Can genetic information be controlled by light?

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Can genetic information be controlled by light?

http://www.eurekalert.org/pub_releases/2008-10/ku-cgi101008.php

DNA, the molecule that acts as the carrier of genetic information in

all forms of life, is highly resistant against alteration by

ultraviolet light, but understanding the mechanism for its

photostability presents some puzzling problems. A key aspect is the

interaction between the four chemical bases that make up the DNA

molecule.

Researchers at Kiel University have succeeded in showing that DNA

strands differ in their light sensitivity depending on their base

sequences. Their results are reported by Nina Schwalb and colleagues

in the current issue of the journal Science appearing on October 10,

2008.

It has been known for many years that the individual bases that code

the genetic information contained in DNA show a high degree of

photostability, as the energy that they take up from UV radiation is

immediately released again. Surprisingly, however, it is found that

in DNA, which consists of many bases, those mechanisms are

ineffective or only partially effective. It seems that the

deactivation of UV-excited DNA molecules must instead occur by some

completely different mechanisms specific to DNA, which are not yet

understood. Through measurements by a variety of methods on DNA

molecules with different base sequences, the research group led by

Professor Friedrich Temps at the Institute of Physical Chemistry of

Kiel University has now been able to confirm and clarify that

assumption.

According to Professor Temps, " DNA achieves its high degree of

photostability through its complex double-helix structure. The

interactions between bases that are stacked one above another within

a DNA strand, and the hydrogen bonds between the base pairs of the

two complementary single strands in the double-helix play key roles.

Through the different interactions that we have observed the DNA acts

to some extent as its own sun-protection " .

Nina Schwalb investigated many different base combinations in

synthetically-produced DNA molecules. Using a femtosecond pulsed

laser spectroscope, she measured the characteristic energy release

for each combination. She was able to measure the time for which the

molecules continued to fluoresce, and thus how long they stored the

light energy. She found that for some base combinations these

fluorescence 'lifetimes' were only about 100 femtoseconds, whereas

for others they were up to a thousand times longer. A femtosecond is

one millionth of a billionth of a second.

Commenting on the conclusions from her research, Nina Schwalb

says: " We have investigated the photophysical properties and have

found that different base combinations have widely different

fluorescence lifetimes. This could lead to the development of a new

diagnostic method whereby laser light could be used to directly

recognise certain genetic sequences without, for example, having to

mark the DNA with dyes as in the method used at present " .

One might also envisage linking the photophysical properties to

genetic characteristics. When these mechanisms are better understood,

it might in the long term become possible to repair gene mutations

using laser radiation.

" In the field of nano-electronics it has already been shown that

synthetically produced DNA can be used as 'nano-wires'. On the basis

of the different reaction times of the molecules it might one day

become possible to use laser pulses to 'switch' specific molecules.

It might even be possible under some circumstances to make

transistors from DNA that would work through the hydrogen bonds, "

explains Professor Temps.