In {HEAD ~ other embodiments}, {TAIL ~ X2} is selected from D leucine, D valine, glycine and D proline 
In { HEAD ~ other embodiments } , { TAIL ~ X2 } is selected from D leucine , D valine , glycine and D proline
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH