title: Relating domain size distribution to line tension and molecular dipole density in model cytoplasmic myelin lipid monolayers.
abstract: We fit the size distribution of liquid-ordered (L(o)) domains measured from fluorescence images of model cytoplasmic myelin monolayers with an equilibrium thermodynamic expression that includes the competing effects of line tension, λ, dipole density difference, Δm, and the mixing entropy. From these fits, we extract the line tension, λ, and dipole density difference, Δm, between the L(o) and liquid-disordered (L(d)) phases. Both λ and Δm decrease with increasing surface pressure, , although λ/Δm(2) remains roughly constant as the monolayer approaches the miscibility surface pressure. As a result, the mean domain size changed little with surface pressure, although the polydispersity increased significantly. The most probable domain radius was significantly smaller than that predicted by the energy alone, showing that the mixing entropy promotes a greater number of smaller domains. Our results also explain why domain shapes are stable; at equilibrium, only a small fraction of the domains are large enough to undergo theoretically predicted shape fluctuations. Monolayers based on the composition of myelin from animals with experimental allergic encephalomyelitis had slightly lower values of λ and Δm, and a higher area fraction of domains, than control monolayers at all . While it is premature to generalize these results to myelin bilayers, our results show that the domain distribution in myelin may be an equilibrium effect and that subtle changes in surface pressure and composition can alter the distribution of material in the monolayer, which will likely also alter the interactions between monolayers important to the adhesion of the myelin sheath.
authors: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
authors: Dong Woog
authors: DW
authors: Lee
authors: Younjin
authors: Y
authors: Min
authors: Prajnaparamitra
authors: P
authors: Dhar
authors: Arun
authors: A
authors: Ramachandran
authors: Jacob N
authors: JN
authors: Israelachvili
authors: Joseph A
authors: JA
authors: Zasadzinski
references: Curr Opin Cell Biol. 2001 Aug;13(4):470-7
references: 11454454
references: Biophys J. 2004 Feb;86(2):905-12
references: 14747326
references: Immunol Rev. 2001 Oct;183:159-72
references: 11782255
references: Trends Cardiovasc Med. 2004 Feb;14(2):37-42
references: 15030787
references: Nature. 2003 Oct 23;425(6960):821-4
references: 14574408
references: J Phys Chem B. 2007 Sep 27;111(38):11091-4
references: 17764170
references: Biophys J. 2005 Aug;89(2):1067-80
references: 15894634
references: Glycoconj J. 2000 Mar-Apr;17(3 -4):143-51
references: 11201785
references: J Cell Sci. 2000 May;113 ( Pt 10):1771-81
references: 10769208
references: Science. 2010 Jan 1;327(5961):46-50
references: 20044567
references: Crit Rev Clin Lab Sci. 1993;30(1):29-64
references: 7683887
references: Biophys J. 2011 Mar 16;100(6):1490-8
references: 21402031
references: Biophys J. 2009 Aug 19;97(4):1087-94
references: 19686656
references: Biophys J. 2005 Feb;88(2):1120-33
references: 15542550
references: J Phys Chem B. 2008 Jul 10;112(27):8063-8
references: 18598009
references: Biophys J. 1988 Feb;53(2):235-45
references: 3345332
references: Biophys J. 2008 Jul;95(1):236-46
references: 18424504
references: J Physiol. 2010 Sep 1;588(Pt 17):3169-78
references: 20519314
references: Proc Natl Acad Sci U S A. 2009 Mar 3;106(9):3154-9
references: 19218452
references: Biophys J. 2008 Jun;94(12):4725-36
references: 18339739
references: Nat Med. 1999 Feb;5(2):170-5
references: 9930864
references: J Biol Chem. 2002 Mar 29;277(13):11292-6
references: 11792705
references: Biochim Biophys Acta. 2004 Jan 20;1688(1):10-7
references: 14732476
references: J Clin Invest. 2004 Mar;113(6):788-94
references: 15067307
references: Proc Natl Acad Sci U S A. 2001 Feb 13;98(4):1353-7
references: 11171954
references: Biochim Biophys Acta. 1978 Apr 10;515(1):1-21
references: 76479
references: Nature. 1979 May 17;279(5710):258-60
references: 440439
references: Biophys J. 2010 Mar 17;98(6):L21-3
references: 20303848