Peptides were deprotected and released from the resin by TFA treatment in the presence of appropriate scavengers. The peptides were lyophilized and their purity was assessed by both HPLC (Akta Explorer 100) and mass spectrometry (MALDI-TOF/TOF, Autoflex III, Bruker Daltonics Inc.). Peptides were covalently coupled through their C-terminal
click here cysteine to lysine residues of BSA (Capelli-Peixoto et al., 2011). Briefly, BSA, previously diluted in 20 mM sodium phosphate buffer (pH 7.4) containing 0.15 M sodium chloride, was activated by sulfo-SMCC (10 mg/ml; Pierce Chemical Co., Rockford, IL). After 1 h of constant stirring at room temperature, the excess reagent was removed by elution through a PD-10 column. The activated BSA was reacted for 2 h with the cysteine-containing peptide learn more at room temperature under constant stirring and while being protected from light. A buffer containing reduced cysteine (1 mM) was added. The peptides coupled to BSA were separated into aliquots and stored at −20 °C. An analysis of variance (ANOVA) for a factorial experiment design was used for the analyses of the ELISA results. The significance level was set at p < 0.01. The Tukey test was used for the pairwise comparison between the factors; p < 0.05 was considered to be statistically significant. The analyses were performed using the ASSISTAT-7.2 program ( Silva and Azevedo,
2009). The sequences of LiD1 (GenBank: AAQ16123.1) from
L. intermedia, SMase I (GenBank: AAM21154.1) from L. laeta, and A1H-LoxGa (GenBank: AAY42401.1) from L. gaucho were aligned using ClustalW ( Larkin et al., 2007). The epitopes were analyzed in the three dimensional structures of the SMase I (PDB accession code: 1XX1) ( Murakami et al., 2005) using the PyMOL Molecular Graphics System (Version 1.2r3pre, Schrödinger, LLC). The molecular weight and theoretical isoelectric point of the peptides were calculated using the program PEPTIDES MASS (Wilkins et al., 1997). For the solvent accessibility calculation of the LiD1, SMase I, and A1H-LoxGa proteins we used the PSA program Cytidine deaminase and implemented the algorithm by Lee and Richards (1971). Residues were categorized as inaccessible by comparing them to an extended conformation; a 7% relative accessibility cut-off was applied (Hubbard and Blundell, 1987). The amino acid accessibility (in percentage) for the epitope regions was calculated. The amino acid hydrophobicity of each peptide was determined according to the Kyte and Doolittle scale (1982) and as described by Alvarenga et al. (2010a). We assessed whether there was a correlation between the neutralizing potency of anti-Loxosceles horse antisera (measured in vivo) and their ELISA reactivity. Nine Loxosceles antisera and a pre-immunized horse serum were tested by ELISA for reactivity using venoms from three species of Loxosceles (L.