5XBO:
reference: Lanthanoid tagging via an unnatural amino acid for protein structure characterization., Jiang WX, Gu XH, Dong X, Tang C, J Biomol NMR. 2017 Apr;67(4):273-282. doi: 10.1007/s10858-017-0106-9. Epub 2017, Apr 1. PMID: 28365903

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