TOTAL PROTEINS AND 11S PROTEIN-FRACTION (HELIANTHININ) OF SUNFLOWER SEED (HELIANTHUS-ANNUUS L) - EFFECT OF ACETYLATION AND SUCCINYLATION

The total proteins and helianthinin (11S) from sunflower seeds were ch emically modified by acetylation and succinylation. The extent of acet ylation of the total proteins and helianthinin were 12%, 51%, 52%, 56% and 12%, 36%, 69%, 71%, respectively, while the extent of succinylati on were 8%, 21%, 33%, 49% and 10%, 30%, 44%. 61%, respectively. The ex tent of modification was monitored by the availability of free lysyl r esidues in the proteins. The ultraviolet absorption maximum shifted to higher wavelengths in total proteins and in helianthinin; there was a lso an increase in absorbance in the 260 nm wavelength, as a function of increased chemical modification. The sedimentation velocity profile indicated the dissociation of the proteins to low molecular weight fr action (2S) through a 7S component. The dissociation occurred at low m odification levels in both total proteins and in helianthinin. There w as a gradual red shift and quenching in the fluorescence emission maxi mum at higher modification levels indicating the denaturation of the p roteins as a result of this chemical modification. The change in absor bance as a function of temperature indicates minor changes suggesting that the conformation of the proteins is already altered to significan t extents due to the chemical modification.