CIRCULAR DICHROISM OF BENCE-JONES PROTEINS AND IMMUNOGLOBULINS G

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 0.15 M KCI was investigated over the wavelength range from 200 to 325 mμ. All the CD spectra of these proteins had a negative maximum at around 217 mμ 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 240 mμ 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 298 mμ, whereas the type L Bence-Jones proteins showed a positive maximum between 300 and 310 mμ. Only one of the five type L Bence-Jones proteins gave a negative maximum at 310 mμ. 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. © 1968 by the Journal of Biochemistry.