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Integrated data obtained from titration of 20 mM PEI into 1.5 mM DNA in 0.1 M NaCl. The pH values of the PEI solutions are (a) 6, (b) 7, and (c) 8. The solid line represents the fitting data using the SSIS model. The data acquisition was repeated at least two times and the data are summarized as mean ± SD of at least duplicate measurements.
