Polysulfoethyl vs polycat A @ pH 5

[DJ]

Any practical difference between these two columns for separating basic peptides using a salt gradient? How about when various MeCN concentrations (25-60%) is included?

In other words, if I optimize a gradient program on a polycat A at pH 5, can I expect roughly the same results if I were to use the same program on SCX?

[Andy Alpert]

Roughly. Both materials have full negative charge at pH 5. Any differences in performance with 50-60% ACN would be subtle and possibly hard to predict when it's a question of peptides with the extremes of composition that yours have.

I would speculate that peptides with so many Arg's would differ in secondary structure in a manner that might affect the number of basic groups that have access to the stationary phase surface simultanously. If you're lucky, you'll be able to get a separation that way. The only way to find out is to try it, using a shallow salt gradient.

[DJ]

Thanks for the reply.

I now trying to ID this ligand from a natural tissue sample. I chose the higher starting pH because it should be rather exclusive compared to pH 3.0. I'm using a 4 mm polysulfoethyl for the natural separation, but practicing on a polycat with the same particle, pore size.