High-performance liquid chromatography of amino acids, peptides and proteins. CXI. Retention behaviour of proteins with macroporous tentacle-type anion exchangers

The chromatographic behaviour of various proteins with Fractogel-TMAE and LiChrospher-TMAE tentacle-type strong anion-exchange sorbents has been investigated. In particular, the log k versus log 1/c (where k is the median capacity factor and c is the corresponding salt concentration) dependencies for two salt systems (NaCl and KBr) have been documented. The Fractogel-TMAE sorbent exhibited retention characteristics in terms of relative protein charge dependencies (slope Z_c) and affinity values (log K_c, which is log k at c = 10^-6 M, where c is the concentration of the displacer ion) which were similar to the more conventional anion-exchange sorbents such as the Mono-Q sorbent. However, the Z_c and log K_c values obtained with the LiChrospher-TMAE sorbent were significantly decreased for most proteins. Furthermore, proteins such as carbonic anhydrase and myoglobin were not retained at pH values up to 4 and 2 units above their pI values, respectively. These results illustrate the different adsorptive properties of the tentacle-type sorbents compared to other monolayer or polymer layer ion exchangers in terms of accessibility of the charged ligand and the underlying retention mechanism.