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).