FIGURE 2.

Circular dichroism spectroscopy and analytical ultracentrifugation of a_{NT(104–372)}. A, far UV circular dichroism spectrum of a_{NT(104–372)}. The spectrum indicates that the protein is folded, with the characteristic minima at 208 and 222 nm indicating α helix. B, sedimentation velocity analytical ultracentrifugation experiments were used to examine the concentration dependence of a_{NT(104–372)} dimerization. The c(s) distribution is shown for the construct at three protein concentrations (3.2 μm, 16 μm, and 32 μm). A clear concentration dependence on the oligomeric state can be seen, with an ∼93% monomer at 3.2 μm and an ∼55% dimer at 32 μm. As the samples were all concentrated and then diluted for analytical ultracentrifugation experiments, the concentration-dependent oligomerization is reversible. C, table of data for each peak in the overlaid c(s) distribution in B. The molecular mass and s (20, w) values of each species were calculated using the SEDNTERP and SEDFIT software.