{HEAD ~ The dendritic structures} comprise linkers and {TAIL ~ branch groups} covalently bonded to each other in any of various structural combinations 
comprise
{ HEAD ~ The dendritic structures } comprise linkers and { TAIL ~ branch groups } covalently bonded to each other in any of various structural combinations
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH