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Soft Matter and Biological Physics

Eur. Phys. J. E 1, 215-225

Elastic properties of nematoid arrangements formed by amoeboid cells

R. Kemkemer1 - D. Kling1 - D. Kaufmann2 - H. Gruler1

1 Department of Biophysics, University of Ulm, 89069 Ulm, Germany
2 Department of Human Genetics, University of Ulm, 89069 Ulm, Germany
hans.gruler@physik.uni-ulm.de

Received 3 May 1999 and Received in final form 29 September 1999

Abstract
In culture migrating and interacting amoeboid cells can form nematoid arrangements in analogy to a nematic liquid crystal phase. A nematoid arrangement is formed if the interaction has an apolar symmetry. Different cell types like human melanocytes (= pigment cells of the skin), human fibroblasts (= connective tissue cells), human osteoblasts (= bone cells), human adipocytes (= fat cells) etc., form a nematoid structure. Our hypothesis is that elastic properties of these nematoid structures can be described in analogy to that of classical nematic liquid crystals. The orientational elastic energy is derived and the orientational defects (disclination) of nematoid arrangements are investigated. The existence of half-numbered disclinations shows that the nematoid structure has an apolar symmetry. The density- and order parameter dependence of the orientational elastic constants and their absolute values are estimated. From the defect structure, one finds that the splay elastic constant is smaller than the bend elastic constant (melanocytes). The core of a disclination is either a cell free space or occupied by non oriented cells (isotropic state), by a cell with a different symmetry, or by another cell type.

PACS
87.10.+e General theory and mathematical aspects - 61.30.-v Liquid crystals - 61.30.Jf Defects in liquid crystals

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