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. 2011 Sep 17;79(4):729–747. doi: 10.3797/scipharm.1107-19

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© Hill et al.; licensee Österreichische Apotheker-Verlagsgesellschaft m. b. H., Vienna, Austria.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Fig. 3 — Lowest-energy orientation of the π–π complex between camptothecin and caffeine. (A) Face-to face orientation of caffeine (ball and spoke model) in its lowest-energy orientation with camptothecin (tube model). (B) Molecular dipoles of camptothecin (top) and caffeine (bottom). (C) LUMO of camptothecin (top) and HOMO of caffeine (bottom). (D) Frontier molecular orbital overlap of caffeine with camptothecin in the lowest-energy orientation. (E) Electrostatic potential maps of camptothecin (top) and caffeine (bottom). (F) Electrostatic potential map of the lowest-energy π–π complex between camptothecin and caffeine.