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. In general, different EPR experiments are sensitive to different model parameters. Thus, it is extremely useful to have a tool that can assess model or parameter sensitivity in order to optimize the experimental conditions under which data should be collected. The purpose of this subproject is to determine whether information entropy can inform this process. Regions of the spectrum that have high information entropy show the greatest variation in spectral amplitude as model parameters are varied. One may therefore quantify the sensitivity of a model to the available experimental conditions in an objective way. This is a general method that can in principle be used with any spectral simulation software to construct the information entropy as a function of spectral position. These techniques may thus be used to identify the key experiments to perform in order to decide among competing models. ACERT computational resources were used to develop spectral processing software that will be made available to the community. Currently, the software can be used for standard nitroxide experiments at any frequency. Work is underway to increase the range of models that may be studied with this computational tool, including the slowly-relaxing local structure (SRLS) model.