C_beta = Atom('CH3')
pdbmap = [('ALA', {'CB': C_beta, }, ), ]
name = 'ala_sidechain'
opls_atom_type = { C_beta: 'C3'  }
opls_charge = { C_beta: 0.0  }
amber91_atom_type = {C_beta: 'C3', }
