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Equilibrium cluster formation in concentrated protein solutions and colloids


Controlling interparticle interactions, aggregation and cluster formation is of central importance in a number of areas, ranging from cluster formation in various disease processes to protein crystallography and the production of photonic crystals. Recent developments in the description of the interaction of colloidal particles with short-range attractive potentials have led to interesting findings including metastable liquid–liquid phase separation and the formation of dynamically arrested states (such as the existence of attractive and repulsive glasses, and transient gels)1,2,3,4,5,6,7. The emerging glass paradigm has been successfully applied to complex soft-matter systems, such as colloid–polymer systems8 and concentrated protein solutions9. However, intriguing problems like the frequent occurrence of cluster phases remain10,11,12,13. Here we report small-angle scattering and confocal microscopy investigations of two model systems: protein solutions and colloid–polymer mixtures. We demonstrate that in both systems, a combination of short-range attraction and long-range repulsion results in the formation of small equilibrium clusters. We discuss the relevance of this finding for nucleation processes during protein crystallization, protein or DNA self-assembly and the previously observed formation of cluster and gel phases in colloidal suspensions12,13,14,15,16,17.

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Figure 1: Normalized scattered intensity I(q)/c and corresponding effective structure factors Seff(q), as obtained by SAXS from lysozyme solutions of different concentrations c.
Figure 2: Effect of concentration and temperature on the effective structure factor Seff(q) as obtained by SANS.
Figure 3: Clusters in protein solutions and colloidal suspensions.
Figure 4: Effect of temperature and ionic strength on the effective structure factor Seff(q), obtained by SAXS.


  1. Dawson, K. A. The glass paradigm for colloidal glasses, gels, and other arrested states driven by attractive interactions. Curr. Opin. Colloid Interf. Sci. 7, 218–227 (2002)

    CAS  Article  Google Scholar 

  2. Trappe, V., Prasad, V., Cipelletti, L., Segre, P. N. & Weitz, D. A. Jamming phase diagram for attractive particles. Nature 411, 772–775 (2001)

    ADS  CAS  Article  Google Scholar 

  3. Sciortino, F. Disordered materials: one liquid, two glasses. Nature Mater. 1, 145–146 (2002)

    ADS  CAS  Article  Google Scholar 

  4. Pham, K. N. et al. Multiple glassy states in a simple model system. Science 296, 104–106 (2002)

    ADS  CAS  Article  Google Scholar 

  5. Eckert, T. & Bartsch, E. Re-entrant glass transition in a colloid-polymer mixture with depletion attractions. Phys. Rev. Lett. 89, 125701–125704 (2002)

    ADS  CAS  Article  Google Scholar 

  6. Weeks, E. R., Crocker, J. C., Levitt, A. C., Schofield, A. & Weitz, D. A. Three-dimensional direct imaging of structural relaxation near the colloidal glass transition. Science 287, 627–631 (2000)

    ADS  CAS  Article  Google Scholar 

  7. Foffi, G. et al. Phase equilibria and glass transition in colloidal systems with short-ranged attractive interactions: application to protein crystallization. Phys Rev. E 65, 031407–031417 (2002)

    ADS  Article  Google Scholar 

  8. Bergenholtz, J., Poon, W. C. K. & Fuchs, M. Gelation in model colloid-polymer mixtures. Langmuir 19, 4493–4503 (2003)

    CAS  Article  Google Scholar 

  9. Kulkarni, A. M., Dixit, N. M. & Zukoski, C. F. Ergodic and non-ergodic phase transitions in globular protein suspensions. Faraday Discuss. 123, 37–50 (2003)

    ADS  CAS  Article  Google Scholar 

  10. Puertas, A. M., Fuchs, M. & Cates, M. E. Dynamical heterogeneities close to a colloidal gel. J. Chem. Phys. 121, 2813–2822 (2004)

    ADS  CAS  Article  Google Scholar 

  11. Sciortino, F., Mossa, S., Zaccarelli, E. & Tartaglia, P. Equilibrium cluster phases and low-density arrested disordered states: The role of short-range attraction and long-range repulsion. Phys. Rev. Lett. 93, 055701 (2004)

    ADS  Article  Google Scholar 

  12. Groenewold, J. & Kegel, W. K. Anomalously large equilibrium clusters of colloids. J. Phys. Chem. B 105, 11702–11709 (2001)

    CAS  Article  Google Scholar 

  13. Segré, P. N., Prasad, V., Schofield, A. B. & Weitz, D. A. Glasslike kinetic arrest at colloidal-gelation transition. Phys. Rev. Lett. 86, 6042–6045 (2001)

