Expression system for antimicrobial peptides

[skjoedt]

Dear board

I am currently working with the expression of antimicrobial peptides (AMP) in the methylotrophic yeast Pichia pastoris using methanol as inducer, but I was wondering what other expression systems (most likely yeasts) that may be optimal for peptide production in general assuming there is no growth inhibition from the AMP. What are you're experiences on this matter?

Also, I'd like to know what methods of quantification I should look at when working with expression of peptides. The expression allows secretion to the culture medium but I would still anticipate other products in the supernatant that make it hard to identify the peptide by Tricine SDS-PAGE. I am looking for a method that allows some level of quantitative measures and not just intensity comparisons. My initial thought is by HPLC and MS, but I fear the sample handling is difficult when using supernatant samples containing salt and a number of other substrates, specially if the yield (before optimization) is low.

I hope it was clear enough.

Regards,
Christian Hansen

[JackBean]

I think using methods for protein level determination should be OK. Such, which react with the peptide bond, not like Bradford.
http://en.wikipedia.org/wiki/Lowry_protein_assay
http://en.wikipedia.org/wiki/Bicinchoninic_acid_assay