Editing ChargeCalculator:Terminology (section)

= Charges =

ACC operates with charges at several levels of resolution. 

== Atomic charge ==
The smallest resolution visible in ACC is at the atom level. We use the term '''atomic charge''' to refer to a single value which represents the algebraic sum between the atom's nuclear charge (given by the number of protons in the nucleus), and the amount of molecular electron density associated to this atom. In space, the position of the '''atomic charge''' is given at the coordinates of the atomic nucleus.

== Residue charge ==
The next level of resolution in ACC refers to residues. We use the term '''residue charge''' to refer to the sum of atomic charges over all atoms which belong to one residue. The origin of each atom is established according to residue name and serial number, provided this information is present in the input file.

== Molecular charge ==
The '''total molecular charge''' is a formal value based on the molecular structure and the protonation state of all ionizable groups. The process of atomic charge calculation in ACC consists of distributing the amount of electron density given by the '''total molecular charge''' across the molecule, to each atom based on certain criteria and algorithms. Thus, the sum of atomic charges over all atoms in a molecule equals the total molecular charge. Similarly, the sum of residue charges over all residues in a molecule equals the total molecular charge.