1. A polypeptide comprising an amino acid sequence of the general formula I: R1-R2-Phe-R3-R4-R5-R6-R7-R8-R9-R10-R11-R12-R13-R14-R15-R16 (SEQ ID NO: 1 ) wherein: R1 is selected from the group consisting of Ser, Ala, Phe, His, Lys, Met, Asn, Gln, Thr, Val, Tyr, and Asp R2 may be any amino acid R3 is selected from the group consisting of Asp , Ala, Glu, Gly, Asn, Pro, Ser and Tyr R4 is selected from the group consisting of Leu and Phe R5 can be any amino acid R6 is selected from the group consisting of Met, Phe, His, Ile, Leu, Gln and Thr R7 is selected from the group consisting of Arg, Gly, Lys, Gln and Thr R8 is selected from the group consisting of Ile, Asn, Gln, Val, and Trp R9 is selected from the group consisting minutes of Met, Gly, Ile, Lys, Leu, Asn, Arg, Ser, Thr, Val, His and Tyr R10 is selected from the group consisting of Trp and Phe R11 is selected from the group consisting of Ile, Phe, Ser, Thr and Val R12 is selected from the group consisting of Tyr, Cys, Asp, Phe, His, Asn and Ser R13 is selected from the group consisting of Val, Ala, Phe, Ile, Leu, Asn, Gln, Thr, and Tyr R14 is selected from the group consisting of Phe, Glu and Leu R15 is selected from the group consisting of Ala, Gly, Lys, Arg and Ser iR16 selected from the group consisting of Phe, Cys, His, Lys, Leu, Met, Asn, Gln, Arg, Thr, Val, Trp and Tyr.2. The polypeptide of claim 1, wherein the general formula I is: R1-R2-Phe-R3-R4-R5-R6-R7-R8-R9-R10-R11-R12-R13-R14-R15-R16-X1-R17 (SEQ ID NO: 2) wherein: X1 is 4-8 amino acids in length, wherein each state may occupy any amino acid iR17 represents Phe or Tyr.3. A polypeptide comprising the amino acid sequence of the general formula II: R1-R2-R3-R4-R5-R6-R7-R8-R9-Ala-R10-R11-Phe (SEQ ID NO: 83) wherein: R1 is selected from the group consisting from Phe and Val R2 is selected from the group consisting of Ser, Ala, Phe, Gly, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Thr and Val R3 is selected from the group consisting of Glu and Asp R4 is selected
