Nr. 04/2008
Genetic Material under a Magnifying
Glass
Direct sequencing of single RNA strands with
tip-enhanced Raman spectroscopy
The genetic alphabet contains four letters. Although our cells
can readily decipher our genetic molecules, it isn’t so easy for
us to read a DNA sequence in the laboratory. Scientists require
complex, highly sophisticated analytical techniques to crack individual DNA codes. Volker Deckert and his team at the Institute for Analytical Sciences (ISAS) in Dortmund have recently developed a method that could provide a way to directly sequence DNA. Their process is based on a combination of Raman
spectroscopy and atomic force microscopy. As reported in the
journal Angewandte Chemie, Deckert and Elena Bailo have successfully analyzed DNA’s closest relative, RNA.
Direct sequencing means that the letters of the genetic code are
read directly, as if with a magnifying glass. A DNA or RNA
strand has a diameter of only two nanometers, so the magnification must be correspondingly powerful. Deckert’s team uses
an atomic force microscope to achieve this degree of magnification. Steered by the microscope, a tiny, silvered glass tip moves
over the RNA strand. A laser beam focused on the tip excites
the section of the strand being examined and starts it vibrating.
The spectrum of the scattered light (Raman spectrum) gives very
precise information about the molecular structure of the segment. Each genetic “letter”, that is, each of the nucleic acids, vibrates differently and thus has a characteristic spectral “fingerprint”.
The direct resolution of individual bases has not been attainable,
but is also not necessary. The tip only has to be moved over the
RNA strand at intervals corresponding to about the base-to-base
distance. Even if the measured data then consist of overlapped
spectra from several neighboring bases, the information can be
used to derive the sequence of the RNA.
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Angewandte Chemie International Edition ist eine Wiley-VCH-Publikation / is a publication of Wiley-VCH.
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If this method, known as tip-enhanced Raman spectroscopy
(TERS), can be extended to DNA, it could revolutionize the decoding of genetic information. Previous methods for sequencing
DNA are highly complex, work indirectly, and require a large
sample of genetic material. In contrast, the TERS technique developed by Deckert directly “reads” the code without chemical
agents or detours. It also requires only a single strand of DNA.
“DNA sequencing could become very simple,” says Deckert,
“like reading a barcode at the supermarket.”
(2436 characters)
Volker Deckert, ISAS Dortmund (Germany)
http://www.isas.de/index.php?id=491
Tip-Enhanced Raman Spectroscopy of Single RNA Strands: Towards a
Novel Direct-Sequencing Method
Angewandte Chemie International Edition
doi: 10.1002/anie.200704054
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-2Angewandte Chemie International Edition ist eine Wiley-VCH-Publikation / is a publication of Wiley-VCH.
Sitz der Wiley-VCH Verlag GmbH & Co. KGaA / Location of company: Weinheim.
Vorsitzender des Aufsichtsrats: John Herbert Jarvis
Handelsregister/Trade Register: Mannheim Abt. B, Nr. 2833 W USt.-Id. Nr. DE 813481633
Steuernummer: 47020 / 21620
Persönlich haftender Gesellschafter: John Wiley & Sons GmbH, Sitz: Weinheim
Amtsgericht Mannheim, Abt. B, Nr. 2296 W, Geschäftsführer: William Pesce