In certain embodiments, X5 is selected from {HEAD ~ D leucine}, D isoleucine, D alanine, D proline and {TAIL ~ D lysine} 
In certain embodiments , X5 is selected from { HEAD ~ D leucine } , D isoleucine , D alanine , D proline and { TAIL ~ D lysine }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL