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Charpentier MJ, Van Horn RC, Altmann J, Alberts SC.Charpentier MJ, et al.Proc Natl Acad Sci U S A. 2008 Feb 12;105(6):1988-92. doi: 10.1073/pnas.0711219105. Epub 2008 Feb 4.Proc Natl Acad Sci U S A. 2008.PMID: 18250308Free PMC article.