The present invention is related to a peptide selected from the group comprising a) a cyclic peptide of formula (I): Cyclo(AIa-x-x-x-x-x-x-x-x-x-Cys-x-x-x-Pro-x-Cys-Cys-xk-GIn), (I) whereby k is any integer from 0 to 6, preferably any integer from 1 to 6, more preferably k=6; b) a cyclic peptide of formula (II): Cyclo(Ala-x-x-Trp-x-x-Gly-x-Phe-x-Cys-xh-Gln), (II) whereby h is any integer from 0 to 2, preferably 1 or 2; c) a cyclic peptide of formula (III): Cyclo(AIa-x-x-x-x-x-x-x-x-x-Cys-xj-Cys-x-x-x-Pro-x-Cys-Cys-xi-Gln)- ; (HI) whereby j is any integer from 0 to 4, preferably j=4; whereby i is any integer from 0 to 6, preferably any integer from 1 to 6, more preferably i-6; and d) a peptide of formula (IV): Ala-x1-Cys-xm-Cys-x-x-x-Pro-x-Cys-Cys-xn-Gln, (IV) whereby 1 is any integer from 0 to 9, preferably any integer from 1 to 9, more preferably n=9; whereby m is any integer from 0 to 4, preferably any integer from 1 to 4, more preferably m=4; whereby n is any integer from O to 6, preferably any integer from 1 to 6, more preferably n=6; whereby x is any amino acid, preferably any naturally occurring amino acid, more preferably any naturally occurring L-amino acid.