{TAIL ~ each} of Am is independently a moiety based on an amino acid or on an amino acid derivative, or on a number of {HEAD ~ amino acids} or derivatives thereof 
{ TAIL ~ each } of Am is independently a moiety based on an amino acid or on an amino acid derivative , or on a number of { HEAD ~ amino acids } or derivatives thereof
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH