Pseudobiospeciic Ligands

An alternative approach involves the use of biomimetic or pseudobiospecific affinity ligands. These are usually smaller and simpler molecules with higher chemical and physical stability than bio-molecules. The working principle of pseudobio-specific ligands relies on the complementarity of structural features of ligand and ligate rather than on a biological function, whereas biomimetic ligands have a certain structural resemblance with a biological ligand. For example, textile dyes can be used for the separation of proteins, and in particular Cibacron Blue F3GA has been employed as ligand in affinity membranes for the purification of dehydrogenases, since it often binds specifically to the nucleotide-binding site. Other dyes may adsorb proteins less specifically, but by selection of the right dye (a large number of different dyes is currently available) and the appropriate adsorption and elution conditions, highly efficient separations can be obtained.

Proteins carrying accessible histidine residues on their surface have been shown to have affinity for transition metal-chelate ligands. Typical examples are the iminodiacetate-copper(II) complex (IDA-Cu(II)) and the nitrilotriacetate-nickel (NTA-Ni(II)) ligand widely used for purification of recombinant proteins with genetically attached poly-His tails.

A third group are amino acids such as phenylalanine, tryptophane and histidine. Being the least selective, they have nevertheless been successfully employed for protein purification. However, fine-tuned adsorption and elution conditions are necessary to achieve efficient separation. Mention should also be made of the thiophilic affinity system that has been used with affinity membranes. It is based on the salt-promoted adsorption of proteins via thiophilic regions (containing aromatic amino acids) on to sulfone or thioether-containing heteroaliphatic or aromatic ligands.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment