Votavová H, Mátlová R, Sponar J
Institute of Organic Chemistry and Biochemistry, Academy of Sciences ofthe Czech Republic, Prague.
J Biomol Struct Dyn. 1994 Aug;12(1):163-72. doi: 10.1080/07391102.1994.10508094.
Ten oligonucleotides of the length 8-12 base pairs have been synthesized, which contain, in addition to the obligatory sequences CG/CG, sequences not favorable for the transition to the Z conformation (A.T pairs, GG/CC or AA/TT sequences). Conformational transitions of these oligonucleotides in high concentrations of NaClO4 in the absence and in the presence of Ni2+ were investigated using CD spectroscopy. The B-Z transition is affected by the length and sequence of the oligonucleotide. Increasing the NaClO4 concentration alone the transition of only one of the oligonucleotides studied. (CGCGCGTGCACGCGCG)2, can be induced. Other oligonucleotides remain in the B conformation or only partial transition to the Z conformation can be observed. Most other oligonucleotides can be converted into the Z conformation at intermediate concentrations of NaClO4 (2.0-3.2 M) by an addition of Ni2+ ions. In some cases, however, Ni2+ can destabilize the double stranded structure of the sample. We have studied the effect of the presence of A.T pairs in the G.C containing oligonucleotides and the effect of the presence of pu-pu/pyr-pyr sequences. The presence of the latter sequences in the Z form implicates the formation of a Z-Z'junction which makes the transition quite difficult. Despite the fact that some oligonucleotides contained several structural elements not favorable for the transition, we did not find any sequence which would completely block the ability of the oligonucleotide to adopt the Z conformation.
已经合成了10个长度为8 - 12个碱基对的寡核苷酸，除了必需的CG/CG序列外，还包含不利于向Z构象转变的序列（A.T对、GG/CC或AA/TT序列）。使用圆二色光谱法研究了这些寡核苷酸在高浓度高氯酸钠中，在不存在和存在Ni2+的情况下的构象转变。B - Z转变受寡核苷酸的长度和序列影响。仅增加高氯酸钠浓度时，所研究的寡核苷酸中只有一个（CGCGCGTGCACGCGCG）2能够发生转变。其他寡核苷酸保持B构象，或者只能观察到部分向Z构象的转变。大多数其他寡核苷酸在中等浓度的高氯酸钠（2.0 - 3.2 M）下通过添加Ni2+离子可转变为Z构象。然而，在某些情况下，Ni2+会使样品的双链结构不稳定。我们研究了含G.C的寡核苷酸中A.T对的存在以及嘌呤 - 嘌呤/嘧啶 - 嘧啶序列的存在所产生的影响。Z形式中后一种序列的存在意味着形成了一个Z - Z'连接，这使得转变相当困难。尽管一些寡核苷酸包含几个不利于转变的结构元件，但我们没有发现任何会完全阻止寡核苷酸形成Z构象的序列。
