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Sample extraction<br />
Crushed and … Sample extraction<br />
Crushed and frozen samples (10 g) were resuspended in 50 mL of MeOH, including internal standards for standardization of peak areas, and centrifuged (16,000 × g, 3 min, 4°C). Supernatants were dispensed for each analysis as follows: 0.5 mL for ionic metabolites, 1 mL for neutral metabolites, 1 mL for sugars, and 47.5 mL for plant hormones. Because of the small amounts of pear fruit samples obtained in the early periods (2WBB, 1WBB, and B), the initial amounts of these samples were 1 g, extracted in 20 mL of MeOH, and were separately used for each analysis as described above. The residues were subsequently used for starch analysis.<br />
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Untargeted metabolome analysis by LC-QTOF-MS<br />
Extracts (1 mL) containing the internal positive and negative standards 2.5 μM lidocaine and 10-camphorsulfonic acid, respectively, were analyzed using LC-QTOF-MS (LC, Waters Acquity UPLC system; MS, Waters Xevo G2 Q-Tof). Analytical conditions were as follows: LC column, Acquity bridged ethyl hybrid (BEH) C18 (1.7 μm, 2.1 mm × 100 mm, Waters); solvent system, solvent A (water containing 0.1% formic acid) and solvent B (acetonitrile containing 0.1% formic acid); gradient program, 99.5%A/0.5%B at 0 min, 99.5%A/0.5%B at 0.1 min, 20%A/80%B at 10 min, 0.5%A/99.5%B at 10.1 min, 0.5%A/99.5%B at 12.0 min, 99.5%A/0.5%B at 12.1 min and 99.5%A/0.5%B at 15.0 min; flow rate, 0.3 mL/min; column temperature, 40°C; MS detection: capillary voltage, +3.0 keV, cone voltage, 25.0 V, source temperature, 120°C, desolvation temperature, 450°C, cone gas flow, 50 L/h; desolvation gas flow, 800 L/h; collision energy, 6 V; mass range, m/z 100‒1500; scan duration, 0.1 s; interscan delay, 0.014 s; mode, centroid; polarity, positive; Lockspray (leucine enkephalin): scan duration, 1.0 s; interscan delay, 0.1 s. n duration, 1.0 s; interscan delay, 0.1 s.
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