TY - JOUR
T1 - Maximum solubility of cholesterol in phosphatidylcholine and phosphatidylethanolamine bilayers
AU - Huang, Juyang
AU - Buboltz, Jeffrey T.
AU - Feigenson, Gerald W.
N1 - Funding Information:
The authors would like to thank Dr. D. Thiel, Mr. B. Miller, Mr. C. Heaton and Dr. M. Szebenyi for help at CHESS. This work was supported by National Science Foundation Grant MCB-9722818. J.H. was supported, in part, by the W.M. Keck Foundation, and J.T.B., in part, by National Institutes of Health Research Service Award I-T32-GM08267. This work is based upon research conducted at the Cornell High Energy Synchrotron Source (CHESS), which is supported by the National Science Foundation under award DMR-9311772, using the Macromolecular Diffraction at CHESS (MacCHESS) facility, which is supported by award RR-01646 from the National Institutes of Health.
PY - 1999/2/4
Y1 - 1999/2/4
N2 - In any lipid bilayer membrane, there is an upper limit on the cholesterol concentration that can be accommodated within the bilayer structure; excess cholesterol will precipitate as crystals of pure cholesterol monohydrate. This cholesterol solubility limit is a well-defined quantity. It is a first-order phase boundary in the phospholipid/cholesterol phase diagram. There are many different solubility limits in the literature, but no clear picture has emerged that can unify the disparate results. We have studied the effects that different sample preparation methods can have on the apparent experimental solubility limit. We find that artifactual demixing of cholesterol can occur during conventional sample preparation and that this demixed cholesterol may produce artifactual cholesterol crystals. Therefore, phospholipid/cholesterol suspensions which are prepared by conventional methods may manifest variable, falsely low cholesterol solubility limits. We have developed two novel preparative methods which are specifically designed to prevent demixing during sample preparation. For detection of the cholesterol crystals, X-ray diffraction has proven to be quantitative and highly sensitive. Experiments based on these methods yield reproducible and precise cholesterol solubility limits: 66 mol% for phosphatidylcholine (PC) bilayers and 51 mol% for phosphatidylethanolamine (PE) bilayers. We present evidence that these are true, equilibrium values. In contrast to the dramatic headgroup effect (PC vs. PE), acyl chain variations had no effect on the cholesterol solubility limit in four different PC/cholesterol mixtures. Copyright (C) 1999 Elsevier Science B.V.
AB - In any lipid bilayer membrane, there is an upper limit on the cholesterol concentration that can be accommodated within the bilayer structure; excess cholesterol will precipitate as crystals of pure cholesterol monohydrate. This cholesterol solubility limit is a well-defined quantity. It is a first-order phase boundary in the phospholipid/cholesterol phase diagram. There are many different solubility limits in the literature, but no clear picture has emerged that can unify the disparate results. We have studied the effects that different sample preparation methods can have on the apparent experimental solubility limit. We find that artifactual demixing of cholesterol can occur during conventional sample preparation and that this demixed cholesterol may produce artifactual cholesterol crystals. Therefore, phospholipid/cholesterol suspensions which are prepared by conventional methods may manifest variable, falsely low cholesterol solubility limits. We have developed two novel preparative methods which are specifically designed to prevent demixing during sample preparation. For detection of the cholesterol crystals, X-ray diffraction has proven to be quantitative and highly sensitive. Experiments based on these methods yield reproducible and precise cholesterol solubility limits: 66 mol% for phosphatidylcholine (PC) bilayers and 51 mol% for phosphatidylethanolamine (PE) bilayers. We present evidence that these are true, equilibrium values. In contrast to the dramatic headgroup effect (PC vs. PE), acyl chain variations had no effect on the cholesterol solubility limit in four different PC/cholesterol mixtures. Copyright (C) 1999 Elsevier Science B.V.
KW - Cholesterol crystal
KW - Cholesterol monohydrate
KW - Demixing
KW - Liposome preparation
KW - X-ray diffraction
UR - http://www.scopus.com/inward/record.url?scp=0033029569&partnerID=8YFLogxK
U2 - 10.1016/S0005-2736(98)00260-0
DO - 10.1016/S0005-2736(98)00260-0
M3 - Article
C2 - 10076038
AN - SCOPUS:0033029569
SN - 0005-2736
VL - 1417
SP - 89
EP - 100
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 1
ER -