Measurement of binding of terbium to DNA.

This communication demonstrates further that terbium(III) can be used as a probe for DNA. The stoichiometry of terbium binding to DNA was measured by two new methods. In the first method, calf-thymus DNA was titrated with radioactive terbium-160, which is an isotope of the common terbium-159. The resulting DNA-terbium complex was trapped and measured on millipore filters. In the second method, a peak of UV absorption of terbium was found at 219 nm and was used to measure stocichiometry. By both methods, the stoichiometry of binding was one Tb(III) for each three available phosphate groups in DNA. Finally, a rapid method was developed using terbrium-160 to measure the amount of nucleic acid in a solution.