Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2002 Oct 29;99(22):14165-70.
doi: 10.1073/pnas.212507199. Epub 2002 Oct 21.

Effect of polyethylene glycol on the liquid-liquid phase transition in aqueous protein solutions

Onofrio Annunziata  1 , Neer Asherie, Aleksey Lomakin, Jayanti Pande, Olutayo Ogun, George B Benedek
Affiliations

Effect of polyethylene glycol on the liquid-liquid phase transition in aqueous protein solutions

Onofrio Annunziata et al. Proc Natl Acad Sci U S A. .

Abstract

We have studied the effect of polyethylene glycol (PEG) on the liquid-liquid phase separation (LLPS) of aqueous solutions of bovine gammaD-crystallin (gammaD), a protein in the eye lens. We observe that the phase separation temperature increases with both PEG concentration and PEG molecular weight. PEG partitioning, which is the difference between the PEG concentration in the two coexisting phases, has been measured experimentally and observed to increase with PEG molecular weight. The measurements of both LLPS temperature and PEG partitioning in the ternary gammaD-PEG-water systems are used to successfully predict the location of the liquid-liquid phase boundary of the binary gammaD-water system. We show that our LLPS measurements can be also used to estimate the protein solubility as a function of the concentration of crystallizing agents. Moreover, the slope of the tie-lines and the dependence of LLPS temperature on polymer concentration provide a powerful and sensitive check of the validity of excluded volume models. Finally, we show that the increase of the LLPS temperature with PEG concentration is due to attractive protein-protein interactions.

PubMed Disclaimer

Figures

Fig 1.
Fig 1.
LLPS temperature at constant PEG concentration of ≈50 mg/ml for the γD-PEG-water ternary system. The average molecular masses are: 200 g/mol (▪), 400 g/mol (•), 1,000 g/mol (⧫), 1,450 g/mol (▴), and 3,350 g/mol (▾). The solid curves are guides for the eye. The values for the γD-tetraethylene glycol-water ternary system are represented by open squares (□). We draw the coexistence curve for the γD-water binary system (dashed curve). The vertical bars (|) locate the critical point.
Fig 2.
Fig 2.
Coexisting surfaces at constant temperature for the γD-PEG-water ternary system with PEG average molecular mass: 200 g/mol (279.2 K, case A), 400 g/mol (281.7 K, case B), and 1,000 g/mol (290.3 K, case C). The pairs of points representing the coexisting phases (•) are connected by the tie-lines (solid lines). The dashed curves are guides for the eye, and the vertical bars (|) locate the critical point.
Fig 3.
Fig 3.
Dependence of the size ratio, q, as a function of the square root of the PEG average molecular weight, Mn. The filled circles (•) are the value obtained by fitting the experimental coexisting compositions with Eq. 2; the open circles (○) are the values calculated from the polymer gyration radii and the protein molecular volume. The dashed lines are guides for the eye.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Albertsson P. A., (1986) Partition of Cell Particles and Macromolecules (Wiley, New York).
    1. Abbott N. L., Blankschtein, D. & Hatton, T. A. (1991) Macromolecules 24, 4334-4348.
    1. McPherson A., (1999) Crystallization of Biological Macromolecules (Cold Spring Harbor Lab. Press, Plainview, NY).
    1. Finet S. & Tardieu, A. (2001) J. Cryst. Growth 232, 40-49.
    1. Kulkarni A. M., Chatterjee, A. P., Schweizer, K. S. & Zukoski, C. F. (2000) J. Chem. Phys. 113, 9863-9873.

Publication types

LinkOut - more resources