Delta-S-cys-albumin: A lab test that quantifies cumulative exposure of archived human blood plasma and serum samples to thawed conditions

Joshua W. Jeffs, Nilojan Jehanathan, Stephanie M.F. Thibert, Shadi Ferdosi, Linda Pham, Zachary T. Wilson, Christian Breburda, Chad R. Borges

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Exposure of blood plasma/serum (P/S) to thawed conditions (> -30 °C) can produce biomolecular changes that skew measurements of biomarkers within archived patient samples, potentially rendering them unfit for molecular analysis. Because freeze-thaw histories are often poorly documented, objective methods for assessing molecular fitness before analysis are needed. We report a 10-μl, dilute-and-shoot, intact-protein mass spectrometric assay of albumin proteoforms called “Δ S-Cys-Albumin” that quantifies cumulative exposure of archived P/S samples to thawed conditions. The relative abundance of S-cysteinylated (oxidized) albumin in P/S increases inexorably but to a maximum value under 100% when samples are exposed to temperatures > -30 °C. The difference in the relative abundance of S-cysteinylated albumin (S-Cys-Alb) before and after an intentional incubation period that drives this proteoform to its maximum level is denoted as Δ S-Cys-Albumin. Δ S-Cys-Albumin in fully expired samples is zero. The range (mean ± 95% CI) observed for Δ S-Cys-Albumin in fresh cardiac patient P/S (n = 97) was, for plasma 12-29% (20.9 ± 0.75%) and for serum 10 -24% (15.5 ± 0.64%). The multireaction rate law that governs S-Cys-Alb formation in P/S was determined and shown to predict the rate of formation of S-Cys-Alb in plasma and serum samples-a step that enables back-calculation of the time at which unknown P/S specimens have been exposed to room temperature. A blind challenge demonstrated that Δ S-Cys-Albumin can detect exposure of groups (n = 6 each) of P/S samples to 23 °C for 2 h, 4 °C for 16 h, or -20 °C for 24 h-and exposure of individual specimens for modestly increased times. An unplanned case study of nominally pristine serum samples collected under NIH-sponsorship demonstrated that empirical evidence is required to ensure accurate knowledge of archived P/S biospecimen storage history.

Original languageEnglish (US)
Pages (from-to)2121-2137
Number of pages17
JournalMolecular and Cellular Proteomics
Issue number10
StatePublished - 2019

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Molecular Biology


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