Examples of aqueous proteins with unusually long hydrophobic blocks. Images show cartoons of three representative protein structures, with long hydrophobic blocks highlighted in red. (A) Cytidine deaminase, an example of a protein with a hydrophobic block occurring as a partially buried helix; (B) 7,8 diaminopelargonic acid synthase, an example of a protein with a hydrophobic block occurring as a buried strand and turn region; (C) phage PRD1 receptor binding protein P2, illustrating an unusual surface-exposed example of a long hydrophobic block. Prolines in the P2 block are highlighted.