In the present study, using MALDI-TOF MS, 174 molecular masses were observed in Ts-MG venom, among them, a total of 142 (around 82%) was also detected previously ( Pimenta et al., 2001). In a lesser extent, from 171 components observed in Ts-DF venom, 122 (71%) correspond to components detected by Pimenta et al. (2001). As it was presented in the

earlier fingerprinting studies mentioned above and reviewed elsewhere (Rodríguez de la Vega et al., 2010), in the first 25 min of chromatographic separation, which corresponds to 0–25% of acetonitrile in a 1% acetonitrile/min linear gradient elution, elute mainly low molecular mass peptides (<1500 Da), particularly those without disulfide bridges. Among them, there are fragments of larger MEK activation venom toxins and bradykinin potentiating RG7204 ic50 peptides (bpp) that strikingly account for half of the molecular masses identified within this molecular mass (MM) range in T. serrulatus venom ( Rates et al., 2008 and Verano-Braga et al., 2008). It is worth reinforcing that these studies were done with Ts-MG population. Usually, peptides in the range of molecular masses from 3500 to 4500 Da are short-chain K+ channel blockers (KTx) and they start eluting from RP-HPLC usually

after 20% acetonitrile. The molecular masses of the six KTxs previously described for T. serrulatus venom were identified in the present work in Ts-MG venom (see Table 5). Among them, three were not found in Ts-DF venom: alpha-KTX 12.1 (P59936), alpha-KTX 22.1 (P86270) and β-TsTXK (P69940). The alpha-KTX 12.1 has 4508.3 Da, a LD50 in mice of 826 μg/kg (i.v.) and inhibits high conductance calcium-activated potassium channels and, to a lesser extent, Shaker B potassium channels, moreover, inhibits Kv 1.3 ( Novello et al., 1999 and Pimenta

et al., 2003b). The alpha-KTX 22.1 is a 3956.0 Da peptide that preferentially blocks Kv1.2 and Kv1.3 channels with IC50 values of 196 ± 25 and 508 ± 67 nM, respectively ( Cologna et al., 2011). The β-TsTXK, the long-chain KTx described for T. serrulatus, has molecular mass of 6716.1 Da and selectively blocks voltage-gated noninactivating K+ channels in synaptosomes with IC50 values of 30 nM ( Legros et al., 1998 and Rogowski et al., 1994). Buthidae scorpion venom peptides with 6000 to 7500 Da Acyl CoA dehydrogenase mostly affect the activity of Na+-channels (NaScTx) and elute from RP-HPLC fractioning at approximately 33–40% acetonitrile (Batista et al., 2007). In present study, we noticed in Ts-DF and Ts-MG venom the presence of molecular masses corresponding to the seven NaScTxs previously described in T. serrulatus venom (see Table 5). It is known that the most severe cases of scorpionism occur with Buthidae scorpions and the most serious symptoms result from the action of NaScTxs (see review Rodríguez de la Vega and Possani, 2005). In fact, Kalapothakis and Chávez-Olórtegui (1997) suggested that NaScTx found in T.