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| Carl Sagan's COSMOS is one of the most influential science programs ever made.
Q. Does the moon have a dark side?
A. The moon does have a far side which is impossible to see from the earth, but it doesn't mean that it's always dark. Each side of the moon is dark for no longer than 15 days at a time.
Q. Where does sound come from?
A. The air is always filled with sound waves. All things give off vibrations, but some have a low frequency which most cannot hear. The reason: it may take 3 minutes to make a single vibration. They may be caused by earthquakes and storms.
Did You Know?
The microwave was invented after a researcher walked by a radar tube and a chocolate bar melted in his pocket.
Coke-a-Cola was originally green.
Rubberbands last longer when refrigerated.
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DNA’s oscillating double helix hinders electrical conduction
by Netherlands Organization for
Scientific Research. Contact: Michel Philippensphilippens@nwo.nl
DNA has an oscillating double-helix structure. This oscillating means that the DNA molecules conduct electricity much less well than was previously thought. Ultrafast cameras were one of the devices the researchers from Amsterdam used to demonstrate this.
It turns out the DNA does not have a rigid regular structure as stated in textbooks. In reality the double helix of DNA forms a very dynamic chaotic system. The rigid structure in textbooks should be regarded as the average position of many structures taken over a period of time.
The Amsterdam researchers showed that the chaotic movements limit the electrical conductivity properties of DNA. Electrical conductivity, even if it is imperfect, is of vital importance for the cell. For example, the cell uses electrons from the charge transfer in DNA to repair damaged bonds.
According to the researchers the electrical conductivity would be much better if DNA had a fixed double-helix structure in which the individual building blocks were neatly stacked on top of each other.
The results have consequences for scientists who are developing new molecular microelectronics. In this sort of experimental electronics the DNA molecules would have to be able to initiate a range of reactions by means of charge transfer. The electronics specialists must now take the inefficient electrical conductivity of DNA into consideration.
The DNA examined by researchers included a piece of DNA with the form of a hair clip. It is similar to an important piece of RNA in the HIV virus. Researchers incorporated fluorescent molecule groups in a very specific manner. They then bombarded the piece of DNA with extremely short laser pulses. A special type of camera registered how the molecule fluoresced.
The experimental set-up of the Amsterdam researchers can observe movements or vibrations which occur in one millionth of a millionth of a second. Or put scientifically the set-up has a resolution of a picosecond. To put this into perspective: normal film cameras take 24 pictures per second and only detect the vibration if it lasts longer than 0.02 seconds.
Further information can be obtained from Olaf Larsen (Biophysics and Physics of Complex Systems, Free University of Amsterdam), tel. 31-20-422-0903 or 31-62-500-7670 (home), 31-20-444-7426 (work), fax 31-20-444-7999 (work), e-mail olaf@nat.vu.nl and olaf_larsen@hotmail.com. A short film (all rights reserved) about oscillating DNA can be found on the Internet: http://www.nat.vu.nl/n_s_old/vakgroepen/bio/english/research/index4.html. The defence of the doctoral thesis will take place on 3 October 2002. Mr Larsen's supervisor is Prof. Rienk van Grondelle.
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