Fourier Transform Infrared/Raman Spectrometer

Braiman, Mark

Abstract

A state=of-the-art- Fourier-transform (FT) infrared/Raman spectrometer will be used o perform vibrational spectroscopic studies of biomolecules. The instrument selected, a Digilab FTS60A, is capable of step-scanning interferograms obtained either from broadband IR light that is attenuated at selected wavelengths by a thin biological sample, or from near-IR light from an intense 1064-nm laser that is scattered and shifted to a variety of longer wavelengths via the Raman effect. The step-scanning capability of the instrument, along with its fast (400 KHz) digitizer with 19-bit dynamic range, will make it possible to obtain broadband time-resolved IR absorption and Raman scattering measurements with time resolution as fast as 5-mus. Furthermore, using a high- repetition-rate Q-switched Nd+-YAG laser should permit time resolution for Raman experiments down into the 10 nsec range. The beamsplitter and detector combination to be obtained along with spectrometer will allow complete spectral coverage from 10,000-100 cm in the infrared, and of measurements of Stokes-shifted Raman bands from 4,000-75cm. A microscope accessory for the FTS60A will allow sensitive IR absorbance difference measurements to be made on tiny quantities of sample (1 ng). The NIH-supported core group is planning to use the spectrometer principally to examine the structure and dynamics of biomembrane components, including simple lipid bilayer systems, supported planar bilayers with small peptides bound to them, and moderately large membrane proteins reconstituted into lipid vesicles. The proposed core users have all independently published NIH-supported papers demonstrating a capability and interest in using FT-IR and/or Raman spectroscopy to answer structural questions about membrane components involved in a variety of biomedically-important processes such as visual transduction, transmembrane chloride transport, and influenza virus insertion into cell membranes.