Ultrasonic Absorption in Solutions of Proteins and Peptides and in Suspensions of Liposomes
Strom-Jensen, Philip Reed
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https://hdl.handle.net/2142/70707
Description
Title
Ultrasonic Absorption in Solutions of Proteins and Peptides and in Suspensions of Liposomes
Author(s)
Strom-Jensen, Philip Reed
Issue Date
1983
Department of Study
Physiology and Biophysics
Discipline
Biophysics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biophysics, General
Abstract
Ultrasonic absorption in the following media was determined by the cylindrical resonator technique: aqueous solutions of myoglobin, apomyoglobin, (alpha)-lactalbumin, bacitracin, and the C and N-terminal CNBr cleavage fragments of myoglobin and equeous suspensions of large unilamellar lipid vesicles (LUV) of various compositions. Measurements were performed at temperatures between 20(DEGREES)C and 50(DEGREES)C in the frequency range 0.5 MHz to 7 MHz.
A primary mechanism of absorption in solutions of proteins and peptides was perturbation by the ultrasound of the equilibrium between hydrating and bulk water, producing a distribution of relaxation processes, occuring within the frequency range of this investigation. This hypothesis was supported by the dependence of the ultrasonic absorption on solute surface area and molecular weight and by the effect of phosphate ions on ultrasonic absorption. Those proteins with significant globular structure appear to undergo additional relaxation processes at frequencies above 7 MHz.
Ultrasonic absorption in LUV suspensions increased five to ten fold at the thermotropic, crystalline to liquid-crystalline phase transition of the lipids. This temperature induced absorption peak was significantly broadened by incorporation of cholesterol or gramicidin into the LUV bilayer, presumably due to reduction in size of the cooperative unit of lipid molecules undergoing the transition. At the transition temperature, the ultrasonic absorption was characterized by a narrow distribution of relaxation processes, centered at the relaxation frequencies of 2.1 MHz in pure lipid LUV and 0.75 MHz in five mole percent gramicidin LUV, respectively. These relaxation spectra were attributed to the equilibrium between trans and gauche isomers in the hydrocarbon chains of the lipids.
This investigation was supported by the following grants: 5 T32 CA09067 and CA 1-1-20910-01 of the National Cancer Institute, DHHS; GM12281 of the National Institutes of Health; and 82-9 of the American Cancer Society, Illinois Division.
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