Quantitative NMR (Hydroperoxides and aldehydes)
For the high-resolution (HF) 1H NMR quantification of
both hydroperoxides and aldehydes in the LSO samples the procedure
reported by Merkx et al. (2018) was applied. Two aliquots were used per
sample and time point. Single pulse and band selective spectra were
recorded on a Bruker Avance III 600 MHz (14.1 T) NMR spectrometer
(Bruker BioSpin, Switzerland) equipped with a 5 mm BBI-probe or an
Avance III 600 MHz spectrometer equipped with a 5 mm cryo-probe. The
internal temperature of the probe was set at 295 K. The single pulse
experiments were recorded with 4 scans, a relaxation time of 5 s, and an
acquisition time of 4 s. The 90° pulse length was determined
automatically (∼7.2 μs), and the receiver gain was set to the maximum
value. The band-selective pulse used a double echo with gradients using
selective refocusing with a RE-BURP shaped pulse and a 90° pulse in
between the 180° pulses to refocus J-evolution. The length of the shaped
pulses was 1–2 ms, and band-selective spectra were recorded with 16
scans. The relaxation and acquisition times were respectively set to 5
and 2.7 s, the 90° pulse length was determined automatically (∼7.2 μs).
The data was processed with Bruker TopSpin 3.2 software. Before Fourier
transformation, an exponential window function with a line-broadening
factor of 0.3 was applied, followed by automatic baseline correction and
phase correction. The levels of hydroperoxides and aldehydes
(c ox) are both expressed in mmol/kg, calculations
described in Merkx et al (2018).