Fig. 4

MS analysis of trypsin-treated nisin Z samples. A Schematic representation of mature nisin Z. Potential trypsin cleavage sites are indicated by dashed lines and the possible nisin Z fragments that result from complete or partial cleavage and their corresponding molecular mass (in Da) are indicated by different letters (a–e). B Mass spectrometry of untreated nisin Z (−) or after treatment for 10 and 24 h with trypsin. Peaks corresponding to mature active nisin Z or fragments predicted to result from complete or partial cleavage by trypsin are highlighted with red boxes and arrows and their mass/charge ratios are indicated