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Table 2 Cystatin C proteoforms detected by MSIA

From: The association of plasma cystatin C proteoforms with diabetic chronic kidney disease

Theoretical m/z Observed m/z Proteoform Label
13,071.833 13,072.684 Cystatin C lacking N-terminal tripeptide (SSP-) des-SSP CysC
13,256.027 13,256.897 Cystatin C lacking one N-terminal serine residue (S-) des-S CysC
13,272.027 13,272.649 Hydroxylated cystatin C (on 3-Pro residue) lacking N-terminal S-residuea des-S 3Pro-OH CysC
13,343.105 13,344.169 Full length, unmodified cystatin C native CysC
13,359.105 13,359.246 Hydroxylated cystatin C in position 3 on proline (Pro) residuea 3Pro-OH CysC
18,276.162 18,276.500 Beta lactoglobulin (internal reference standard) BL
  1. CysC exists in multiple forms. The three main CysC variants are one containing hydroxyproline and 2 truncated variants; one missing N-terminal serine, and one lacking three N-terminal residues. MSIA: Mass Spectrometric Immunoassay. BL: Beta lactoglobulin is the internal standard
  2. aThe hydroxylated variants were co-integrated with their originating proteoforms, therefore were not individually correlated with the clinical parameters