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

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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).]

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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.

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Vesicles Enclosing ATPS as Model Cell System

PEG 8k, Rg=4nm Dextran 500k, Rg=21nm

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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)

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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=90kBT

Ld=20kBT

M. Heinrich, A. Tian, C. Esposito, T. Baumgart, PNAS, 2010, 107, 7208-7213.

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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.

pde

dpe

sin

sinˆ

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Theoretical Consideration

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

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Competition: Tube Formation and Budding

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.

petuR 2~

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

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Nanotubes: cylindrical or necklace-like

pess

petu RR

2

~,2

~

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Experiments versus Theory

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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.

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QCM (quartz crystal microbalance)

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PEG and Dextran are inert to the membrane

QCM-D monitoring of supported lipid bilayer (SLB) formation on a siliconoxide substrate and polymer adsorption. LUV of DOPC about 100nm, PEG 8k.

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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.

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Conclusions1. 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.

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Acknowledgement

Prof. Reinhard LipowskyDr. Rumiana DimovaDr. Halim Kusumaatmaja

Prof. Xiangling JiMr. Ziliang Zhao

Thank you for your attention!