Hi Azra,

I would recommend HFIP (Hexafluoroisopropanol). If it doesn't work , you can go for formic acid. 

Thank you for your answer Mazda, but could you please add why you have recommended each of these solvents?

The main reason is the peptides that I've worked on that have similar gradient hydrophobicity from N- toward to C- terminus ( and these 2 solvents worked well) . However, HFIP is a good solvent for peptides with helix.

Ok, thank you again for your answer .

I recommend HFIP (Hexafluoroisopropanol). If it doesn't work , you can go for formic acid.

HFIP is an excellent first choice, if you want you can always use DMSO that will dissolve the peptide for sure!