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. 2014 Aug 1;9(8):e103294. doi: 10.1371/journal.pone.0103294

Figure 1. Sequence analysis and purification of selected single domain antibodies.

Figure 1

(A) Sequence alignment of unique single domain VHH antibodies specific to pandemic H1N1 isolated in this study. CDR and framework regions are defined according to the IMGT numbering scheme (http://imgt.cines.fr/). The hallmark residues in framework region 2 (FR2) characteristic of camelid antibodies at positions 42, 49, 50 and 52 are indicated with a arrow head [53]. Conventional VH antibodies almost exclusively have V, G, L and W at these positions whereas in camelid VHH's these residues are replaced by 42(F/Y), 49 (E/Q/R), 50(R) and 52 (F/L) which is consistent with the VHH antibodies isolated in this study.(B) SDS-PAGE analysis of purified monovalent VHH antibodies and bivalent VHH antibodies. Molecular weight markers (Mw) 25, 20, 15 kDa.