Figure 2B. [doi:10.1073/pnas.250492697] Copyright: This image is from Roberts CW; Galusha SA; McMenamin ME; Fletcher CD; Orkin SH, Proc Natl Acad Sci U S A 2000; Dec 97: 13796-800. [PMID:11095756] Copyright 2000 National Academy of Sciences, U.S.A.