title: Volume 354, number 1 (1998), in article no. BB980671, "Cross-linking and disulfide bond formation of introduced cysteine residues suggest a modified model for the tertiary structure of URF13 in the pore-forming Oligomers," by david M. Rhoads, barbara brunner-neuenschwander, charles S. Levings, III, and james N. Siedow, pages 158-164: