I am curating a metabolic model that has compounds such as NADH/NADPH/Etc. that have multiple ionize-able hydrogens. Normally with amino acids there are only a few hydrogen with varying pKas that makes it easy to find what the charge the of the molecule is and the formula at a given pH. However with NAD, I can't get a good idea of what the actual formula is at pH 7ish. I have been using Kegg, ModelSEED, pubChem, etc. There is alot of conflicting information. What is the charge/formula of NAD in particular and more important, what resources are best to determine molecular compound charges at various pHs.