Examples of different assays on the proteome chips. Positive protein targets are indicated by yellow boxes identified in six protein- liposomes interaction assays, a DNA-protein interaction assay, and a calmodulin- binding assay. Each block contains 16X18 protein spots. The positive signals in duplicate (green) appear as horizontal pairs. The duplicate spotting hence serves as an internal control, which is important when the signals are weak relative to the background. A control proteome chip was probed with anti-GST antibodies. The upper panel shows the amounts of GST fusion proteins as detected by the anti-GST antibodies (red); corresponding proteins were probed for the specific activities shown in the lower panel. As demonstrated by the images strong signals are often observed from samples that have little GST fusion protein; thus the binding is sensitive and specific.