A research team from the National Institute of Standards and Technology (NIST), working with the Cleveland Clinic, has demonstrated a dramatically improved technique for analyzing biological cells and tissues based on characteristic molecular vibration "signatures." The new NIST technique is an advanced form of the widely used spontaneous Raman spectroscopy, but one that delivers signals that are 10,000 times stronger than obtained from spontaneous Raman scattering, and 100 times stronger than obtained from comparable "coherent Raman" instruments, and uses a much larger portion of the vibrational spectrum of interest to cell biologists.*
The technique, a version of "broadband, coherent anti-Stokes Raman scattering" (BCARS), is fast and accurate enough to enable researchers to create high-resolution images of biological specimens, containing detailed spatial information on the specific biomolecules present at speeds fast enough to observe changes and movement in living cells, according to the NIST team.
Raman spectroscopy is based on a subtle interplay between light and molecules. Molecules have characteristic vibration frequencies associated with their atoms flexing and stretching the molecular bonds that hold them together. Under the right conditions, a photon interacting with the molecule will absorb some of this energy from a particular vibration and emerge with its frequency shifted by that frequencythis is "anti-Stokes scattering." Recording enough of these energy-enhanced photons reveals a characteristic spectrum unique to the molecule. This is great for biology because in principle it can identify and distinguish between many complex biomolecules without destroying them and, unlike many other techniques, does not alter the specimen with stains or fluorescent or radioactive tags.
Using this intrinsic spectral information to map specific kinds of biomolecules in an image is potentially very powerful, but the signal levels a
|Contact: Michael Baum|
National Institute of Standards and Technology (NIST)