| | Re: Specificity difference between Affinty Labels and Group specific reagents?
I think the distinction is that group-specific ligands bind a general class of proteins or enzymes, whereas affinity ligands tend to be specific for a single protein or enzyme.
NADP-Agarose, for example, would be expected to bind many if not all of the NADP-linked dehydrogenases in a tissue extract and unless you can find specific elution conditions, there may be many such dehydrogenases present in the post NADP-agarose sample. (Thus NADP immobilized on agarose may be described as a group-specific ligand).
On the other hand, Alpha-Cyano-4-hydroxycinnamate, for example, appears to be a very specific affinity ligand in the purification of an aldehyde dehydrogenase, and apparently binds very little else!
See R. C. Poole and A. P Halestrap Biochem J. 1989 April 1; 259(1): 105–110.
Purification of aldehyde dehydrogenase from rat liver mitochondria by alpha-cyanocinnamate affinity chromatography.
I think that both group-specific and affinity ligands may bind the target protein very tightly.