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Competition between budding and tubular formation in vesicles enclosing aqueous polymer solutions

Competition between budding and tubular formation in vesicles enclosing aqueous polymer solutions. Yonggang Liu 1 Theory & Bio-systems, Max Planck Institute of Colloids and Interfaces, Germany

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Competition between budding and tubular formation in vesicles enclosing aqueous polymer solutions

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  1. Competition between budding and tubular formation in vesicles enclosing aqueous polymer solutions Yonggang Liu 1 Theory & Bio-systems, Max Planck Institute of Colloids and Interfaces, Germany 2 State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (CAS)

  2. Outline • Background & Motivation • Experimental Results • Theoretical Consideration • Conclusions

  3. Background & Motivation Macromolecular Crowding within Cell. The cytosol of Escherichia coli contains about 0.3-0.4 g/mL macromolecules. [Zimmerman SB, Trach SO J. Mol. Biol. 222(3), 599–620 (1991).] Diagram of an eukaryotic cell. (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth endoplasmic reticulum (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles within centrosome www.wikipedia.org

  4. Background & Motivation Cell synthesize a large number of macromolecules (for example protein), which were sorted and transported with the help of vesicles. Membranes of endoplasmic reticulum and Golgi apparatus have a rather complex architecture consisting of both sheet-like and tube-like membrane structures. www.wikipedia.org

  5. PEG 8k, Rg=4nm Dextran 500k, Rg=21nm Vesicles Enclosing ATPS as Model Cell System

  6. Membrane transformations Budding versus tubular formation. properties of membrane and membrane-polymer interaction (bending rigidity, spontaneous curvature, wetting, tension) R. Dimova, R. Lipowsky, Soft Matter 2012, in press.

  7. Lo=90kBT Ld=20kBT Multi-Component Vesicles Liquid disordered (Ld) phase: DOPC rich; lower bending rigidity (). Liquid ordered (Lo) phase: DPPC and Cholesterol rich, higher . S. L. Veatch, S. L. Keller, Biophys. J., 2003, 85, 3074–3083. M. Heinrich, A. Tian, C. Esposito, T. Baumgart, PNAS, 2010, 107, 7208-7213.

  8. Spontaneous curvature Nanotubes stabilized by a negative spontaneous curvature of -1/(240nm) Y. Li, R. Lipowsky, R. Dimova, PNAS, 2011, 108, 4731-4736. H. Kusumaatmaja, Y. Li, R. Dimova,R. Lipowsky, PRL 2009, 103, 238103. Y. Liu, R. Lipowsky, R. Dimova, Langmuir 2012, 28, 3831-3839.

  9. Theoretical Consideration H. Kusumaatmaja, Y. Liu, R. Dimova, R. Lipowsky, in preparation (2012).

  10. DOPC/DPPC/Cholesterol=64/15/21, Ld=20kBT, m=-1/150nm, Rtu=75±25nm. DOPC/DPPC/Cholesterol=13/44/43, Lo=90kBT, m=-1/850nm, Rtu=425±150nm. Competition: Tube Formation and Budding H. Kusumaatmaja, Y. Liu, R. Dimova, R. Lipowsky, in preparation (2012).

  11. Nanotubes: cylindrical or necklace-like

  12. Experiments versus Theory

  13. Anchored polymer Non-anchored polymer Desorption (M>0) Adsorption (M<0) Desorption (M<0) Adsorption (M>0) Polymer induced spontaneous curvature R. Lipowsky, Europhys. Lett., 1995, 30, 197-202. R. Lipowsky, et al. Molecular Physics, 2005, 103, 3169-3183.

  14. QCM (quartz crystal microbalance)

  15. PEG and Dextran are inert to the membrane QCM-D monitoring of supported lipid bilayer (SLB) formation on a silicon oxide substrate and polymer adsorption. LUV of DOPC about 100nm, PEG 8k.

  16. Spontaneous curvature induced by non-adhesive polymers/particles R2=4nm (PEG), R1=21nm (dextran) Ld=20kBT, m=-1/(250nm), experiments: m=-1/(150nm). Lo=90kBT, m=-1/(1125nm), experiments: m=-1/(850nm). R. Lipowsky, et al. Europhys. Lett., 1998, 43, 219-225.

  17. Conclusions 1. The competition between budding and tubular formation, is resulting from the competition of the bending energy and the interfacial tension. 2. For vesicles enclosing aqueous polymer solutions, both PEG and dextran were depleted from the membrane, inducing a negative spontaneous curvature.

  18. Acknowledgement Prof. Reinhard LipowskyDr. Rumiana DimovaDr. Halim Kusumaatmaja Prof. Xiangling JiMr. Ziliang Zhao Thank you for your attention!

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