AI Article Synopsis
- The study examined the stability of DNA in solutions mixed with dodecyltrimethylammonium bromide (DTAB) using various techniques like circular dichroism and UV absorption.
- The findings revealed that DNA exists predominantly as single-stranded in pure solutions but can transition to a double-helix structure with the introduction of a small amount of salt (NaBr).
- Additionally, the research suggests that differences in how single-stranded and double-stranded DNA interact with surfactants, influenced by both hydrophobic and electrostatic forces, could be exploited to separate the two forms of DNA effectively through the addition of DTAB.
Article Abstract
The stability of DNA in solution and the phase behavior in mixtures with dodecyltrimethylammonium bromide (DTAB) were investigated. By means of circular dichroism, UV absorption, and differential scanning calorimetry, we found that for dilute solutions of DNA with no addition of salt the DNA molecules are in the single-stranded conformation, whereas the addition of a small amount of NaBr, 1 mM, is sufficient to stabilize the DNA double-helix. Furthermore, at higher DNA concentrations, native DNA becomes the most stable structure, which is due to a self-screening effect. By phase diagram determinations of the DNA-surfactant system, we found that the effect of salt on phase behavior mainly relates to a difference in interaction of the amphiphile between single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The difference in association between ss and dsDNA with surfactants of different chain lengths can be interpreted in terms of an interplay between hydrophobic and electrostatic interactions, the latter being influenced by polymer flexibility. In this way, a nonmonotonic variation can be rationalized. A crossing of the phase separation lines with DNA concentration can be rationalized in terms of a change in relative stability of ss and dsDNA. The fact that ssDNA phase separates earlier than dsDNA in association with DTAB, may serve as a basis for a method of easily separating dsDNA from ssDNA by the addition of surfactant; this is verified as monitored by circular dichroism measurements.
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| http://dx.doi.org/10.1021/bm050137n | DOI Listing |
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