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Zhang J, Pritchard E, Hu X, Valentin T, Panilaitis B, Omenetto FG, Kaplan DL.Zhang J, et al. Among authors: pritchard e.Proc Natl Acad Sci U S A. 2012 Jul 24;109(30):11981-6. doi: 10.1073/pnas.1206210109. Epub 2012 Jul 9.Proc Natl Acad Sci U S A. 2012.Retraction in: Proc Natl Acad Sci U S A. 2016 Jun 28;113(26):E3810. doi: 10.1073/pnas.1608261113PMID: 22778443Free PMC article.Retracted.