Local Motions in Proteins as Investigated by the Thermal Coefficient of the Frictional Resistance to Rotation (Protein Dynamics, Fluorescence, Viscosity)

The thermal coefficient of the viscosity (b) was measured through the fluorescence polarization of tryptophan and tyrosine both free in solution and as intrinsic protein chromophores. For free fluorophores it was found: (1) b is a function of the solvent only and is independent of the probe used in its measurement, (2) the values of b are equal to those determined by flow viscometry. In proteins two values of b are observed; one at lower temperatures, b(S) equal to the thermal coefficient of the solvent viscosity and at higher temperatures a second, reduced value (b(U)) is seen, the magnitude of which is distinctive of the individual protein. The transition from b(S) to b(U) occurs at the rotational amplitude at which the motions of the chromophore become limited by the surrounding peptide. The magnitude of b(U) appears to depend on the extent of coupling between the motions of the chromophore and the surrounding protein subdomain. This subdomain is characterized by only a few amino acids, indicating the importance of the immediate environment. Through a simple thermodynamic model, the enthalpy change for these coupling in motions can be calculated. In certain proteins containing two sets of fluorophores in very heterogeneous environments, the individual parameters for each can be discerned.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Scarlata, Suzanne Frances

• Chemistry, Physical

Identifier

(UMI)AAI8502289

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70282