3. Results and discussion
3.1. Efficient single-step affinity purification of Con A over developed Con A aptamer-affinity chromatography
The conventional methods of Con A isolation and purification are multistep procedures involving protein precipitation, dialysis, size exclusion and other purification steps to get pure and concentrated Con A. Affinity purification is usually performed as last stage purification over carbohydrate-based affinity matrices. Since carbohydrates act as ligands to all the lectins, there is a possibility that other lectins may also enrich and cross contaminate the affinity purified preparation of Con A. To overcome these limitations, we have developed an aptamer-based method as a standalone platform to isolate and purify Con A.
The developed aptamer-affinity chromatography consists of a Con A aptamer (aptabody) functionalized stationary phase that act as affinity matrix for selective retention of Con A (Fig. 1). The Con A aptabody is a 41 nt ssDNA aptamer modified at its terminal end with amine moiety [−H2N−(CH2)6] to enable its site-selective immobilization on activated gel matrix. The hexamer C6 linkage at the end of aptamer provides structural flexibility to Con A aptabody and therefore ensures maximal target binding. Coupling efficiency of Con A-aptabody on NHS activated agarose resin was calculated using UV absorption measurement to estimate the final concentration of aptabody in coupled agarose resin, which was calculated to be 5 mM. Coupling efficiency of Con A aptabody over NHS activated agarose resin was 80%. The remaining unreached active sites on agarose were then quenched with 1 M Tris-buffer.