Hello Shijun,
I also just saw your post. Your well solution of 30% isopropanol with PEG 1000 may be a good cryoprotective agent. If you are able to loop a crystal, you might try placing the crystalcap with looped crystal in a cryovial containing 500 microliters of your well solution. Plug the liquid nitrogen escape holes with a little clay. The crystal will then move back towards vapor equilibration with the original well solution. Let the crystal recover for a couple minutes (back up to full isopropanol concentration) before transferring the crystalcap rapidly to liquid nitrogen. If you get ice rings, then increase the isopropanol concentration in the cryovial.
http://www.ncbi.nlm.nih.gov/pubmed/25286441
-Doug
Douglas Juers
Associate Professor
Physics Department
Program in BBMB, Director
Whitman College
Walla Walla, WA 99362
Phone: 509-527-5229 FAX: 509-527-5904
Web: http://www.whitman.edu/~juersdh/
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