1. the time in -80c, depends on the cryo-vial and temperature decreasing rate. if the temperature decreasing at -1C per minute, eg, Bicell. it would be more than enough to keep cells in -80 for 4hours. To cryopreserve cells for a short time,1-3 mon, you can just leave it in -80c 4 d$ t; q$ W5 w9 n6 y7 C! B2. For longterm preservation, it is better to transfer your cells into LN29 L1 t+ K! y+ O! U
3. Overnight in -80, it is just for the work convinience. ! b2 b8 k6 Y' a0 J) W
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过夜是为了好安排工作,-80 放4小时就可以