Partial atomic charges serve as a simple model for the electrostatic distribution of a molecule that drives its interactions with its surroundings. Since partial atomic charges are frequently used in computational chemistry, chemoinformatics and bioinformatics, many computational approaches for calculating them have been introduced. The most applicable are fast and reasonably accurate empirical charge calculation approaches. Here, we introduce Atomic Charge Calculator II (ACC II), a web application that enables the calculation of partial atomic charges via all the main empirical approaches and for all types of molecules. ACC II implements 17 empirical charge calculation methods, including the highly cited (QEq, EEM), the recently published (EQeq, EQeq+C), and the old but still often used (PEOE). ACC II enables the fast calculation of charges even for large macromolecular structures. The web server also offers charge visualization, courtesy of the powerful LiteMol viewer. The calculation setup of ACC II is very straightforward and enables the quick calculation of high-quality partial charges. The application is available at https://acc2.ncbr.muni.cz.

CEITEC Central European Institute of Technology Masaryk University Brno 625 00 Czech Republic National Centre for Biomolecular Research Faculty of Science Masaryk University Brno 602 00 Czech Republic

CEITEC Central European Institute of Technology Masaryk University Brno 625 00 Czech Republic National Centre for Biomolecular Research Faculty of Science Masaryk University Brno 602 00 Czech Republic Faculty of Informatics Masaryk University Brno 602 00 Czech Republic

Regional Centre of Advanced Technologies and Materials Department of Physical Chemistry Faculty of Science Palacký University Olomouc Olomouc 771 46 Czech Republic

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