Biomedical EPR Part-B Methodology Instrumentation and Dynamics - Sandra R. Eaton
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SANDRA S. EATON AND GARETH R. EATON |
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Software is available, some commercially and some from individual labs |
(easily locatable via the EPR Society software exchange), for simulation of many spin systems. The understanding of many spin systems is now at the stage that a full simulation of the experimental line shape is a necessary step in interpreting an EPR spectrum. There will always remain important problems for which the key is to understand the spin system, so simulation is at the edge of the state of the art. For example, for many high-spin Fe(III) systems there is little information about ZFS terms, so one does not even know which transitions should be included in the simulation. At the other extreme, for S = 1/2 organic radicals in fluid solution one should be able to fit spectra within experimental error if the radical has been correctly identified. Future directions include combining spectral interpretation as outlined above with quantum mechanical and molecular dynamics descriptions of the biological system.
The application of EPR to biological systems has become sophisticated enough, with a large arsenal of tools, each available in at least a few labs, that the main problems are now biological. That is, the EPR spectroscopy is discriminating enough that it becomes increasingly important to have a very well-defined biological system, or one will focus in great detail on an impurity, or on an ill-poised pH or redox condition. Putting “dirty” illdefined samples into the spectrometer will lead to “dirty” ill-defined ideas about what the EPR spectra mean. The spectroscopy can give very welldefined results for whatever sample happens to be put into the resonator.
As we said in the Preface, there are spins everywhere, and recognition of the importance of studying them in biological systems will increase, EPR is uniquely suited to this study. Instrumentation, methodology, software for analysis and simulation will develop in concert, simultaneously optimizing particular experiments as the horizons expand within a multi-frequency, multidimensional milieu. As electronic components with the needed capabilities become available, data acquisition will, for example, move toward direct digitization of signals so that multiple harmonics can be extracted from the raw data as outlined by Hyde in the chapter on future trends. We also envision that the EPR response region between slow-scan CW and pulsed EPR, a CW region where relaxation times affect the signal even in the absence of saturation, will increasingly be exploited. Finally, computers will be used increasingly to create new types of graphic displays to communicate multidimensional data sets to the biomedical researchers.
The focus in these two volumes has been on methodology and instrumentation. Advances in theory, and in computational methods, are also needed. Beyond these, there is an even more important element - education. There needs to be greater focus on educating the next generation of scientists who will use the powerful methods described in these volumes.
in CdSe. 
NMR Experiments with Hemoproteins
NMR to Biological Systems
and Deuterium Spin Probes for Biomedical Electron Paramagnetic Resonance Investigations
and Deuterium Substituted Spin Labels
Signal in Proton FT/NMR Spectroscopy: A Review
Magnetic Resonance Spectroscopy of