Biology 5357: Membranes

Transcription

1 s 5357 Biology 5357: s Assembly and Thermodynamics of Soft Matter Paul H. MD, PhD Department of Cell Biology and Physiology pschlesinger@.wustl.edu

2 Characteristics s 5357 s are polymorphic

3 s 5357 Differential Scanning Calorimetry

4 s 5357 Analysis of a Temperature Transition The peak is a direct measure of the enthalpy of the transiton ( H cal ) At the midpoint, T m, the G = 0 so that S = H cal /T m (4)

5 s 5357 DPPC Thermal Transitions Equilibration of the sample Three transitons

6 s 5357 DPPC Thermal Transitions T m T 1/2 H cal S Revisit the membrane structure for each phase.

7 s 5357 Pseudocrystalline L c Extended aliphatic chains with Φ angle and packing similar to that seen in available crystals of similar phsopholipids

8 s 5357 Gel L β Increased hydration of the headgroup (2 to 15), decreases packing in alkyl chains and some increase in cross sectional area

9 s 5357 Ripple P β At these temperatures long axis rotation dramatically increases but the tilt is retained producing the ripple

10 s 5357 Fluid L α This generates internal rotation in the alkane chains producing kinks that shorten the chains producing thinner and more spread membranes

11 Factors that influence phase behavior s 5357 Non-biological factors Degree of hydration Barotropic effects

12 s 5357 Vesicle size The curvature of vesicles affects the order of the chain packing and the interaction of the head groups.

13 s 5357 Alkane chain length Linear relationship with carbons in the alkane chains Indicates a co-operative threshold at 4 to 5 carbons Use of chain length to respond to environmental changes

14 s 5357 Alkane chain chemistry Linear, branched, cyclohexal substituted chains Mono-unsaturated Position of unsaturation (opt at 9-10) Position of unsaturated chain

15 Interdigitation s 5357 Structural, acyl asymmetry, sphingolipids Head group chain area asymmetry Interdigitation decreases void potential Consequence: Thickness, charge density, coupling loss of midplane

16 s 5357 Head group chemistry Size, polarity, charged groups Isolation of components for study Small, uncharged etc that let alkane chains dominate Charged groups ph, ionic strength Ion layers at the membrane surface

17 s 5357 Interfacial Chemistry Acyl to ether change reduce the Tm (phase destabilization) Amide groups, sphingolipids, increase T m (phase stabilization)

18 s 5357 Intrinsic. Add in the curvature and Helfrich

19 s 5357 curvature Add in the curvature and Helfrich

20 T Heimburg. Thermal Biophysics of s, chapter Introduction to Thermodynamics, pages Wiley-VHC, Weinheim, K.E. van Holde, W.C. Johnson, and P.S. Ho. Principles of Physical Biochemistry, chapter Macromolecules in Solution: Thermodynamics and Equilibrium, pages Prentice Hall, Upper Saddle River, New Jersey USA, s 5357 Add in the curvature and Helfrich S Blundell and K Blundell. Concepts in Thermal Physics, chapter 28. Phase. Oxford University Press, 2009.

21 Emiliano Brini, Christopher J. Fennell, Marivi Fernandez-Serra, Barbara Hribar-Lee, Miha Luksic, and Ken A. Dill. How water s properties are encoded in its molecular structure and energies. Chemical Reviews, 0(0):null, 0. PMID: J. N. Israelachvili. Intermolecular and Surface, chapter Thermodynamic Principles of Self-Assembly, pages Elsevier Inc., s 5357 Add in the curvature and Helfrich

22 D. G. Hall and B. A Pethica. Nonionic surfactants. Marcel Dekker, New York, New York: Dover Pubns. Hill, T. L. Benjamin. Thermodynamics of small systems. Dover Publications, Sarah L. Veatch, Olivier Soubias, Sarah L. Keller, and Klaus Gawrisch. Critical fluctuations in domain-forming lipid mixtures. Proceedings of the National Academy of Sciences, 104(45): , November s 5357 Add in the curvature and Helfrich

23 T. Heimburg. Thermal Biophysics of s, chapter Phase Diagrams, pages Wiley-VHC, Weinheim, Derek Marsh. Liquid-ordered phases induced by cholesterol: A compendium of binary phase diagrams. Biochimica et Biophysica Acta (BBA) - Biomembranes, January s 5357 Add in the curvature and Helfrich

24 Derek Marsh. Cholesterol-induced fluid membrane domains: a compendium of lipid-raft ternary phase diagrams. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1788: , August S. M. Gruner. The Structure of Biological s, chapter Nonlamellar s, pages CRC Press, s 5357 Add in the curvature and Helfrich

25 R. N. A. H. Lewis and R. N. McElhaney. The Structure of Biological s, chapter The Mesomorphic Phase of Lipid Bilayers, pages CRC Press, W. Helfrich. Elastic properties of lipid bilayers: theory and possible experiments. Z. Naturforsch., 28: , s 5357 Add in the curvature and Helfrich

26 H. A. Pinnow and W. Helfrich. Effect of thermal undulations on the bending elasticity and spontaneous curvature of fluid membranes. The European Physical Journal E, 3(2): , Michael F. Brown. Curvature forces in membrane Lipid-Protein interactions. Biochemistry, 51(49): , December s 5357 Add in the curvature and Helfrich

27 S Blundell and K Blundell. Concepts in Thermal Physics, chapter 17. Rods Bubbles and Magnets, pages Oxford University Press, P. H. and M. Saito. The bax pore in liposomes, biophysics. Cell Death and Differentiation, 13: , s 5357 Add in the curvature and Helfrich