The name is absent

PC with increasing mole fractions of anionic PS (X_ps) to increase the surface charge
density and potential in a predictable way. Electrostatic measurements were made in
buffer with different tips, on membranes with X_ps varying from 0.05 to 0.5.

2.2 Materials and methods

2.2.1 Preparation of DOPC:DOPS supported Iipid membranes

Following the general methods described in [1], Lyophilized dioleoylphosphatidylserine
(DOPS-anionic lipid) and dioleoylphosphatidylcholine (DOPC-Zwitterionic lipid)
obtained from Avanti Polar Lipids, Alabaster, AL, were dissolved in chloroform and
mixed at various relative mole fractions. The mixtures were dried under nitrogen gas,
placed under low vacuum for at least 1 h, and then hydrated with deoxygenated double
deionized water for a final lipid concentration of ~2 mg∕mL. The lipid solutions stood
overnight in a dark, room-temperature environment followed by vigorous agitation for at
least 1 h. The resulting multilamellar vesicle solutions were refrigerated and stored for up
to two weeks. Supported lipid bilayer membranes for AFM analysis were formed on mica
substrates by vesicle fusion [17]. A 100 mL drop of the multilamellar vesicle solution at a
lipid concentration of 20-200 mg∕mL (diluted from stock in double deionized water) was
placed on the mica for 20 min at 35—40 ⁰C. The sample was then rinsed with double
deionized water and placed under a 0.5 mM solution of Tris buffer at pH 7 for AFM
imaging and analysis in fluid tapping mode (Multimode NanoScope ΓV, Veeco
Metrology, Santa Barbara, CA).

15

<<   24   25   26   27   28   29   30   >>

More intriguing information