Figure 4

Mass spectrometry of ASP-2 samples at ph 5 and 8.5 Pure ASP-2 samples that were prepared as described were titrated to pH 5 and pH 8.5 and incubated at room temperature. The first panel shows a profile following incubation at pH 8.5 and the second panel, at pH 5. The pro-peptide has an estimated Mw = 2535-Da. the ph 5 contains two peaks of 1094.4 and 1352.3 that are not present at pH 8.5. These correspond closely to the estimated mw of two fragments of the pro-sequence namely, QHGIRLPLR (1089) and SGLGGAPLGLRLPR (1364). Solid lines display the detected peaks in each sample. Dotted lines indicate the estimated positions corresponding to the pro-peptide fragments as calculated above; these estimated values of these peaks are boxed. The profiles seen indicate percentage of intensity against mass/charge ratio.