passages.id: split_6_test_2008_passage
passages.type: progene_text
passages.text: Here we report the refined solution structure of this complex by NMR spectroscopy and further derived structure - activity relationships by using ligand peptide libraries with truncated sequences and a substitution analysis that yielded acetyl - PPPPY as the smallest high - affinity binding peptide ( K(d) = 60 microM ) .