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. 2009 Jan;20(1):123–130. doi: 10.1681/ASN.2007111233

Figure 1.

Figure 1.

Formation of N-terminal albumin fragments in NRK cell supernatants. (A) MALDI-TOF-MS analysis of supernatants from NRK cells exposed or not to rat serum albumin (0.5 mg/ml). Samples were acidified to pH 2.5 and extracted on C18 ZipTip. The most abundant newly formed compounds were identified as ALB1-24, ALB1-27, and ALB1-30. *Corresponds to a modified form of ALB1-24, with pyroglutamic acid at position 1 (see Supplemental Figure 1). (B) Sequence and monoisotopic molecular mass of the [M+H]+ ions of ALB1-24, ALB1-27, and ALB1-30. (C) MALDI-TOF-MS analysis of supernatants from NRK cells exposed to albumin in the presence or absence of pepstatin A (10 μg/ml). The two peak groups refer to the isotopic cluster of ALB1-24 and to the internal standard 15N, 13C-ALB1-24, respectively (labels refer to the monoisotopic peak). In the presence of pepstatin A, signals of ALB1-24 but not those of the internal standard disappeared, indicating complete suppression of ALB1-24 formation (n = 3).