NTA Chips for SPR

NTA sensor chips can be successfully used for immobilization of molecules carrying more then two his-tags, as shown by Nieba et al. #his1, e.g. with oligomeric proteins. Sometimes immobilization can even succeed with two his-tags per molecule, while affinity of singly his-tagged proteins to the NiNTA complex is insufficient to immobilize such proteins.

Also, Nieba et al. #his1 studied several other parameters affecting level of ligand immobilization (starting point conditions listed in parentheses, but they may need to be re-optimized for a particular system): Surface regeneration conditions were optimized as well.
 * conditions for NTA surface activation with Ni2+: [NiCl2], [NaCl] and pH of activation buffer (good starting points: 0.3-4 min pulse 300&mu;M NiCl2, pH 6.4-8.4, 0-0.5M NaCl)
 * effects of pH, [NaCl] and detergent (tween) concentration in the ligand immobilization buffer
 * effect of Na2EDTA (0-300 mM) in the running and ligand buffers (50 μM EDTA does not negatively impact ligand immobilization, recommended to scavange free metal ions in solution competing for His-tag binding)
 * concentration of his-tagged ligand (<1 &mu;M, needs to be determined experimentally - too much ligand prevents multidentate binding and some his-tagged protein will be leaching out)