Harrison J G, Balasubramanian S
University Chemical Laboratory, Cambridge University, Lensfield Road, Cambridge CB2 1EW, UK.
Nucleic Acids Res. 1998 Jul 1;26(13):3136-45. doi: 10.1093/nar/26.13.3136.
A small library of 49 peptide-oligonucleotide conjugates were synthesized to explore the influence of various peptide side chains on the hybridization properties of the DNA. An invariant 8mer oligonucleotide was coupled to a peptide portion that contained a five residue variable region composed of the cationic amino acids lysine, ornithine, histidine and arginine, the hydrophobic amino acid tryptophan, and alanine as a spacer. Melting temperature analysis indicated that T m depended principally on the number of cationic residues. The free energies of binding for polycationic peptide-oligonucleotides were enhanced compared with the unmodified 8mer. The origin of this stabilizing effect was found to be derived from a more exothermic enthalpic term. Improvement in Delta G vH was found to depend on the presence of positive charge and also the exact identity of the cationic amino acid, with the polyarginine peptide giving the most favourable Delta G vH value and the most exothermic Delta H vH. Further exploration suggested that the cationic peptide fragments interacted mainly with single-stranded rather than duplex DNA. A study of pH dependence showed that the polyhistidine conjugate was particularly sensitive to pH changes near neutrality, as indicated by a significant rise in T m from 19.5 degrees C at pH 8.0 to 28.5 degrees C at pH 6.0.
合成了一个包含49种肽 - 寡核苷酸共轭物的小型文库，以探究各种肽侧链对DNA杂交特性的影响。一个固定的8聚体寡核苷酸与一个肽部分相连，该肽部分包含一个由阳离子氨基酸赖氨酸、鸟氨酸、组氨酸和精氨酸、疏水氨基酸色氨酸以及作为间隔的丙氨酸组成的五残基可变区。熔解温度分析表明，熔解温度主要取决于阳离子残基的数量。与未修饰的8聚体相比，聚阳离子肽 - 寡核苷酸的结合自由能有所增强。发现这种稳定作用的来源是更放热的焓项。发现吉布斯自由能变化的改善取决于正电荷的存在以及阳离子氨基酸的确切身份，聚精氨酸肽给出了最有利的吉布斯自由能变化值和最放热的焓变。进一步的探究表明，阳离子肽片段主要与单链而非双链DNA相互作用。一项pH依赖性研究表明，组氨酸共轭物对接近中性的pH变化特别敏感，如熔解温度从pH 8.0时的19.5℃显著升高到pH 6.0时的28.5℃所示。
