Conformational change of poly(L-lysine) induced by lipid vesicles of dilauroylphosphatidic acid.
The effect of negatively charged dilauroylphosphatidic acid (DLPA) vesicles on the conformation of poly(L-lysine) was investigated by circular dichroism measurements. DLPA vesicles induced a conformational change of poly(L-lysine) from the random coil to beta-structure in 5 mM Tes, pH 7.0. The fraction of induced beta-structure (F beta) was determined via a procedure of curve fitting of the observed spectra to the reference spectra. F beta increased linearly with the molar ratio, r, of DLPA to lysine residues up to r congruent to 0.7, and reached a saturation value of 1 at r greater than 1. Within the range 0.7 less than or equal to r less than or equal to 1, precipitation occurred. The effect of dilution of the negative charge on vesicle membranes was examined by mixing DLPA with dilauroylphosphatidylcholine (DLPC). Although the beta-structure of poly(L-lysine) was also induced by mixed vesicles, the saturation value of F beta decreased with decreasing DLPA content in mixed vesicles. The variation in saturation value of F beta with the composition of mixed vesicles was interpreted in terms of the change in average distance between DLPA head groups in mixed vesicles.
Fukushima
K
K
Department of Chemistry, Faculty of Science, Fukuoka University, Japan.
Muraoka
Y
Y
Inoue
T
T
Shimozawa
R
R
D002942:Circular Dichroism; D008081:Liposomes; D008954:Models, Biological; D010713:Phosphatidylcholines; D011107:Polylysine; D011487:Protein Conformation
D008081:Liposomes; D010713:Phosphatidylcholines; C015153:1,2-dilauroylphosphatidylcholine; D011107:Polylysine