Living State Physics - Week 5

The aim of this week is to understand the elastic, electric and entropic properties of a biomembrane.

"When it comes to atoms, language can be used only as in poetry. The poet, too,

is not nearly so concerned with describing facts as with creating images" (Niels Bohr)

Navigator Tobias Ambjörnsson (VASA11-5038/7723377)

Monday 20/11: 10.00-11.45 (FL71) Bilayers and Membranes.

• Introductory topology and differential geometry
• Free energy for biomembranes
• Curvature elasticity model of lipid membranes
• Shapes of membranes

Monday 20/11: 13.15 - 15.00 (FL71) Bilayers and Membranes (continued)

• Film: Deformation of red blood cells in small vessels.

• Effect of electric fields

• Adhesion

Background material

• W. Helfrich, Elastic Properties of Bilayers: Theory and Possible Experiments, Z. Naturforsch. 28c, 693-703, 1973.

  (The original article in which the elastic energy of lipid membranes is desribed.)

• F. David, S. Leibler, Vanishing tension of fluctuating membranes, J. Phys. II France 1, 959-976, 1991

  (The elastic energy of a lipid membrane is purely governed by bending; it has vanishing tension.

  This rather techniqual article discusses the physical origin of vanishing tension.)

• M. Nakahara, Geometry, Topology and Physics, Institute of Physics Publishing, Bristol, 1990

  (Membranes are mathematically described as a curved surface. Techniques to handle such objects are desribed in this book.

  Particularly section 2.4, which discusses topological invariants, is relevant for the course.)

• M. Do Carmo, Differential Geometry of Curves and Surfaces, Prentice-Hall, New Jersey, 1976.

  (A fairly readable book on differential geometry. Chapter 2 deals with the theory of curved surfaces.

  Section 4.5 desribes the important connection between topology and geometry known as the Gauss-Bonnet theorem.)

• R. Lipowski, E. Sackmann, Structure and Dynamics of Membranes, Elsevier Science B.V., 1995

  (The book to read for a person interested in biological membranes. The elastic theory is described in chapter 8.)

• Peliti: "Shapes and fluctuations of membranes". from "Physics of Biological Systems" by Henrik Flyvbjerg et al.

  Springer-Verlag Berlin 1977 (A good introduction to the elastic properties of membranes)

• The elastic theory of biomembranes, T. Ambjörnsson (1999). (HO25)