Fig. 1. DNA oligonucleotides used for crystallization. (A) DNA used in initial crystallizations. The sequence is the same as that in the IHF–DNA cocrystals but the nicks (indicated by arrows) are placed 9 bp apart in an effort to phase otherwise non-specific binding by HU. The IHF-binding consensus sequence is underlined and the four individual oligonucleotides are labeled TL (top left), BR (bottom right), etc. Crystals containing this duplex diffract poorly. (B) Oligonucleotide TR3 forms a pseudo-self-complementary duplex with three T:T mismatches and four unpaired Ts.