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

3. 3 Background & Motivation www.wikipedia.org 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 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).]

4. 4 Background & Motivation www.wikipedia.org 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.

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

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

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

8. 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. 9 Theoretical Consideration H. Kusumaatmaja, Y. Liu, R. Dimova, R. Lipowsky, in preparation (2012).

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

11. 11 Nanotubes: cylindrical or necklace-like

12. 12 Experiments versus Theory

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

14. 14 QCM (quartz crystal microbalance)

15. 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. 16 Spontaneous curvature induced by non- adhesive polymers/particles R 2 =4nm (PEG), R 1 =21nm (dextran)  Ld =20k B T, m=-1/(250nm), experiments: m=-1/(150nm).  Lo =90k B T, m=-1/(1125nm), experiments: m=-1/(850nm). R. Lipowsky, et al. Europhys. Lett., 1998, 43, 219-225.

17. 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. 18 Acknowledgement Prof. Reinhard Lipowsky Dr. Rumiana Dimova Dr. Halim Kusumaatmaja Prof. Xiangling Ji Mr. Ziliang Zhao Thank you for your attention!