Layer-by-Layer Deposition with Polymers Containing Nitrilotriacetate, A Convenient Route to Fabricate Metal- and Protein-Binding Films.

This paper describes a convenient synthesis of nitrilotriacetate (NTA)-containing polymers and subsequent layer-by-layer adsorption of these polymers on flat surfaces and in membrane pores. The resulting films form NTA-metal-ion complexes and capture 2-3 mmol of metal ions per mL of film. Moreover, these coatings bind multilayers of polyhistidine-tagged proteins through association with NTA-metal-ion complexes.

Immobilization of carboxymethylated polyethylenimine-metal-ion complexes in porous membranes to selectively capture his-tagged protein.

Membrane adsorbers rapidly capture tagged proteins because flow through membrane pores efficiently conveys proteins to binding sites. Effective adsorbers, however, require membrane pores coated with thin films that bind multilayers of proteins. This work employs adsorption of polyelectrolytes that chelate metal ions to create functionalized membranes that selectively capture polyhistidine-tagged (His-tagged) proteins with binding capacities equal to those of high-binding commercial beads.

Layer-by-layer assembly of thick, Cu(2+)-chelating films.

Layer-by-layer adsorption of protonated poly(allylamine) (PAH) and deprotonated poly(N,N-dicarboxymethylallylamine) (PDCMAA) yields thick films with a high density of iminodiacetic acid (IDA) ligands that bind metal ions. When film deposition occurs at pH 3.0, PAH/PDCMAA bilayer thicknesses reach 200 nm, and Cu(2+) binding capacities are ~2.

Increased protein sorption in poly(acrylic acid)-containing films through incorporation of comb-like polymers and film adsorption at low pH and high ionic strength.

In principle, incorporation of comb-like block copolymers in multilayer polyelectrolyte films can both increase film thickness relative to coatings containing linear polymers and provide more swollen films for increased sorption of proteins. In the absence of added salt, alternating adsorption of 5 bilayers of protonated poly(allylamine) (PAH) and comb-like poly(2-hydroxyethyl methacrylate)-graft-poly(acrylic acid) (PHEMA-g-PAA) leads to ∼2-fold thicker coatings than adsorption of PAH and linear PAA, and the difference in the thicknesses of the two coatings increases with the number of bilayers. Moreover, the (PAH/PHEMA-g-PAA)n films sorb 2- to 4-fold more protein than corresponding films prepared with linear PAA, and coatings deposited at pH 3.

Separation of alpha- from beta-arylalanines by nickel nitrilotriacetate chromatography.

A method is described to separate alpha- from beta-arylalanines by ligand exchange chromatography on a nickel nitrilotriacetate agarose column with UV monitoring of the effluent. Separate mixtures containing an alpha- and beta-arylalanine pair (1 mg of each) were individually loaded onto the nickel resin pre-equilibrated with the mobile phase at room temperature, and the amino acids were eluted from the column with a gradient from pH 12.0-8.