Transition of Double-Stranded DNA Chains between Random Coil and Compact Globule States Induced by Cooperative Binding of Cationic Surfactant

Abstract

Interaction between cetyltrimethylammonium bromide (CTAB) and large T4DNA was studied by potentiometric titration using an ion-selective membrane electrode. The data obtained were assessed in terms of recently reported results regarding the higher order structure of T4DNA with the addition of CTAB: individual DNA chains exhibit discrete phase-transition between random coil and compact globule states. The apparent cooperativity represented as a sigmoidal function is attributed to bimodality in the distribution between the elongated coil and compact globule states of T4DNA chains. In addition, the globule-coil transition of single T4DNA is reversible, demonstrated by single-molecule observation with fluorescence microscopy. At a fixed concentration of CTAB, transition from the globule to the coil state is brought about by the addition of polyacrylic acid, suggesting that this reversible transition may be used for the purification of giant DNA molecules.

Cationic agents for DNA compaction

“…However, Fig. 7 presents some trends that are compatible with previous observations [14]. First, the overall behaviour consists of a decrease in size as the surfactant concentration increases.…”

“…Previous experimental results have show this same separation [9,14,22,25,32]. Predictions on the action of polycation chains upon model DNA molecules are also clearly compatible with these results [20].…”

“…Chemical agents cause compaction by modifying electrostatic interactions between DNA segments, by modifying DNA-solvent interactions, by excluding volume to the worm-like coil (and/or counterions), by causing localized bending or distorsion of the helical structure, or by some combination of these effects. Compaction of DNA chains is induced in vitro by the addition of agents such as polyamines [8], multivalent metal cations [9], hydrophilic polymers [10], cationic polymers [11,12], catanionic liposomes [13], and cationic [14] and nonionic surfac-* Corresponding author. tants [15].…”

“…An important addition to this list is fluorescence microscopy (FM), which was used to observe the condensation of single large T4 DNA molecules [5,6,17]. It has been used in a large number of studies on the interaction between DNA and different compacting agents [4,9,10,14]. Commonly, observations are consistent with a phase diagram that comprises three regions.…”

DNA-lipid systems: A physical chemistry study

“…The general aspects of DNA compaction by cationic surfactants have been monitored by Yoshikawa s group (6,15,16,(30)(31)(32) and others and by our group recently (11,33). Some illustrative fluorescence micrographs are presented in Figure 6.…”