, a Bruker variable-temperature
unit, a field frequency lock system Bruker ER 033 M and equipped with
an NMR Gaussmeter Bruker ER 035 M. The modulation amplitude was kept
well below the line width, and the microwave power was well below
saturation. All liquid samples were previously degassed with Ar. A
quantitative EPR study was performed for G3-Tyr-PROXYL-ONa under the
same conditions and at the same concentration as for G0- to G3-Tyr-PROXYL-OLi,28 (link) comparing the corresponding double integration
value of the EPR spectrum with those of the former ones, resulting
in an area matching the full radical substitution. EPR spectra of
urine were carried out in a quartz flat cell, and the different organ
tissues were analyzed using a quartz tissue cell. Previously,
tissue organs were weighed in an analytical balance.
6
Comprehensive Materials Characterization Protocol
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All reagents were purchased from
commercial sources and used without further purification. Carbon,
nitrogen, and hydrogen were determined on a EuroVector EA 3000 CHNSO
analyzer. Fourier transform-infrared (FT-IR) spectra were recorded
on KBr pellets using a Shimadzu FTIR-8400S spectrophotometer (400–4000
cm–1 range, 4 cm–1 resolution,
20 scans per spectrum). Thermogravimetric analyses (TGA) were carried
out from room temperature to 600 °C at a rate of 5 °C min–1 on a Mettler-Toledo TGA/SDTA 851e thermobalance
under a 50 cm3 min–1 flow of synthetic
air. Powder X-ray diffraction (PXRD) patterns were collected on a
Bruker D8 Advance diffractometer operating at 40 kV/40 mA and equipped
with Cu Kα radiation (λ = 1.5418 Å), a Vantec-1 PSD
detector, an Anton Parr HTK2000 high-temperature furnace, and Pt sample
holder. Data sets were acquired in 2θ steps of 0.033° in
the 5 ≤ 2θ ≤ 40 range (a) from 30 to 600 °C
every 10 °C, (b) from 30 to 150 °C every 5 °C, and
(c) from 150 to 30 °C every 5 °C. Electron spin resonance
(ESR) spectra were recorded on Bruker ELEXSYS 500 (superhigh-Q resonator
ER-4123-SHQ) and Bruker EMX (ER-510-QT resonator) continuous wave
spectrometers for the Q- and X-bands, respectively.
commercial sources and used without further purification. Carbon,
nitrogen, and hydrogen were determined on a EuroVector EA 3000 CHNSO
analyzer. Fourier transform-infrared (FT-IR) spectra were recorded
on KBr pellets using a Shimadzu FTIR-8400S spectrophotometer (400–4000
cm–1 range, 4 cm–1 resolution,
20 scans per spectrum). Thermogravimetric analyses (TGA) were carried
out from room temperature to 600 °C at a rate of 5 °C min–1 on a Mettler-Toledo TGA/SDTA 851e thermobalance
under a 50 cm3 min–1 flow of synthetic
air. Powder X-ray diffraction (PXRD) patterns were collected on a
Bruker D8 Advance diffractometer operating at 40 kV/40 mA and equipped
with Cu Kα radiation (λ = 1.5418 Å), a Vantec-1 PSD
detector, an Anton Parr HTK2000 high-temperature furnace, and Pt sample
holder. Data sets were acquired in 2θ steps of 0.033° in
the 5 ≤ 2θ ≤ 40 range (a) from 30 to 600 °C
every 10 °C, (b) from 30 to 150 °C every 5 °C, and
(c) from 150 to 30 °C every 5 °C. Electron spin resonance
(ESR) spectra were recorded on Bruker ELEXSYS 500 (superhigh-Q resonator
ER-4123-SHQ) and Bruker EMX (ER-510-QT resonator) continuous wave
spectrometers for the Q- and X-bands, respectively.
7
Quantifying Protein-Ligand Interactions via CW-EPR
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Continuous wave X-band EPR spectroscopy data were collected on a Bruker ELEXSYS 500 spectrometer (Bruker BioSpin Corporation, Billerica, MA) using an ER4122 cavity at room temperature under nonsaturating conditions over 100 G with a 1.5 G modulation amplitude and a 42 s scan time. Samples were contained in a glass capillary. Quantitation of the IreB-bound population was obtained by deconvoluting the multicomponent EPR spectra through spectral subtraction of the corresponding apo spectrum from each composite spectrum and comparison of the integrated values (Schultz & Klug, 2018 ). Spectral data were analyzed and quantitated in triplicate.
8
EPR Spectroscopy under Cryogenic Conditions
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Measurements were performed on Bruker Elexsys-500 (9 GHz) under 30 K with modulation frequency 100 KHz.
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