| The spin-lattice relaxation rate of an electron (R1e) is the rate of magnetization decay by 180°, or spin flip type decay. R1e is determined by the magnetic environment of the electron. Continuous wave electron paramagnetic (CW-EPR) resonance techniques have traditionally been used to study the dynamics of nucleic acids, and in this body of work R1e measurements are combined with CW-EPR measurement to give detailed information on conformational equilibria at bulged DNA sites. Herein is demonstrated that experimental DNA R1e measurements are about twice the rate predicted by R1e theory for rigid cylindrical molecules, and so R1e theory is adapted to flexible DNA molecules. Comparisons of R1e measurements with and without oxygen (DeltaR 1e) at eleven different spin labeled sites of the p47 phox domain are used to shed light on conformational rearrangement of the protein upon binding to a lipid membrane. DeltaR1e measurements are extended to observing binding of drug candidate peptides to HIV-1 TAR RNA. It was determined by Lai, that the presence of a GAAA endloop versus the wild-type CUGGGA loop had a significant impact on the binding at U23 within the bulge site of TAR, and CW-EPR indicated the identity of the end-loop had large ramifications on the dynamics of the TAR-peptide complexes. R1e and also R2e measurements on an electron within a ZnO quantum dot showed the size- and temperature-dependence of relaxation effects on the electron. These results demonstrate the utility of R1e measurement and theory in answering diverse questions in biophysics and nanotechnology. |
