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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。
Observing the condensation of DNA, a DNA participant in the organism, will help to understand the tight storage mechanism of DNA in the body. In this paper, atomic force microscopy (AFM) was used to study the morphological changes of spermidine-DNA aggregates at different DNA concentrations. Studies have shown that with changes in DNA concentration in the system, spermidine induces DNA to form two types of aggregates (type I and type II). When the concentration of λ-DNA is less than 1 ng / μl, spermidine induces the formation of a special ring-shaped aggregate of λ-DNA with a volume that approximates the volume of a single λ-DNA (type I) Between 1 ng / μl and 10 ng / μl, a multimodal aggregated annulus (Type II) with many small particles accumulated is observed. A high degree of type II analysis indicates that it may have a hierarchical structure and statistics show that its constituent particles are similar in particle size to single type I aggregates. These observations suggest that spermidine-induced DNA aggregation may be a hierarchical self-assembly process.