The ultraviolet rotatory dispersion and conformation of Bence-Jones proteins.

The optical rotatory dispersion of five individual specimens of Bence-Jones proteins was investigated, including the far ultraviolet spectral zone. The Mo5tt constants (bo) were determined, and either low positive or low negative values were found. The rotatory dispersion curves of all specimens had flat negative minima at 220 to 235 rnp and positive maxima at 204 to 212 rnp. Denaturation with acid indicated disorganization of the macromolecules, whereas heating at 50” with decyl sulfate induced a transition indicating the presence of the a-helical conformation in a part of the chains. The finding of Hamaguchi and Migita that the antigenic Type K (or I) proteins in 40% chloroethanol have more negative b0 values than the Type L (or II) proteins was confirmed. The shallow negative minimum in the curves of the Type K proteins was found at 220 to 224 rnp, whereas the minimum of the Type L proteins was at 228 to 235 rnp.