The Ac-Cys 1 pP0 peptide (CH3CO-1 CAAGGGAAAAKPEESKKEEAK 21 ) derived from Rhipicephalus sp. ticks (AJQ18906) acetylated at the N-terminal end was synthesized in the Peptide Synthesis Laboratory at CIGB . Peptide was purified by preparative rp-HPLC and analytical fractions with a purity higher than 95 % were pooled and the identity was verified by ESI-MS using an experimental setup reported previously .