| 26 |
|
bilayers form a corrugated or ``rippled'' phase ($P_{\beta'}$) which |
| 27 |
|
appears as an intermediate phase between the gel ($L_\beta$) and fluid |
| 28 |
|
($L_{\alpha}$) phases. The $P_{\beta'}$ phase has attracted |
| 29 |
< |
substantial experimental interest over the past 30 years. Most |
| 30 |
< |
structural information of the ripple phase has been obtained by the |
| 31 |
< |
X-ray diffraction~\cite{Sun96,Katsaras00} and freeze-fracture electron |
| 32 |
< |
microscopy (FFEM).~\cite{Copeland80,Meyer96} The X-ray diffraction |
| 33 |
< |
work by Katsaras {\it et al.} showed that a rich phase diagram |
| 34 |
< |
exhibiting both {\it asymmetric} and {\it symmetric} ripples is |
| 35 |
< |
possible for lecithin bilayers.\cite{Katsaras00} Recently, Kaasgaard |
| 36 |
< |
{\it et al.} used atomic force microscopy (AFM) to observe ripple |
| 37 |
< |
phase morphology in bilayers supported on mica.~\cite{Kaasgaard03} The |
| 38 |
< |
experimental results provide strong support for a 2-dimensional |
| 39 |
< |
triangular packing lattice of the lipid molecules within the ripple |
| 40 |
< |
phase. This is a notable change from the observed lipid packing |
| 41 |
< |
within the gel phase,~\cite{Cevc87} although Tenchov {\it et al.} have |
| 42 |
< |
recently observed near-hexagonal packing in some phosphatidylcholine |
| 43 |
< |
(PC) gel phases.~\cite{Tenchov2001} There have been a number of |
| 44 |
< |
theoretical |
| 29 |
> |
substantial experimental interest over the past 30 |
| 30 |
> |
years,~\cite{Sun96,Katsaras00,Copeland80,Meyer96,Kaasgaard03} and |
| 31 |
> |
there have been a number of theoretical |
| 32 |
|
approaches~\cite{Marder84,Carlson87,Goldstein88,McCullough90,Lubensky93,Misbah98,Heimburg00,Kubica02,Bannerjee02} |
| 33 |
|
(and some heroic |
| 34 |
|
simulations~\cite{Ayton02,Jiang04,Brannigan04a,deVries05,deJoannis06}) |
