Yonuschot G, Mushrush G W
Biochemistry. 1975 Apr 22;14(8):1677-81. doi: 10.1021/bi00679a020.
Terbium reacted with DNA and chromatin to form a complex in which terbium acted as a sensitive fluorescent probe. By measuring the narrow-line emission of Tb-3+ when DNA is selectively excited, the relative amount of Tb-3+ bound to the DNA can be calculated. Terbium was bound to DNA until one Tb-3+ was present for each phosphate group. After this point no more terbium was bound. TbCl3 was bound to chromatin in a linear manner until approximately 0.48 TbCl3 was added for each phosphate group in the chromatin-DNA solution. From these data it appears that 52% of the phosphate groups in chromatin were unavailable for binding. The binding of Tb-3+ to DNA can be reversed by prolonged dialysis against 0.5 M NaCl and chelating agents. The terbium ion is ideal in that it binds DNA tight enough so that completion of the reaction can be assumed but loose enough so that it can be removed by gentle means. Low concentrations of salt (up to 2 mM NaCl) enhance the quantum efficiency. Below pH 3 and above pH 7 the DNA-terbium complex will not form. Between pH 3 and pH 7 the quantum efficiency of the DNA terbium complex increases from either pH to a maximum at pH 5.5 to 5.6. Several biochemical uses for Tb-3+ ion are suggested.
铽与DNA和染色质反应形成一种复合物，其中铽充当灵敏的荧光探针。通过在选择性激发DNA时测量Tb-3+的窄线发射，可以计算出与DNA结合的Tb-3+的相对量。铽与DNA结合，直到每个磷酸基团存在一个Tb-3+。在此之后，不再有铽结合。TbCl3以线性方式与染色质结合，直到在染色质-DNA溶液中为每个磷酸基团添加约0.48个TbCl3。从这些数据来看，染色质中52%的磷酸基团无法用于结合。通过用0.5 M NaCl和螯合剂进行长时间透析，Tb-3+与DNA的结合可以逆转。铽离子很理想，因为它与DNA结合得足够紧密，以至于可以假定反应完成，但又足够松散，以至于可以通过温和的方式去除。低浓度的盐（高达2 mM NaCl）可提高量子效率。在pH 3以下和pH 7以上，DNA-铽复合物不会形成。在pH 3至pH 7之间，DNA铽复合物的量子效率从任一pH值增加到pH 5.5至5.6时的最大值。文中提出了Tb-3+离子的几种生化用途。
