Hello all,

I was wondering if anyone has input on the isolation of gramicidin components. I know that it is really a mix of peptides that vary by either a valine or isoleucine unit in one position, and the change of another position to result in 6 independent components.

I've attempted some isocratic separation on a Synergi column, but have noticed that the peptides are adopting problematic confirmations that are broadening the peaks into almost full minute elutions with massive shoulders. Does anyone know of a good strategy for trapping these peptides (or similar ones) into confirmations that are more amenable to chromatographic separation?

Currently, my mobile phases are all at 0.02% Formic Acid. Should I try upping that? Lowering it? I have also attempted a tertiary mixture using a small percentage of ACN, but have not found the magic number for this solution as of yet.

Thanks!

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