def get_restype_from_titgroup(group):
    """Given a titratable group unique id e.g. (A:0112:CTERM or A:0111:ASP), return the residue type (ASP)"""
    ptype=group.split(':')[-1].upper()
    if ptype=='NTERM' or ptype=='CTERM':
        return None
    else:
        return ptype