Theoretical and experimental peptide masses.

The Thrombin-cleaved sulfated FLAG tag was purified from the remaining proteins (NA and Thrombin) by using a peptide column as described in the Materials and Methods section. Purified peptides were then subjected to negative and positive mode MS.依照材料与方法部分所述的实验流程，通过肽柱从残留蛋白（NA与凝血酶）中纯化得到经凝血酶切割的硫酸化FLAG标签（sulfated FLAG tag）。所得纯化肽段随后分别在正离子模式与负离子模式下进行质谱（MS）分析。