Spermidine trihydrochloride, also called N,- (3-Aminopropyl)butane-1,4-diamine hydrochloride, its molecular formula is C7H19N3.3HCl. Application: Inhibits neuronal synthase (nNOS) activity; it can bind to DNA and precipitate DNA is used for the purification of DNA combined with protein; it stimulates the activity of T4 polynucleotide kinase.