A polypeptide having the general amino acid sequence written in the single letter code Z1 I X2 R W X5 X6 K X8 P X10 X11 S Z3, wherein X2 = V, M or L, in particular L, X5 = S or T, X6 = K or R, in particular R, X8 = V, M, L or F, in particular M, X10 = Q or C, in particular C, X11 = V, M or F, in particular V； Z1 = 0, Z2, or pyro glutamate, wherein Z2 = is a modification of the N-terminal nitrogen atom of the peptide chain which modification forms together with the amino group of the N-terminal amino acid of the peptide a moiety having the structure -NR2R3 wherein R2 and/or R3 are independently from each other H or a substituted or unsubstitued acyl, alkyl, aryl, aralkyl, cyclo alkyl and heterocyclo alkyl group； Z3 = 0, or Z4, wherein Z4 = is a modification of the C-terminal carboxyl group of the peptide chain, which modification forms together with the carboxyl group of the C-terminal amino acid of the peptide a moiety having the structure -C(O)-O-R1 or -C(O)- NR2R3, wherein R1 is a substituted or unsubstitued alkyl, aryl, aralkyl, cyclo alkyl and heterocyclo alkyl group； and R2 and R3 are defined as above.
