本文研究了2700 bp DNA片段在金属离子作用下,折叠缩合为复曲面的形成过程。以电子显微镜术为手段,经大量观测抽提出几种典型中间结构,并计算了各典型结构的尺度分布。作者由此推论,DNA缩合结构的形成过程是DNA链折叠与排列的过程;是无序到有序的转化过程。研究不仅证实缩合是有规则与有方向的,还进一步证实短DNA片段的缩合是多分子的缩合。 相似文献
The superior surfactant properties of cationic gemini surfactants are applied to the complex problem of introducing genes into cells. Of almost 250 new compounds tested, of some 20 different structural types, a majority showed very good transfection activity in vitro. The surfactant is shown to bind and compact DNA efficiently, and structural studies and calculations provide a working picture of the \"lipoplex\" formed. The lipoplex can penetrate the outer membranes of many cell types, to appear in the cytoplasm encapsulated within endosomes. Escape from the endosome--a key step for transfection--may be controlled by changes in the aggregation behavior of the lipoplex as the pH falls. The evidence suggests that DNA may be released from the lipoplex before entry into the nucleus, where the new gene can be expressed with high efficiency. 相似文献
In difference to compact objects of a similar size, toroidal structures have some distinguishing properties that originate from their open inner cavity and closed circuit. Here, a general facile methodology is developed to prepare composite rings with varied compositions on a large scale by using core‐shell toroids assembled from tri‐block copolymers of poly(4‐vinyl pyridine) (PVP)/polystyrene (PS)/PVP. Taking advantage of the complexation ability of the PVP shell, varied components that range from polymers, inorganic materials, metals and their compounds, as well as pre‐formed nanoparticles are introduced to the toroidal structures to form composite nanostructures. Metal ions can be adsorbed by PVP through complexation. After in situ reduction, a large number of metal‐based functional materials can be prepared. PVP is alkaline, and thus capable of catalyzing the sol‐gel process to generate an inorganic shell. Furthermore, pre‐formed nanoparticles can also be absorbed by the shell through specific interactions. The PS core is not infiltrative during synthesis, and hollow rings can be derived after the polymer templates are removed.
A new class of biodegradable cationic macromolecules for DNA binding and condensation was developed by end‐group‐functionalization of poly(trimethylene carbonate). A series of one‐ and two‐armed structures was synthesized and their interaction with DNA was evaluated. To aid data interpretation, a non‐linear modeling method was applied to show efficient DNA binding that was intimately related to cationic charge density and macromolecular architecture. One‐armed, low charge density structures were consistently found to bind to DNA at lower charge ratios than their two‐armed, high charge density counterparts. This suggests that polymer backbone structure and characteristics are important considerations in the development of efficient cationic polymer systems for DNA condensation and delivery.
Layered double hydroxides (LDHs) exhibit characteristic anion-exchange chemistry making them ideal carriers of negatively charged molecules like deoxyribonucleic acid (DNA). In this study, hydrotalcite (Mg−Al) and hydrotalcite-like compounds (Mg−Fe, Zn−Al, and Zn−Fe), also known as LDHs, were evaluated for their potential application as a carrier of DNA. LDHs were prepared by coprecipitation at low supersaturation and characterized by Powder X-ray diffraction (XRD), infrared (IR), Raman, and inductively coupled plasma—optical emission spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD patterns showed strong and sharp diffraction peaks for the (003) and (006) planes indicating well-ordered crystalline materials. TEM images yielded irregular circular to hexagonal-shaped particles of 50–250 nm in size. Varying degrees of DNA binding was observed for all the compounds, and nuclease digestion studies revealed that the LDHs afford some degree of protection to the bound DNA. Minimal toxicity was observed in human embryonic kidney (HEK293), cervical cancer (HeLa) and hepatocellular carcinoma (HepG2) cell lines with most showing a cell viability in excess of 80 %. All LDH complexes promoted significant levels of luciferase gene expression, with the DNA:Mg−Al LDHs proving to be the most efficient in all cell lines. 相似文献
In this study, dissipative particle dynamics is employed to investigate the complexation of poly(amido amine) dendrimer and single‐stranded DNA (ssDNA). A coarse‐grained model for ssDNA is constructed, which reproduces correctly the conformational behavior of the ssDNA molecules. The effects of pH, dendrimer generation, ionic strength, and dendrimer/ssDNA charge ratio on DNA–dendrimer complexes are explored. Simulation results show that ssDNA molecules can be significantly condensed by dendrimers and stable complexes are obtained by regulating the pH value. The ssDNA chain penetration would complicate its release from dendrimer, while this can be tuned by different generations of dendrimer. Salt concentration affects the size and stability of the complexes through ion screening effect. Dendrimer/ssDNA charge ratio can be used to control the size and morphology of the complex. This work can help design dendrimer‐based gene vectors. 相似文献
