Assign charges of a ioinc structure

Hello everyone,
I am trying to construct “ ([3-(methacryloylamino)propyl]-dimethyl(3-sulfopropyl)
ammonium hydroxide)
” molecule with the below structure:


In order to that, firstly I assign charge +1 and -1 on the N and O respectively, then selected all other atoms expect than these two atoms(N with +1 and O with -1)and by applying Modify->charges->Gateiger the partial charge of other atoms were assign. The final created structure is indicated as follow:

 Would you tell me is this method true? If no would please guide me?