Size-Exclusion Chromatography of Circulating Cardiac Troponin T

In a recent issue of Clinical Chemistry , Fahie-Wilson et al. (1) reported their use of gel-filtration chromatography and size-exclusion chromatography (SEC), combined with off-line measurement, to investigate circulating forms of cardiac troponin T (cTnT). We believe that the presented data did not justify the main conclusion of the paper, that cTnT circulates predominantly in the free, intact form in serum of patients with kidney failure and patients with acute coronary syndrome. Behavior of proteins in SEC is determined mainly by their hydrodynamic volume (expressed as Stokes radius, Rs). Nonglobular proteins are known to have a larger Rs than globular proteins with a comparable relative molecular mass ( M r), and cTnT is far from globular (2). Therefore, as is generally agreed, the separation of the nonglobular cTnT protein in an SEC column is better described with the Rs than the Mw(3). Hence, we used Rs to …