Hydroxyapatite-mediated transfer of DNA from diluted solutions to nitrocellulose or nylon membranes

Transfer of DNA (from 0.1 to 10 micrograms) from diluted solutions of variable volumes (1-10 ml) and various composition (2 M NaCl; 4 M LiCl, 8 M urea; 4 M CsCl; 20% sucrose) to nitrocellulose or nylon membranes was achieved with the use of hydroxyapatite. This absorbent that binds nucleic acids effectively and independently of ionic strength and composition of solution (except for chelators and phosphate ions) easily dissolves in small volumes of acids (for example, in 10% TCA). This phenomenon provides the opportunity to deliver the acid-insoluble precipitates to membrane filters. After alkaline denaturation on the filter followed by a fixation step (baking or UV irradiation for nitrocellulose or nylon filters, respectively), DNA hybridizes effectively with nick-translated DNA probes. The method is simple, reproducible, sensitive, and useful for working with diluted DNA solutions containing interfering substances.