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