    ADS  Article  Google Scholar 

  14. Guillot, S., Delsanti, M., Désert, S. & Langevin, D. Surfactant-induced collapse of polymer chains and monodisperse growth of aggregates near the precipitation boundary in carboxymethylcellulose-DTAB aqueous solutions. Langmuir 19, 230–237 (2003)

    CAS  Article  Google Scholar 

  15. Muschol, M. & Rosenberger, F. Liquid-liquid phase separation in supersaturated lysozyme solutions and associated precipitate formation/crystallization. J. Chem. Phys. 107, 1953–1962 (1997)

    ADS  CAS  Article  Google Scholar 

  16. Pedersen, J. S., Hansen, S. & Bauer, R. The aggregation behavior of zinc-free insulin studied by small-angle neutron scattering. Eur. Biophys. J. 22, 379–389 (1994)

    CAS  Article  Google Scholar 

  17. Piazza, R. Interactions and phase transitions in protein solutions. Curr. Opin. Colloid Interf. Sci. 5, 38–43 (2000)

    CAS  Article  Google Scholar 

  18. Malfois, M., Bonnete, F., Belloni, L. & Tardieu, A. A model of attractive interactions to account for fluid-fluid phase separation of protein solutions. J. Chem. Phys. 105, 3290–3300 (1996)

    ADS  CAS  Article  Google Scholar 

  19. Broide, M. L., Tomic, T. M. & Saxowsky, M. D. Using phase transitions to investigate the effect of salts on protein interactions. Phys. Rev. E 53, 6325–6335 (1996)

    ADS  CAS  Article  Google Scholar 

  20. Schurtenberger, P., Chamberlin, R. A., Thurston, G. M., Thomson, J. A. & Benedek, G. B. Observation of critical phenomena in a protein-water solution. Phys. Rev. Lett. 63, 2064–2067 (1989)

    ADS  CAS  Article  Google Scholar 

  21. Yethiraj, A. & Van Blaaderen, A. A colloidal model system with an interaction tunable from hard sphere to soft and dipolar. Nature 421, 513–517 (2003)

    ADS  CAS  Article  Google Scholar 

  22. Poon, W. C. K. The physics of a model colloid-polymer mixture. J. Phys. Condens. Matter 14, R859–R880 (2002)

    ADS  CAS  Article  Google Scholar 

  23. Pham, K. N., Egelhaaf, S. U., Pusey, P. N. & Poon, W. C. K. Glasses in hard spheres with short-range attraction. Phys. Rev. E 69, 11503–11516 (2004)

    ADS  CAS  Article  Google Scholar 

  24. Rojas, L., Urban, C., Schurtenberger, P., Gisler, T. & Grünberg, H. H. Reappearance of structure in charge-stabilized suspensions. Europhys. Lett. 60, 802–808 (2002)

    ADS  CAS  Article  Google Scholar 

  25. Tanford, C. & Roxby, R. Interpretation of protein titration curves. Application to lysozyme. Biochemistry 11, 2192–2198 (1972)

    CAS  Article  Google Scholar 

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We thank the Swiss spallation source at the Paul Scherrer Institut (PSI) in Villigen, Switzerland, for the neutron beam time and we acknowledge the help of our local contacts J. Kohlbrecher and S. van Petegem. We thank J. Groenewold, W. Kegel, F. Sciortino, K. Kroy and M. Cates for discussions. We thank A. Schofield for preparing the fluorescent PMMA particles. This work was supported by the Swiss National Science Foundation, the UK Engineering and Physical Sciences Research Council, the Scottish Higher Education Funding Council, and the Marie Curie Network on Dynamical Arrest of Soft Matter and Colloids. A.S. and P.S. conceived and performed the protein experiments; F.C. prepared the pH stabilized protein samples for the control experiments; H.S., W.C.K.P. and S.U.E. carried out and analysed the experiments with the colloid–polymer samples.

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Correspondence to Peter Schurtenberger.

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Supplementary information

Supplementary Figure 1

This figure shows cluster aggregation numbers Nc obtained from samples where the pH is constant at all concentrations compared with those from samples where the pH slightly increases at high concentrations. It demonstrates that there is no measurable influence on Nc upon a small shift in pH. (DOC 38 kb)

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Stradner, A., Sedgwick, H., Cardinaux, F. et al. Equilibrium cluster formation in concentrated protein solutions and colloids. Nature 432, 492–495 (2004).

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