In certain embodiments, X6 is selected from {HEAD ~ D arginine}, D tryptophan, D tyrosine, {TAIL ~ D proline} and D valine 
In certain embodiments , X6 is selected from { HEAD ~ D arginine } , D tryptophan , D tyrosine , { TAIL ~ D proline } and D valine
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH