I'd like to regularly coat some dishes with collagen (Rat Tail, Sigma C7661) for use with PC12 cells. As I only need a small amount each time, I would like to know about any experience in freezing collagen aliquotes to about -20C. The vendors all state that it is not recommended, but the sources have some conflict in interest... Did you find any deterioration in quality? What is your thawing protocol? In what solution do you freeze it and does the concentration matter?