Verification of type I and type II SPIB binding probes by EMSA with purified SPIB protein. Gels A and B represent type I SPIB binding probes, gels C and D contain type II SPIB binding probes. SPIB means purified SPIB protein. The label of each column: C+ represents positive control of previously published SPIB binding probe , and - is the negative control, S is DNA size standard (lowest band 100bp, highest band 3000bp), and the number is the corresponding probe number in Additional file 1: Tables S4 and S5 for type I SPIB binding probes (i.e. 1 to 10) and type II SPIB binding probes (i.e. 11 to 20), respectively. The black arrow is pointing to the shifted band.