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