Preparation of chelating exchangers with a polysaccharide network and low cross-linkage

Metal chelate-interaction chromatography of proteins with iminodiacetic acid-bonded stationary phases on silica support

An iminodiacetic acid (IDA)-bonded stationary phase on a wide-pore microparticulate silica support was used for the chromatography of amino acids and proteins at pH 5.0 and 6.0. Without chelated metal the retention behavior of the stationary phase parallelled that of other silica-bound cation exchangers used in high-performance liquid chromatography of proteins. In metal chelate-interaction chromatography (MCIC) with IDA, chelated by Cu(II), Zn(II), Ni(II), Fe(II), or Fe(III), amino acids were most strongly retained on Cu(II)-IDA, whereas all metal chelates separated the proteins under investigation but with different selectivity. The effect of salt concentration in the eluent on protein retention was investigated and the pertinent electrostatic and hydrophobic interaction parameters were evaluated. The proteins were separated by MCIC with increasing salt gradient and, using the same column, by hydrophobic-interaction chromatography with decreasing salt gradient. In MCIC the addition of methanol to the mobile phase had disparate effect on protein retention, whereas addition of histidine or glycine, which acted as competing ligands, reduced the retention.

Metal chelate affinity chromatography. I. Influence of various parameters on the retention of nucleotides and related compounds

The influence of various parameters, such as pH, ionic strength and temperature, on the retention of different nucleotides and related compounds on copper chelate gels has been investigated in order to understand the respective roles played by the different solute constituents (i.e., heterocyclic bases, sugars and phosphate groups) in the interaction and to define optimal conditions for subsequent application to the fractionation of oligo- and polynucleotides.

Ligand-exchange separation of amino acids. II. Influence of the eluent composition and of the nature of the ion exchanger

The ligand-exchange separation of amino acids in protein hydrolysates has been studied in ammoniacal media. The various factors influencing the chromatographic behaviour have been investigated. The selectivity of the process and the column efficiency depend appreciably on the resin matrix and the nature of the functional groups. The best results have been obtained with the acrylic-type Bio Rex 70 resin, in the copper(II) form. The zinc(II) form of this support has also been tested; the elution order of glycine, alanine and leucine is the same as with the copper(II) form, but the affinities of these molecules for the zinc(II) resin are weaker. The influence of the concentrations of copper(II) and ammonia on the elution volumes obtained for all the amino acids with the copper(II) Bio Rex 70 resin has been studied. The general variation of retention and selectivity with eluent composition confirms the theoretical expressions established previously. Ligand-exchange chromatography has been compared to the conventional ion-exchange process using acidic or basic species. This study reveals analogies and differences between both techniques, and shows that ligand exchange can provide new opportunities for the separation of amino acids.