i am working with active form of vitamin D3 or calcitriol. I made an initial stock of 10mM stock in DMSO and further diluted to 1mM stock. I think the vitamin D3 is not showing its affect on the cell line which we are using, RAW macrophages. we stored the aliquots in -20C freezer. Kindly suggest me the probable reason. I tried my best to store the vitamin D aliquots knowing its air and light sensitive.