Mi. Angelova et al., Shape transformations of giant unilamellar vesicles induced by ethanol andtemperature variations, COLL SURF A, 149(1-3), 1999, pp. 201-205
Citations number
11
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
The shape transformations of giant unilamellar vesicles (GUVs) of dimyristo
ylphosphatidylcholine (DMPC) in water/ethanol solutions were investigated a
s a function of temperature (18-43 degrees C) and ethanol content (0-40 vol
%). GUVs were prepared by electroformation and their shapes were monitored
by phase-contrast microscopy furnished with an image-recording set-up. Two
systems were compared: (1) GUVs formed in presence of ethanol; and (2) GUVs
preformed in distilled water with ethanol added subsequently. In the first
case, GWs in the gel state are typified by a multifaceted, irregular shape
that transforms into a smooth, rounded shape with increase of temperature.
This transformation is reversible and takes place at about or below 24 deg
rees C. It coincides in temperature with the DMPC gel-liquid crystalline ph
ase transition in the respective water/ethanol solutions. The effect of eth
anol added to GUVs preformed in distilled water is strikingly different. Th
e temperature of the multifaceted (folded)-to-smooth shape transformation f
irst increases from 24 to 37 degrees C with increase of ethanol content up
to 10 vol%, then decreases back to 24 degrees C upon further increase of et
hanol up to 40 vol%. The reversal point of this biphasic effect at 10 vol%
of ethanol coincides with that for formation of DMPC interdigitated phase.
The shape transformations are reversible with a temperature hysteresis of 2
-3 degrees C. They are rather cooperative and take place in a narrow range
of less than 0.2 degrees C at temperatures that remain constant for times o
f up to 15 h. (C) 1999 Elsevier Science B.V. All rights reserved.