As expected the proteins, P21 and HA33, were not identified. P21, a positive

regulator of gene expression, lies just upstream of NTNH on the toxin plasmid (Figure 2) [10]. The purpose of P21, in complex development, is not completely understood and previous reports have not identified it as part of the/G complex [11]. HA33, a hemagglutinin component, is not found on the/G plasmid. The lack of evidence of the protein’s presence BAY 57-1293 research buy further endorsed the theory that, unlike the other serotypes, HA33 is not associated with the/G complex [10]. Two gel slices (Figure 4; #6 and 11) out of 17 visually had protein but did not return any identifiable

peptides when digested and analyzed. This could be due to a number of factors: the protein was relatively difficult to digest, there was not a sufficient amount of protein to digest, Selleckchem Pictilisib the sequence was not present in the database used, or post-translational modifications (PTMs) altered the protein sequence and did not allow for identification. The SDS-Page gel and in gel digestions confirmed visually and analytically which proteins are present in the commercial toxin complex and allowed us to continue to in solution digestions with some prior knowledge of which proteins should be identified. As anticipated, the same proteins that were identified with the in gel digestions were also identified in the analysis of the in solution digestions. The four main complex components– BoNT, NTNH, HA70, and HA17–were all identified with high confidence, and returned a large number of peptides. Hines et al. reported the use of a reduction and alkylation overnight digestion method that produced sequence coverages

of 16% for BoNT, 10% for NTNH, 38% for HA70, and 49% for HA17 [18]. The method used in our study allowed the recovery of more than Non-specific serine/threonine protein kinase four times the sequence coverage for BoNT at 66%, more than five times for NTNH at 57%, and more than double for both HA70 and HA17 at 91% and 99%, respectively. BoNT complexes are difficult to digest in solution [18]. This rapid high-temperature digestion method does not involve reduction and alkylation, unlike classical methods; instead, it uses an acid labile surfactant to solubilize the hydrophobic proteins. The increased solubility allows a denatured protein to be more susceptible to tryptic digestion, thereby increasing the rate of digestion and the number of tryptic peptides produced [25]. It has also been previously reported that the use of high temperature for a short period of time is the best condition for the enzymatic activity of trypsin [26].