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|Title:||A Multifrequency Phase and Modulation Lifetime Analysis of Solvent Relaxation and Protein Dynamics (Papain, Bovine, Serum, Albumin)|
|Author(s):||Hall, Robert Duane|
|Department / Program:||Biochemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Steady-state fluorescence spectroscopy has been used to analyze solvent-fluorophor interactions. Two different studies have been carried out, one with conjugates of the polar, biological label, dansylaziridine; and the other with two non-polar molecules, triphenylene and anthracene.
Dansylaziridine was used to label the single sulfhydryls of two proteins, papain (DAZ-papain) and bovine serum albumin (DAZ-BSA). Then the nature of the dipolar environment surrounding the dansyl moieties of the two proteins was established by observing the emission spectra and lifetimes across the emission band of the dansyl fluorescence of several temperatures between 4(DEGREES)C and 60(DEGREES)C.
Fluorescence lifetimes were obtained with a cross-correlation phase and modulation lifetime fluorometer with continuously variable modulation frequencies between 3 and 40 MHz, permitting a multicomponent least-squares analysis of the rates of dipolar relaxation. A two-state analysis has been used to determine the relaxation and anti-relaxation rates, the emissive rate, and the fractions of the two states at various temperatures for a model compound and DAZ-BSA. The dipolar relaxation rates were too fast in the case of papain to obtain quantitative information.
For a model compound, S-(dansylaminoethyl)-2-thioethanol, rates and an activation energy for the dipolar relaxation between -20(DEGREES)C and -60(DEGREES)C were obtained. The anti-relaxation was found to be negligible.
In the case of DAZ-BSA, non-Arrhenius behaviour has been observed for the change in the relaxation rate as a function of temperature. A model has been proposed which assumes dipolar relaxation in the protein to be dependent upon external solvent conditions.
The excitation polarization spectra and emission spectra of triphenylene in propylene glycol at -70(DEGREES)C have been observed in order to study red-edge excitation anomalies claimed by other authors. No anomalous behavior has been found, consistent with the low energies of interaction between polar solvent molecules and non-polar fluorophors.
Emission red shifts produced by red-edge excitation of the last absorption band of anthracene has also been studied. A mixed solvent study with cyclohexanol and methylcyclohexane demonstrates that the energy of interaction between the non-polar anthracene and the polar cyclohexanol is about 200 cal/mole, less than kT at room temperature.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.
|Date Available in IDEALS:||2014-12-15|