BIOL 173 |
| 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) or UV (cis) light. As a result, surfactant binding to DNA and the resulting DNA condensation can be tuned with light. Dynamic light scattering (DLS) measurements are used to follow λ-DNA compaction from the elongated-coil (end-to-end distance of 1.27 μm) to the compact globular (hydrodynamic radius of 120 nm) form as a function of surfactant addition and light illumination. Moreover, the light-scattering results demonstrate that the compaction process is completely photoreversible. Fluorescence microscopy with T4-DNA is 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. The combined results clearly show the ability to control the interaction between DNA and the complexing agent and, therefore, DNA condensation with light. |
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Chemistry and Metabolism
4:30 PM-6:30 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster
Division of Biological Chemistry |