Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New study sheds light on 'dark states' in DNA

11.01.2007
Chemists at Ohio State University have probed an unusual high-energy state produced in single nucleotides -- the building blocks of DNA and RNA -- when they absorb ultraviolet (UV) light.

This is the first time scientists have been able to probe the "dark" energy state -- so called because it cannot be detected by fluorescence techniques used to study other high-energy states created in DNA by UV light.

The study suggests that DNA employs a variety of means to dissipate the energy it absorbs when bombarded by UV light.

Scientists know that UV light can cause genetic alterations that prevent DNA from replicating properly, and these mutations can lead to diseases such as cancer.

The faster a DNA molecule can dissipate UV energy, the lesser the chance that it will sustain damage -- so goes the conventional scientific wisdom. So the dark states, which are much longer lived than previously known states created by UV light, may be linked to DNA damage.
... more about:
»DNA »dissipate »picosecond

The existence of this dark energy state -- dubbed n(pi)* (pronounced "n-pi-star") -- had previously been predicted by calculations. Other experiments hinted at its existence, but this is the first time it has been shown to exist in three of the five bases of the genetic code -- cytosine, thymine and uracil.

The detection of this dark state in single bases in solution increases the chances that it may be found in the DNA double helix, said Bern Kohler, associate professor of chemistry at Ohio State and head of the research team.

The Ohio State chemists determined that, when excited by ultraviolet light, these three bases dissipate energy through the dark state anywhere from 10-50 percent of the time.

The rest of the time, energy is dissipated through a set of energy states that do fluoresce in the lab. These "bright" energy states dissipate the energy much faster, in less than one picosecond.

A picosecond is one millionth of one millionth of a second -- an inconceivably short length of time. Light travels at 186,000 miles per second, but in twenty picoseconds it would only travel just under a quarter of an inch. Still, a picosecond is not so fast compared to the speed of some chemical reactions in living cells.

In tests of single DNA bases, the dark state lasted for 10-150 picoseconds -- much longer than the bright state. The chemists reported their results in the Proceedings of the National Academy of Sciences.

"We want to know, what makes DNA resist damage by UV light?" said Kohler. "In 2000, we showed that single DNA bases can dissipate UV energy in less than one picosecond. But now we know that there are other energy states that have relatively long lifetimes."

"Now we see that there is a family of energy states in DNA responsible for energy dissipation, and this is a major correction in how we view DNA photostability."

Until now, the proposed dark energy state of DNA was a little like the dark matter in the universe – there was no direct way of probing it. The Ohio State chemists used a technique called transient absorption, which is based on the idea that molecules absorb light at specific wavelengths, and allows them to study events happening in less than a picosecond.

They found that DNA dissipates UV energy through the dark state 10-50 percent of the time, depending on which DNA base is excited, and whether a sugar molecule is attached to the base or not.

Next, Kohler's lab is investigating whether the dark state can be linked to DNA damage.

"What are the photochemical consequences of long-lived states? Are they precursors to some of the chemical photoproducts that we know cause damage? That's the Holy Grail in this field -- connecting our growing knowledge of the electronic states of DNA with the photoproducts that damage it," he said.

Kohler's coauthors include Carlos E. Crespo-Hernandez, a former postdoctoral researcher at Ohio State, and Patrick M. Hare, who just obtained his Ph.D. from the university and is about to begin a position as a postdoctoral researcher at the University of Notre Dame.

Bern Kohler | EurekAlert!
Further information:
http://www.osu.edu

Further reports about: DNA dissipate picosecond

More articles from Life Sciences:

nachricht Newly designed molecule binds nitrogen
23.02.2018 | Julius-Maximilians-Universität Würzburg

nachricht Atomic Design by Water
23.02.2018 | Max-Planck-Institut für Eisenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>