Circular Dichroism of Bence-Jones Proteins and Immunoglobulins G

Abstract

The circular dichroism (CD) of ten individual samples of Bence-Jones proteins (with five each of type K and type L), and a normal human immunoglobulin G and a myeloma immunoglobulin G of type K in 0.15m KCl was investigated over the wavelength range from 200 to 325mμ. All the CD spectra of these proteins had a negative ma-ximum at around 217mμ which is characteristic of the β structure. The negative ellipticity at this wavelength of the type K Bence Jones proteins was generally smaller than that of the type L Bence Jones proteins except in the case of one K and one L Bence Jones proteins. In the 220 to 240mμ region, three type K Bence Jones proteins exhibited a positive CD band at 228 or 234 mμ, while none of the type L Bence-Jones proteins showed any corresponding extremum. In a still longer wavelength region, the CD spectra of type K Bence Jones proteins had a small but distinct positive maximum between 292 and 298mμ, whereas the type L Bence Jones proteins showed a positive maximum between 300 and 310 mu. Only one of the five type L Bence Jones proteins gave a negative maximum at 310mμ. The CD spectra of a normal and a myeloma immunoglobulin G were very similar to those of Bence Jones proteins. One type K myeloma protein studied here gave a CD spectrum similar to those of type K Bence Jones proteins.