FIGURE 3.

Heat resistance of anti-hCG VHH with different preparations and anti-β-lactamase VHH. A, anti-hCG VHH samples prepared from E. coli soluble (circles) and insoluble (squares) fractions were subjected to continuous incubation at 90 °C. Both samples were histidine-tagged at their C termini. B, anti-β-lactamase VHH was subjected to heating-cooling cycles (circles) or continuous incubation at 90 °C (triangles). In heating-cooling cycles, a given number of reaction segments, which consisted of heating at 90 °C for 5 min (m) and cooling at 20 °C for 5 min, were repeated. Both experiments were carried out at pH 7.4 in HBS-EP buffer at a protein concentration of 1.3 μg/ml. Error bars represent S.D. Sup, supernatant; Ppt, precipitate.