Calcium chloride is a reagent commonly used in biochemistry. Calcium has important functions in many biological processes, including signal transduction, muscle contraction and maintenance of cell membrane and cell wall stability. It is used in the preparation and transformation of E. coli cells and in the transfection of eukaryotic cells with plasmid or genomic DNA. It is also used in the crystallization of proteins and in the concentration of virus vectors. Its effect on total fluorescence in the polymerization of the E. coli FtsZ cleavage protein FtsZ was studied by fluorescent assay.