SLOW-TUMBLING ANALYSIS FOR 2D-ELDOR FOR TWO COUPLED NITROXIDES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. There is a considerable interest at ACERT to measure distances between two NO spin probes in membranes from 2D-ELDOR spectra taking into account the electronic dipolar interaction between two spin labels. The advantage is that here one can measure these distances in membranes at ambient temperatures. At present, there is available no computational technique to rigorously take into account the interaction between two spin probes, that is between two electrons and two nuclei for 2D-ELDOR. In order to accomplish this, the technique developed by Schneider and Freed applicable to simulation of slow motion CW EPR spectrum for one spin label, that is one electron coupled to one nucleus, was studied in detail for possible extension using the Lanczos algorithm. First, the extension was made for a system of one electron spin coupled to two nuclear spins by extending the starting vector, and taking into account the interaction of the additional nucleus with the electron. This extension was tested on a sample system, and was found to work satisfactorily, and published: S.K. Misra, 2007. Simulation of slow-motion CW EPR spectrum using Stochastic Liouville equation for an electron spin coupled to two nuclei with arbitrary spins: Matrix elements of the Liouville superoperator, J. Mag. Reson. 189, 59-77.