3HWL:
reference: Site-directed spin labeling of a genetically encoded unnatural amino acid., Fleissner MR, Brustad EM, Kalai T, Altenbach C, Cascio D, Peters FB, Hideg K, Peuker S, Schultz PG, Hubbell WL, Proc Natl Acad Sci U S A. 2009 Dec 22;106(51):21637-42. Epub 2009 Dec 7. PMID: 19995976

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