Photoreversible DNA Condensation Using Light-Responsive Surfactants

Abstract

A means to control DNA compaction with light illumination has been developed using the interaction of DNA with a photoresponsive cationic surfactant. The surfactant undergoes a reversible photoisomerization upon exposure to visible (trans isomer, more hydrophobic) or UV (cis isomer, more hydrophilic) light. As a result, surfactant binding to DNA and the resulting DNA condensation can be tuned with light. Dynamic light scattering (DLS) measurements were used to follow lambda-DNA compaction from the elongated-coil to the compact globular form as a function of surfactant addition and light illumination. The results reveal that compaction occurs at a surfactant-to-DNA base pair ratio of approximately 7 under visible light, while no compaction is observed up to a ratio of 31 under UV light. Upon compaction, the measured diffusion coefficient increases from a value of 0.6 x 10(-8) cm2/s (elongated coil with an end-to-end distance of 1.27 microm) to a value of 1.7 x 10(-8) cm2/s (compact globule with a hydrodynamic radius of 120 nm). Moreover, the light-scattering results demonstrate that the compaction process is completely photoreversible. Fluorescence microscopy with T4-DNA was used to further confirm the light-scattering results, allowing single-molecule detection of the light-controlled coil-to-globule transition. These structural studies were combined with absorbance and fluorescence spectroscopy of crystal violet in order to elucidate the binding mechanism of the photosurfactant to DNA. The results indicate that both electrostatic and hydrophobic forces are important in the compaction process. Finally, a DNA-photosurfactant-water phase diagram was constructed to examine the effects of both DNA and surfactant concentration on DNA compaction. The results reveal that precipitation, which occurs during the latter stages of condensation, can also be reversibly controlled with light illumination. The combined results clearly show the ability to control the interaction between DNA and the complexing agent and, therefore, DNA condensation with light.

Release of DNA from cryogel PVA-DNA membranes

“…That is, the presence of bromide ions affects the PVA structure by decreasing its crystallinity due to the ability of NaBr as a hydrogen bond breaker [26]; consequently, it can be suggested that in more amorphous gels, due to the higher mobility of the PVA chains between the crystalline parts, DNA molecules evidenced stronger self interactions, generating aggregate structures and, thus, increasing the retention (α) of DNA inside the gel membrane. On the other hand, the effect of NaBr, on the DNA structure, in the gel membrane, is similar to that found by the addition of an azobenzene trimethylammonium bromide surfactant in DNA aqueous solution upon exposure to visible radiation [27]. Using the same arguments, the decrease in the rate constant of the DNA release with an increase of the retention degree can be attributed to a stabilization of DNA in the gel state.…”

Photomodulation of bacterial growth and biofilm formation using carbohydrate-based surfactants

“…An increase in the CMC was accompanied by trans – cis photoisomerization, which was attributed to the increased polarity and altered molecular geometry of the cis isomer relative to the more hydrophobic and planar trans isomer (Table 1). 20 However, in some cases the magnitude of this change was significant, in particular that of AzoGlcNAc incorporating an N -acetyl glucosamine head group. In contrast, virtually no difference in the CMC was observed between the trans (0.33 mM) and cis (0.34 mM) dominated PSS of AzoXyl , further highlighting the effect of subtle head group configuration and polarity on the interfacial activity of this class of photosurfactants.…”

Light and host–guest inclusion mediated salmon sperm DNA/surfactant interactions

“…Compared with the other external stimuli to trigger DNA decompaction and release, light input is considered to be advantageous benefitting from its capability of remote control [40][41][42]. For example, Lee developed a means to control DNA compaction and gene delivery by light input in cationic or cationic-anionic surfactant system [43,44]. Andreasson and coworkers described the photo-switched DNA-binding of a spiropyran amphiphile [45].…”