A paper by researchers at the National Institute of Standards and Technology (NIST) may breathe new life into the use of a powerfulbut trickydiagnostic technique for cell biology. The paper,* appearing this week in the Biophysical Journal, demonstrates that with improved hardware and better signal processing, a powerful form of molecular vibration spectroscopy can quickly deliver detailed molecular maps of the contents of cells without damaging them. Earlier studies have suggested that to be useful, the technique would need power levels too high for cells.
The technique, "B-CARS,"** is one of several variations on Raman spectroscopy, which measures the frequencies associated with different modes of vibration of atoms and their bonds in a molecule. The exact mix of these frequencies is an extremely discriminating "fingerprint" for any particular molecule, so Raman spectroscopy has been used as a chemical microscope, able to detail the structure of complex objects by mapping the chemical composition at each point in a three-dimensional space.
In the biosciences, according to NIST chemist Marcus Cicerone, Raman spectroscopy has been used to detect microscopic cellular components such as mitochondria, detect how stem cells differentiate into new forms and distinguish between subtly different cell and tissue types. It can, for example, detect minor differences between various precancerous and cancerous cells, potentially providing valuable medical diagnostic information. Even better, it does this without the need to add fluorescent dyes or other chemical tags to identify specific proteins.
The catch, says Cicerone, is speed. The usual method, spontaneous Raman scattering takes a long time to gather enough data to generate a single spectrumas much as seven minutes for fine detailand that's for each point in the image. "Seven minutes or even five seconds per spectrum is not feasible when we need a million spectra for an image," he
|Contact: Michael Baum|
National Institute of Standards and Technology (NIST)