Aminobutyl-NTA (AB-NTA) free acid replaces AB-NTA (disodium salt form; former Product Code: A296-10). The new free acid form is less hygroscopic than the disodium salt form. Dissolving the new acid form in a buffer involves the same procedure as dissolving disodium salt in a buffer. The new acid form can also be dissolved in water with sonication (up to 3%). Aminobutyl-NTA was first used by Dr. Hochuli in 1987 to purify recombinant proteins (the “Histag” technique). Since then, the AB=NTA has become an indispensable tool for immobilizing proteins with high specificity on solid surfaces, such as glass or the gold electrode. A solid surface is modified by AB-NTA and bio-functionalized via Ni (II) with a genetically expressed protein bearing a hexahistidine extension at its terminus. The His-tag technique has become increasingly important, particularl in surface plasmon resonance and structural analyses of proteins by x-ray interference. Using the His-tag technique, Dr. Noji was able to directly observe the rotation of F1-ATPase by fluorescence microscope.
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