In section 2. Materials and methods, 2.8. Liquid chromatography and mass spectrometry conditions, the gradient elution was decribed: “The gradient elution started with 5% eluent B, which linearly increased to 15% from 1 to 2.5 min, and to 35% from 2.5 to 5 min. The next 4 min were used to re-equilibrate the system to 5% eluent B.” This should be described as: “The gradient elution started with 5% eluent B, which was linearly increased to 20% eluent B from 0.1 to 2 min. From 2.1 min to 4.1 min, it linearly descreased back to 5%. The next 5 min were used to re-equilibrate the system.” The authors would like to apologise for any inconvenience caused.