Gemini Surfactant-Induced DNA Condensation into a Beadlike Structure

Abstract

Using a magnetic tweezers (MT) apparatus and an atomic force microscope (AFM), we studied the condensation of DNA induced by the cationic gemini surfactant hexyl-alpha,omega-bisdodecyldimethylammonium bromide (C12 C6 C12 Br2). Stepwise condensation events were found for forces from 0.5 to 4 pN, with a decrease in DNA extension by approximately 100 nm in each condensation event. Applied stretching forces larger than 6 pN were found to be able to decondense the condensates in a similar intermittent stepwise manner, but with approximately 60 nm of DNA released in each decondensation event. These observations are consistent with AFM images that show beadlike structures on DNA. The results lead to a model in which, during condensation, independent beadlike structures are initially formed on DNA, and as the local density of the beads increases, they compact into higher-order structures while maintaining their independence. The condensation process is different from any previously reported condensation process, but it is somewhat similar to that of chromatin assembly.

Supramolecular Systems Based on Novel Mono‐ and Dicationic Pyrimidinic Amphiphiles and Oligonucleotides: A Self‐Organization and Complexation Study

“…Different dicationic agents have been explored, with the structure of the head groups and spacers being varied. [36][37][38][39][40][41] To improve the stability and biocompatibility of amphiphile-DNA complexes, cationic surfactant/lipid mixtures have been used or biofragments have been introduced into the surfactant molecules. [42][43][44][45][46][47][48] A perspective approach in gene therapy has been connected with the use of oligonucleotides (ONus) and the development of cationic agents for their delivery.…”

Micellization of cationic gemini surfactant and its interaction with DNA in dilute brine

“…4b). The existence of this type of aggregate was proposed by Wang et al [39]. With increase of such beadlike structures, they may tend to approach to each other and reassemble to form more condensed toroidal aggregates with higher order structure, shown in Fig.…”

Ionic Mixed Interactions in Macromolecules

“…[27,28] Figure 4 a evidences the time evolution of a pearls-on-a-string structure induced by a Gemini surfactant on DNA (48.5 kbp). [27] The authors suggested that the beads (diameters in the order of 10 nm) are formed by wrapping up of DNA around micellarlike structures of the surfactant, and suggest a possible similarity to the chromatin assembly. However, as reported by Perico and Ciferri, [8] it is difficult to justify the bending of a DNA segment around a small micellar structure stabilized by weak cohesion forces.…”