摘要
观察生物体内DNA凝聚参与物—亚精胺对DNA的凝缩作用将有利于深入理解DNA在体内的紧密存储机制。本文采用原子力显微镜(AFM)研究了在不同的DNA浓度下亚精胺—DNA凝聚体的形态变化。研究表明:随着体系中DNA浓度的变化,亚精胺将诱导DNA形成两种类型的凝聚物(类型Ⅰ和类型Ⅱ)。当λ-DNA浓度低于1ng/μl,亚精胺可诱导λ-DNA形成一种特殊的结构—环形凝聚体,其体积与单个λ-DNA的体积近似(类型Ⅰ);当λ-DNA浓度介于1ng/μl和10ng/μl之间,可观察到由许多小颗粒堆积而成的多分子凝聚的环状体(类型Ⅱ)。对类型Ⅱ的高度分析表明它可能具有分层结构,统计表明其组成颗粒在粒径上和单个类型Ⅰ凝聚体相近。这些观察暗示了亚精胺诱导DNA凝聚可能是一个分级自组装过程。
Condensation of DNA by multivalent cations can provide useful insights into the physical factors governing the folding and packaging of DNA in vivo.In this work,local ordered structures of spermidine DNA complexes prepared from different DNA concentrations have been examined by using atomic force microscopy (AFM).Two types (Types Ⅰ and Ⅱ) of DNA condensates,significantly different in sizes,were observed.It was found that for extremely dilute solutions (DNA concentrations around 1 ng/μl or below),the DNA molecules would collapse into toroidal structures with volume equivalent to a single λ DNA (Type Ⅰ).In relatively dilute solutions (DNA concentrations between 1ng/μl to 10ng/μl),a significantly larger structure of multimolecular toroids (type Ⅱ) were formed,which were constructed by many fine particles.Measurements show that the average diameter of these fine particles were similar to the outer diameter of the monomolecular toroids observed in extremely dilute solutions and the thickness of the multimolecular toroids had a distribution of multi layers with height increments of 11nm,indicating that the multimolecular toroidal structures have lamellar characteristics.These observations suggest that DNA spermidine condensation could have multiple stages,which are very sensitive to the DNA and spermidine concentrations.
出处
《电子显微学报》
CAS
CSCD
1999年第1期106-110,共5页
Journal of Chinese Electron Microscopy Society
基金
国家自然科学基金
关键词
环形凝聚体
亚精胺
分级自组装
DNA凝聚
AFM
toroidal condensates
spermidine
atomic force microscope
multiple stages self assemble process