Light-scattering measurement of lipid-glycoprotein interaction

Light-scattering measurements of DHPC (1,2 dihehadecyl-sn-glycero-3-phosphatidylcholine) vesicles and complex DHPC-ovomucoid were used to follow the time course of the osmotic response after mixing with solutions containing various salts and neurtral molecules. The osmotic effects of these salts and neutral molecules. on pure DHPC vesicles and vesicles formed by the complex DHPC-ovomucoid can be used to characterize the membrane permeability under the conditions of the experiment. The half-permeation times were determined in the presence and absence of the ovomucoid. The presence of ovomucoid on the vesicles appears to increase the half-permeation times of positively charged salt ions in comparison to the negatively charged dipicrylamine, (DPA^-) lipophilic ion. This phenomenon is explained in terms of complex formation thereby diminishing the available negatively charged ionic groups which presumably are involved in the transition process across the lipid vesicles. The half-permeation times for neutral molecules did not change in the presence of ovomucoid. This indicates a mechanism of transition quite different from the one characteristic for the salt ions. On the basis of this evidence and the electrostatic bonding it is concluded that the ovomucoid is bound on the polar surface of the lipid vesicles.