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Hi, I am trying to find an appropriate cryo-condition for my protein crystals. The mother liquid is 2-2.5M Ammonium phosphate dibasic 100mM TrisHCL pH8. The room-temperature diffraction looks not bad (mosaicity 0.8, resolution 2.6) But the diffraction turned to be very mosaic if I freeze the crytals in the absence of cryos or in the presence of mother liquid plus different concentration of glycerol (5%,10%,15%.20%). I don't think the ice formation is the problem since I didn't see any ice by my eyes or ice diffraction in the presence or absence of cryos. Also, I didn't see any cracks on my crystals when I transfered them to the cryo conditions I have already tried. My question here is: 1)what's the role of cryo? I know it helps prevent ice formation. Based on my case, it looks like cryo might also help to keep the crytal packing good when frozed. 2) What do I need to do to find a good cryo? What in my mind is to try other cryos like sucrose, PEG400, ethylene glycol. Thanks a lot for your attention! Yuan