def get_dna_mw_no_ppi_dict(model):
    """
    Return the molecular weight of dna component with the diphosphate group
    removed.
    """
    dna_mw_no_ppi = {}
    ppi_mw = model.metabolites.ppi_c.formula_weight
    for dna in ['dctp', 'dgtp', 'datp', 'dttp']:
        dna_mw = model.metabolites.get_by_id(dna + '_c').formula_weight
        dna_mw_no_ppi[dna] = dna_mw - ppi_mw

    return dna_mw_no_ppi