A chemical group attached to one end of a DNA molecule seems to cause a damaged DNA patch later in the double helix to be repaired. This amazing case of "Remote chemistry" as a scientific name, suggests that DNA repair long distance of some type may play a role in normal cells. The discovery, published in today's issue of Science * could also pave the way for therapies that could patch up damaged DNA, preventing the cancer.
A team of chemists from the California Institute of Technology led by Jackie Barton manufactured DNA helices with high-damage: a small crease in the propeller called a thymine dimer. This is the kind of damage caused by ultraviolet rays of the sun, and it can be a first step towards cancer melanoma deadly skin. Then they inserted an electron acceptor metal complex to the end of the DNA. Exposing the sample to light excites the metal compound, triggering absorb an electron thymine dimer and repair DNA damage. Because the compound can catalyze the repair reaction repeatedly Barton said the experience "may be a strategy to rationally design molecules that can accomplish this kind of therapeutic relief." In the heart of DNA base pairs form a BORDER = 0> said stack (gray, shown in top view and side) along which electrons can tunnel from a remote site to an acceptor artificial electrons (yellow).
Dandliker ET AL.
And because the electrons released by the thymine dimer must move down the DNA helix to the metal compound, the result may indicate that the unique structure of the DNA allows behave like a thread - unlike proteins, which are insulators. Barton thinks electrons can "tunnel" through the canal that runs through the center of the joined bases of the propeller. "There is no doubt that these results say DNA is a different system than proteins," she said.
The feat chemistry to distance impressed the other researchers, but they are divided about what it says on the electrical properties of DNA. Barton experiments "clearly show that there is a long distance to chemicals that can be performed on DNA, and the transfer of electrons can be done, "said Nick Turro of Columbia University. Others, however, believe that the chemical change can be explained in a more classic image, in which electrons jump from one atom to DNA rather than tunneling down the helix in a single step. It would be the distance to chemistry, says the University of North Carolina Holden Thorp chemist, "with a credible mechanism. And there are a lot of cool things [Barton] could do with it."
* For details, science Online Subscribers can create a link to the full report.
0 Komentar