Dear ccp4bb members,

    Sorry for asking a non-crystallographic question where google search cannot provide any valuable answer.

pppGpp was synthesized by relQ enzyme using ATP and GTP, the product was purified by anion exchange chromatography.  The problem is that the concentration of pppGpp is too low for crystal soaking. 

My question is that using volatile buffer, how can I concentrate my substrate, and how can I desalt it?

Should I need a freeze dried machine?

Best wishes!

Lu Zuokun