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