Femtosecond time-resolved infrared laser study of the J−K transition of bacteriorhodopsin

✍ Scribed by Rolf Diller; Sudipta Maiti; Gilbert C Walker; Benjamin R Cowen; Robert Pippenger; Roberto A Bogomolni; Robin M Hochstrasser

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 684 KB
• Volume: 241
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(95)00598-x

✦ Synopsis

The J-K transition of the bacteriorhodopsin photocycle was monitored by sub-picosecond time-resolvt$d infrared spectroscopy. IR difference spectra in the region between 1670 and 1600 cm-' were taken at 1.5 and 9 ps, respectively, after photoexcitation of BR,,, at 540 nm. Spectral shifts of the bands at 1607 and 1661 cm-' reflect the chromophoric conformational changes during the J to K transition. Kinetics, taken at 1640 and 1607 cm-', show rise times determined by the dephasing times of the vibrational modes. The partial decrease of the bleach signal at 1640 cm-' is intermeted as a recovery of the vibrationally cooled BR,,, electronic ground state and provides a new method to measure the ~photocycle quantum yield. The development of the bleach at 1661 cm-' occurred faster than 500 fs, suggesting an almost in$tantaneous protein response to the electronic excitation.