Takeuchi S, Maeda A
Biochim Biophys Acta. 1976 Dec 1;454(2):309-18. doi: 10.1016/0005-2787(76)90233-1.
Fluorescein mercuric acetate (fluorescein Hg Ac), which is a fluorescent thiol reagent, was shown to bind to various nucleic acids by measuring the changes in its absorption and fluorescence properties. Up to a critical concentration of free fluorescein Hg Ac (1-10(-7) M for calf thymus DNA, with 42% GC, and 2-10(-7) M for Micrococcus lysodeikticus DNA, with 72% GC) this reagent appears to bind selectively to single-stranded sections in DNA. Above this critical concentration, cooperative binding to double helical DNA occurs, and denatured DNA is obtained after removal of bound fluorescein Hg Ac by dialysis against 1 M KCl. These facts indicate that fluorescein Hg Ac causes the denaturation of double helical DNA prior to binding as has been shown in the case of methylmercuric hydroxide. The binding of fluorescein Hg Ac to DNA is much stronger than that of methylmercuric hydroxide. The number of total binding sites for fluorescein Hg Ac is close to the number of base pairs for both calf thymus DNA and M. lysodeikticus DNA. Furthermore, it was shown that fluorescein Hg Ac binds to thymidine, deoxyguanosine, poly(U) and poly(G). Since fluorescence quenching of fluorescein Hg Ac accompanies its complex formation with DNA and the affinity is markedly high as indicated by the association constant of 6.8-10(7) M(-1) for single-stranded calf thymus DNA, fluorescein Hg Ac can be used for the structural studies of small amounts of nucleic acids.
荧光素汞乙酸盐（fluorescein Hg Ac）是一种荧光硫醇试剂，通过测量其吸收和荧光特性的变化，已证明它能与各种核酸结合。对于小牛胸腺DNA（GC含量为42%），游离荧光素汞乙酸盐的临界浓度高达1 - 10⁻⁷ M，而对于溶壁微球菌DNA（GC含量为72%），临界浓度为2 - 10⁻⁷ M。在此临界浓度以下，该试剂似乎选择性地结合到DNA的单链部分。高于此临界浓度，会发生与双螺旋DNA的协同结合，通过用1 M KCl透析去除结合的荧光素汞乙酸盐后可得到变性DNA。这些事实表明，荧光素汞乙酸盐在结合之前会导致双螺旋DNA变性，就像氢氧化甲基汞的情况一样。荧光素汞乙酸盐与DNA的结合比氢氧化甲基汞强得多。荧光素汞乙酸盐的总结合位点数接近小牛胸腺DNA和溶壁微球菌DNA的碱基对数。此外，已证明荧光素汞乙酸盐能与胸腺嘧啶、脱氧鸟苷、聚尿苷酸和聚鸟苷酸结合。由于荧光素汞乙酸盐与DNA形成复合物时会伴随荧光猝灭，且结合常数表明其亲和力非常高（对于单链小牛胸腺DNA，结合常数为6.8 - 10⁷ M⁻¹），因此荧光素汞乙酸盐可用于少量核酸的结构研究。
