R. Vladkova et al., Detection of the metastable rippled gel phase in hydrated phosphatidylcholine by fluorescence spectroscopy, BIOPHYS CH, 84(2), 2000, pp. 159-166
Steady-state and time-resolved emission spectroscopy of 1-anilinonaphthalen
e-8-sulfonic acid (ANS) have been used for characterization of the metastab
le rippled gel phase, P-beta'(mst), formed in fully-hydrated diparmitoylpho
sphatidylcholine (DPPC) upon cooling from the liquid crystalline phase L-al
pha [Tenchov et al., Biophys. J. 56 (3989) 757]. The P-beta'(mst) phase of
DPPC clearly differs from the stable P-beta' phase by increased (approximat
e to 27%) ANS emission intensity, by enhanced (approximate to 23%) average
radiative rate constant, and by reduced (approximate to 18%) non-radiative
quenching rate constant. The fluorescence intensity peak at the P-beta' -->
L-alpha transition temperature is replaced by a large, reversible stepwise
intensity drop at the P-beta'(mst) --> L-alpha transition. No such effects
have been found for dimiristoylphosphatidylcholine (DMPC) dispersions conf
irming previous results that DMPC does not form a P-beta'(mst) phase. Since
ANS is known to predominantly reside in the interfacial region, the observ
ed effects indicate differences between the stable and metastable rippled p
hases in the organization and dynamics of their lipid/water interfaces. The
data demonstrate that the metastable rippled phase manifests its appearanc
e also through interactions with small molecules (ANS size similar to 8 Ang
strom). (C) 2000 Elsevier Science B.V. All rights reserved.