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Oesterhelt D, Stoeckenius W.Oesterhelt D, et al. Among authors: stoeckenius w.Proc Natl Acad Sci U S A. 1973 Oct;70(10):2853-7. doi: 10.1073/pnas.70.10.2853.Proc Natl Acad Sci U S A. 1973.PMID: 4517939Free PMC article.