Germann M W, Schoenwaelder K H, van de Sande J H
Biochemistry. 1985 Oct 8;24(21):5698-702. doi: 10.1021/bi00342a002.
The partial self-complementary 24-mer oligodeoxynucleotide d(C-G)5T4(C-G)5 forms a hairpin which can be enzymatically dimerized to a dumbbell structure. The blunt-ended nature of the hairpin is indicated by its ability to inhibit the T4 DNA ligase catalyzed joining of phi X174 HaeIII fragments. The hairpin monomer and dimer (dumbbell) undergo a reversible B to Z transition as shown by ultraviolet, circular dichroism, and 31P NMR spectroscopy. The Z form of the hairpin monomer and dimer is supported by monovalent ions (Na+), divalent ions (Mg2+ but not Mn2+), and dehydrating (ethanol) conditions. The conformational transition of d(C-G)5T4(C-G)5 monomer requires higher ionic or dehydrating conditions than those necessary for the corresponding linear oligomer d(C-G)5. The contribution of the loop (-T4-) of the hairpin to the apparent free energy change for the B to Z conformational transition at the midpoint was calculated to be 3.8 kJ mol-1.
部分自我互补的24聚体寡聚脱氧核苷酸d(C-G)5T4(C-G)5形成一个发夹结构，该发夹结构可通过酶促二聚化形成哑铃状结构。发夹的平端性质通过其抑制T4 DNA连接酶催化的φX174 HaeIII片段连接的能力得以体现。如紫外光谱、圆二色光谱和31P NMR光谱所示，发夹单体和二聚体（哑铃状）经历可逆的B型到Z型转变。发夹单体和二聚体的Z型由单价离子（Na+）、二价离子（Mg2+而非Mn2+）和脱水（乙醇）条件所支持。与相应的线性寡聚物d(C-G)5相比，d(C-G)5T4(C-G)5单体的构象转变需要更高的离子强度或脱水条件。计算得出，发夹环（-T4-）对中点处B型到Z型构象转变的表观自由能变化的贡献为3.8 kJ mol-1。
