Study of the Intramolecular Triplex Formation with Oligonucleotides Containing 5-Bromocytosine in Aqueous Solution

含5-溴胞核酸鹼基之寡核酸鏈能自行折疊成核酸三螺旋之研究

林維政(Wei-Chen Lin) ； 林淑萍(Shwu-Bing Lin) ； 鄭鍾秀(Jong-Shiow Cheng) ； 魏明財(Ming-Tsair Wey) ； 趙珮雯(Pei-Wen Chao) ； 甘魯生(Lou-Sing Kan) ； Utz Dorberger ； Hartmut Fritzsche

《中央研究院化學研究所集刊》 47期 (2000/08) Pp. 43-54

https://doi.org/10.6522/BICAS.2000.47.5

並列摘要

Three 5-bromocytosine base containing oligonucleotides (5'-TCTCTCTTYTYTYTCCAGAGAG (TCY); 5'-TYTYTYTTCTCTCTCCAGAGAG (YTC); 5'-TYTYTYTTYTYTYTCCAGAGAG (YTCY)) as well as TCTCTCTTCTCTCTCCAGAGAG (TC), have been designed and synthesized for the study of intramolecular triplex formation. The stability and formation of the triplexes were monitored by UV, CD and IR spectra employing pH potentials of 4.5, 6.0, and 8.0, respectively, in 20mM sodium cacodylate buffer and 150mM NaCI in a temperature range of 5 to 90 °C. These four oligomers form triplex and duplex at low pH and high pH values, respectively, as monitored by UV melting experiments. However, both triplex and duplex are formed at pH 6.0. The conclusion has been approved by CD spectra, Namely, a triplex characteristic band at 218 nm was observed for all three oligomers at pH 4.5 at low temperature, On the contrary, the CD curve of all three oligomers demonstrated a typical B-form DNA at high pH, Both triplex and duplex CD characters were shown for all three oligomers at pH 6.0. Their stability can be monitored with the CD bands at 218nm and 258 nm, respectively. The conformation of the sugar pucker favors N-type conformation in triplex and the duplex favors the S-type conformation as analyzed by FT-IR spectroscopy. When the triplex dissociated to the duplex, the N-type shifted to the S-type in proportion. Therefore, our study will shed light on the design of triplex formation.