Sodium Potassium Exclusion by a Non-bulk Like Water Fraction in Hen Egg White

Cameron IL1* and Fullerton GD2

1Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, TX 78229-3900 USA

Department of Radiology, University of Colorado, 12700 East 19th Ave., Aurora, CO 80045-2507 USA

*Correspondence E-mail:

Key Words: Water solvency, Ion distribution, Egg white, Solute exclusion

Received June 7th, 2012; Accepted April 23rd, 2013; Published May 20th, 2013; Available online May 30th, 2013

doi: 10.14294/WATER.2013.3



Hen egg white thick gel and thin sol fractions are naturally adjacent membraneless but non-miscible fractions in the egg. Their sodium and potassium concentration was measured by flame photometry. Sodium and potassium were in higher concentration in the thick gel than in the thin sol. Centrifugal force of the thick gel forced its particle rich birefringent domains towards the bottom of the centrifuge tube and a particle poor sol fraction formed at the top of the tube. With time of centrifugation the concentration of sodium and potassium continued to increase in this top particle poor sol fraction. This finding is attributed to the partitioning of sodium and potassium into a more solvent water fraction. The greater extent of protein aggregation and decrease in solvent (water) accessible surface area in thick gel vs. thin sol is proposed to decrease the solute (ion) excluding non-bulk like water fraction towards the bottom of the centrifuge tube and increase the solute solvent water fraction towards the top of the centrifuge tube. This proposed mechanism explains the heterogeneous distribution of ions between thick and thin egg white and is probably applicable to other biological systems.

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