Oligonucleotide conjugation to a cell-penetrating (TAT) peptide by Diels–Alder cycloaddition
作者:Victoria Steven、Duncan Graham
DOI:10.1039/b807843b
日期:——
Modifed oligonucleotides are routinely employed as analytical probes for use in diagnostics, e.g. in the examination of specific RNA sequences for infectious diseases, however, a major limiting factor in oligonucleotide-based diagnostics is poor cellular uptake of naked oligonucleotides. This problem can be overcome by covalent attachment of a so-called âcell-penetrating peptideâ to form an oligonucleotide peptide conjugate. Stepwise solid phase synthesis of such a conjugate is difficult and expensive due to the conflicting chemistries of oligonucleotides and peptides. A simple approach to overcome this is post-synthetic conjugation. DielsâAlder cycloaddition is an attractive methodology for oligonucleotide peptide conjugation; the reaction is fast, chemoselective and the reaction rate is greatly enhanced in aqueous media â ideal conditions for biological moieties. An oligodeoxyribonucleotide sequence has been derivatised with a series of dienes at the 5â²-terminus, using a series of unique dienyl-modified phosphoramidites, and investigation into the effect of diene type on the efficiency of conjugation, using DielsâAlder cycloaddition with a maleimido-derivatised cell-penetrating (TAT) peptide, has been performed. This led to the observation that the optimal diene for conjugation was cyclohexadiene, allowing conjugation of oligodeoxyribonucleotides to a cell-penetrating peptide by DielsâAlder cycloaddition for the first time.
经过修饰的寡核苷酸通常被用作诊断分析探针,例如用于检测传染性疾病的特定RNA序列。然而,寡核苷酸诊断的一个主要限制因素是裸寡核苷酸的细胞吸收率低。通过共价连接所谓的 "细胞穿透肽 "来形成寡核苷酸肽共轭物,可以克服这一问题。由于寡核苷酸和肽的化学性质相互冲突,逐步固相合成这种共轭物既困难又昂贵。克服这一问题的简单方法是合成后共轭。DielsâAlder 环加成法是寡核苷酸与肽共轭的一种有吸引力的方法;该反应速度快、化学选择性好,而且在水介质中反应速率大大提高,是生物分子的理想反应条件。利用一系列独特的二烯基修饰的磷酰胺,在寡脱氧核苷酸序列的 5²-末端用一系列二烯进行了衍生,并利用 DielsâAlder 环加成法与马来酰亚胺衍生化的细胞穿透(TAT)肽进行了二烯类型对共轭效率影响的研究。结果发现,最适合共轭的二烯是环己二烯,从而首次实现了通过 DielsâAlder 环加成法将寡脱氧核苷酸与细胞穿透肽共轭。