Berlin, Jan 29 : Using a combination of spectroscopy based on the "Raman Effect" and atomic force microscopy, scientists have developed a method that could provide a way to directly sequence DNA.
The "Raman Effect" is a theory conceptualized by C.V. Raman in 1928, according to which light is made up of particles known as 'photons'. This theory has since then helped in the study of the molecular and crystal structures of different substances.
According to a report in Angewandte Chemie International, the direct sequencing of DNA was made by Volker Deckert and his team at the Institute for Analytical Sciences (ISAS) in Dortmund, Germany.
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.
Now, a process based on a combination of Raman spectroscopy and atomic force microscopy, has made it possible to directly sequence DNA.
Direct sequencing means that the letters of the genetic code are read directly, as if with a magnifying glass.
Because a DNA or RNA strand has a diameter of only two nanometers, the magnification must be correspondingly powerful. Therefore, 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 its vibration.
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".
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.
According to the report, if this method, known as tip-enhanced Raman spectroscopy (TERS), can be extended to DNA, it could revolutionize the decoding of genetic information.
"DNA sequencing could become very simple, like reading a barcode at the supermarket," said Deckert.