text: This technique can be applied to study membrane-bound ion channels by tagging parts of the channel with nitro groups and using this method to approximate the distance.
full_question: This technique can be applied to study membrane-bound ion channels by tagging parts of the channel with nitro groups and using this method to approximate the distance. This method was used to measure the effects of symmetry-enhanced or forbidden hyperconjugation in cyclic systems by David Whiffen. High-frequency and parallel-mode variants of this technique are used to probe intermediates in the catalytic cycles of ribonucleotide reductase and phenylalanine hydroxylase. Information on the coupling between the centers studied in this technique and their environment can be studied using pulsed ENDOR. Peak splitting in this technique is caused by hyperfine coupling. Absorbances in this technique occur in multiples of the Bohr magneton times the magnetic field strength times the Lande g-factor. This technique is analogous to NMR, but it studies the spins of electrons rather than nuclei. For 10 points, name this method used to probe unpaired electron systems such as free radicals.
first_sentence: This technique can be applied to study membrane-bound ion channels by tagging parts of the channel with nitro groups and using this method to approximate the distance.
raw_answer: EPR spectroscopy [or electron paramagnetic resonance spectroscopy; or electron spin resonance spectroscopy; or ESR spectroscopy]