Thermal stability of of TriFabs. Temperature-induced aggregation and unfolding of various TriFabs (hapten-specificity in the stem-Fv) was measured by light scattering and tryptophan fluorescence (details in M&M and supplemental data, Figure S2). Listed are aggregation onset temperatures (Tagg) defined as the temperature at which the scattered light intensity begins to increase, and denaturation temperatures (Tm) defined as inflection points of curves that represent ratios of fluorescence intensities at 350 and 330 nm.