{HEAD ~ R11} is {TAIL ~ H}, CH3, a carboxylic acid or a biologically compatible salt of a carboxylic acid 
is
{ HEAD ~ R11 } is { TAIL ~ H } , CH3 , a carboxylic acid or a biologically compatible salt of a carboxylic acid
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH