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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