Glycerol is just another additive to crystallizations and a reasonably good cryoprotectant. Sometimes it helps to grow crystals, sometimes it has no effect, and sometimes it interferes with crystal growth. Have I covered all the possiblities? One thing is the glycerol often makes a protein more soluble, so one will often need a higher protein concentration or higher precipitant concentration in order to get crystals. If someone tells me that glycerol prevented crystal growth, I always ask them if they increased the protein concentration or precipitant concentration or if they just used their old recipe. That is a revealing question. Also note that ethylene glycol has a similar effect, yet is sometimes very different. Furthermore, these compounds can bind in active sites and elsewhere on proteins and interfere with assays and other stuff. Nevertheless, they are always one of the first additives to try.
_____ From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Ray Brown Sent: Thursday, March 10, 2011 4:05 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] glycerol Hi all, I was intrigued by the recent question of whether glycerol had any adverse effects on the final purity of protein isolated by chromatography. Glycerol certainly helps to solubilize some proteins. Does anyone know of any negative effects of glycerol in protein purification, on protein crystal quality or use in cryocrystallography and on X-ray diffraction results? Cheers. Ray Brown
