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Further Understanding the Physical Phenomena of Crowded Protein Osmotic Pressure and Its Application to Medical Devices

  • Author(s): McBride, Devin William
  • Advisor(s): Rodgers, Victor G J
  • et al.
Abstract

Extending the understanding of the Physical Phenomenon of Crowded and Concentrated Protein Osmotic Pressure is the focus of this dissertation. Herein, three osmotic pressure models are further developed to gain insight into the mechanisms which cause the non-ideal osmotic pressure associated with crowded and concentrated solutions.

The free-solvent osmotic pressure model has been extended to allow for the solvent accessible surface area (SASA) of proteins to the determined. The free-solvent model predicted SASA is in excellent agreement with the SASA computed using the molecular structure for various macromolecules. The physical parameters of the free-solvent model are assessed to determine the sensitivity of these parameters when overlapping osmotic pressure data is observed for two proteins. Finally, the free-solvent model is extended to allow for protein-protein interactions to be incorporated into the prediction of osmotic pressure.

The fitted parameters of two empirical osmotic pressure models, the activity coefficient and the virial coefficient, are given new meaning based on solute-solvent interactions. The activity coefficient of water is shown to be the appropriate parameter rather than the activity coefficient of the protein. The virial coefficient was given new meaning using the solute-solvent parameters for solutions in which protein-protein interactions do not occur. The virial coefficients based on solute-solvent interactions are shown to provide similar values to those obtained by osmotic pressure data curve fitting. Finally, the virial coefficients are also correlated to the ionic strength of the solute influenced solvent and the conditions for achieving negative virial coefficients are examined.

A concentrating osmometer is developed to allow for a sinlge protein solution to be used to obtain the entire osmotic pressure vs. concentration profile. The concentrating osmoter is tested using bovine serum albumin solutions which have known osmotic pressure profiles for near-saturation concentrations.

In the second part of this dissertation, the use of concentrated protein osmotic pressure for the development of a treatment for cerebral edema is presented. A novel therapy, direct osmotherapy (DOT), is proposed and a device which utilizes this therapy, an osmotic transport device (OTD), is developed. DOT using an OTD is shown to successfully enhance the survival of animals which have received fatal water intoxication and reduce the edema associated with posttraumatic cerebral edema induced by a traumatic brain injury. The OTD components are examined as a preliminary analysis of the optimal OTD conditions for the treatment of severe cerebral edema.

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