Heparin-Sepharose affinity chromatography. Three results are aligned but that in (C; adapted and reprinted with permission from Chang and Harper12) was performed using a different affinity heparin and consequently has noncomparable elution concentrations. (A) Chromatography of the slow component (lane 4, Fig1A) gives a result identical to that obtained with a crystal of the heterodimer,16 with separation into equivalent peaks of -antithrombin and latent antithrombin. (B) Elution profile of antithrombin from plasma incubated for 72 hours at 37°C. The first peak, including fraction 1, had no thrombin-inhibitory activity. (Reprinted with permission.12) (C) Previous larger scale heparin-Sepharose chromatography of a pasteurized commercial concentrate of antithrombin.12 The inactive L (latent) forms make up 40% of the total antithrombin, but the presence of additional peaks reinforces other unpublished evidence that the latent transition may also involve minor stable intermediate forms. All of these forms apparently dimerize, as shown by the single band with dimer mobility on electrophoresis of the concentrate (Fig 3CII).