Abstract:
:Membranes made of dimyristoylphosphatidylcholine and cholesterol, one of the simplest paradigms for the study of liquid ordered-disordered phase separation, were investigated using a pulse-EPR spin-labeling method in which bimolecular collision of molecular oxygen with the nitroxide spin label is measured. This method allowed discrimination of liquid-ordered, liquid-disordered, and solid-ordered domains because the collision rates (OTP) differ in these domains. Furthermore, the oxygen transport parameter (OTP) profile across the bilayer provides unique information about the three-dimensional dynamic organization of the membrane domains. First, the OTP in the bilayer center in the liquid-ordered domain was comparable to that in the liquid-disordered domain without cholesterol, but the OTP near the membrane surface (up to carbon 9) was substantially smaller in the ordered domain, i.e., the cholesterol-based liquid-ordered domain is ordered only near the membrane surface, still retaining high levels of disorder in the bilayer center. This property may facilitate lateral mobility in ordered domains. Second, in the liquid-disordered domain, the domains with approximately 5 mol % cholesterol exhibited higher OTP than those without cholesterol, everywhere across the membrane. Third, the transmembrane OTP profile in the liquid-ordered domain that contained 50 mol % cholesterol dramatically differed from that which contained 27 mol % cholesterol.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Subczynski WK,Wisniewska A,Hyde JS,Kusumi Adoi
10.1529/biophysj.106.097568subject
Has Abstractpub_date
2007-03-01 00:00:00pages
1573-84issue
5eissn
0006-3495issn
1542-0086pii
S0006-3495(07)70965-7journal_volume
92pub_type
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