Structural changes of the 11 S globulin from sunflower seed (Helianthus annuus L.) after succinylation

The influence of various levels of succinylation on the structure of the 11 S globulin from sunflower seed has been studied by the techniques of sedimentation velocity, viscometry and by circular dichroism spectroscopy in the near and far ultraviolet region. The protein dissociates gradually with increasing degree of succinylation forming 7 S and 5 S intermediates. At a level of 70% succinylation a 2.5 S component occurs as the final product of dissociation. The intrinsic viscosity of the protein does not change remarkably until a succinylation of about 70%, where a drastic viscosity increase is observed. At this level of modification a decrease of the positive circular dichroism bands in the near ultraviolet region takes place. Contrary to this, the negative ellipticity of the far ultraviolet region increases at a high level of modification, suggesting an enhancement of the amount of helix conformation.