A) View of the asymmetric unit in a negative stain projection of two-dimensional crystal grown without ligand. B) View of the asymmetric unit in a negative stain projection of two-dimensional crystal grown in the presence of cAMP. C) Phase error plots for the data collected from negative stained crystals grown with and without cAMP. Resolution circles: 40Å, 20Å, 17Å; phase errors are encoded as follows: 1<8°, 2<14°, 3<20°, 4<30°, 5<40°, 6<50°, 7<80°, 8<90° where 90° is random. The size of the plot symbols depends on the error of the reflection, with categories 1–4 individually labelled.