Aligns the N-CA and CA-CB vector of the target monomer.

    Parameters
    ----------
    tar: ampal.Residue
        The residue that will be aligned to the reference.
    ref: ampal.Residue
        The reference residue for the alignment.

def align_nab(tar, ref):
    """Aligns the N-CA and CA-CB vector of the target monomer.

    Parameters
    ----------
    tar: ampal.Residue
        The residue that will be aligned to the reference.
    ref: ampal.Residue
        The reference residue for the alignment.
    """
    rot_trans_1 = find_transformations(
        tar['N'].array, tar['CA'].array, ref['N'].array, ref['CA'].array)
    apply_trans_rot(tar, *rot_trans_1)
    rot_ang_ca_cb = dihedral(tar['CB'], ref['CA'], ref['N'], ref['CB'])
    tar.rotate(rot_ang_ca_cb, ref['N'].array - ref['CA'].array, ref['N'].array)
    return