has anyone alrerady tried that C tag and the corresponding material?
We have tried this tag and it works very nicely and can easily be incorporated into PCR primers. You'll have to buy the resin from Life Technologies though, and I do find it quite pricy (roughly £500 for 5 ml of resin). The advantage is gentle elution (we use peptides from our in-house facility) and that you don't have to adjust the pH of insect cell supernatants (or be concerned about stripping of columns in the case of NiNTA). Moreover, there are quite good detection reagents for the tag, so all-in-all, it is good, but comes at a price.