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. Author manuscript; available in PMC: 2013 Sep 28.
Published in final edited form as: J Control Release. 2012 Aug 3;162(3):538–544. doi: 10.1016/j.jconrel.2012.07.033

Figure 1.

Figure 1

13C-NMR spectra of morphine 1, diacid 3, and PolyMorphine 5, showing the preservation of the chemical integrity of the drug; key peaks for the nitrogen-containing ring and the cyclic ether are indicated.