ATR FT-IR DIFFERENCE SPECTROSCOPY OF BIOLOGICAL MATTER WITH MICROSECOND TIME RESOLUTION/

Attenuated total reflection (ATR) spectroscopy allows precise control of external parameters vital for proper functioning of biological matt er. For the first time in biospectroscopy, ATR difference spectroscopy has been combined with the step-scan technique. The current setup int egrates a broad frequency range (800-25,000 cm (1)) with high temporal resolution (5 mu s). Vibrations are detected that arise from single a mino acids (<10-3 absorbance units) of the chromoprotein bacteriorhodo psin. Time-resolved ATR/FT-IR difference spectra are compared with con ventional transmission spectra. The high mirror stability enables time -resolved FT-vis spectroscopy of the same sample with the same instrum ent. Potential applications even to non-light-absorbing biomaterial ar e discussed.