PDB: 3CW1; “CRYSTAL STRUCTURE OF HUMAN SPLICEOSOMAL U1 SNRNP”; D. A. Pomeranz Krummel, C. Oubridge, A. K. Leung, J. Li, K. Na; Crystal Structure Of Human Spliceosomal U1 Snrnp At Resolution. Nature 458:475 (2009); Image provided by the Jena Library of Biological Macromolecules—JenaLib