H. Matsumura et al., EFFECT OF AMINO-ACIDS, POLYPEPTIDES AND PROTEINS ON ELECTROPHORETIC MOBILITIES OF PHOSPHOLIPID LIPOSOMES, Colloids and surfaces. A, Physicochemical and engineering aspects, 92(1-2), 1994, pp. 87-93
The electrophoretic mobilities of liposomes prepared from egg phosphat
idylcholine (PC) immersed in solutions which contain amino acids, poly
peptides or proteins have been studied. Amino acids (lysine - a basic
amino acid, or glutamic acid - an acidic amino acid) cause a pH variat
ion which changes the acid-base dissociation equilibria of charged com
pounds in the PC membranes. Polypeptides (poly(L-lysine) - a cationic
polymer and poly(L-glutamic acid) - an anionic polymer) can adsorb ont
o the membrane surface of the PC liposomes because of their high affin
ity for the membrane, which causes significant changes in the electrop
horetic mobilities towards more positive values in the case of poly(L-
lysine) and causes slight negative shifts in the case of poly(L-glutam
ic acid). Proteins (serum albumin: isoelectric point, pH 4.9; and cyto
chrome c: isoelectric point, pH 10.1) adsorb on the membrane surface,
which decreases the negative value of the electrophoretic mobilities i
n both cases. Furthermore, both proteins shift the zero point of zeta
potential of the lipid liposomes towards the isoelectric point of the
proteins.