Brillouin Scattering off of Biomolecules

Julia Benton
Prof. Bernard Chasan and Prof. Micheal El-Batanouny
Brillouin Scattering Lab
Reasearch Internship Program
Summer 1994


Low frequency vibrations play an essential role in the primary functions of biomolecules. These frequencies can be detected by introducing a laser beam to a sample of such molecules. The acoustic vibrations of the biomolecules will interact with the monochromatic laser light, altering the energies of some of the photons. The scattered light is then filtered through a Fabry-Perot interferometer which allows light of only a specific frequency to through the system at a time. As the etalon (a set of parallel semi-transparent mirrors) in the interferometer changes distance, the filtered light passes out of the Fabry-Perot and on into the photo-multiplier. The photo-multiplier counts the number of photons that enter the system over a period of time, as the etalon changes distance. The light which remains unaltered by the sample creates the elastic peaks and the altered light forms smaller peaks on either side of the elastic peaks called Brillouin peaks. The Brillouin peaks represent the light whose energy was either raised or lowered by a specific amount through its interactions with the photons of the sample; therefore, the peaks can be analyzed to better understand the acoustic vibrations of the sample itself. Thus far, work in this experiment has been geared towards creating a system that could produce results precise enough for such investigations. A mirror was used for the primary alignment of the system. Then we moved on to gelatin, latex spheres, ethanol and Lucite in order to test the accuracy and reliability of the system. Collagen, a fibrous protein, was the final sample chosen for study. Soon biomolecules such as hemoglobin will be studies because they have low frequency vibrations which may hold the key to understanding their fundamental functions.